refactor: collapse fp8 recipe hierarchy and state property layers

- Merge DelayedScaling/DynamicScaling and the abstract FP8Recipe base into one FP8Recipe dataclass with a dynamic flag; dispatch now reads cfg.recipe.dynamic instead of isinstance checks
- Drop the _ActiveOrDefault descriptor and the FP8State property views; the persistent defaults are plain default_* attributes and get_weight_meta takes the active recipe explicitly
- Convert FP8TensorMeta to a NamedTuple of the three per-operand rings
- Update tests to the new API; the autocast context test now asserts _active_config push/restore directly

.github/workflows/release.yml

@@ -54,6 +54,9 @@ jobs:
       - name: Build wheel (with CUDA kernels)
         run: |
           CSRC_KERNELS=true pip wheel . --no-deps --no-build-isolation -w dist/
+          for f in dist/*.whl; do
+            mv "$f" "dist/$(basename "$f" .whl)+${{ matrix.cuda_tag }}.whl"
+          done
 
       - uses: actions/upload-artifact@v4
         with:

CONTRIBUTING.md

@@ -39,11 +39,12 @@ ruff format .    # re-format after fix
 python -u -m pytest tests/ -v
 ```
 
-> Failed tests may leave orphan tempdirs under `%TEMP%`. Clean them manually if needed.
+> Failed tests may leave orphan tempdirs under the system temp directory
+> (`$TMPDIR` on Linux/macOS, `%TEMP%` on Windows). Clean them manually if needed.
 
 ### 4. (Optional) Full pre-commit check script
 
-If you have Git Bash available:
+If you have `bash` available (Git Bash on Windows works too):
 
 ```bash
 bash scripts/pre_commit.sh

Dockerfile

@@ -57,8 +57,17 @@ COPY docs/ ./docs/
 COPY pyproject.toml .
 COPY README.md .
 
-# Create non-root user
-RUN useradd -m astrai && chown -R astrai:astrai /app
+# Create non-root user matching the host uid/gid (passed via build args).
+# ubuntu:24.04 ships a default 'ubuntu' user/group at uid/gid 1000, so remove
+# it first to free those ids before creating astrai.
+ARG USER_UID=1000
+ARG USER_GID=1000
+RUN userdel -r ubuntu 2>/dev/null || true \
+    && groupdel ubuntu 2>/dev/null || true \
+    && groupadd -g "${USER_GID}" astrai \
+    && useradd -m -u "${USER_UID}" -g astrai astrai \
+    && chown -R astrai:astrai /app
+ENV HOME=/home/astrai
 USER astrai
 
 ENV PYTHONUNBUFFERED=1 \

README.md

@@ -51,7 +51,7 @@ AstrAI is an end-to-end Transformer framework for building, training, evaluating
 | **Data** | Declarative JSON preprocessing, configurable masking and packing, binary/JSONL storage, and streaming datasets |
 | **Inference** | Continuous batching, paged KV cache, radix prefix caching, streaming generation, and Torch/CUDA/FlashAttention backends |
 | **Serving** | FastAPI server with OpenAI and Anthropic chat completion protocols, including SSE streaming and tool calls |
-| **Evaluation** | Perplexity, MMLU, HumanEval, IFEval, IFD, and ROUGE evaluation tools |
+| **Evaluation** | Perplexity, MMLU, HumanEval, IFEval, IFD, ROUGE, and weight-analysis evaluation tools |
 | **Extensibility** | Factory and registry architecture for models, datasets, training strategies, callbacks, kernels, and protocol components |
 
 ### Getting Started
@@ -65,8 +65,9 @@ AstrAI requires Python 3.12+ and pins PyTorch exactly to `2.11.0`. Training, `sc
 ```bash
 git clone https://github.com/ViperEkura/AstrAI.git
 cd AstrAI
-pip install -e .                                          # pure PyTorch (no CUDA kernels)
-# CSRC_KERNELS=true pip install -e . --no-build-isolation  # optional: fused CUDA kernels
+pip install -e .                                          # kernels auto-build when nvcc + CUDA are detected
+# CSRC_KERNELS=false pip install -e .                     # skip kernels (pure PyTorch)
+# CSRC_KERNELS=true pip install -e . --no-build-isolation  # force the fused CUDA kernel build
 # pip install -e ".[dev]"                                  # dev dependencies (pytest, ruff)
 ```
 
@@ -191,6 +192,9 @@ docker compose up -d
 
 # Docker Compose CPU server profile (CUDA-only generation scripts/demos are unavailable)
 docker compose --profile cpu up -d
+
+# YAML-driven serving (see serve.yaml; up/run/down/logs/status...)
+bash scripts/serve.sh up
 ```
 
 > **Note**: `--gpus all` is required for CUDA support. Without it, `torch.cuda.is_available()` will return `False`.
@@ -236,6 +240,8 @@ See [Inference Guide](docs/guides/inference.md) for SSE streaming format, error
 | [Data Flow](./docs/developer/dataflow.md) | Data pipeline, storage backends & dataset architecture |
 | [Internals](./docs/developer/internals.md) | Training internals: loss formulas, callback lifecycle, KV cache |
 | [CUDA Kernels](./docs/developer/cuda_kernels.md) | Custom CUDA attention kernels & benchmarks |
+| [Docker Serving](./docs/developer/docker-serving.md) | YAML-driven containerized serving (`serve.yaml`, `serve.sh`) |
+| [Docker Training](./docs/developer/docker-training.md) | YAML-driven containerized training (`train.yaml`, `train.sh`) |
 
 ### Contributing
 

astrai/__init__.py

@@ -1,9 +1,6 @@
-__version__ = "1.3.12"
+__version__ = "1.3.13"
 __author__ = "ViperEkura"
 
-import logging
-import os
-
 from astrai.config import (
     AutoRegressiveLMConfig,
     BaseModelConfig,
@@ -20,15 +17,10 @@ from astrai.dataset import (
     StoreFactory,
 )
 from astrai.factory import BaseFactory
-from astrai.inference import (
-    GenerationRequest,
-    InferenceEngine,
-    ProtocolHandler,
-    SamplingPipeline,
-    get_app,
-    run_server,
-    sample,
-)
+from astrai.inference import InferenceEngine, get_app, run_server, sample
+from astrai.inference.network import ProtocolHandler
+from astrai.inference.runtime.sample import SamplingPipeline
+from astrai.logging import setup_logging
 from astrai.model import (
     AutoModel,
     AutoRegressiveLM,
@@ -56,30 +48,6 @@ from astrai.trainer import (
     Trainer,
 )
 
-
-def setup_logging(level: str = "INFO"):
-    """Attach a handler to the ``astrai`` logger (only, not root).
-
-    Call once per process, e.g. at the top of CLI scripts.
-    Set ``ASTR_LOG_LEVEL`` to override the default ``INFO``.
-    """
-    _logger = logging.getLogger("astrai")
-    if _logger.handlers:
-        return
-    _level = getattr(
-        logging, os.environ.get("ASTR_LOG_LEVEL", level).upper(), logging.INFO
-    )
-    _logger.setLevel(_level)
-    _handler = logging.StreamHandler()
-    _handler.setFormatter(
-        logging.Formatter(
-            "%(asctime)s | %(levelname)-7s | %(name)s | %(message)s",
-            datefmt="%Y-%m-%d %H:%M:%S",
-        )
-    )
-    _logger.addHandler(_handler)
-
-
 __all__ = [
     "AutoRegressiveLM",
     "AutoRegressiveLMConfig",
@@ -98,7 +66,6 @@ __all__ = [
     "EmbeddingEncoder",
     "EncoderConfig",
     "ExecutorFactory",
-    "GenerationRequest",
     "InferenceEngine",
     "LoRAConfig",
     "Pipeline",
@@ -124,3 +91,5 @@ __all__ = [
     "setup_logging",
     "spawn_parallel_fn",
 ]
+
+setup_logging()

astrai/config/train_config.py

@@ -11,10 +11,10 @@ from torch.utils.data import Dataset
 from astrai.config.base import BaseConfig
 from astrai.model.components.lora import LoRAConfig
 
-_TRAIN_TYPES = frozenset({"seq", "sft", "dpo", "grpo", "online_grpo", "online_dpo"})
-_PARALLEL_MODES = frozenset({"none", "ddp", "fsdp"})
-_BACKENDS = frozenset({"nccl", "gloo"})
-_START_METHODS = frozenset({"spawn", "fork", "forkserver"})
+TRAIN_TYPES = frozenset({"seq", "sft", "dpo", "grpo", "online_grpo", "online_dpo"})
+PARALLEL_MODES = frozenset({"none", "ddp", "fsdp"})
+BACKENDS = frozenset({"nccl", "gloo"})
+START_METHODS = frozenset({"spawn", "fork", "forkserver"})
 _COMPILE_MODES = frozenset({"default", "reduce-overhead", "max-autotune"})
 
 
@@ -48,6 +48,7 @@ class TrainConfig(BaseConfig):
         random_seed (int): Random seed. Defaults to 3407.
         num_workers (int): Number of workers for dataloader. Defaults to 0.
         prefetch_factor (Optional[int]): Prefetch factor for dataloader. Defaults to None.
+        persistent_workers (bool): Keep DataLoader workers alive between epochs. Defaults to False.
         pin_memory (bool): Pin memory for dataloader. Defaults to False.
         collate_fn (Optional[Callable[[List[Any]], Any]]): Collate function for dataloader (e.g. dpo_collate_fn). Defaults to None.
         nprocs (int): Number of processes for distributed training. Defaults to 1.
@@ -69,7 +70,7 @@ class TrainConfig(BaseConfig):
         rollout_max_tokens (int): Maximum generated tokens per response in rollout. Defaults to 1024.
         reward_model_fn (Optional[Callable]): Factory for reward model, required for online RL strategies. Defaults to None.
         executor_kwargs (Dict[str, Any]): Extra kwargs passed to ExecutorFactory.create(). Defaults to {}.
-        extra_kwargs (Dict[str, Any]): Other arguments. Defaults to {}.
+        strategy_kwargs (Dict[str, Any]): Extra strategy arguments. Defaults to {}.
     """
 
     model_fn: Callable[[], nn.Module]
@@ -98,6 +99,7 @@ class TrainConfig(BaseConfig):
     random_seed: int = 3407
     num_workers: int = 0
     prefetch_factor: Optional[int] = None
+    persistent_workers: bool = False
     pin_memory: bool = False
     collate_fn: Optional[Callable[[List[Any]], Any]] = None
 
@@ -123,35 +125,35 @@ class TrainConfig(BaseConfig):
     reward_model_fn: Optional[Callable] = None
 
     executor_kwargs: Dict[str, Any] = field(default_factory=dict)
-    extra_kwargs: Dict[str, Any] = field(default_factory=dict)
+    strategy_kwargs: Dict[str, Any] = field(default_factory=dict)
 
     @field_validator("strategy")
     def _validate_strategy(cls, v: str) -> str:
-        if v not in _TRAIN_TYPES:
+        if v not in TRAIN_TYPES:
             raise ValueError(
-                f"strategy must be one of {sorted(_TRAIN_TYPES)}, got {v!r}"
+                f"strategy must be one of {sorted(TRAIN_TYPES)}, got {v!r}"
             )
         return v
 
     @field_validator("parallel_mode")
     def _validate_parallel_mode(cls, v: str) -> str:
-        if v not in _PARALLEL_MODES:
+        if v not in PARALLEL_MODES:
             raise ValueError(
-                f"parallel_mode must be one of {sorted(_PARALLEL_MODES)}, got {v!r}"
+                f"parallel_mode must be one of {sorted(PARALLEL_MODES)}, got {v!r}"
             )
         return v
 
     @field_validator("backend")
     def _validate_backend(cls, v: str) -> str:
-        if v not in _BACKENDS:
-            raise ValueError(f"backend must be one of {sorted(_BACKENDS)}, got {v!r}")
+        if v not in BACKENDS:
+            raise ValueError(f"backend must be one of {sorted(BACKENDS)}, got {v!r}")
         return v
 
     @field_validator("start_method")
     def _validate_start_method(cls, v: str) -> str:
-        if v not in _START_METHODS:
+        if v not in START_METHODS:
             raise ValueError(
-                f"start_method must be one of {sorted(_START_METHODS)}, got {v!r}"
+                f"start_method must be one of {sorted(START_METHODS)}, got {v!r}"
             )
         return v
 

astrai/dataset/dataset.py

@@ -25,20 +25,50 @@ function (pure ``record -> Dict[str, Tensor]``) is forwarded to
 
 from abc import ABC, abstractmethod
 from functools import partial
+from pathlib import Path
 from typing import Callable, Dict, List, Optional
 
 import torch
 from torch import Tensor
 from torch.utils.data import Dataset
 
+from astrai.config.preprocess_config import PipelineConfig
 from astrai.dataset.storage import (
     Store,
     StoreFactory,
     detect_format,
 )
 from astrai.factory import BaseFactory
+from astrai.preprocessing.transform import TokenizeTransform
 from astrai.tokenize import AutoTokenizer
 
+_DEFAULT_MESSAGES_CONFIG = {
+    "version": 1,
+    "input": {"sections": [{"field": "messages", "action": "$role", "template": True}]},
+    "mask": {"system": "mask", "user": "mask", "assistant": "train"},
+    "mask_default": "mask",
+    "output": {"position_ids_mode": "doc_reset"},
+}
+
+
+def _build_jsonl_transform(
+    path: str, tokenizer_path: Optional[str] = None
+) -> Optional["TokenizeTransform"]:
+    """Auto-build a TokenizeTransform for JSONL eager loading.
+
+    Reads ``dataset_config.json`` from the data dir if present, or
+    falls back to the built-in chatml SFT config when *tokenizer_path*
+    is provided.
+    """
+    root = Path(path)
+    config_path = root / "dataset_config.json" if root.is_dir() else None
+    if config_path is not None and config_path.exists():
+        return TokenizeTransform.from_config_file(str(config_path))
+    if tokenizer_path:
+        config = PipelineConfig.from_dict(_DEFAULT_MESSAGES_CONFIG)
+        return TokenizeTransform(config, tokenizer_path)
+    return None
+
 
 def dpo_tokenize(
     record: dict,
@@ -349,16 +379,18 @@ class DatasetFactory(BaseFactory["BaseDataset"]):
         )
         if processor is not None:
             store.load(load_path, processor=processor, **kwargs)
+        elif storage_type == "jsonl":
+            transform = _build_jsonl_transform(load_path, tokenizer_path)
+            if transform is None:
+                raise FileNotFoundError(
+                    "JSONL dataset config not found. Expected "
+                    "dataset_config.json alongside *.jsonl files, pass "
+                    "tokenizer_path= for the built-in messages config, or "
+                    "use processor= for lazy on-the-fly tokenisation."
+                )
+            store.load(load_path, transform=transform, **kwargs)
         else:
-            load_kwargs = dict(kwargs)
-            if (
-                tokenizer_path is not None
-                and storage_type == "jsonl"
-                and train_type in ("seq", "sft")
-                and "tokenizer_path" not in load_kwargs
-            ):
-                load_kwargs["tokenizer_path"] = tokenizer_path
-            store.load(load_path, **load_kwargs)
+            store.load(load_path, **kwargs)
 
         return cls.create(train_type, store=store)
 
@@ -460,9 +492,6 @@ class DPODataset(BaseDataset):
 
     required_keys = ["chosen", "rejected", "chosen_mask", "rejected_mask"]
 
-    def make_processor(self, tokenizer, max_len: int):
-        return partial(dpo_processor, tokenizer=tokenizer, max_len=max_len)
-
     def __getitem__(self, index: int) -> Dict[str, Tensor]:
         return {
             "chosen": self.store.fetch_record(index, "chosen").to(dtype=torch.long),

astrai/dataset/storage.py

@@ -55,9 +55,7 @@ from typing import Callable, Dict, List, Optional, Tuple, Union
 import torch
 from torch import Tensor
 
-from astrai.config.preprocess_config import PipelineConfig
 from astrai.factory import BaseFactory
-from astrai.preprocessing.transform import TokenizeTransform
 from astrai.serialization import (
     load_bin,
     load_bin_offsets,
@@ -219,7 +217,7 @@ class Store(ABC):
         """
         if self._window_size <= 0:
             raise RuntimeError("sample_window() requires window_size > 0 (stream mode)")
-        if self._window_size <= 0 or self._length <= self._window_size:
+        if self._length <= self._window_size:
             raise IndexError(
                 f"Data too short for window: token_count={self._length}, "
                 f"window_size={self._window_size}"
@@ -536,19 +534,8 @@ class JsonlStore(Store, Streamable, Recordable):
       ``len(store)`` returns ``num_records``; stream primitives raise.
     """
 
-    CONFIG_NAME = "dataset_config.json"
     segments_are_records = True
 
-    _DEFAULT_MESSAGES_CONFIG = {
-        "version": 1,
-        "input": {
-            "sections": [{"field": "messages", "action": "$role", "template": True}]
-        },
-        "mask": {"system": "mask", "user": "mask", "assistant": "train"},
-        "mask_default": "mask",
-        "output": {"position_ids_mode": "doc_reset"},
-    }
-
     def __init__(
         self,
         window_size: int = 0,
@@ -569,22 +556,10 @@ class JsonlStore(Store, Streamable, Recordable):
             return
 
         if transform is None:
-            root = Path(path)
-            config_path = root / self.CONFIG_NAME if root.is_dir() else None
-            if config_path is not None and config_path.exists():
-                transform = TokenizeTransform.from_config_file(str(config_path))
-            else:
-                tokenizer_path = kwargs.get("tokenizer_path")
-                if not tokenizer_path:
-                    raise FileNotFoundError(
-                        f"JSONL dataset config not found. Expected "
-                        f"{self.CONFIG_NAME} alongside *.jsonl files, pass an "
-                        f"explicit transform, pass processor= for lazy "
-                        f"on-the-fly tokenisation, or pass tokenizer_path= to "
-                        f"use the built-in messages config."
-                    )
-                config = PipelineConfig.from_dict(self._DEFAULT_MESSAGES_CONFIG)
-                transform = TokenizeTransform(config, tokenizer_path)
+            raise ValueError(
+                "JsonlStore eager mode requires transform=. "
+                "Use DatasetFactory.load() which auto-constructs it."
+            )
 
         transformed = transform.apply(records)
         self._normalize(transformed)

astrai/extension/__init__.py

@@ -15,25 +15,25 @@ Each wrapper calls its compiled CUDA kernel directly. Fallback to torch
 SDPA is handled by the attention backend, not the wrapper functions.
 """
 
-from astrai.extension.attention_backend import (
+from astrai.extension.backend import (
     ATTN_BACKEND,
     AttentionBackend,
     AttentionBackendFactory,
     CudaBackend,
     FlashAttnBackend,
     TorchNativeBackend,
+    apply_rotary_emb,
     attention,
     attn_backend,
     get_backend,
 )
-from astrai.extension.attention_ops import (
+from astrai.extension.loader import KERNEL_NAMES, is_available
+from astrai.extension.ops import (
     TensorLayout,
     attn_decode,
     attn_paged_decode,
     attn_prefill,
 )
-from astrai.extension.loader import KERNEL_NAMES, is_available
-from astrai.extension.rotary_backend import apply_rotary_emb
 
 __all__ = [
     "ATTN_BACKEND",

astrai/extension/attention_backend.py

@@ -1,570 +0,0 @@
-"""Attention backend abstraction with context-manager switching.
-
-The backend encapsulates KV cache I/O and attention computation. The
-attention module (GQA/MLA) keeps projections, rotary, QK-norm, gating,
-and output projection; the backend handles everything from "write K/V
-to cache" through "SDPA output".
-
-Usage — mirroring ``torch.nn.attention.sdpa_kernel``:
-
-    from astrai.extension import attn_backend, ATTN_BACKEND
-
-    with attn_backend(ATTN_BACKEND.TORCH_NATIVE):
-        engine.generate("hello")
-
-    # or with an instance:
-    with attn_backend(TorchNativeBackend()):
-        ...
-
-    # or the shorthand (instance is itself a context manager):
-    with TorchNativeBackend():
-        ...
-
-Thread-safe via ``contextvars`` — each scheduler thread gets its own
-active backend. ``get_backend()`` returns the active one, falling back
-to a process-wide ``TorchNativeBackend`` singleton.
-
-Layout convention: all q/k/v are ``[batch, seq_len, n_heads, head_dim]``
-(blhd). The backend returns ``[batch, seq_len, n_heads * head_dim]``.
-"""
-
-import contextvars
-import enum
-import importlib
-import threading
-from abc import ABC, abstractmethod
-from contextlib import contextmanager
-from typing import Optional, Union
-
-import torch
-import torch.nn.functional as F
-from torch import Tensor
-
-from astrai.extension.attention_ops import (
-    attn_paged_decode,
-    attn_paged_prefill,
-)
-from astrai.factory import BaseFactory
-from astrai.inference.core.cache import KVCache
-
-_current_backend: contextvars.ContextVar["AttentionBackend"] = contextvars.ContextVar(
-    "attn_backend"
-)
-
-_lock = threading.Lock()
-_flash_available: Optional[bool] = None
-
-
-def flash_attn_available() -> bool:
-    """Return ``True`` if the optional ``flash-attn`` package is usable.
-
-    ``flash-attn`` is not a hard dependency (declared only as an optional
-    extra and imported lazily), so this is checked at first use and cached.
-    The check is stronger than "import works": it also gates on the GPU
-    compute capability for the installed major version and smoke-tests a
-    real tiny kernel call, because wheels that import fine can still fail
-    at the first actual invocation (wrong arch build, torch mismatch, or a
-    missing ``flash_attn_func`` entry point).  It never raises.
-    """
-    global _flash_available
-    if _flash_available is None:
-        with _lock:
-            if _flash_available is None:
-                _flash_available = _flash_attn_check()
-    return _flash_available
-
-
-_flash_attn_module = None
-_flash_attn_import_tried = False
-
-
-def _get_flash_attn():
-    """Lazily import and cache the optional ``flash_attn`` module.
-
-    Uses ``importlib.import_module`` so no static import binds the name when
-    the package is absent.  Returns the module object, or ``None`` if the
-    package is not installed or cannot be imported.  Never raises.
-    """
-    global _flash_attn_module, _flash_attn_import_tried
-    if not _flash_attn_import_tried:
-        _flash_attn_import_tried = True
-        try:
-            _flash_attn_module = importlib.import_module("flash_attn")
-        except Exception:
-            _flash_attn_module = None
-    return _flash_attn_module
-
-
-def _flash_attn_check() -> bool:
-    if not torch.cuda.is_available():
-        return False
-    fa = _get_flash_attn()
-    if fa is None:
-        return False
-
-    # version + compute-capability gate:
-    #   FlashAttention-2 kernels need sm_70+; FlashAttention-3 (tcgen05,
-    #   sm_90/sm_100) needs sm_90+.
-    try:
-        major = int(fa.__version__.split(".")[0])
-        cc = torch.cuda.get_device_capability()
-        cc_num = cc[0] * 10 + cc[1]
-    except Exception:
-        major, cc_num = 0, 0
-    if (major >= 3 and cc_num < 90) or (major < 3 and 0 < cc_num < 70):
-        return False
-
-    # smoke-test the real kernel: a wheel that imports but was built for a
-    # different arch/torch fails here instead of at the first real forward.
-    try:
-        if not hasattr(fa, "flash_attn_func"):
-            return False
-        x = torch.zeros(1, 1, 1, 64, device="cuda", dtype=torch.bfloat16)
-        out = fa.flash_attn_func(x, x, x, causal=True)
-        return bool(torch.isfinite(out).all().item())
-    except Exception:
-        return False
-
-
-class ATTN_BACKEND(enum.Enum):
-    """Backend selector enum, mirroring ``torch.nn.attention.SDPBackend``."""
-
-    TORCH_NATIVE = "torch_native"
-    CUDA = "cuda"
-    FLASH = "flash"
-
-
-def get_backend() -> "AttentionBackend":
-    """Return the active backend for the current thread/context.
-
-    Falls back to a ``TorchNativeBackend`` singleton when no backend
-    has been activated via ``with``.
-    """
-    try:
-        return _current_backend.get()
-    except LookupError:
-        return _default_backend
-
-
-@contextmanager
-def attn_backend(backend: Union[str, ATTN_BACKEND, "AttentionBackend", type]):
-    """Context manager to select an attention backend.
-
-    Mirrors ``torch.nn.attention.sdpa_kernel``. Accepts an
-    registered name, ``ATTN_BACKEND`` enum value, backend class, or instance.
-
-    Examples::
-
-        with attn_backend(ATTN_BACKEND.TORCH_NATIVE):
-            ...
-        with attn_backend(TorchNativeBackend):
-            ...
-        with attn_backend(TorchNativeBackend()):
-            ...
-    """
-    if isinstance(backend, ATTN_BACKEND):
-        instance = AttentionBackendFactory.create(backend.value)
-    elif isinstance(backend, str):
-        instance = AttentionBackendFactory.create(backend)
-    elif isinstance(backend, type) and issubclass(backend, AttentionBackend):
-        instance = backend()
-    elif isinstance(backend, AttentionBackend):
-        instance = backend
-    else:
-        raise TypeError(
-            f"expected a registered name, ATTN_BACKEND, AttentionBackend type, "
-            f"or instance, "
-            f"got {type(backend).__name__}"
-        )
-    token = _current_backend.set(instance)
-    try:
-        yield instance
-    finally:
-        _current_backend.reset(token)
-
-
-def repeat_kv(x: Tensor, n_rep: int) -> Tensor:
-    """Expand KV heads to match Q heads for GQA."""
-    bs, slen, n_heads, head_dim = x.shape
-    if n_rep == 1:
-        return x
-    return (
-        x[:, :, :, None, :]
-        .expand(bs, slen, n_heads, n_rep, head_dim)
-        .reshape(bs, slen, n_heads * n_rep, head_dim)
-    )
-
-
-def attention(
-    q: Tensor,
-    k: Tensor,
-    v: Tensor,
-    kv_cache: Optional[KVCache] = None,
-    layer_id: int = 0,
-    attn_mask: Optional[Tensor] = None,
-    is_causal: bool = False,
-) -> Tensor:
-    """Functional attention entry point — mirrors ``F.scaled_dot_product_attention``.
-
-    Delegates to the active backend (set via ``with attn_backend(...)``).
-    Handles KV cache I/O, GQA head expansion, and causal masking so the
-    caller only needs to provide projected q/k/v.
-
-    Args:
-        q: [batch, q_len, n_heads, head_dim] (blhd)
-        k: [batch, q_len, n_kv_heads, head_dim] (blhd)
-        v: [batch, q_len, n_kv_heads, head_dim] (blhd)
-        kv_cache: cache dataclass, or None for training (no cache).
-        layer_id: transformer layer index for buffer access.
-        attn_mask: pre-built attention mask (SDPA-compatible).
-        is_causal: whether to apply causal masking.
-
-    Returns:
-        [batch, q_len, n_heads * head_dim]
-    """
-    backend = get_backend()
-    return backend.forward(q, k, v, kv_cache, layer_id, attn_mask, is_causal)
-
-
-class AttentionBackend(ABC):
-    """Abstract base for attention computation strategies.
-
-    Subclasses implement ``fwd_decode`` (q_len == 1, with cache) and
-    ``fwd_prefill`` (q_len > 1, with or without cache). The public
-    ``forward`` method dispatches based on q_len.
-
-    Three equivalent ways to activate a backend::
-
-        with attn_backend(ATTN_BACKEND.TORCH_NATIVE):  # enum
-            ...
-        with attn_backend(TorchNativeBackend):          # class
-            ...
-        with TorchNativeBackend():                       # instance
-            ...
-    """
-
-    def __enter__(self) -> "AttentionBackend":
-        self._token = _current_backend.set(self)
-        return self
-
-    def __exit__(self, *exc) -> None:
-        _current_backend.reset(self._token)
-
-    def forward(
-        self,
-        q: Tensor,
-        k: Tensor,
-        v: Tensor,
-        kv_cache: Optional[KVCache],
-        layer_id: int,
-        attn_mask: Optional[Tensor] = None,
-        is_causal: bool = False,
-    ) -> Tensor:
-        """Dispatch to decode or extend based on q_len.
-
-        Args:
-            q: [batch, q_len, n_heads, head_dim]
-            k: [batch, q_len, n_kv_heads, head_dim]
-            v: [batch, q_len, n_kv_heads, head_dim]
-            kv_cache: cache dataclass, or None for training (no cache).
-            layer_id: transformer layer index for buffer access.
-            attn_mask: pre-built attention mask compatible with SDPA.
-            is_causal: whether to apply causal masking.
-
-        Returns:
-            [batch, q_len, n_heads * head_dim]
-        """
-        if kv_cache is not None and q.size(1) == 1:
-            return self.fwd_decode(q, k, v, kv_cache, layer_id, attn_mask, is_causal)
-        return self.fwd_prefill(q, k, v, kv_cache, layer_id, attn_mask, is_causal)
-
-    @abstractmethod
-    def fwd_decode(
-        self,
-        q: Tensor,
-        k: Tensor,
-        v: Tensor,
-        kv_cache: Optional[KVCache],
-        layer_id: int,
-        attn_mask: Optional[Tensor] = None,
-        is_causal: bool = False,
-    ) -> Tensor:
-        """Single-token decode with KV cache."""
-
-    @abstractmethod
-    def fwd_prefill(
-        self,
-        q: Tensor,
-        k: Tensor,
-        v: Tensor,
-        kv_cache: Optional[KVCache],
-        layer_id: int,
-        attn_mask: Optional[Tensor] = None,
-        is_causal: bool = False,
-    ) -> Tensor:
-        """Multi-token prefill or training forward."""
-
-
-class AttentionBackendFactory(BaseFactory[AttentionBackend]):
-    """Factory for registered attention backends."""
-
-
-@AttentionBackendFactory.register(ATTN_BACKEND.TORCH_NATIVE.value)
-class TorchNativeBackend(AttentionBackend):
-    """Reference backend using torch SDPA with indirect KV cache indexing.
-
-    Writes new K/V into the cache buffers, gathers the full sequence K/V
-    via ``req_to_token`` indirect indexing, then calls
-    ``F.scaled_dot_product_attention``.
-
-    For training (``kv_cache is None``), skips cache I/O entirely and
-    runs SDPA directly on the projected q/k/v.
-    """
-
-    def fwd_decode(
-        self,
-        q: Tensor,
-        k: Tensor,
-        v: Tensor,
-        kv_cache: Optional[KVCache],
-        layer_id: int,
-        attn_mask: Optional[Tensor] = None,
-        is_causal: bool = False,
-    ) -> Tensor:
-        return self._forward(q, k, v, kv_cache, layer_id, attn_mask, is_causal)
-
-    def fwd_prefill(
-        self,
-        q: Tensor,
-        k: Tensor,
-        v: Tensor,
-        kv_cache: Optional[KVCache],
-        layer_id: int,
-        attn_mask: Optional[Tensor] = None,
-        is_causal: bool = False,
-    ) -> Tensor:
-        return self._forward(q, k, v, kv_cache, layer_id, attn_mask, is_causal)
-
-    def _forward(
-        self,
-        q: Tensor,
-        k: Tensor,
-        v: Tensor,
-        kv_cache: Optional[KVCache],
-        layer_id: int,
-        attn_mask: Optional[Tensor] = None,
-        is_causal: bool = False,
-    ) -> Tensor:
-        if kv_cache is not None:
-            kv_cache.k_buffer[layer_id, kv_cache.out_cache_loc] = k
-            kv_cache.v_buffer[layer_id, kv_cache.out_cache_loc] = v
-
-            max_len = kv_cache.max_len
-            indices = kv_cache.req_to_token[kv_cache.req_pool_indices, :max_len]
-            # Zero out padding positions so gather never touches invalid slots.
-            # Decode: attn_mask[:,0,0] is exactly the per-position validity
-            # mask ([B, max_len], True=keep).  Prefill: fall back to seq_lens.
-            if q.size(1) == 1 and attn_mask is not None and attn_mask.dim() == 4:
-                pos_mask = attn_mask[:, 0, 0]
-            else:
-                pos_mask = (
-                    torch.arange(max_len, device=q.device)[None, :]
-                    < kv_cache.seq_lens[:, None]
-                )
-            indices = torch.where(pos_mask, indices, torch.zeros_like(indices))
-            k = kv_cache.k_buffer[layer_id, indices]
-            v = kv_cache.v_buffer[layer_id, indices]
-
-        n_rep = q.size(2) // k.size(2)
-        if n_rep > 1:
-            k = repeat_kv(k, n_rep)
-            v = repeat_kv(v, n_rep)
-
-        out = F.scaled_dot_product_attention(
-            q.permute(0, 2, 1, 3),
-            k.permute(0, 2, 1, 3),
-            v.permute(0, 2, 1, 3),
-            attn_mask,
-            is_causal=is_causal,
-        )
-        out = out.permute(0, 2, 1, 3).contiguous().flatten(2)
-        return out
-
-
-_default_backend = TorchNativeBackend()
-
-
-@AttentionBackendFactory.register(ATTN_BACKEND.CUDA.value)
-class CudaBackend(AttentionBackend):
-    """CUDA kernel backend with direct KV cache access.
-
-    Decode path: writes K/V to the flat pool, then calls
-    ``attn_paged_decode`` with req_to_token + kv_indptr.
-
-    Prefill path: writes K/V to the flat pool, then calls
-    ``attn_paged_prefill`` with ragged-batch support via qo_indptr +
-    kv_indptr.
-
-    ``kv_cache is None`` (training) is not handled — use
-    ``TorchNativeBackend`` for training.
-
-    Raises ``RuntimeError`` if the required kernel is not available.
-    """
-
-    def fwd_decode(
-        self,
-        q: Tensor,
-        k: Tensor,
-        v: Tensor,
-        kv_cache: Optional[KVCache],
-        layer_id: int,
-        attn_mask: Optional[Tensor] = None,
-        is_causal: bool = False,
-    ) -> Tensor:
-        if kv_cache is None:
-            raise RuntimeError("CudaBackend does not support training (kv_cache=None)")
-
-        kv_cache.k_buffer[layer_id, kv_cache.out_cache_loc] = k
-        kv_cache.v_buffer[layer_id, kv_cache.out_cache_loc] = v
-
-        b = q.size(0)
-        q_3d = q.squeeze(1)
-
-        kv_indptr = kv_cache.kv_indptr
-
-        out = attn_paged_decode(
-            q_3d,
-            kv_cache.k_buffer[layer_id],
-            kv_cache.v_buffer[layer_id],
-            kv_cache.req_to_token,
-            kv_cache.req_pool_indices,
-            kv_indptr,
-            kv_cache.max_len,
-            mask=attn_mask,
-            is_causal=is_causal,
-        )
-        return out.unsqueeze(1).flatten(2)
-
-    def fwd_prefill(
-        self,
-        q: Tensor,
-        k: Tensor,
-        v: Tensor,
-        kv_cache: Optional[KVCache],
-        layer_id: int,
-        attn_mask: Optional[Tensor] = None,
-        is_causal: bool = False,
-    ) -> Tensor:
-        if kv_cache is None:
-            raise RuntimeError("CudaBackend does not support training (kv_cache=None)")
-
-        kv_cache.k_buffer[layer_id, kv_cache.out_cache_loc] = k
-        kv_cache.v_buffer[layer_id, kv_cache.out_cache_loc] = v
-
-        b = q.size(0)
-        q_len = q.size(1)
-
-        kv_indptr = kv_cache.kv_indptr
-        qo_indptr = kv_cache.qo_indptr
-
-        q_flat = q.reshape(b * q_len, q.size(2), q.size(3))
-
-        out = attn_paged_prefill(
-            q_flat,
-            kv_cache.k_buffer[layer_id],
-            kv_cache.v_buffer[layer_id],
-            kv_cache.req_to_token,
-            kv_cache.req_pool_indices,
-            kv_indptr,
-            qo_indptr,
-            attn_mask,
-            q_len,
-            is_causal=is_causal,
-        )
-        return out.reshape(b, q_len, q.size(2), q.size(3)).flatten(2)
-
-
-@AttentionBackendFactory.register(ATTN_BACKEND.FLASH.value)
-class FlashAttnBackend(AttentionBackend):
-    """FlashAttention (FA2/FA3) backend via the optional ``flash-attn`` package.
-
-    Uses the general ``flash_attn_func`` entry point for both prefill and
-    single-token decode, mirroring ``TorchNativeBackend``'s KV-cache gather.
-    This backend only does flash attention — inputs ``flash-attn`` cannot
-    express (missing package, custom attention mask, fp32, unsupported
-    head_dim) raise a clear error instead of silently falling back to torch.
-
-    For a torch fallback, select ``TorchNativeBackend`` instead.
-    """
-
-    def fwd_decode(
-        self,
-        q: Tensor,
-        k: Tensor,
-        v: Tensor,
-        kv_cache: Optional[KVCache],
-        layer_id: int,
-        attn_mask: Optional[Tensor] = None,
-        is_causal: bool = False,
-    ) -> Tensor:
-        return self._forward(q, k, v, kv_cache, layer_id, attn_mask, is_causal)
-
-    def fwd_prefill(
-        self,
-        q: Tensor,
-        k: Tensor,
-        v: Tensor,
-        kv_cache: Optional[KVCache],
-        layer_id: int,
-        attn_mask: Optional[Tensor] = None,
-        is_causal: bool = False,
-    ) -> Tensor:
-        return self._forward(q, k, v, kv_cache, layer_id, attn_mask, is_causal)
-
-    def _forward(
-        self,
-        q: Tensor,
-        k: Tensor,
-        v: Tensor,
-        kv_cache: Optional[KVCache],
-        layer_id: int,
-        attn_mask: Optional[Tensor] = None,
-        is_causal: bool = False,
-    ) -> Tensor:
-        if kv_cache is not None:
-            kv_cache.k_buffer[layer_id, kv_cache.out_cache_loc] = k
-            kv_cache.v_buffer[layer_id, kv_cache.out_cache_loc] = v
-
-            max_len = kv_cache.max_len
-            indices = kv_cache.req_to_token[kv_cache.req_pool_indices, :max_len]
-            if q.size(1) == 1 and attn_mask is not None and attn_mask.dim() == 4:
-                pos_mask = attn_mask[:, 0, 0]
-            else:
-                pos_mask = (
-                    torch.arange(max_len, device=q.device)[None, :]
-                    < kv_cache.seq_lens[:, None]
-                )
-            indices = torch.where(pos_mask, indices, torch.zeros_like(indices))
-            k = kv_cache.k_buffer[layer_id, indices]
-            v = kv_cache.v_buffer[layer_id, indices]
-
-        n_rep = q.size(2) // k.size(2)
-        if n_rep > 1:
-            k = repeat_kv(k, n_rep)
-            v = repeat_kv(v, n_rep)
-
-        if attn_mask is not None and not is_causal:
-            raise ValueError(
-                "FlashAttnBackend does not support a custom attention mask; "
-                "use a causal mask or select TorchNativeBackend."
-            )
-        fa = _get_flash_attn()
-        if fa is None:
-            raise RuntimeError(
-                "FlashAttnBackend requires the optional 'flash-attn' package. "
-                "Install with `pip install flash-attn`."
-            )
-        out = fa.flash_attn_func(
-            q.contiguous(), k.contiguous(), v.contiguous(), causal=is_causal
-        )
-        return out.contiguous().flatten(2)

astrai/extension/backend/__init__.py

@@ -0,0 +1,27 @@
+"""Backend selection, fallbacks, and execution policies."""
+
+from astrai.extension.backend.attention import (
+    ATTN_BACKEND,
+    AttentionBackend,
+    AttentionBackendFactory,
+    CudaBackend,
+    FlashAttnBackend,
+    TorchNativeBackend,
+    attention,
+    attn_backend,
+    get_backend,
+)
+from astrai.extension.backend.rotary import apply_rotary_emb
+
+__all__ = [
+    "ATTN_BACKEND",
+    "AttentionBackend",
+    "AttentionBackendFactory",
+    "CudaBackend",
+    "FlashAttnBackend",
+    "TorchNativeBackend",
+    "apply_rotary_emb",
+    "attention",
+    "attn_backend",
+    "get_backend",
+]

astrai/extension/backend/attention.py

@@ -0,0 +1,819 @@
+"""Attention backend abstraction with context-manager switching.
+
+The backend encapsulates KV cache I/O and attention computation. The
+attention module (GQA/MLA) keeps projections, rotary, QK-norm, gating,
+and output projection; the backend handles everything from "write K/V
+to cache" through "SDPA output".
+
+Usage — mirroring ``torch.nn.attention.sdpa_kernel``:
+
+    from astrai.extension import attn_backend, ATTN_BACKEND
+
+    with attn_backend(ATTN_BACKEND.TORCH_NATIVE):
+        engine.generate("hello")
+
+    # or with an instance:
+    with attn_backend(TorchNativeBackend()):
+        ...
+
+    # or the shorthand (instance is itself a context manager):
+    with TorchNativeBackend():
+        ...
+
+Thread-safe via ``contextvars`` — each scheduler thread gets its own
+active backend. Backend resolution follows a strict precedence:
+
+1. explicit ``attn_backend(...)`` context (wins over everything),
+2. the process-wide ``ASTR_BACKEND`` environment override,
+3. an implicit default picked from the available backends
+   (cuda > flash > torch).
+
+Capability is polymorphic: every backend declares ``available()``
+(machine-level) and ``supports_call(...)`` (per-call), so adding a new
+backend requires no changes to the resolution logic. Training calls
+(``fwd=None``, no KV cache) resolve through the same priority list: the
+CUDA cache kernels cannot run without a cache, so they fall back to
+flash (when it can handle the call — mask-free/causal only) and finally
+to the reference ``TorchNativeBackend``.
+
+Layout convention: all q/k/v are ``[batch, seq_len, n_heads, head_dim]``
+(blhd). The backend returns ``[batch, seq_len, n_heads * head_dim]``.
+"""
+
+import contextvars
+import enum
+import functools
+import logging
+import os
+import threading
+from abc import ABC, abstractmethod
+from contextlib import contextmanager
+from typing import TYPE_CHECKING, Dict, Optional, Tuple, Union
+
+import torch
+import torch.nn.functional as F
+from torch import Tensor
+
+from astrai.extension.loader import is_available
+from astrai.extension.ops.attention import (
+    attn_paged_decode,
+    attn_paged_prefill,
+)
+from astrai.factory import BaseFactory
+
+try:
+    import flash_attn as _flash_attn
+except Exception:
+    _flash_attn = None
+
+if TYPE_CHECKING:
+    from astrai.inference.cache import KVCache
+
+logger = logging.getLogger(__name__)
+
+
+_default_backend_lock = threading.Lock()
+_env_backend_name: Optional[str] = None
+_env_backend: Optional["AttentionBackend"] = None
+_current_backend: contextvars.ContextVar[Optional["AttentionBackend"]] = (
+    contextvars.ContextVar("attn_backend", default=None)
+)
+
+# Backends are stateless — one canonical instance per class, created lazily
+# and reused everywhere (resolution, fallback, context managers).
+_singletons: Dict[type, "AttentionBackend"] = {}
+
+
+@functools.lru_cache(maxsize=1)
+def flash_attn_available() -> bool:
+    if not torch.cuda.is_available():
+        return False
+    fa = _flash_attn
+    if fa is None:
+        return False
+
+    try:
+        major = int(fa.__version__.split(".")[0])
+        cc = torch.cuda.get_device_capability()
+        cc_num = cc[0] * 10 + cc[1]
+    except Exception:
+        major, cc_num = 0, 0
+    if (major >= 3 and cc_num < 90) or (major < 3 and 0 < cc_num < 70):
+        return False
+
+    try:
+        if not hasattr(fa, "flash_attn_func"):
+            return False
+        x = torch.zeros(1, 1, 1, 64, device="cuda", dtype=torch.bfloat16)
+        out = fa.flash_attn_func(x, x, x, causal=True)
+        return bool(torch.isfinite(out).all().item())
+    except Exception:
+        return False
+
+
+class ATTN_BACKEND(enum.Enum):
+    """Backend selector enum, mirroring ``torch.nn.attention.SDPBackend``."""
+
+    TORCH_NATIVE = "torch_native"
+    CUDA = "cuda"
+    FLASH = "flash"
+
+
+def _instance(backend_cls: type) -> "AttentionBackend":
+    """Return the canonical singleton instance for a backend class.
+
+    Backends hold no per-instance state, so a single cached instance is
+    safe and avoids per-call allocation on the attention hot path.
+    """
+    backend = _singletons.get(backend_cls)
+    if backend is None:
+        backend = backend_cls()
+        _singletons[backend_cls] = backend
+    return backend
+
+
+@functools.lru_cache(maxsize=1)
+def _priority_backends() -> Tuple["AttentionBackend", ...]:
+    """Available backends in priority order: cuda -> flash -> torch.
+
+    Computed once (machine availability cannot change at runtime) and
+    cached forever; the tuple always ends with ``TorchNativeBackend``,
+    which is unconditionally available.
+    """
+    return tuple(
+        _instance(cls)
+        for cls in (CudaBackend, FlashAttnBackend, TorchNativeBackend)
+        if cls.available()
+    )
+
+
+def _resolve_default_backend() -> "AttentionBackend":
+    """Pick the highest-priority available backend (cuda -> flash -> torch).
+
+    Resolved lazily on first use and cached via ``_priority_backends``.
+    Per-call capability fallback happens in ``attention()``, so the
+    default is safe for training and fp32 models.
+    """
+    return _priority_backends()[0]
+
+
+def _environment_backend() -> Optional["AttentionBackend"]:
+    """Resolve the process-wide ``ASTR_BACKEND`` override, if configured."""
+    global _env_backend, _env_backend_name
+    name = os.environ.get("ASTR_BACKEND", "").strip().lower()
+    if not name:
+        return None
+    if name != _env_backend_name:
+        with _default_backend_lock:
+            if name != _env_backend_name:
+                try:
+                    _env_backend = _resolve_backend(name)
+                except (ValueError, RuntimeError):
+                    _env_backend = None
+                    logger.warning(
+                        "ASTR_BACKEND=%r is not a registered attention backend; "
+                        "falling back to default resolution",
+                        name,
+                    )
+                _env_backend_name = name
+    return _env_backend
+
+
+def _resolve_backend(
+    backend: Optional[Union[str, ATTN_BACKEND, "AttentionBackend", type]] = None,
+) -> "AttentionBackend":
+    """Resolve a backend configuration to its canonical instance.
+
+    Accepts a registered name, ``ATTN_BACKEND`` enum value, backend class,
+    or instance.  Names/classes resolve to the shared singleton; a caller
+    may still pass its own instance to opt out of sharing.
+    """
+    if backend is not None:
+        if isinstance(backend, ATTN_BACKEND):
+            return _instance(AttentionBackendFactory.get_component_class(backend.value))
+        if isinstance(backend, str):
+            return _instance(AttentionBackendFactory.get_component_class(backend))
+        if isinstance(backend, type) and issubclass(backend, AttentionBackend):
+            return _instance(backend)
+        if isinstance(backend, AttentionBackend):
+            return backend
+        raise TypeError(
+            f"expected a registered name, ATTN_BACKEND, AttentionBackend type, "
+            f"or instance, got {type(backend).__name__}"
+        )
+    return _resolve_default_backend()
+
+
+def get_backend(
+    use_default: bool = True,
+) -> Optional["AttentionBackend"]:
+    """Resolve the active backend: explicit context > env > default.
+
+    An ``attn_backend(...)`` context is the caller's explicit choice and
+    always wins.  ``ASTR_BACKEND`` is a process-wide override consulted
+    only when no context is set.  Pass ``use_default=False`` at request
+    submission to retain only an environment override or the caller's
+    :func:`attn_backend` value.
+    """
+    context_backend = _current_backend.get()
+    if context_backend is not None:
+        return context_backend
+    env_backend = _environment_backend()
+    if env_backend is not None:
+        return env_backend
+    return _resolve_default_backend() if use_default else None
+
+
+@contextmanager
+def attn_backend(backend: Union[str, ATTN_BACKEND, "AttentionBackend", type]):
+    """Context manager to select an attention backend.
+
+    Mirrors ``torch.nn.attention.sdpa_kernel``. Accepts an
+    registered name, ``ATTN_BACKEND`` enum value, backend class, or instance.
+
+    Examples::
+
+        with attn_backend(ATTN_BACKEND.TORCH_NATIVE):
+            ...
+        with attn_backend(TorchNativeBackend):
+            ...
+        with attn_backend(TorchNativeBackend()):
+            ...
+    """
+    instance = _resolve_backend(backend)
+    token = _current_backend.set(instance)
+    try:
+        yield instance
+    finally:
+        _current_backend.reset(token)
+
+
+def repeat_kv(x: Tensor, n_rep: int) -> Tensor:
+    """Expand KV heads to match Q heads for GQA."""
+    if n_rep == 1:
+        return x
+    n_heads, head_dim = x.shape[-2:]
+    return (
+        x.unsqueeze(-2)
+        .expand(*x.shape[:-2], n_heads, n_rep, head_dim)
+        .reshape(*x.shape[:-2], n_heads * n_rep, head_dim)
+    )
+
+
+def attention(
+    q: Tensor,
+    k: Tensor,
+    v: Tensor,
+    kv_cache: Optional["KVCache"] = None,
+    layer_id: int = 0,
+    attn_mask: Optional[Tensor] = None,
+    is_causal: bool = False,
+    fwd: Optional[str] = None,
+    backend: Optional[Union[str, ATTN_BACKEND, "AttentionBackend", type]] = None,
+) -> Tensor:
+    """Functional attention entry point — mirrors ``F.scaled_dot_product_attention``.
+
+    Delegates to the active backend.  ``backend`` (optional) is an explicit
+    escape hatch; when omitted the backend is resolved as
+    explicit context > ``ASTR_BACKEND`` env > default (cuda > flash > torch).
+    Handles KV cache I/O, GQA head expansion, and causal masking so the
+    caller only needs to provide projected q/k/v.
+
+    Training calls (``fwd=None``, ``kv_cache=None``) resolve through the
+    same capability chain — the CUDA cache kernels cannot run without a
+    cache, so they fall back to flash (mask-free/causal calls only) and
+    finally to torch SDPA.  An explicitly-selected backend that cannot
+    handle the call raises — an implicit one falls back down the priority
+    list to the first capable backend.
+
+    Args:
+        q: [batch, q_len, n_heads, head_dim] (blhd)
+        k: [batch, q_len, n_kv_heads, head_dim] (blhd)
+        v: [batch, q_len, n_kv_heads, head_dim] (blhd)
+        kv_cache: cache dataclass, or None for training (no cache).
+        layer_id: transformer layer index for buffer access.
+        attn_mask: pre-built attention mask (SDPA-compatible).
+        is_causal: whether to apply causal masking.
+        fwd: "prefill" / "decode" for inference, None for training.
+        backend: optional explicit backend (name, enum, class, or instance).
+
+    Returns:
+        [batch, q_len, n_heads * head_dim]
+    """
+    if backend is not None:
+        selected = _resolve_backend(backend)
+        explicit = True
+    else:
+        context_backend = _current_backend.get()
+        explicit = context_backend is not None
+        # Resolve through the same chain as inference: explicit context >
+        # ASTR_BACKEND env > default.  Training calls (fwd=None, no cache)
+        # land on the CUDA backend and fall back by capability below —
+        # flash when it can handle the call, else torch SDPA.
+        selected = get_backend()
+        assert selected is not None
+
+    if not selected.supports_call(q, kv_cache, attn_mask, is_causal, fwd):
+        if explicit:
+            raise RuntimeError(
+                f"Explicitly-set backend {type(selected).__name__} cannot "
+                f"handle this attention call (shape={q.shape}, "
+                f"dtype={q.dtype}, kv_cache={'none' if kv_cache is None else 'present'}, "
+                f"attn_mask={'none' if attn_mask is None else 'present'}). "
+                f"Remove the attn_backend() context or switch to a compatible backend."
+            )
+        selected = next(
+            (
+                candidate
+                for candidate in _priority_backends()
+                if candidate.supports_call(q, kv_cache, attn_mask, is_causal, fwd)
+            ),
+            _instance(TorchNativeBackend),
+        )
+    return selected.forward(q, k, v, kv_cache, layer_id, attn_mask, is_causal, fwd)
+
+
+class AttentionBackend(ABC):
+    """Abstract base for attention computation strategies.
+
+    Subclasses implement ``fwd_decode`` (q_len == 1, with cache) and
+    ``fwd_prefill`` (q_len > 1, with or without cache). The public
+    ``forward`` method dispatches based on q_len.
+
+    Capability contract — every backend declares:
+
+    * ``available()`` — machine-level: can this backend exist here
+      (kernel ``.so`` loaded, flash-attn present, GPU available)?
+      Used once to build the default priority list.
+    * ``supports_call(q, kv_cache, attn_mask, is_causal, fwd)`` — can this
+      backend run this *specific* call (shape/dtype/cache/mask)?  Used by
+      ``attention()`` for the per-call fallback.  Resolution logic never
+      checks concrete backend types, so adding a backend requires no
+      changes outside its own class.
+
+    Three equivalent ways to activate a backend::
+
+        with attn_backend(ATTN_BACKEND.TORCH_NATIVE):  # enum
+            ...
+        with attn_backend(TorchNativeBackend):          # class
+            ...
+        with TorchNativeBackend():                       # instance
+            ...
+    """
+
+    def __enter__(self) -> "AttentionBackend":
+        self._token = _current_backend.set(self)
+        return self
+
+    def __exit__(self, *exc) -> None:
+        _current_backend.reset(self._token)
+
+    @classmethod
+    @abstractmethod
+    def available(cls) -> bool:
+        """Return True if this backend can run on the current machine.
+
+        Checks static availability only (compiled kernels, optional
+        packages, GPU presence) — not call-specific constraints.
+        """
+
+    @abstractmethod
+    def supports_call(
+        self,
+        q: Tensor,
+        kv_cache: Optional["KVCache"],
+        attn_mask: Optional[Tensor],
+        is_causal: bool,
+        fwd: Optional[str],
+    ) -> bool:
+        """Return True if this backend can run this specific attention call.
+
+        Called on the canonical singleton instance (or a caller-provided
+        one); must be side-effect free.
+        """
+
+    def forward(
+        self,
+        q: Tensor,
+        k: Tensor,
+        v: Tensor,
+        kv_cache: Optional["KVCache"],
+        layer_id: int,
+        attn_mask: Optional[Tensor] = None,
+        is_causal: bool = False,
+        fwd: Optional[str] = None,
+    ) -> Tensor:
+        """Dispatch to decode or extend based on q_len.
+
+        Args:
+            q: [batch, q_len, n_heads, head_dim]
+            k: [batch, q_len, n_kv_heads, head_dim]
+            v: [batch, q_len, n_kv_heads, head_dim]
+            kv_cache: cache dataclass, or None for training (no cache).
+            layer_id: transformer layer index for buffer access.
+            attn_mask: pre-built attention mask compatible with SDPA.
+            is_causal: whether to apply causal masking.
+
+        Returns:
+            [batch, q_len, n_heads * head_dim]
+        """
+        if fwd == "decode":
+            return self.fwd_decode(q, k, v, kv_cache, layer_id, attn_mask, is_causal)
+        if fwd == "prefill" or fwd is None:
+            return self.fwd_prefill(q, k, v, kv_cache, layer_id, attn_mask, is_causal)
+        raise ValueError(f"unsupported attention forward mode: {fwd}")
+
+    @abstractmethod
+    def fwd_decode(
+        self,
+        q: Tensor,
+        k: Tensor,
+        v: Tensor,
+        kv_cache: Optional["KVCache"],
+        layer_id: int,
+        attn_mask: Optional[Tensor] = None,
+        is_causal: bool = False,
+    ) -> Tensor:
+        """Single-token decode with KV cache."""
+
+    @abstractmethod
+    def fwd_prefill(
+        self,
+        q: Tensor,
+        k: Tensor,
+        v: Tensor,
+        kv_cache: Optional["KVCache"],
+        layer_id: int,
+        attn_mask: Optional[Tensor] = None,
+        is_causal: bool = False,
+    ) -> Tensor:
+        """Multi-token prefill or training forward."""
+
+    @staticmethod
+    def supports_graph() -> bool:
+        """Return True if this backend supports CUDA-graph capture.
+
+        Override in subclasses that can run under ``torch.cuda.graph``.
+
+        Called on the *active* backend instance (or its class) — a cheap
+        boolean check with no side-effects.
+        """
+        return False
+
+
+class AttentionBackendFactory(BaseFactory[AttentionBackend]):
+    """Factory for registered attention backends."""
+
+
+@AttentionBackendFactory.register(ATTN_BACKEND.TORCH_NATIVE.value)
+class TorchNativeBackend(AttentionBackend):
+    """Reference backend using torch SDPA with indirect KV cache indexing.
+
+    Writes new K/V into the cache buffers, gathers the full sequence K/V
+    via ``req_to_token`` indirect indexing, then calls
+    ``F.scaled_dot_product_attention``.
+
+    For training (``kv_cache is None``), skips cache I/O entirely and
+    runs SDPA directly on the projected q/k/v.
+    """
+
+    @classmethod
+    def available(cls) -> bool:
+        return True
+
+    def supports_call(
+        self,
+        q: Tensor,
+        kv_cache: Optional["KVCache"],
+        attn_mask: Optional[Tensor],
+        is_causal: bool,
+        fwd: Optional[str],
+    ) -> bool:
+        return True
+
+    def fwd_decode(
+        self,
+        q: Tensor,
+        k: Tensor,
+        v: Tensor,
+        kv_cache: Optional["KVCache"],
+        layer_id: int,
+        attn_mask: Optional[Tensor] = None,
+        is_causal: bool = False,
+    ) -> Tensor:
+        return self._forward(q, k, v, kv_cache, layer_id, attn_mask, is_causal)
+
+    def fwd_prefill(
+        self,
+        q: Tensor,
+        k: Tensor,
+        v: Tensor,
+        kv_cache: Optional["KVCache"],
+        layer_id: int,
+        attn_mask: Optional[Tensor] = None,
+        is_causal: bool = False,
+    ) -> Tensor:
+        return self._forward(q, k, v, kv_cache, layer_id, attn_mask, is_causal)
+
+    def _forward(
+        self,
+        q: Tensor,
+        k: Tensor,
+        v: Tensor,
+        kv_cache: Optional["KVCache"],
+        layer_id: int,
+        attn_mask: Optional[Tensor] = None,
+        is_causal: bool = False,
+    ) -> Tensor:
+        if q.ndim == 4:
+            n_rep = q.size(2) // k.size(2)
+            if n_rep > 1:
+                k = repeat_kv(k, n_rep)
+                v = repeat_kv(v, n_rep)
+            return (
+                F.scaled_dot_product_attention(
+                    q.permute(0, 2, 1, 3),
+                    k.permute(0, 2, 1, 3),
+                    v.permute(0, 2, 1, 3),
+                    attn_mask,
+                    is_causal=is_causal,
+                )
+                .permute(0, 2, 1, 3)
+                .contiguous()
+            )
+
+        if kv_cache is None or kv_cache.qo_indptr is None:
+            raise ValueError("packed attention requires KV cache metadata")
+        kv_cache.k_buffer[layer_id, kv_cache.out_cache_loc] = k
+        kv_cache.v_buffer[layer_id, kv_cache.out_cache_loc] = v
+        outputs = []
+        n_rep = q.size(1) // k.size(1)
+        for i in range(kv_cache.req_pool_indices.numel()):
+            q_start = int(kv_cache.qo_indptr[i])
+            q_end = int(kv_cache.qo_indptr[i + 1])
+            indices = kv_cache.req_to_token[
+                kv_cache.req_pool_indices[i], : kv_cache.seq_lens[i]
+            ]
+            k_i = kv_cache.k_buffer[layer_id, indices]
+            v_i = kv_cache.v_buffer[layer_id, indices]
+            if n_rep > 1:
+                k_i = repeat_kv(k_i, n_rep)
+                v_i = repeat_kv(v_i, n_rep)
+            q_len = q_end - q_start
+            kv_len = k_i.size(0)
+            q_pos = torch.arange(kv_len - q_len, kv_len, device=q.device)
+            causal_mask = q_pos[:, None] >= torch.arange(kv_len, device=q.device)
+            out = F.scaled_dot_product_attention(
+                q[q_start:q_end].transpose(0, 1).unsqueeze(0),
+                k_i.transpose(0, 1).unsqueeze(0),
+                v_i.transpose(0, 1).unsqueeze(0),
+                attn_mask=causal_mask,
+            )
+            outputs.append(out.squeeze(0).transpose(0, 1))
+        return torch.cat(outputs)
+
+
+@AttentionBackendFactory.register(ATTN_BACKEND.CUDA.value)
+class CudaBackend(AttentionBackend):
+    """CUDA kernel backend with direct KV cache access.
+
+    Decode path: writes K/V to the flat pool, then calls
+    ``attn_paged_decode`` with req_to_token + kv_indptr.
+
+    Prefill path: writes K/V to the flat pool, then calls
+    ``attn_paged_prefill`` with ragged-batch support via qo_indptr +
+    kv_indptr.
+
+    ``kv_cache is None`` (training) raises — the per-call fallback to
+    torch SDPA for training / fp32 / unsupported head_dim happens in the
+    ``attention()`` entry point.
+
+    Raises ``RuntimeError`` if the required kernel is not available.
+    """
+
+    # Head dims supported by the CUDA kernels (single source of truth).
+    HEAD_DIMS = (32, 64, 128, 256)
+
+    @classmethod
+    def available(cls) -> bool:
+        return (
+            torch.cuda.is_available()
+            and is_available("attn_paged_decode")
+            and is_available("attn_paged_prefill")
+        )
+
+    def supports_call(
+        self,
+        q: Tensor,
+        kv_cache: Optional["KVCache"],
+        attn_mask: Optional[Tensor],
+        is_causal: bool,
+        fwd: Optional[str],
+    ) -> bool:
+        # The CUDA kernels are bf16-only, support head_dim in
+        # HEAD_DIMS, and need a KV cache (decode/prefill); everything
+        # else falls back down the priority list to torch.
+        return (
+            fwd in ("prefill", "decode")
+            and kv_cache is not None
+            and q.ndim == 3
+            and q.dtype == torch.bfloat16
+            and q.size(-1) in self.HEAD_DIMS
+            and is_available(f"attn_paged_{fwd}")
+        )
+
+    @staticmethod
+    def supports_graph() -> bool:
+        return True
+
+    def fwd_decode(
+        self,
+        q: Tensor,
+        k: Tensor,
+        v: Tensor,
+        kv_cache: Optional["KVCache"],
+        layer_id: int,
+        attn_mask: Optional[Tensor] = None,
+        is_causal: bool = False,
+    ) -> Tensor:
+        if kv_cache is None:
+            raise RuntimeError("CudaBackend does not support training (kv_cache=None)")
+
+        kv_indptr = kv_cache.kv_indptr
+
+        out = attn_paged_decode(
+            q,
+            kv_cache.k_buffer[layer_id],
+            kv_cache.v_buffer[layer_id],
+            kv_cache.req_to_token,
+            kv_cache.req_pool_indices,
+            kv_indptr,
+            new_k=k,
+            new_v=v,
+            is_causal=True,
+            o_part_buf=kv_cache.decode_o_part,
+            ml_part_buf=kv_cache.decode_ml_part,
+            out_buf=kv_cache.decode_out,
+        )
+        return out
+
+    def fwd_prefill(
+        self,
+        q: Tensor,
+        k: Tensor,
+        v: Tensor,
+        kv_cache: Optional["KVCache"],
+        layer_id: int,
+        attn_mask: Optional[Tensor] = None,
+        is_causal: bool = False,
+    ) -> Tensor:
+        if kv_cache is None:
+            raise RuntimeError("CudaBackend does not support training (kv_cache=None)")
+
+        loc = kv_cache.out_cache_loc
+        kv_cache.k_buffer[layer_id, loc] = k
+        kv_cache.v_buffer[layer_id, loc] = v
+
+        out = attn_paged_prefill(
+            q,
+            kv_cache.k_buffer[layer_id],
+            kv_cache.v_buffer[layer_id],
+            kv_cache.req_to_token,
+            kv_cache.req_pool_indices,
+            kv_cache.kv_indptr,
+            kv_cache.qo_indptr,
+            kv_cache.q_tile_to_batch,
+            kv_cache.q_tile_to_index,
+            attn_mask,
+            is_causal=is_causal,
+        )
+        return out
+
+
+@AttentionBackendFactory.register(ATTN_BACKEND.FLASH.value)
+class FlashAttnBackend(AttentionBackend):
+    """FlashAttention backend via the optional ``flash-attn`` package.
+
+    Decode (q_len=1, contiguous cache): writes K/V to the pool, gathers
+    flat K/V via the ``req_to_token`` page table, and calls
+    ``flash_attn_varlen_func`` over the ragged batch
+    (``qo_indptr``/``kv_indptr``).
+
+    Prefill: packed 3-D calls share the ``flash_attn_varlen_func`` path;
+    dense 4-D calls go through ``flash_attn_func`` (mask-free only).
+    """
+
+    @classmethod
+    def available(cls) -> bool:
+        return flash_attn_available()
+
+    def supports_call(
+        self,
+        q: Tensor,
+        kv_cache: Optional["KVCache"],
+        attn_mask: Optional[Tensor],
+        is_causal: bool,
+        fwd: Optional[str],
+    ) -> bool:
+        if not self.available():
+            return False
+        if q.dtype not in (torch.float16, torch.bfloat16):
+            return False
+        if fwd is not None:
+            return q.ndim == 3 and hasattr(_flash_attn, "flash_attn_varlen_func")
+        # Dense (training) path: flash_attn_func cannot apply a custom
+        # mask, so only mask-free calls are supported — ``is_causal`` is
+        # a flag, not a mask.  Masked training (SFT/DPO/GRPO) must fall
+        # back to TorchNativeBackend instead of silently ignoring the mask.
+        return attn_mask is None
+
+    def fwd_decode(
+        self,
+        q: Tensor,
+        k: Tensor,
+        v: Tensor,
+        kv_cache: Optional["KVCache"],
+        layer_id: int,
+        attn_mask: Optional[Tensor] = None,
+        is_causal: bool = False,
+    ) -> Tensor:
+        return self._forward_packed(q, k, v, kv_cache, layer_id)
+
+    def fwd_prefill(
+        self,
+        q: Tensor,
+        k: Tensor,
+        v: Tensor,
+        kv_cache: Optional["KVCache"],
+        layer_id: int,
+        attn_mask: Optional[Tensor] = None,
+        is_causal: bool = False,
+    ) -> Tensor:
+        if q.ndim == 3:
+            return self._forward_packed(q, k, v, kv_cache, layer_id)
+        return self._forward_dense(q, k, v, attn_mask, is_causal)
+
+    def _forward_dense(
+        self,
+        q: Tensor,
+        k: Tensor,
+        v: Tensor,
+        attn_mask: Optional[Tensor] = None,
+        is_causal: bool = False,
+    ) -> Tensor:
+        n_rep = q.size(2) // k.size(2)
+        if n_rep > 1:
+            k = repeat_kv(k, n_rep)
+            v = repeat_kv(v, n_rep)
+
+        if attn_mask is not None:
+            raise ValueError(
+                "FlashAttnBackend cannot handle a custom attention mask; "
+                "use a causal mask or select TorchNativeBackend."
+            )
+        fa = _flash_attn
+        if fa is None:
+            raise RuntimeError(
+                "FlashAttnBackend requires the optional 'flash-attn' package. "
+                "Install with `pip install flash-attn`."
+            )
+        out = fa.flash_attn_func(
+            q.contiguous(),
+            k.contiguous(),
+            v.contiguous(),
+            causal=is_causal,
+        )
+        return out.contiguous()
+
+    def _forward_packed(
+        self,
+        q: Tensor,
+        k: Tensor,
+        v: Tensor,
+        kv_cache: "KVCache",
+        layer_id: int,
+    ) -> Tensor:
+        fa = _flash_attn
+        if fa is None or not hasattr(fa, "flash_attn_varlen_func"):
+            raise RuntimeError("packed inference requires flash_attn_varlen_func")
+        kv_cache.k_buffer[layer_id, kv_cache.out_cache_loc] = k
+        kv_cache.v_buffer[layer_id, kv_cache.out_cache_loc] = v
+        page_table = kv_cache.req_to_token[
+            kv_cache.req_pool_indices, : kv_cache.max_len
+        ]
+        positions = torch.arange(kv_cache.max_len, device=q.device)
+        indices = page_table[positions.unsqueeze(0) < kv_cache.seq_lens.unsqueeze(1)]
+        k_flat = kv_cache.k_buffer[layer_id, indices].contiguous()
+        v_flat = kv_cache.v_buffer[layer_id, indices].contiguous()
+        out = fa.flash_attn_varlen_func(
+            q.contiguous(),
+            k_flat,
+            v_flat,
+            kv_cache.qo_indptr,
+            kv_cache.kv_indptr,
+            int((kv_cache.qo_indptr[1:] - kv_cache.qo_indptr[:-1]).max()),
+            int(kv_cache.seq_lens.max()),
+            dropout_p=0.0,
+            causal=True,
+        )
+        return out

astrai/extension/backend/rotary.py

@@ -11,6 +11,7 @@ import torch
 from torch import Tensor
 
 from astrai.extension.loader import is_available
+from astrai.extension.ops.rotary import rotary_emb as _cuda_rotary
 
 _cache = {"available": None}
 
@@ -26,7 +27,7 @@ def _torch_apply(x: Tensor, freqs_cis: Tensor) -> Tensor:
     dtype = x.dtype
     x_ = x.float().reshape(*x.shape[:-1], -1, 2)
     x_complex = torch.view_as_complex(x_)
-    freqs_cis_complex = torch.complex(cos, sin).unsqueeze(2)
+    freqs_cis_complex = torch.complex(cos, sin).unsqueeze(-2)
     x_rotated = x_complex * freqs_cis_complex
     x_out = torch.view_as_real(x_rotated).flatten(-2)
     return x_out.to(dtype)
@@ -48,7 +49,5 @@ def apply_rotary_emb(x: Tensor, freqs_cis: Tensor) -> Tensor:
         and x.is_cuda
         and x.dtype == torch.bfloat16
     ):
-        from astrai.extension.rotary_ops import rotary_emb as _cuda_rotary
-
         return _cuda_rotary(x, freqs_cis)
     return _torch_apply(x, freqs_cis)

astrai/extension/fp8.py

@@ -0,0 +1,450 @@
+"""FP8 training: scaling recipes, per-tensor state, and aten::linear dispatch.
+
+Layered (see ``ops/fp8.py`` for the CUDA interface adapter):
+1. ``ops.fp8`` — the only module touching the pybind.
+2. This module (strategy layer): scaling *recipes* (TE-style delayed scaling
+   or dynamic current-amax scaling), per-tensor scales + amax history, and the
+   ``fp8_autocast`` context manager (like ``torch.autocast``).
+3. aten::linear integration: registers the CUDA + AutogradCUDA impls.
+
+Usage::
+
+    from astrai.extension.fp8 import fp8_autocast
+    with fp8_autocast(enabled=True, fp8_format="hybrid"):
+        logits = model(input_ids)
+    loss.backward()  # fp8 backward runs anywhere; fwd captured state on the node
+
+Format defaults follow the ecosystem consensus: E4M3 forward / E5M2 backward
+("hybrid"); every operand's scale is a quantization step derived from its amax
+history by the active recipe.
+
+The context mirrors ``torch.autocast`` (``autocast_mode.py``): the active
+``(enabled, recipe, fp8_format)`` triple is thread-local (a ``contextvars``
+``ContextVar``, absent outside any region), and the manager is class-based and
+reentrant with nested ``enabled=False`` disabling dispatch inside it. The module
+targets *training*: every step quantizes x/w/g fresh (no weight-cast cache — the
+optimizer bumps the weight version each step, so a torch-style cached_cast would
+miss anyway), and the per-operand scales come from the delayed/dynamic recipe.
+"""
+
+import functools
+from contextvars import ContextVar, Token
+from dataclasses import dataclass
+from enum import Enum
+from typing import Dict, List, NamedTuple, Optional
+
+import torch
+from torch.library import Library
+
+from astrai.extension.ops.fp8 import mm_fp8, quantize, quantize_dual
+
+# Max representable value per FP8 format (E4M3: 448, E5M2: 57344).
+FP8_MAX = {"e4m3": 448.0, "e5m2": 57344.0}
+
+
+class FP8Format(str, Enum):
+    """Per-direction FP8 format. HYBRID = E4M3 forward / E5M2 backward."""
+
+    E4M3 = "e4m3"
+    E5M2 = "e5m2"
+    HYBRID = "hybrid"
+
+    def fwd(self) -> str:
+        return "e4m3" if self is FP8Format.HYBRID else self.value
+
+    def bwd(self) -> str:
+        return "e5m2" if self is FP8Format.HYBRID else self.value
+
+
+@dataclass
+class FP8Recipe:
+    """Scale-from-amax policy: ``scale = (amax / FP8_MAX[fmt]) / 2^margin``.
+
+    ``dynamic=False`` (default) is TE-style delayed scaling: max over the
+    amax history window (amax from *previous* steps; the window trades
+    responsiveness against stability). ``dynamic=True`` is current-amax
+    scaling (torchao DYNAMIC): measure, then quantize — no history, at an
+    extra pass. ``scale_from_history`` receives the operand's amax tensor
+    (a ring window / the current amax) and returns the quantization step.
+    """
+
+    history_len: int = 16
+    margin: int = 0
+    dynamic: bool = False
+
+    def scale_from_history(self, amax: torch.Tensor, fmt: str) -> torch.Tensor:
+        peak = amax.max()
+        return ((peak / FP8_MAX[fmt]) / (2**self.margin)).clamp_min(1e-12)
+
+
+class _ScaleRing:
+    """One operand's delayed-scaling state: a float32 buffer
+    ``[hist[n] | scale | legacy | amax | done]`` (views). The quantize
+    kernel folds its fused amax into ``hist[idx]`` and publishes the next
+    scale from the window in its own last block (``fold_args`` passes the
+    buffer + recipe constants); ``idx`` advances host-side each use. The
+    ``amax``/``done`` tail slots are kernel scratch (self-cleaning across
+    launches); the legacy slot keeps state-buffer compatibility.
+    """
+
+    __slots__ = ("recipe", "state", "hist", "scale", "idx", "initialized")
+
+    def __init__(self, device: torch.device, recipe: FP8Recipe):
+        self.recipe = recipe
+        n = recipe.history_len
+        self.state = torch.zeros(n + 4, device=device, dtype=torch.float32)
+        self.hist = self.state[:n]
+        self.scale = self.state[n : n + 1]
+        self.idx = 0
+        self.initialized = False
+
+    def advance(self) -> None:
+        """Rotate to the next history slot after metadata update."""
+        self.idx = (self.idx + 1) % self.hist.numel()
+
+    def seed(self, t: torch.Tensor, fmt: str) -> None:
+        amax = t.abs().amax().to(torch.float32).clamp_min(1e-12)
+        self.hist.fill_(amax)
+        self.scale.copy_(self.recipe.scale_from_history(self.hist, fmt))
+        self.initialized = True
+
+    def fold_args(self, fmt: str) -> dict:
+        """Keyword arguments for quantize()'s in-kernel history fold."""
+        return {
+            "ring_state": self.state,
+            "hist_idx": self.idx,
+            "fp8_max": FP8_MAX[fmt],
+            "pow2_margin": float(2**self.recipe.margin),
+        }
+
+
+class FP8TensorMeta(NamedTuple):
+    """Per-weight delayed-scaling rings for ``w``, ``x`` and ``g``.
+
+    Dynamic scaling never allocates a meta; it measures the current amax inline.
+    """
+
+    w: _ScaleRing
+    x: _ScaleRing
+    g: _ScaleRing
+
+
+@dataclass(frozen=True)
+class _ActiveConfig:
+    """The immutable (enabled, recipe, format) triple of one open region."""
+
+    enabled: bool
+    recipe: FP8Recipe
+    fp8_format: FP8Format
+
+
+# Thread-local active configuration (torch's autocast TLS analog): set by
+# fp8_autocast on __enter__, absent outside any region. Autograd engine
+# threads run backwards with their own empty context — fine, since backward
+# only reads state captured on ctx at forward time.
+_active_config: ContextVar[Optional[_ActiveConfig]] = ContextVar(
+    "astrai_fp8_active_config", default=None
+)
+
+
+class FP8State:
+    """Global fp8 training state: per-tensor metas + out-of-region defaults.
+
+    The active ``(enabled, recipe, fp8_format)`` triple is a ``ContextVar``
+    set by ``fp8_autocast`` (see ``_active``/``_current_config``); these plain
+    attributes are the persistent defaults applied outside any region —
+    ``fp8_linear_enable`` writes ``default_enabled``. The metas registry is
+    shared across threads (GIL-protected); fp8 backward runs on autograd
+    engine threads and only touches metas captured on ``ctx`` at forward time.
+    """
+
+    def __init__(self):
+        self.default_enabled = False
+        self.default_recipe: FP8Recipe = FP8Recipe()
+        self.default_format: FP8Format = FP8Format.HYBRID
+        self._metas: Dict[tuple, FP8TensorMeta] = {}
+
+    def get_weight_meta(self, w: torch.Tensor, recipe: FP8Recipe) -> FP8TensorMeta:
+        key = (w.data_ptr(), w.shape, w.dtype)
+        meta = self._metas.get(key)
+        if meta is None:
+            meta = FP8TensorMeta(
+                _ScaleRing(w.device, recipe),
+                _ScaleRing(w.device, recipe),
+                _ScaleRing(w.device, recipe),
+            )
+            self._metas[key] = meta
+        return meta
+
+    def reset(self) -> None:
+        """Restore construction defaults (switch, recipe, format) and drop all
+        per-weight metas — a full state reset for tests / reconfiguration."""
+        self.default_enabled = False
+        self.default_recipe = FP8Recipe()
+        self.default_format = FP8Format.HYBRID
+        self._metas.clear()
+
+
+# Process-wide singleton; per-thread/per-region state lives in _active_config.
+_state = FP8State()
+
+
+def fp8_state() -> FP8State:
+    return _state
+
+
+def _active() -> Optional[_ActiveConfig]:
+    """The active config when fp8 dispatch is on, else ``None`` (fast guard).
+
+    A region config wins (honoring nested ``enabled=False`` regions); with no
+    region open this falls back to the persistent global switch
+    (``fp8_linear_enable``), so that flag still routes aten::linear to fp8.
+    """
+    cfg = _active_config.get()
+    if cfg is not None:
+        return cfg if cfg.enabled else None
+    if _state.default_enabled:
+        return _ActiveConfig(True, _state.default_recipe, _state.default_format)
+    return None
+
+
+def _current_config() -> _ActiveConfig:
+    """Like ``_active()`` but always returns a config (disabled regions and
+    out-of-region direct calls resolve to the global defaults)."""
+    cfg = _active_config.get()
+    if cfg is not None:
+        return cfg
+    return _ActiveConfig(
+        _state.default_enabled, _state.default_recipe, _state.default_format
+    )
+
+
+class fp8_autocast:
+    """Autocast-style context: fp8 linear dispatch on this thread.
+
+    Mirrors ``torch.autocast`` — a class-based, reentrant, nestable context
+    over thread-local state::
+
+        with fp8_autocast(enabled=True, fp8_format="hybrid"):
+            logits = model(input_ids)   # aten::linear -> fp8 path
+        loss.backward()  # fp8 backward; state was captured at forward time
+
+    Nesting follows torch: each ``__enter__`` pushes the new active config, each
+    ``__exit__`` restores the previous one, and a nested ``enabled=False`` region
+    simply disables dispatch inside it. The instance doubles as a decorator.
+    """
+
+    def __init__(
+        self,
+        enabled: bool = True,
+        update_interval: int = 16,
+        recipe: Optional[FP8Recipe] = None,
+        fp8_format: str = "hybrid",
+        margin: int = 0,
+    ):
+        if recipe is None:
+            recipe = FP8Recipe(history_len=update_interval, margin=margin)
+        self._config = _ActiveConfig(bool(enabled), recipe, FP8Format(fp8_format))
+        self._tokens: List[Token] = []
+
+    def __enter__(self) -> "fp8_autocast":
+        self._tokens.append(_active_config.set(self._config))
+        return self
+
+    def __exit__(self, exc_type, exc_val, exc_tb) -> bool:
+        token = self._tokens.pop()
+        _active_config.reset(token)
+        return False
+
+    def __call__(self, func):
+        @functools.wraps(func)
+        def decorate(*args, **kwargs):
+            with self:
+                return func(*args, **kwargs)
+
+        return decorate
+
+
+# ---------------------------------------------------------------------------
+# Strategy-level forward / backward (called from the aten::linear impl)
+# ---------------------------------------------------------------------------
+
+
+def _dynamic_scale(t: torch.Tensor, recipe: FP8Recipe, fmt: str) -> torch.Tensor:
+    amax = t.abs().amax().to(torch.float32).clamp_min(1e-12)
+    return recipe.scale_from_history(amax, fmt)
+
+
+def _is_fp8(dtype: torch.dtype) -> bool:
+    """A pre-quantized weight takes the GEMM directly (no re-quantize)."""
+    return dtype in (torch.float8_e4m3fn, torch.float8_e5m2)
+
+
+def fp8_linear_forward(
+    x: torch.Tensor, w: torch.Tensor, bias=None, cfg: Optional[_ActiveConfig] = None
+):
+    """Scaled fp8 linear forward (called from the aten::linear impl).
+
+    Composed from the two stateless primitives: quantize x/w with the active
+    scales, run the pre-quantized GEMM with the bias fused into its epilogue.
+    Delayed scaling lets the quantize kernel fold the fused amax into the
+    history ring and publish the next scale in its own last block; dynamic
+    scaling measures the current amax itself. Training quantizes the weight
+    every step (the optimizer bumps its version, so there is no cast cache,
+    matching ``cached_cast``-less behavior).
+    """
+    state = fp8_state()
+    if cfg is None:
+        cfg = _current_config()
+    fmt = cfg.fp8_format.fwd()
+    if cfg.recipe.dynamic:
+        sx = _dynamic_scale(x.reshape(-1, w.size(1)), cfg.recipe, fmt)
+        sw = _dynamic_scale(w, cfg.recipe, fmt)
+        x8, _ = quantize(x, sx.reciprocal(), fmt)
+        w8 = w if _is_fp8(w.dtype) else quantize(w, sw.reciprocal(), fmt)[0]
+        # Bias fuses into the GEMM epilogue (fp32 add before the single bf16
+        # rounding — one rounding fewer than the separate out + bias pass);
+        # None passes through to the kernel's no-bias path.
+        out = mm_fp8(
+            x8.reshape(-1, x8.size(-1)), w8, sx * sw, trans_b=True, bias=bias
+        ).reshape(*x.shape[:-1], w.size(0))
+        return out, sx, sw
+
+    meta = state.get_weight_meta(w, cfg.recipe)
+    if not meta.w.initialized:
+        meta.w.seed(w, fmt)
+    if not meta.x.initialized:
+        meta.x.seed(x, fmt)
+    sx, sw = meta.x.scale.clone(), meta.w.scale.clone()
+    # The clones feed this call's kernels (stream-ordered before the in-kernel
+    # fold overwrites the ring scale slots); the fp8 quantize kernel folds the
+    # amax into the history window and publishes the next scale itself.
+    x8, _ = quantize(x, sx.reciprocal(), fmt, **meta.x.fold_args(fmt))
+    if _is_fp8(w.dtype):
+        w8 = w
+    else:
+        w8, _ = quantize(w, sw.reciprocal(), fmt, **meta.w.fold_args(fmt))
+    out = mm_fp8(
+        x8.reshape(-1, x8.size(-1)), w8, sx * sw, trans_b=True, bias=bias
+    ).reshape(*x.shape[:-1], w.size(0))
+    meta.x.advance()
+    if not _is_fp8(w.dtype):
+        meta.w.advance()
+    return out, sx, sw
+
+
+class _LinearFp8(torch.autograd.Function):
+    """The fp8 linear forward/backward pair (standard Function style).
+
+    The forward runs inside ``fp8_autocast`` and captures the active
+    fmt/recipe/meta on ``ctx``; the backward reads only that captured state, so
+    ``loss.backward()`` may run after the context exits. The gradient is
+    quantized once (E5M2 in hybrid) and both dX/dW GEMMs share it; the output
+    masks come from ``needs_input_grad``.
+    """
+
+    @staticmethod
+    def forward(ctx, x, w, bias):
+        cfg = _current_config()
+        out, sx, sw = fp8_linear_forward(x, w, bias, cfg)
+        ctx.save_for_backward(x, w, sx, sw)
+        ctx.fmt_bwd = cfg.fp8_format.bwd()
+        ctx.recipe = cfg.recipe
+        ctx.is_dynamic = cfg.recipe.dynamic
+        ctx.meta = None if ctx.is_dynamic else _state.get_weight_meta(w, cfg.recipe)
+        return out
+
+    @staticmethod
+    @torch.autograd.function.once_differentiable
+    def backward(ctx, g):
+        x, w, _sx_fwd, _sw_fwd = ctx.saved_tensors
+        fmt = ctx.fmt_bwd
+        # Flatten leading dims (the forward GEMMs ran on [-1, N] / [-1, K]
+        # views; the kernels only accept 2D operands).
+        g2 = g.reshape(-1, g.size(-1))
+        if ctx.is_dynamic:
+            sg = _dynamic_scale(g2, ctx.recipe, fmt)
+            sw = _dynamic_scale(w, ctx.recipe, fmt)
+            sx = _dynamic_scale(x, ctx.recipe, fmt)
+        else:
+            meta = ctx.meta
+            if not meta.g.initialized:
+                meta.g.seed(g2, fmt)
+            sg = meta.g.scale.clone()
+            sw, sx = _sw_fwd, _sx_fwd
+        # Backward GEMMs route through the NT fast path via transposed
+        # quantize outputs: g8 [m,n] with w8T [k,n] (trans_b=True) gives
+        # grad_x, g8T [n,m] with x8T [k,m] gives grad_w — no NN-swap or TT
+        # crosswise kernel in the training path. g is consumed in both
+        # orientations, so quantize_dual's single pass feeds both.
+        # The g quantize folds the gradient amax into its ring in-kernel;
+        # the x8T/w8T orientation copies discard amax (those rings were
+        # folded at forward time).
+        g8, g8T, _ = quantize_dual(g2, sg.reciprocal(), fmt, **meta.g.fold_args(fmt))
+        x8T, _ = quantize(
+            x.reshape(-1, x.size(-1)), sx.reciprocal(), fmt, transposed=True
+        )
+        if _is_fp8(w.dtype):
+            # Pre-quantized weight has no transposed copy: keep the swap
+            # path for grad_x (grad_w is unaffected).
+            grad_x = mm_fp8(g8, w, sg * sw).reshape(x.shape)
+        else:
+            w8T, _ = quantize(w, sw.reciprocal(), fmt, transposed=True)
+            grad_x = mm_fp8(g8, w8T, sg * sw, trans_b=True).reshape(x.shape)
+        grad_w = mm_fp8(g8T, x8T, sg * sx, trans_b=True)  # g8.T @ x8
+        # bias-free linears must not pay the column-sum
+        # reduce: g2.sum(0) is another full read of the gradient.
+        grad_b = g2.sum(0).to(torch.bfloat16) if ctx.needs_input_grad[2] else None
+        if not ctx.is_dynamic:
+            meta.g.advance()
+        return grad_x, grad_w, grad_b
+
+
+# ---------------------------------------------------------------------------
+# aten::linear integration
+# ---------------------------------------------------------------------------
+
+
+def fp8_linear_enable(enabled: bool = True) -> None:
+    """Toggle fp8 dispatch for aten::linear globally (the out-of-region default;
+    ``fp8_autocast`` regions override it thread-locally)."""
+    fp8_state().default_enabled = enabled
+
+
+def fp8_linear_enabled() -> bool:
+    """Whether fp8 dispatch is active right now (region config or global)."""
+    return _active() is not None
+
+
+def _fp8_supported(x: torch.Tensor, w: torch.Tensor) -> bool:
+    """Shape guard for the fp8 path. Unlike a strict 16-alignment requirement,
+    the kernels handle unaligned M/N via boundary checks (slower but correct) —
+    so no whole-call bf16 fallback for small decode batches. Only the K-dimension
+    contraction must match and the weight must be 2D."""
+    return x.dim() >= 2 and w.dim() == 2 and x.size(-1) == w.size(1)
+
+
+def _linear_cuda_impl(x: torch.Tensor, w: torch.Tensor, bias=None):
+    if (
+        _active() is not None
+        and x.dtype is torch.bfloat16
+        and w.dtype is torch.bfloat16
+        and _fp8_supported(x, w)
+    ):
+        return _LinearFp8.apply(x, w, bias)
+    return torch.ops.aten.linear.default.redispatch(
+        torch._C.DispatchKeySet(torch._C.DispatchKey.CompositeImplicitAutograd),
+        x,
+        w,
+        bias,
+    )
+
+
+_lib = Library("aten", "IMPL", "CUDA")
+_lib.impl("linear", _linear_cuda_impl)
+# Also replace torch's generated linear autograd formula (which would call
+# aten::linear_backward after the fp8_autocast region exits). The fp8 backward
+# is owned by _LinearFp8 with state captured at forward time, so loss.backward()
+# works wherever it is called; the CUDA registration still covers inference_mode.
+_lib_autograd = Library("aten", "IMPL", "AutogradCUDA")
+_lib_autograd.impl("linear", _linear_cuda_impl)

astrai/extension/loader.py

@@ -1,42 +1,83 @@
 """Dynamic discovery and loading of compiled CUDA kernel modules.
 
-Each kernel is registered in ``csrc/build.py`` and built into a ``.so`` placed
-in this package directory. On import we try to load each one; kernels that
-failed to build (or are running on a CPU-only machine) are marked unavailable
-so the wrapper functions can fall back to ``torch`` SDPA.
+Each kernel is built by the CMake build in ``csrc/CMakeLists.txt`` into a
+``.so`` placed in ``astrai/extension/lib/`` — the module name equals the
+``.so`` name equals the pybind name (e.g. ``attn_decode``, defined via
+``TORCH_EXTENSION_NAME``). ``KERNEL_NAMES`` is discovered automatically from
+the ``.so`` files present, so adding a kernel to the CMake ``KERNELS``
+registry needs no change here.
+
+Loading is **lazy and centralized**: module names are discovered eagerly
+(cheap glob), but each ``.so`` is imported on first use via the single
+``get_module`` accessor, then cached. The wrapper modules (``ops/*.py``) never
+touch the internals or keep their own caches — they call ``get_module(name)``
+(or ``is_available(name)`` when a torch fallback is acceptable). A kernel that
+failed to build (or is running on a CPU-only machine) is ``None`` in the cache,
+so ``is_available`` returns ``False`` and ``get_module`` raises a clear error.
 """
 
+import glob
 import importlib
 import logging
+import os
 
 logger = logging.getLogger(__name__)
 
-KERNEL_NAMES = [
-    "attn_decode",
-    "attn_prefill",
-    "attn_paged_decode",
-    "attn_paged_prefill",
-    "rotary_emb",
-]
+_LIB_DIR = os.path.join(os.path.dirname(__file__), "lib")
+
+
+def _discover_kernel_names() -> list[str]:
+    """Return the module names of the compiled kernel ``.so`` files in lib/."""
+    names: list[str] = []
+    for path in glob.glob(os.path.join(_LIB_DIR, "*.so")):
+        # strip the "<soabi>.so" suffix, e.g. attn_decode.cpython-312-...so
+        names.append(os.path.basename(path).split(".", 1)[0])
+    return sorted(names)
+
+
+KERNEL_NAMES = _discover_kernel_names()
 
 _available: dict[str, bool] = {}
 _modules: dict[str, object] = {}
 
-for _name in KERNEL_NAMES:
-    try:
-        _mod = importlib.import_module(f".lib.{_name}", package=__package__)
-        _available[_name] = True
-        _modules[_name] = _mod
-    except ImportError:
-        _available[_name] = False
-        _modules[_name] = None
+
+def _try_load(name: str) -> object:
+    """Import and cache the ``name`` kernel module (lazy, one attempt).
+
+    Returns the module, or ``None`` if it is unavailable. Cached so each
+    ``.so`` is imported at most once per process.
+    """
+    if name not in _modules:
+        try:
+            _modules[name] = importlib.import_module(
+                f".lib.{name}", package=__package__
+            )
+            _available[name] = True
+        except ImportError:
+            logger.warning("kernel '%s' failed to import; marking unavailable", name)
+            _modules[name] = None
+            _available[name] = False
+    return _modules[name]
 
 
 def is_available(name: str) -> bool:
-    """Return ``True`` if the compiled kernel ``name`` was loaded."""
+    """Return ``True`` if the compiled kernel ``name`` could be loaded."""
+    if name not in _available:
+        _try_load(name)
     return _available.get(name, False)
 
 
 def get_module(name: str) -> object:
-    """Return the loaded kernel module for ``name``, or ``None`` if unavailable."""
-    return _modules.get(name)
+    """Return the loaded kernel module for ``name``, importing it on first use.
+
+    Raises ``RuntimeError`` if the kernel is unavailable (not built, or failed
+    to import) — callers that can tolerate a torch fallback should check
+    ``is_available(name)`` first instead.
+    """
+    mod = _try_load(name)
+    if mod is None:
+        raise RuntimeError(
+            f"CUDA kernel '{name}' is not available. "
+            f"Build with CSRC_KERNELS=true (or use the torch-native fallback)."
+        )
+    return mod

astrai/extension/ops/__init__.py

@@ -0,0 +1,19 @@
+"""Stateless wrappers around compiled extension kernels."""
+
+from astrai.extension.ops.attention import (
+    TensorLayout,
+    attn_decode,
+    attn_paged_decode,
+    attn_paged_prefill,
+    attn_prefill,
+)
+from astrai.extension.ops.rotary import rotary_emb
+
+__all__ = [
+    "TensorLayout",
+    "attn_decode",
+    "attn_paged_decode",
+    "attn_paged_prefill",
+    "attn_prefill",
+    "rotary_emb",
+]

astrai/extension/ops/attention.py

@@ -1,4 +1,4 @@
-"""Attention kernel wrapper functions — one entry point per compiled kernel.
+"""Attention kernel wrapper functions - one entry point per compiled kernel.
 
 Each wrapper calls its CUDA kernel directly. If the kernel is not
 available, raises ``RuntimeError``. Fallback to torch SDPA is the
@@ -17,7 +17,7 @@ from typing import Optional
 
 import torch
 
-from astrai.extension.loader import _available, _modules
+from astrai.extension.loader import get_module
 
 
 class TensorLayout(enum.IntEnum):
@@ -30,14 +30,6 @@ class TensorLayout(enum.IntEnum):
     BLHD = 1  # [batch, seq_len, n_heads, head_dim]
 
 
-def _check_available(name: str):
-    if not _available.get(name):
-        raise RuntimeError(
-            f"CUDA kernel '{name}' is not available. "
-            f"Build with CSRC_KERNELS=true or use a torch-native backend."
-        )
-
-
 def attn_decode(
     q: torch.Tensor,
     k: torch.Tensor,
@@ -57,9 +49,9 @@ def attn_decode(
     Returns:
         [batch, 1, n_heads, head_dim] (blhd, bf16)
     """
-    _check_available("attn_decode")
+    mod = get_module("attn_decode")
     causal_offset = (k.size(1) - 1) if is_causal else -1
-    return _modules["attn_decode"].attn_decode(
+    return mod.attn_decode(
         q, k, v, mask=mask, causal_offset=causal_offset, layout=TensorLayout.BLHD
     )
 
@@ -83,9 +75,9 @@ def attn_prefill(
     Returns:
         [batch, q_len, n_heads, head_dim] (blhd, bf16)
     """
-    _check_available("attn_prefill")
+    mod = get_module("attn_prefill")
     causal_offset = (k.size(1) - q.size(1)) if is_causal else -1
-    return _modules["attn_prefill"].attn_prefill(
+    return mod.attn_prefill(
         q, k, v, mask=mask, causal_offset=causal_offset, layout=TensorLayout.BLHD
     )
 
@@ -97,9 +89,13 @@ def attn_paged_decode(
     req_to_token: torch.Tensor,
     req_pool_indices: torch.Tensor,
     kv_indptr: torch.Tensor,
-    max_seq_len: int,
+    new_k: Optional[torch.Tensor] = None,
+    new_v: Optional[torch.Tensor] = None,
     mask: Optional[torch.Tensor] = None,
     is_causal: bool = False,
+    o_part_buf: Optional[torch.Tensor] = None,
+    ml_part_buf: Optional[torch.Tensor] = None,
+    out_buf: Optional[torch.Tensor] = None,
 ) -> torch.Tensor:
     """SGLang-style paged decode (q_len == 1, flat KV pool).
 
@@ -111,28 +107,36 @@ def attn_paged_decode(
         q: [batch, n_heads, head_dim] (bf16, 3D — no seq dim)
         k_cache: [pool_size, n_kv_heads, head_dim] (bf16, flat)
         v_cache: same as k_cache
-        req_to_token: [num_reqs, max_context_len] (int64) — token -> slot
-        req_pool_indices: [batch] (int64) — rows into req_to_token
+        req_to_token: [num_reqs, max_context_len] (int32) — token -> slot
+        req_pool_indices: [batch] (int32) — rows into req_to_token
         kv_indptr: [batch+1] (int32) — prefix sum of per-request seq_lens
-        max_seq_len: max per-request seq_len (Python int, for split computation)
-        mask: 2D [batch, max_seq_len] (bool, True=keep) or None
+        new_k: current-token K to append, [batch, n_kv_heads, head_dim]
+        new_v: current-token V to append, same shape as new_k
+        mask: 2D [batch, max_context_len] (bool, True=keep) or None
         is_causal: apply causal mask
+        o_part_buf: pre-allocated split-KV o partial buffer (workflow bypass)
+        ml_part_buf: pre-allocated split-KV m/l buffer (workflow bypass)
+        out_buf: pre-allocated output buffer [batch, n_heads, head_dim] (graph-safe)
 
     Returns:
         [batch, n_heads, head_dim] (bf16, 3D)
     """
-    _check_available("attn_paged_decode")
+    mod = get_module("attn_paged_decode")
     causal_offset = 0 if is_causal else -1
-    return _modules["attn_paged_decode"].attn_paged_decode(
+    return mod.attn_paged_decode(
         q,
         k_cache,
         v_cache,
         req_to_token,
         req_pool_indices,
         kv_indptr,
-        max_seq_len,
+        new_k=new_k,
+        new_v=new_v,
         mask=mask,
         causal_offset=causal_offset,
+        o_part_buf=o_part_buf,
+        ml_part_buf=ml_part_buf,
+        out_buf=out_buf,
     )
 
 
@@ -144,8 +148,9 @@ def attn_paged_prefill(
     req_pool_indices: torch.Tensor,
     kv_indptr: torch.Tensor,
     qo_indptr: torch.Tensor,
+    q_tile_to_batch: torch.Tensor,
+    q_tile_to_index: torch.Tensor,
     mask: Optional[torch.Tensor] = None,
-    max_q_len: int = 0,
     is_causal: bool = False,
 ) -> torch.Tensor:
     """SGLang-style paged prefill (ragged batch, flat KV pool).
@@ -158,20 +163,21 @@ def attn_paged_prefill(
         q: [total_q, n_heads, head_dim] (bf16, 3D — flattened across requests)
         k_cache: [pool_size, n_kv_heads, head_dim] (bf16, flat)
         v_cache: same as k_cache
-        req_to_token: [num_reqs, max_context_len] (int64)
-        req_pool_indices: [batch] (int64)
+        req_to_token: [num_reqs, max_context_len] (int32)
+        req_pool_indices: [batch] (int32)
         kv_indptr: [batch+1] (int32) — prefix sum of per-request kv_lens
         qo_indptr: [batch+1] (int32) — prefix sum of per-request q_lens
+        q_tile_to_batch: [num_q_tiles] (int32) — request index per Q tile
+        q_tile_to_index: [num_q_tiles] (int32) — local Q tile index per request
         mask: 4D [batch, 1, q_len, kv_len] (bool, True=keep) or None
-        max_q_len: max per-request q_len (Python int, for grid computation)
         is_causal: apply causal mask
 
     Returns:
         [total_q, n_heads, head_dim] (bf16, 3D)
     """
-    _check_available("attn_paged_prefill")
+    mod = get_module("attn_paged_prefill")
     causal_offset = 0 if is_causal else -1
-    return _modules["attn_paged_prefill"].attn_paged_prefill(
+    return mod.attn_paged_prefill(
         q,
         k_cache,
         v_cache,
@@ -179,7 +185,8 @@ def attn_paged_prefill(
         req_pool_indices,
         kv_indptr,
         qo_indptr,
+        q_tile_to_batch,
+        q_tile_to_index,
         mask,
-        max_q_len,
         causal_offset=causal_offset,
     )

astrai/extension/ops/fp8.py

@@ -0,0 +1,116 @@
+"""FP8 CUDA kernel interface adapter (the only module touching the pybind).
+
+Attention-style thin wrappers: one Python entry per binding, called directly
+— no torch.library dispatch layer. Optional arguments (``ring_state``,
+``bias``) keep native Optional semantics at the pybind boundary, and
+in-place buffer updates (the delayed-scaling ring fold, like attention's
+KV-cache appends) happen on-stream without mutation declarations. CUDA-only:
+non-CUDA or unsupported inputs raise from the binding's TORCH_CHECKs.
+
+- ``quantize(x, scale, fmt, transposed=False) -> (x8|x8T, amax)`` — BF16/FP16/FP32
+  → FP8 with fused amax (``transposed`` picks the orientation; arity is fixed)
+- ``quantize_dual(x, scale, fmt) -> (x8, x8T, amax)`` — both orientations, one read
+- ``mm_fp8(a8, b8, sa, sb) -> out`` — pre-quantized FP8 GEMM (BF16 output)
+
+``scale`` is the quantization multiplier (device scalar); ``fmt`` is
+``"e4m3"`` or ``"e5m2"``. ``amax`` values are *returned*, never passed as
+output arguments.
+
+Policy (scales, amax history, delayed scaling, autocast) lives in ``fp8.py``;
+this module is stateless.
+"""
+
+from typing import Optional, Tuple
+
+import torch
+
+from astrai.extension.loader import get_module
+
+# fmt string -> kernel int (0 = E4M3, 1 = E5M2)
+_FMT_TO_INT = {"e4m3": 0, "e5m2": 1}
+
+
+def _fmt_int(fmt: str) -> int:
+    try:
+        return _FMT_TO_INT[fmt]
+    except KeyError:
+        raise ValueError(f"unsupported fp8 format {fmt!r} (expected 'e4m3' or 'e5m2')")
+
+
+def quantize(
+    x: torch.Tensor,
+    scale: torch.Tensor,
+    fmt: str = "e4m3",
+    transposed: bool = False,
+    ring_state: Optional[torch.Tensor] = None,
+    hist_idx: int = 0,
+    fp8_max: float = 448.0,
+    pow2_margin: float = 1.0,
+) -> Tuple[torch.Tensor, torch.Tensor]:
+    """Float (bf16/fp16/fp32) -> FP8 quantize with fused amax.
+
+    ``scale`` is the quantization multiplier (device scalar); ``fmt`` selects
+    E4M3 or E5M2. ``amax`` is a fresh 1-element float32 tensor.
+    ``transposed=True`` swaps ``x8`` for ``x8T``, the ``[cols][rows]``
+    row-major transpose of the quantized input — the K-contiguous operand
+    orientation NT GEMMs want — at the same 2-tuple arity.
+
+    ``ring_state`` (a 1D float32 CUDA buffer laid out
+    ``[hist n | scale | legacy | amax | done]``) switches on the in-kernel
+    delayed-scaling fold: the kernel's last block folds the amax into
+    ``hist[hist_idx]`` and publishes the next scale as
+    ``max(hist) / fp8_max / pow2_margin`` — the returned ``amax`` is then the
+    self-cleaned persistent slot (reads zero). None keeps the classic
+    fresh-amax return.
+    """
+    return get_module("fp8_ops").quantize(
+        x,
+        scale,
+        _fmt_int(fmt),
+        transposed,
+        ring_state,
+        hist_idx,
+        fp8_max,
+        pow2_margin,
+    )
+
+
+def quantize_dual(
+    x: torch.Tensor,
+    scale: torch.Tensor,
+    fmt: str = "e4m3",
+    ring_state: Optional[torch.Tensor] = None,
+    hist_idx: int = 0,
+    fp8_max: float = 448.0,
+    pow2_margin: float = 1.0,
+) -> Tuple[torch.Tensor, torch.Tensor, torch.Tensor]:
+    """Dual-orientation quantize: one read of ``x`` produces both the
+    row-major ``x8`` and its transposed ``x8T`` (plus ``amax``), for tensors
+    consumed by GEMMs in both orientations (backward ``g``).
+
+    ``ring_state`` switches on the in-kernel delayed-scaling fold exactly as
+    in :func:`quantize`.
+    """
+    return get_module("fp8_ops").quantize_dual(
+        x, scale, _fmt_int(fmt), ring_state, hist_idx, fp8_max, pow2_margin
+    )
+
+
+def mm_fp8(
+    a: torch.Tensor,
+    b: torch.Tensor,
+    scale: torch.Tensor,
+    trans_a: bool = False,
+    trans_b: bool = False,
+    bias: Optional[torch.Tensor] = None,
+) -> torch.Tensor:
+    """Pre-quantized FP8 GEMM: ``a @ b * scale (+ bias)``.
+
+    ``a``/``b`` must be FP8 tensors of the same format, 2D or 3D (batched,
+    matmul-style broadcast on the batch dim). Inner-transposed views (e.g.
+    ``x.t()``) fold into the layout at zero copy. ``scale`` is their combined
+    dequantization scale. ``bias`` (CUDA bf16 1D of length n) adds inside the
+    kernel epilogue in fp32 — no separate elementwise pass. The result is
+    BF16; FP8 output is a separate quantize operation.
+    """
+    return get_module("fp8_ops").mm_fp8(a, b, scale, trans_a, trans_b, bias)

astrai/extension/ops/rotary.py

@@ -0,0 +1,31 @@
+"""Rotary embedding CUDA kernel wrapper.
+
+Calls the compiled CUDA kernel directly. If the kernel is not available,
+raises ``RuntimeError``. Fallback to torch complex multiply is the
+responsibility of ``astrai.extension.backend.rotary.apply_rotary_emb``.
+
+Layout: x is packed [tokens, n_heads, head_dim] or dense
+[batch, seq_len, n_heads, head_dim]. ``freqs_cis`` has matching token axes.
+"""
+
+import torch
+
+from astrai.extension.loader import get_module
+
+
+def rotary_emb(x: torch.Tensor, freqs_cis: torch.Tensor) -> torch.Tensor:
+    """Fused rotary embedding kernel.
+
+    Args:
+        x: packed 3D or dense 4D bf16 tensor.
+        freqs_cis: matching token axes followed by [head_dim/2, 2].
+
+    Returns:
+        Tensor with the same shape as ``x``.
+    """
+    mod = get_module("rotary_emb")
+    if not x.is_contiguous():
+        x = x.contiguous()
+    if not freqs_cis.is_contiguous():
+        freqs_cis = freqs_cis.contiguous()
+    return mod.rotary_emb(x, freqs_cis)

astrai/extension/rotary_ops.py

@@ -1,39 +0,0 @@
-"""Rotary embedding CUDA kernel wrapper.
-
-Calls the compiled CUDA kernel directly. If the kernel is not available,
-raises ``RuntimeError``. Fallback to torch complex multiply is the
-responsibility of ``astrai.extension.rotary_backend.apply_rotary_emb``.
-
-Layout: x is [batch, seq_len, n_heads, head_dim] (bf16, contiguous).
-freqs_cis is [batch, seq_len, head_dim/2, 2] (f32, contiguous) — [cos, sin] pairs.
-"""
-
-import torch
-
-from astrai.extension.loader import _available, _modules
-
-
-def _check_available():
-    if not _available.get("rotary_emb"):
-        raise RuntimeError(
-            "CUDA kernel 'rotary_emb' is not available. "
-            "Build with CSRC_KERNELS=true or use the torch fallback."
-        )
-
-
-def rotary_emb(x: torch.Tensor, freqs_cis: torch.Tensor) -> torch.Tensor:
-    """Fused rotary embedding kernel.
-
-    Args:
-        x: [batch, seq_len, n_heads, head_dim] (bf16, contiguous)
-        freqs_cis: [batch, seq_len, head_dim/2, 2] (f32, contiguous) — [cos, sin] pairs
-
-    Returns:
-        [batch, seq_len, n_heads, head_dim] (bf16)
-    """
-    _check_available()
-    if not x.is_contiguous():
-        x = x.contiguous()
-    if not freqs_cis.is_contiguous():
-        freqs_cis = freqs_cis.contiguous()
-    return _modules["rotary_emb"].rotary_emb(x, freqs_cis)

astrai/inference/__init__.py

@@ -1,95 +1,33 @@
 """Inference module for continuous batching.
 
-Layers:
-  - core/:        Core inference loop (cache, executor, scheduler, task)
-  - api/:         HTTP orchestration (ProtocolHandler, server)
-  - protocols/:   Response builders (OpenAI, Anthropic)
-  - transport/:   SSE transport utilities
-  - engine.py:    Facade (InferenceEngine), Value Object (GenerationRequest)
-  - sample.py:    Strategy pattern (TemperatureStrategy, TopKStrategy, TopPStrategy, FrequencyPenaltyStrategy)
+Subpackages:
+  - cache/:     KV cache (buffers, strategies, pool)
+  - runtime/:   Execution + sampling (executor, CUDA graph, sampling strategies)
+  - task/:      Request lifecycle + performance metrics
+  - network/:   HTTP protocol handling (server, protocol, OpenAI/Anthropic builders)
+
+Modules:
+  - scheduler.py:  Continuous batching loop
+  - workspace.py:  Pre-allocated GPU buffers
+  - engine.py:     Facade (InferenceEngine)
 """
 
-from astrai.inference.api import (
-    AnthropicMessage,
-    BaseToolParser,
-    ChatCompletionRequest,
-    ChatMessage,
-    FunctionDef,
-    GenContext,
-    MessagesRequest,
-    ProtocolHandler,
-    SimpleJsonToolParser,
-    StopChecker,
-    ToolDef,
-    ToolParserFactory,
-    get_app,
-    run_server,
-)
-from astrai.inference.api.anthropic import AnthropicResponseBuilder
-from astrai.inference.api.openai import OpenAIResponseBuilder
-from astrai.inference.core import (
-    STOP,
-    Allocator,
-    Executor,
-    InferenceScheduler,
-    KVCache,
-    KVStorage,
-    PagePool,
-    RadixCache,
-    ReqToTokenPool,
-    Task,
-    TaskManager,
-    TaskStatus,
-    page_hash,
-)
-from astrai.inference.engine import GenerationRequest, InferenceEngine
-from astrai.inference.sample import (
-    BaseSamplingStrategy,
-    FrequencyPenaltyStrategy,
-    SamplingPipeline,
-    TemperatureStrategy,
-    TopKStrategy,
-    TopPStrategy,
-    sample,
-)
+from astrai.inference.engine import InferenceEngine
+from astrai.inference.network import get_app, run_server
+from astrai.inference.runtime.executor import Executor
+from astrai.inference.runtime.sample import sample
+from astrai.inference.scheduler import InferenceScheduler
+from astrai.inference.task import STOP, Task, TaskManager, TaskStatus
 
 __all__ = [
     "InferenceEngine",
-    "GenerationRequest",
     "InferenceScheduler",
     "Executor",
     "STOP",
     "Task",
     "TaskManager",
     "TaskStatus",
-    "Allocator",
-    "KVCache",
-    "KVStorage",
-    "PagePool",
-    "RadixCache",
-    "ReqToTokenPool",
-    "page_hash",
     "sample",
-    "BaseSamplingStrategy",
-    "TemperatureStrategy",
-    "TopKStrategy",
-    "TopPStrategy",
-    "FrequencyPenaltyStrategy",
-    "SamplingPipeline",
-    "ProtocolHandler",
-    "StopChecker",
-    "GenContext",
-    "BaseToolParser",
-    "SimpleJsonToolParser",
-    "ToolParserFactory",
-    "OpenAIResponseBuilder",
-    "AnthropicResponseBuilder",
-    "ChatMessage",
-    "ChatCompletionRequest",
-    "FunctionDef",
-    "ToolDef",
-    "AnthropicMessage",
-    "MessagesRequest",
     "get_app",
     "run_server",
 ]

astrai/inference/cache/__init__.py

@@ -0,0 +1,27 @@
+"""KV cache subsystem: buffers, strategies, pool management."""
+
+from astrai.inference.cache.buffer import KVCache, KVStorage, ReqToTokenPool
+from astrai.inference.cache.pool import PagePool, TaskCacheManager, page_hash
+from astrai.inference.cache.strategy import (
+    AllocationStrategy,
+    Allocator,
+    ContiguousStrategy,
+    PagedStrategy,
+    RadixCache,
+    TaskCacheState,
+)
+
+__all__ = [
+    "KVCache",
+    "KVStorage",
+    "ReqToTokenPool",
+    "Allocator",
+    "RadixCache",
+    "TaskCacheState",
+    "AllocationStrategy",
+    "ContiguousStrategy",
+    "PagedStrategy",
+    "PagePool",
+    "TaskCacheManager",
+    "page_hash",
+]

astrai/inference/cache/buffer.py

@@ -0,0 +1,96 @@
+"""Physical KV cache buffers.
+
+Layer 1 — ``KVStorage``:   flat token-level K/V GPU buffers [n_layers, size, n_kv_heads, head_dim]
+Layer 2 — ``ReqToTokenPool``: index table [req_idx, pos] → physical token slot
+Layer 3 — ``KVCache``:       pure dataclass passed to the model for direct buffer access
+
+These classes have no knowledge of tasks, allocation policies, or scheduling.
+They are the "dumb" physical storage layer.
+"""
+
+import threading
+from dataclasses import dataclass
+from typing import List, Optional
+
+import torch
+from torch import Tensor
+
+
+class ReqToTokenPool:
+    """Maps [req_idx, pos] → physical token slot in KV storage.
+
+    Each row is one request; each column is a sequence position.  The value
+    at [req_idx, pos] is the flat index into the KV storage buffers.
+    """
+
+    def __init__(self, size: int, max_context_len: int, device: torch.device):
+        self.size = size
+        self.max_context_len = max_context_len
+        self.req_to_token = torch.zeros(
+            (size, max_context_len), dtype=torch.int32, device=device
+        )
+        self.free_slots = list(range(size))
+        self._lock = threading.Lock()
+
+    def alloc(self, num_reqs: int) -> Optional[List[int]]:
+        with self._lock:
+            if num_reqs > len(self.free_slots):
+                return None
+            slots = self.free_slots[:num_reqs]
+            self.free_slots = self.free_slots[num_reqs:]
+            return slots
+
+    def free(self, req_indices: List[int]):
+        with self._lock:
+            self.free_slots.extend(req_indices)
+
+    def write(self, indices, values):
+        self.req_to_token[indices] = values
+
+
+class KVStorage:
+    """Token-level KV cache storage.
+
+    Buffers: ``[n_layers, size, n_kv_heads, head_dim]``.  Each token occupies
+    one slot indexed by ``ReqToTokenPool``.
+    """
+
+    def __init__(
+        self,
+        size: int,
+        n_layers: int,
+        n_kv_heads: int,
+        head_dim: int,
+        device: torch.device,
+        dtype: torch.dtype,
+    ):
+        self.size = size
+        self.k_buffer = torch.empty(
+            (n_layers, size, n_kv_heads, head_dim), device=device, dtype=dtype
+        )
+        self.v_buffer = torch.empty(
+            (n_layers, size, n_kv_heads, head_dim), device=device, dtype=dtype
+        )
+
+
+@dataclass
+class KVCache:
+    """Pure data struct passed to model for KV cache I/O.
+
+    The attention layer does raw buffer indexing — no methods, no abstraction.
+    """
+
+    k_buffer: Tensor
+    v_buffer: Tensor
+    req_to_token: Tensor
+    req_pool_indices: Tensor
+    seq_lens: Tensor
+    out_cache_loc: Tensor
+    max_len: int = 0
+    kv_indptr: Optional[Tensor] = None
+    qo_indptr: Optional[Tensor] = None
+    q_tile_to_batch: Optional[Tensor] = None
+    q_tile_to_index: Optional[Tensor] = None
+    decode_o_part: Optional[Tensor] = None
+    decode_ml_part: Optional[Tensor] = None
+    decode_out: Optional[Tensor] = None

astrai/inference/cache/pool.py

@@ -0,0 +1,382 @@
+"""KV cache orchestration: PagePool + TaskCacheManager.
+
+PagePool owns the physical buffers (``KVStorage`` + ``ReqToTokenPool``)
+and wires them to an allocation strategy.  It assembles the ``KVCache``
+dataclass passed to the model forward.
+
+TaskCacheManager owns the ``task_id`` → ``TaskCacheState`` mapping and
+delegates physical slot allocation to the strategy, and KV bind to the pool.
+
+See ``cache_buffer.py`` for the raw buffer primitives and ``cache_strategy.py``
+for the allocation policies.
+"""
+
+from dataclasses import dataclass
+from typing import Dict, List, Optional
+
+import torch
+
+from astrai.inference.cache.buffer import KVCache, KVStorage, ReqToTokenPool
+from astrai.inference.cache.strategy import (
+    AllocationStrategy,
+    Allocator,
+    ContiguousStrategy,
+    PagedStrategy,
+    RadixCache,
+    TaskCacheState,
+)
+from astrai.inference.workspace import Q_TILE_ROWS, InferenceWorkspace
+
+# Re-export everything so existing ``from astrai.inference.cache import ...``
+# continues to work unchanged after the file split.
+__all__ = [
+    "KVCache",
+    "KVStorage",
+    "ReqToTokenPool",
+    "Allocator",
+    "RadixCache",
+    "AllocationStrategy",
+    "ContiguousStrategy",
+    "PagedStrategy",
+    "PagePool",
+    "TaskCacheManager",
+    "TaskCacheState",
+    "page_hash",
+]
+
+# ---- helpers ----
+
+
+def page_hash(
+    token_ids: List[int], page_idx: int, page_size: int, parent_hash: int = 0
+) -> int:
+    start = page_idx * page_size
+    end = min(start + page_size, len(token_ids))
+    h = parent_hash
+    for i in range(start, end):
+        h = (h * 31 + token_ids[i]) & 0xFFFFFFFFFFFFFFFF
+    return h
+
+
+def _is_steady_increment(
+    prev_sig: Optional[tuple],
+    prev_vals: Optional[List[int]],
+    cur_sig: tuple,
+    cur_vals: List[int],
+) -> bool:
+    return (
+        prev_sig is not None
+        and prev_vals is not None
+        and prev_sig == cur_sig
+        and len(prev_vals) == len(cur_vals)
+        and all(c == p + 1 for c, p in zip(cur_vals, prev_vals))
+    )
+
+
+# ---- task-scoped bind state ----
+@dataclass
+class _BindState:
+    """Cached bind metadata for steady-state decode increment detection."""
+
+    sig: tuple
+    seq_lens: List[int]
+
+
+# ---- pool + manager ----
+
+
+class PagePool:
+    """Physical KV cache: buffers + req-to-token table + allocation strategy + bind.
+
+    Does not know about tasks — task lifecycle is managed by
+    :class:`TaskCacheManager`, which holds a reference to this pool.
+    """
+
+    def __init__(
+        self,
+        n_layers: int,
+        n_kv_heads: int,
+        head_dim: int,
+        max_batch_size: int,
+        max_seq_len: int,
+        device: torch.device,
+        dtype: torch.dtype,
+        page_size: int = 1,
+        n_tokens: Optional[int] = None,
+    ):
+        self.page_size = page_size
+        self.max_batch_size = max_batch_size
+        self.max_seq_len = max_seq_len
+        self.device = device
+        self.dtype = dtype
+        self.n_layers = n_layers
+        self.n_kv_heads = n_kv_heads
+        self.head_dim = head_dim
+
+        self.contiguous = n_tokens is None
+        self.n_tokens = max_batch_size * max_seq_len if self.contiguous else n_tokens
+        if self.n_tokens > torch.iinfo(torch.int32).max:
+            raise ValueError("KV cache token count exceeds the int32 slot index limit")
+
+        self._storage = KVStorage(
+            self.n_tokens, n_layers, n_kv_heads, head_dim, device, dtype
+        )
+        self._req_pool = ReqToTokenPool(max_batch_size, max_seq_len, device)
+
+        if self.contiguous:
+            for i in range(max_batch_size):
+                self._req_pool.req_to_token[i] = torch.arange(
+                    i * max_seq_len,
+                    (i + 1) * max_seq_len,
+                    dtype=torch.int32,
+                    device=device,
+                )
+            self._strategy: AllocationStrategy = ContiguousStrategy()
+        else:
+            n_pages = self.n_tokens // page_size
+            alloc = Allocator(n_pages)
+            prefix = RadixCache(page_size) if page_size > 1 else None
+            if prefix is not None:
+                alloc.on_evict = prefix.evict
+            self._strategy = PagedStrategy(
+                alloc, prefix, page_size, self._req_pool, device
+            )
+
+    @property
+    def strategy(self) -> AllocationStrategy:
+        return self._strategy
+
+    @property
+    def req_pool(self) -> ReqToTokenPool:
+        return self._req_pool
+
+    def bind_tasks(
+        self,
+        req_indices: List[int],
+        seq_lens: List[int],
+        workspace: InferenceWorkspace,
+        device: Optional[torch.device] = None,
+        start_pos: Optional[int] = None,
+        incremental: bool = False,
+    ) -> KVCache:
+        """Assemble the ``KVCache`` metadata for a batch of tasks.
+
+        Args:
+            req_indices: request slot indices (from ``ReqToTokenPool``).
+            seq_lens:    current sequence length per task.
+            workspace:   pre-allocated fixed-shape buffers (CUDA-graph safe).
+            start_pos:   if set, produce **prefill** cache (full q_len range).
+                         If ``None``, produce **decode** cache (last position).
+            incremental: if ``True``, reuse workspace state from previous step
+                         by incrementing counters in-place (decode hot path).
+
+        Returns:
+            ``KVCache`` dataclass with the correct output shapes for the
+            attention backend (prefill: ``[B, q_len]``, decode: ``[B, 1]``).
+        """
+        if device is None:
+            device = workspace.device
+        b = len(req_indices)
+
+        rpi_buf = workspace.req_pool_indices
+        sl_buf = workspace.seq_lens
+        kvp_buf = workspace.kv_indptr
+        inc_buf = workspace.inc
+        ocl_buf = workspace.out_cache_loc
+
+        if incremental:
+            sl_buf[:b] += 1
+            kvp_buf[: b + 1] += inc_buf[: b + 1]
+        else:
+            rpi_buf[:b].copy_(
+                torch.tensor(req_indices, dtype=torch.int32, device=device)
+            )
+            sl_buf[:b].copy_(torch.tensor(seq_lens, dtype=torch.long, device=device))
+            kvp_buf[: b + 1].zero_()
+            kvp_buf[1 : b + 1] = sl_buf[:b].cumsum(0).to(torch.int32)
+
+        req_pool_indices = rpi_buf[:b]
+        seq_lens_t = sl_buf[:b]
+        kv_indptr = kvp_buf[: b + 1]
+
+        if start_pos is not None:
+            # Packed prefill concatenates each request's query tokens.
+            q_lens = [seq_len - start_pos for seq_len in seq_lens]
+            if any(q_len <= 0 for q_len in q_lens):
+                raise ValueError("prefill sequence lengths must exceed start_pos")
+            out_cache_loc = torch.cat(
+                [
+                    self._req_pool.req_to_token[
+                        req_pool_indices[i], start_pos : seq_lens[i]
+                    ]
+                    for i in range(b)
+                ]
+            )
+            workspace.qo_indptr[: b + 1].zero_()
+            workspace.qo_indptr[1 : b + 1].copy_(
+                torch.tensor(q_lens, dtype=torch.int32, device=device).cumsum(0)
+            )
+            qo_indptr = workspace.qo_indptr[: b + 1]
+            tile_batches = []
+            tile_indices = []
+            for batch, q_len in enumerate(q_lens):
+                n_tiles = (q_len + Q_TILE_ROWS - 1) // Q_TILE_ROWS
+                tile_batches.extend([batch] * n_tiles)
+                tile_indices.extend(range(n_tiles))
+            n_tiles = len(tile_batches)
+            workspace.q_tile_to_batch[:n_tiles].copy_(
+                torch.tensor(tile_batches, dtype=torch.int32, device=device)
+            )
+            workspace.q_tile_to_index[:n_tiles].copy_(
+                torch.tensor(tile_indices, dtype=torch.int32, device=device)
+            )
+            q_tile_to_batch = workspace.q_tile_to_batch[:n_tiles]
+            q_tile_to_index = workspace.q_tile_to_index[:n_tiles]
+            decode_o_part = decode_ml_part = decode_out = None
+        else:
+            # ---- decode: out_cache_loc is a single column (last position) ----
+            write_pos = seq_lens_t - 1
+            loc = self._req_pool.req_to_token[req_pool_indices, write_pos].unsqueeze(-1)
+            ocl_buf[:b].copy_(loc)
+            out_cache_loc = ocl_buf[:b].reshape(-1)
+            workspace.qo_indptr[: b + 1].copy_(inc_buf[: b + 1])
+            qo_indptr = workspace.qo_indptr[: b + 1]
+            q_tile_to_batch = q_tile_to_index = None
+            decode_o_part = getattr(workspace, "decode_o_part", None)
+            decode_ml_part = getattr(workspace, "decode_ml_part", None)
+            decode_out = getattr(workspace, "decode_out", None)
+
+        return KVCache(
+            k_buffer=self._storage.k_buffer,
+            v_buffer=self._storage.v_buffer,
+            req_to_token=self._req_pool.req_to_token,
+            req_pool_indices=req_pool_indices,
+            seq_lens=seq_lens_t,
+            out_cache_loc=out_cache_loc,
+            max_len=max(seq_lens),
+            kv_indptr=kv_indptr,
+            qo_indptr=qo_indptr,
+            q_tile_to_batch=q_tile_to_batch,
+            q_tile_to_index=q_tile_to_index,
+            decode_o_part=decode_o_part,
+            decode_ml_part=decode_ml_part,
+            decode_out=decode_out,
+        )
+
+
+class TaskCacheManager:
+    """Task ↔ KV slot lifecycle manager.
+
+    Sole owner of ``task_id → TaskCacheState``.  Delegates physical slot
+    allocation to the strategy (via ``pool.strategy``) and KV bind to
+    ``pool.bind_tasks()``.
+
+    Usage::
+
+        pool = PagePool(...)
+        mgr = TaskCacheManager(pool)
+        mgr.task_alloc("req_1", [101, 202, 303])
+        ...
+        kv = mgr.bind(["req_1"], workspace)
+    """
+
+    def __init__(self, pool: PagePool):
+        self._pool = pool
+        self._strategy = pool.strategy
+        self._req_pool = pool.req_pool
+        self._max_seq_len = pool.max_seq_len
+        self._states: Dict[str, TaskCacheState] = {}
+        self._bind_state: Optional[_BindState] = None
+        self._bind_was_steady = False
+
+    # -- public task lifecycle --
+
+    def task_alloc(self, task_id: str, prompt_ids: List[int]) -> bool:
+        self._bind_state = None
+        req_slots = self._req_pool.alloc(1)
+        if req_slots is None:
+            return False
+        state = TaskCacheState(req_idx=req_slots[0])
+        self._states[task_id] = state
+        if not self._strategy.alloc(state, prompt_ids):
+            self._rollback(state, task_id)
+            return False
+        self._strategy.write_indices(state, prompt_ids)
+        state.length = len(prompt_ids)
+        return True
+
+    def task_free(self, task_id: str):
+        self._bind_state = None
+        state = self._states.pop(task_id, None)
+        if state is None:
+            return
+        self._strategy.free(state)
+        self._req_pool.free([state.req_idx])
+
+    def task_extend(self, task_id: str, pos: int) -> bool:
+        state = self._states.get(task_id)
+        if state is None or pos >= self._max_seq_len:
+            return False
+        if not self._strategy.extend(state, pos):
+            return False
+        state.length = pos + 1
+        return True
+
+    def task_cached(self, task_id: str) -> int:
+        state = self._states.get(task_id)
+        return state.cached if state is not None else 0
+
+    def task_record_hashes(
+        self, task_id: str, prompt_ids: List[int], start_logical_page: int = 0
+    ):
+        state = self._states.get(task_id)
+        if state is not None:
+            self._strategy.record_hashes(state, prompt_ids, start_logical_page)
+
+    @staticmethod
+    def task_cacheable_ids(task_id: str, prompt_ids: List[int], output_ids: List[int]):
+        return list(prompt_ids) + list(output_ids[:-1])
+
+    # -- bind (assemble KVCache for the model forward) --
+
+    def bind(
+        self,
+        task_ids: List[str],
+        workspace: InferenceWorkspace,
+        device: Optional[torch.device] = None,
+        start_pos: Optional[int] = None,
+    ) -> KVCache:
+        """Build ``KVCache`` for an ordered list of task IDs."""
+        states = [self._states[tid] for tid in task_ids]
+        req_indices = [s.req_idx for s in states]
+        seq_lens = [s.length for s in states]
+        sig = tuple(req_indices)
+
+        prev = self._bind_state
+        incremental = (
+            start_pos is None
+            and prev is not None
+            and _is_steady_increment(prev.sig, prev.seq_lens, sig, seq_lens)
+        )
+        self._bind_state = _BindState(sig, list(seq_lens))
+        self._bind_was_steady = incremental
+
+        return self._pool.bind_tasks(
+            req_indices,
+            seq_lens,
+            workspace,
+            device=device,
+            start_pos=start_pos,
+            incremental=incremental,
+        )
+
+    @property
+    def bind_was_steady(self) -> bool:
+        return self._bind_was_steady
+
+    # -- internals --
+
+    def _rollback(self, state: TaskCacheState, task_id: str):
+        self._strategy.free(state)
+        self._req_pool.free([state.req_idx])
+        self._states.pop(task_id, None)

astrai/inference/cache/strategy.py

@@ -0,0 +1,318 @@
+"""KV cache allocation layer.
+
+Encapsulates the physical slot allocation policy, isolated from GPU buffers
+and task lifecycle management.
+
+- ``TaskCacheState``: data contract between strategy and manager (per-task slot state)
+- ``Allocator``:       bitmask-based page allocator with LRU eviction
+- ``RadixCache``:      page-granular prefix index (exact token match)
+- ``AllocationStrategy``: ABC for physical slot allocation
+- ``ContiguousStrategy``: statically partitioned, no dynamic allocation
+- ``PagedStrategy``:    dynamic paged allocation from a shared pool
+"""
+
+import threading
+from abc import ABC, abstractmethod
+from dataclasses import dataclass, field
+from typing import Callable, Dict, List, Optional, OrderedDict
+
+from astrai.inference.cache.buffer import ReqToTokenPool
+
+# ---- data contract: per-task slot state ----
+
+
+@dataclass
+class TaskCacheState:
+    """Per-task cache allocation state.
+
+    Co-locates all task-owned cache metadata so the alloc/free/extend
+    lifecycle is atomic.  Owned by ``TaskCacheManager``, consumed by
+    every ``AllocationStrategy`` method.
+    """
+
+    req_idx: int
+    length: int = 0
+    cached: int = 0
+    pages: List[int] = field(default_factory=list)
+
+
+# ---- allocation primitives ----
+
+
+class Allocator:
+    """Bitmask-based page allocator with ref-counting and LRU eviction."""
+
+    def __init__(self, n_pages: int):
+        self._free_mask = (1 << n_pages) - 1
+        self._refs: List[int] = [0] * n_pages
+        self._lru: OrderedDict[int, None] = OrderedDict()
+        self.on_evict: Optional[Callable[[int], None]] = None
+        self._lock = threading.Lock()
+
+    def alloc(self) -> int:
+        with self._lock:
+            if self._free_mask:
+                lsb = self._free_mask & -self._free_mask
+                idx = lsb.bit_length() - 1
+                self._free_mask ^= lsb
+                self._refs[idx] = 1
+                return idx
+            if self._lru:
+                idx, _ = self._lru.popitem(last=False)
+                if self.on_evict:
+                    self.on_evict(idx)
+                self._refs[idx] = 1
+                self._free_mask &= ~(1 << idx)
+                return idx
+            return -1
+
+    def free(self, idx: int, keep_cached: bool = False):
+        with self._lock:
+            self._refs[idx] -= 1
+            if self._refs[idx] == 0:
+                if keep_cached:
+                    self._lru[idx] = None
+                else:
+                    self._free_mask |= 1 << idx
+
+    def inc_ref(self, idx: int):
+        with self._lock:
+            self._refs[idx] += 1
+            self._lru.pop(idx, None)
+
+    def ref_count(self, idx: int) -> int:
+        with self._lock:
+            return self._refs[idx]
+
+    def touch(self, idx: int):
+        with self._lock:
+            if idx in self._lru:
+                self._lru.move_to_end(idx)
+
+
+class RadixNode:
+    """A page-aligned edge in the CPU-side prefix radix trie."""
+
+    __slots__ = ("parent", "children", "page_idx", "tokens", "lock_ref")
+
+    def __init__(self, parent=None, tokens=(), page_idx=None):
+        self.parent = parent
+        self.children: Dict[tuple, "RadixNode"] = {}
+        self.page_idx = page_idx
+        self.tokens = tuple(tokens)
+        self.lock_ref = 0
+
+
+class RadixCache:
+    """Page-granular radix prefix index with exact token matching."""
+
+    def __init__(self, page_size: int):
+        self._page_size = page_size
+        self._root = RadixNode()
+        self._page_to_node: Dict[int, RadixNode] = {}
+        self._lock = threading.Lock()
+
+    def evict(self, idx: int):
+        with self._lock:
+            node = self._page_to_node.pop(idx, None)
+            if node is None:
+                return
+            node.page_idx = None
+            parent = node.parent
+            if parent is not None:
+                parent.children.pop(node.tokens, None)
+
+    def has_page(self, idx: int) -> bool:
+        with self._lock:
+            return idx in self._page_to_node
+
+    def lookup(self, token_ids: List[int]) -> List[int]:
+        with self._lock:
+            full_pages = len(token_ids) // self._page_size
+            hits: List[int] = []
+            node = self._root
+            for i in range(full_pages):
+                start = i * self._page_size
+                page_tokens = tuple(token_ids[start : start + self._page_size])
+                child = node.children.get(page_tokens)
+                if child is None or child.page_idx is None:
+                    break
+                hits.append(child.page_idx)
+                node = child
+            return hits
+
+    def record(self, page_idx: int, token_ids: List[int], logical_page_idx: int):
+        with self._lock:
+            full_pages = len(token_ids) // self._page_size
+            if logical_page_idx >= full_pages:
+                return
+            old = self._page_to_node.pop(page_idx, None)
+            if old is not None and old.parent is not None:
+                old.parent.children.pop(old.tokens, None)
+
+            node = self._root
+            for i in range(logical_page_idx + 1):
+                start = i * self._page_size
+                page_tokens = tuple(token_ids[start : start + self._page_size])
+                child = node.children.get(page_tokens)
+                if child is None:
+                    child = RadixNode(node, page_tokens)
+                    node.children[page_tokens] = child
+                node = child
+            if node.page_idx is not None and node.page_idx != page_idx:
+                replaced = node.page_idx
+                self._page_to_node.pop(replaced, None)
+            node.page_idx = page_idx
+            self._page_to_node[page_idx] = node
+
+    def release(self, pages: List[int]) -> None:
+        with self._lock:
+            for page_idx in pages:
+                node = self._page_to_node.get(page_idx)
+                if node is not None and node.lock_ref:
+                    node.lock_ref -= 1
+
+
+class AllocationStrategy(ABC):
+    """Physical slot allocation policy.
+
+    Subclasses implement the actual allocation semantics.  This ABC declares
+    the contract; there are no default implementations.
+    """
+
+    @abstractmethod
+    def alloc(self, state: TaskCacheState, prompt_ids: List[int]) -> bool: ...
+
+    @abstractmethod
+    def free(self, state: TaskCacheState) -> None: ...
+
+    @abstractmethod
+    def extend(self, state: TaskCacheState, pos: int) -> bool: ...
+
+    @abstractmethod
+    def write_indices(self, state: TaskCacheState, prompt_ids: List[int]) -> None: ...
+
+    @abstractmethod
+    def record_hashes(
+        self,
+        state: TaskCacheState,
+        prompt_ids: List[int],
+        start: int,
+    ) -> None: ...
+
+
+class ContiguousStrategy(AllocationStrategy):
+    """Static contiguous allocation: slots are pre-assigned at pool init.
+
+    No dynamic allocation or prefix caching.  All operations are no-ops
+    because ``ReqToTokenPool`` is pre-filled with contiguous ranges.
+    """
+
+    def alloc(self, state: TaskCacheState, prompt_ids: List[int]) -> bool:
+        return True
+
+    def free(self, state: TaskCacheState) -> None:
+        pass
+
+    def extend(self, state: TaskCacheState, pos: int) -> bool:
+        return True
+
+    def write_indices(self, state: TaskCacheState, prompt_ids: List[int]) -> None:
+        pass
+
+    def record_hashes(
+        self,
+        state: TaskCacheState,
+        prompt_ids: List[int],
+        start: int,
+    ) -> None:
+        pass
+
+
+class PagedStrategy(AllocationStrategy):
+    """Dynamic paged allocation from a shared bitmask pool.
+
+    ``page_size`` is a parameter, not a separate strategy: at ``page_size=1``
+    each allocated page *is* one token slot (``page * 1 + 0``), and prefix
+    caching is simply disabled (``prefix=None``).  The unified page formula
+    ``pages[page_idx] * page_size + offset`` holds for both.
+    """
+
+    def __init__(
+        self,
+        alloc: Allocator,
+        prefix: Optional[RadixCache],
+        page_size: int,
+        req_pool: ReqToTokenPool,
+        device,
+    ):
+        self._alloc = alloc
+        self._prefix = prefix
+        self._page_size = page_size
+        self._req_pool = req_pool
+        self._device = device
+
+    def alloc(self, state: TaskCacheState, prompt_ids: List[int]) -> bool:
+        if self._prefix is not None:
+            hits = self._prefix.lookup(prompt_ids)
+            state.cached = len(hits) * self._page_size
+            for p in hits:
+                self._alloc.inc_ref(p)
+            state.pages = list(hits)
+
+        remaining = len(prompt_ids) - state.cached
+        if remaining <= 0:
+            return True
+        n_new = (remaining + self._page_size - 1) // self._page_size
+        for _ in range(n_new):
+            p = self._alloc.alloc()
+            if p < 0:
+                return False
+            state.pages.append(p)
+        return True
+
+    def free(self, state: TaskCacheState) -> None:
+        if self._prefix is not None:
+            for p in state.pages:
+                keep = self._prefix.has_page(p)
+                self._alloc.free(p, keep_cached=keep)
+                if not keep:
+                    self._prefix.evict(p)
+        else:
+            for p in state.pages:
+                self._alloc.free(p)
+
+    def extend(self, state: TaskCacheState, pos: int) -> bool:
+        page_idx = pos // self._page_size
+        if page_idx >= len(state.pages):
+            p = self._alloc.alloc()
+            if p < 0:
+                return False
+            state.pages.append(p)
+        offset = pos % self._page_size
+        self._req_pool.req_to_token[state.req_idx, pos] = (
+            state.pages[page_idx] * self._page_size + offset
+        )
+        return True
+
+    def write_indices(self, state: TaskCacheState, prompt_ids: List[int]) -> None:
+        total = len(prompt_ids)
+        for pos in range(total):
+            page_idx = pos // self._page_size
+            offset = pos % self._page_size
+            if page_idx < len(state.pages):
+                self._req_pool.req_to_token[state.req_idx, pos] = (
+                    state.pages[page_idx] * self._page_size + offset
+                )
+
+    def record_hashes(
+        self,
+        state: TaskCacheState,
+        prompt_ids: List[int],
+        start: int,
+    ) -> None:
+        if self._prefix is None:
+            return
+        full = len(prompt_ids) // self._page_size
+        for i in range(start, min(full, len(state.pages))):
+            self._prefix.record(state.pages[i], prompt_ids, i)

astrai/inference/core/__init__.py

@@ -1,30 +0,0 @@
-"""Inference core: cache, executor, scheduler, task management."""
-
-from astrai.inference.core.cache import (
-    Allocator,
-    KVCache,
-    KVStorage,
-    PagePool,
-    RadixCache,
-    ReqToTokenPool,
-    page_hash,
-)
-from astrai.inference.core.executor import Executor
-from astrai.inference.core.scheduler import InferenceScheduler
-from astrai.inference.core.task import STOP, Task, TaskManager, TaskStatus
-
-__all__ = [
-    "Allocator",
-    "KVCache",
-    "KVStorage",
-    "PagePool",
-    "RadixCache",
-    "ReqToTokenPool",
-    "page_hash",
-    "Executor",
-    "InferenceScheduler",
-    "STOP",
-    "Task",
-    "TaskManager",
-    "TaskStatus",
-]

astrai/inference/core/cache.py

@@ -1,623 +0,0 @@
-"""KV cache architecture: three-layer separation (SGLang-inspired).
-
-Layer 1 — KVStorage:      flat token-level K/V buffers [n_layers, size, H, D]
-Layer 2 — ReqToTokenPool:  index table [req_idx, pos] → physical token slot
-Layer 3 — Allocator:       slot/page allocation with ref-counting and LRU
-
-PagePool orchestrates all three plus RadixCache (prefix addressing).
-KVCache is a pure dataclass passed to the model for direct buffer access.
-
-Two modes:
-  - contiguous (default): pre-allocated per-request blocks, no dynamic alloc
-  - paged: shared pool with on-demand allocation, prefix caching support
-"""
-
-import threading
-from collections import OrderedDict
-from dataclasses import dataclass
-from typing import Callable, Dict, List, Optional
-
-import torch
-from torch import Tensor
-
-from astrai.inference.core.workspace import InferenceWorkspace
-
-
-def page_hash(
-    token_ids: List[int], page_idx: int, page_size: int, parent_hash: int = 0
-) -> int:
-    start = page_idx * page_size
-    end = min(start + page_size, len(token_ids))
-    h = parent_hash
-    for i in range(start, end):
-        h = (h * 31 + token_ids[i]) & 0xFFFFFFFFFFFFFFFF
-    return h
-
-
-class Allocator:
-    """Bitmask-based page allocator with ref-counting and LRU eviction."""
-
-    def __init__(self, n_pages: int):
-        self._free_mask = (1 << n_pages) - 1
-        self._refs: List[int] = [0] * n_pages
-        self._lru: OrderedDict[int, None] = OrderedDict()
-        self.on_evict: Optional[Callable[[int], None]] = None
-        self._lock = threading.Lock()
-
-    def alloc(self) -> int:
-        with self._lock:
-            if self._free_mask:
-                lsb = self._free_mask & -self._free_mask
-                idx = lsb.bit_length() - 1
-                self._free_mask ^= lsb
-                self._refs[idx] = 1
-                return idx
-            if self._lru:
-                idx, _ = self._lru.popitem(last=False)
-                if self.on_evict:
-                    self.on_evict(idx)
-                self._refs[idx] = 1
-                self._free_mask &= ~(1 << idx)
-                return idx
-            return -1
-
-    def free(self, idx: int, keep_cached: bool = False):
-        with self._lock:
-            self._refs[idx] -= 1
-            if self._refs[idx] == 0:
-                if keep_cached:
-                    self._lru[idx] = None
-                else:
-                    self._free_mask |= 1 << idx
-
-    def inc_ref(self, idx: int):
-        with self._lock:
-            self._refs[idx] += 1
-            self._lru.pop(idx, None)
-
-    def ref_count(self, idx: int) -> int:
-        with self._lock:
-            return self._refs[idx]
-
-    def touch(self, idx: int):
-        with self._lock:
-            if idx in self._lru:
-                self._lru.move_to_end(idx)
-
-
-class RadixNode:
-    """A page-aligned edge in the CPU-side prefix radix."""
-
-    __slots__ = ("parent", "children", "page_idx", "tokens", "lock_ref")
-
-    def __init__(self, parent=None, tokens=(), page_idx=None):
-        self.parent = parent
-        self.children: Dict[tuple, "RadixNode"] = {}
-        self.page_idx = page_idx
-        self.tokens = tuple(tokens)
-        self.lock_ref = 0
-
-
-class RadixCache:
-    """Page-granular radix prefix index with exact token matching."""
-
-    def __init__(self, page_size: int):
-        self._page_size = page_size
-        self._root = RadixNode()
-        self._page_to_node: Dict[int, RadixNode] = {}
-        # Retained as an introspection-compatible map; matching never relies on
-        # this lossy value.
-        self._page_to_hash: Dict[int, int] = {}
-        self._lock = threading.Lock()
-
-    def evict(self, idx: int):
-        with self._lock:
-            node = self._page_to_node.pop(idx, None)
-            self._page_to_hash.pop(idx, None)
-            if node is None:
-                return
-            node.page_idx = None
-            parent = node.parent
-            if parent is not None:
-                parent.children.pop(node.tokens, None)
-
-    def has_page(self, idx: int) -> bool:
-        with self._lock:
-            return idx in self._page_to_node
-
-    def lookup(self, token_ids: List[int]) -> List[int]:
-        with self._lock:
-            full_pages = len(token_ids) // self._page_size
-            hits: List[int] = []
-            node = self._root
-            for i in range(full_pages):
-                start = i * self._page_size
-                page_tokens = tuple(token_ids[start : start + self._page_size])
-                child = node.children.get(page_tokens)
-                if child is None or child.page_idx is None:
-                    break
-                hits.append(child.page_idx)
-                node = child
-            return hits
-
-    def record(self, page_idx: int, token_ids: List[int], logical_page_idx: int):
-        with self._lock:
-            full_pages = len(token_ids) // self._page_size
-            if logical_page_idx >= full_pages:
-                return
-            old = self._page_to_node.pop(page_idx, None)
-            self._page_to_hash.pop(page_idx, None)
-            if old is not None and old.parent is not None:
-                old.parent.children.pop(old.tokens, None)
-
-            node = self._root
-            for i in range(logical_page_idx + 1):
-                start = i * self._page_size
-                page_tokens = tuple(token_ids[start : start + self._page_size])
-                child = node.children.get(page_tokens)
-                if child is None:
-                    child = RadixNode(node, page_tokens)
-                    node.children[page_tokens] = child
-                node = child
-            if node.page_idx is not None and node.page_idx != page_idx:
-                replaced = node.page_idx
-                self._page_to_node.pop(replaced, None)
-                self._page_to_hash.pop(replaced, None)
-            node.page_idx = page_idx
-            self._page_to_node[page_idx] = node
-            self._page_to_hash[page_idx] = page_hash(
-                token_ids, logical_page_idx, self._page_size
-            )
-
-    def release(self, pages: List[int]) -> None:
-        with self._lock:
-            for page_idx in pages:
-                node = self._page_to_node.get(page_idx)
-                if node is not None and node.lock_ref:
-                    node.lock_ref -= 1
-
-
-class ReqToTokenPool:
-    """Maps [req_idx, pos] -> physical token slot in KV storage.
-
-    Each row is one request; each column is a sequence position. The value
-    at [req_idx, pos] is the flat index into the KV storage buffers.
-    """
-
-    def __init__(self, size: int, max_context_len: int, device: torch.device):
-        self.size = size
-        self.max_context_len = max_context_len
-        self.req_to_token = torch.zeros(
-            (size, max_context_len), dtype=torch.long, device=device
-        )
-        self.free_slots = list(range(size))
-        self._lock = threading.Lock()
-
-    def alloc(self, num_reqs: int) -> Optional[List[int]]:
-        with self._lock:
-            if num_reqs > len(self.free_slots):
-                return None
-            slots = self.free_slots[:num_reqs]
-            self.free_slots = self.free_slots[num_reqs:]
-            return slots
-
-    def free(self, req_indices: List[int]):
-        with self._lock:
-            self.free_slots.extend(req_indices)
-
-    def write(self, indices, values):
-        self.req_to_token[indices] = values
-
-
-class KVStorage:
-    """Token-level KV cache storage.
-
-    Buffers: [n_layers, size, n_kv_heads, head_dim]. Each token occupies
-    one slot indexed by ReqToTokenPool.
-    """
-
-    def __init__(
-        self,
-        size: int,
-        n_layers: int,
-        n_kv_heads: int,
-        head_dim: int,
-        device: torch.device,
-        dtype: torch.dtype,
-    ):
-        self.size = size
-        self.k_buffer = torch.empty(
-            (n_layers, size, n_kv_heads, head_dim), device=device, dtype=dtype
-        )
-        self.v_buffer = torch.empty(
-            (n_layers, size, n_kv_heads, head_dim), device=device, dtype=dtype
-        )
-
-    def get_key_buffer(self, layer_id: int) -> Tensor:
-        return self.k_buffer[layer_id]
-
-    def get_value_buffer(self, layer_id: int) -> Tensor:
-        return self.v_buffer[layer_id]
-
-    def set_kv_buffer(self, layer_id: int, loc: Tensor, k: Tensor, v: Tensor) -> None:
-        self.k_buffer[layer_id, loc] = k
-        self.v_buffer[layer_id, loc] = v
-
-
-@dataclass
-class KVCache:
-    """Pure data struct passed to model for KV cache I/O.
-
-    The attention layer does raw buffer indexing — no methods, no abstraction.
-
-    Attributes:
-        k_buffer: [n_layers, size, n_kv_heads, head_dim]
-        v_buffer: [n_layers, size, n_kv_heads, head_dim]
-        req_to_token: [num_reqs, max_ctx_len] — index table
-        req_pool_indices: [batch_size] — row indices into req_to_token
-        seq_lens: [batch_size] — per-request total sequence lengths
-        out_cache_loc: [batch, new_seq_len] or [batch, 1] — write indices
-        max_len: max(seq_lens) as Python int — avoids GPU sync in decode
-        kv_indptr: [batch+1] int32 — prefix sum of seq_lens, precomputed once
-            per step so the attention backend avoids rebuilding it per layer.
-    """
-
-    k_buffer: Tensor
-    v_buffer: Tensor
-    req_to_token: Tensor
-    req_pool_indices: Tensor
-    seq_lens: Tensor
-    out_cache_loc: Tensor
-    max_len: int = 0
-    kv_indptr: Optional[Tensor] = None
-    qo_indptr: Optional[Tensor] = None
-
-
-class PagePool:
-    """Top-level KV cache manager.
-
-    Combines KVStorage + ReqToTokenPool + Allocator + RadixCache.
-
-    Args:
-        n_layers: Number of transformer layers.
-        n_kv_heads: Number of KV attention heads.
-        head_dim: Dimension per head.
-        max_batch_size: Maximum concurrent requests.
-        max_seq_len: Maximum sequence length per request.
-        device, dtype: Tensor device and dtype.
-        page_size: Page size for paged mode (1 = token-level).
-        n_tokens: Total token slots for paged mode. None = contiguous mode
-            (pre-allocates max_batch_size * max_seq_len).
-    """
-
-    def __init__(
-        self,
-        n_layers: int,
-        n_kv_heads: int,
-        head_dim: int,
-        max_batch_size: int,
-        max_seq_len: int,
-        device: torch.device,
-        dtype: torch.dtype,
-        page_size: int = 1,
-        n_tokens: Optional[int] = None,
-    ):
-        self.page_size = page_size
-        self.max_batch_size = max_batch_size
-        self.max_seq_len = max_seq_len
-        self.device = device
-        self.dtype = dtype
-        self.n_layers = n_layers
-        self.n_kv_heads = n_kv_heads
-        self.head_dim = head_dim
-
-        self.contiguous = n_tokens is None
-        if self.contiguous:
-            self.n_tokens = max_batch_size * max_seq_len
-        else:
-            self.n_tokens = n_tokens
-
-        self._storage = KVStorage(
-            self.n_tokens, n_layers, n_kv_heads, head_dim, device, dtype
-        )
-        self._req_pool = ReqToTokenPool(max_batch_size, max_seq_len, device)
-
-        if self.contiguous:
-            for i in range(max_batch_size):
-                self._req_pool.req_to_token[i] = torch.arange(
-                    i * max_seq_len, (i + 1) * max_seq_len, device=device
-                )
-            self._alloc: Optional[Allocator] = None
-            self._prefix: Optional[RadixCache] = None
-        else:
-            n_pages = self.n_tokens // page_size
-            self._alloc = Allocator(n_pages)
-            self._prefix = RadixCache(page_size) if page_size > 1 else None
-            if self._prefix is not None:
-                self._alloc.on_evict = self._prefix.evict
-
-        self._task_req: Dict[str, int] = {}
-        self._task_len: Dict[int, int] = {}
-        self._task_cached: Dict[str, int] = {}
-        self._task_slots: Dict[str, List[int]] = {}
-        self._task_pages: Dict[str, List[int]] = {}
-        self._lock = threading.Lock()
-
-        # Steady-state decode validation state: the ordered task set and its
-        # Python seq_lens mirror.  When the same set advances every sequence
-        # by exactly one token per step, bind_tasks updates the stable
-        # buffers in-place (+=1 / +=inc) instead of re-cumsumming.  Any
-        # task-set change is a miss and rebuilds.
-        self._bind_sig: Optional[tuple] = None
-        self._bind_seq_lens: Optional[List[int]] = None
-
-    # ---- task lifecycle ----
-
-    def task_alloc(self, task_id: str, prompt_ids: List[int]) -> bool:
-        req_slots = self._req_pool.alloc(1)
-        if req_slots is None:
-            return False
-        req_idx = req_slots[0]
-        self._task_req[task_id] = req_idx
-
-        if self.contiguous:
-            self._task_len[req_idx] = len(prompt_ids)
-            self._task_cached[task_id] = 0
-            return True
-
-        n_tokens_needed = len(prompt_ids)
-        cached = 0
-
-        if self._prefix is not None:
-            hits = self._prefix.lookup(prompt_ids)
-            cached = len(hits) * self.page_size
-            for p in hits:
-                self._alloc.inc_ref(p)
-            self._task_pages[task_id] = list(hits)
-            self._task_slots[task_id] = []
-        else:
-            self._task_pages[task_id] = []
-            self._task_slots[task_id] = []
-
-        remaining = n_tokens_needed - cached
-        if remaining > 0:
-            if self.page_size == 1:
-                slots = self._alloc_tokens(remaining)
-                if slots is None:
-                    for p in self._task_pages[task_id]:
-                        self._alloc.free(p)
-                    self._req_pool.free([req_idx])
-                    del self._task_req[task_id]
-                    return False
-                self._task_slots[task_id] = slots
-            else:
-                n_new_pages = (remaining + self.page_size - 1) // self.page_size
-                new_pages = []
-                for _ in range(n_new_pages):
-                    p = self._alloc.alloc()
-                    if p < 0:
-                        for hp in self._task_pages[task_id]:
-                            self._alloc.free(hp)
-                        for np_ in new_pages:
-                            self._alloc.free(np_)
-                        self._req_pool.free([req_idx])
-                        del self._task_req[task_id]
-                        return False
-                    new_pages.append(p)
-                self._task_pages[task_id].extend(new_pages)
-
-        self._write_req_to_token(task_id, prompt_ids, cached)
-        self._task_len[req_idx] = len(prompt_ids)
-        self._task_cached[task_id] = cached
-        return True
-
-    def task_free(self, task_id: str):
-        req_idx = self._task_req.pop(task_id, None)
-        if req_idx is None:
-            return
-        self._task_len.pop(req_idx, None)
-        self._task_cached.pop(task_id, None)
-
-        if not self.contiguous:
-            if self._prefix is not None:
-                for p in self._task_pages.get(task_id, []):
-                    keep = self._prefix.has_page(p)
-                    self._alloc.free(p, keep_cached=keep)
-                    if not keep:
-                        self._prefix.evict(p)
-            else:
-                for p in self._task_pages.get(task_id, []):
-                    self._alloc.free(p)
-            self._task_pages.pop(task_id, None)
-            self._task_slots.pop(task_id, None)
-
-        self._req_pool.free([req_idx])
-
-    def task_extend(self, task_id: str, pos: int) -> bool:
-        req_idx = self._task_req.get(task_id)
-        if req_idx is None or pos >= self.max_seq_len:
-            return False
-
-        # Paged mode must also claim a physical slot for the new token;
-        # contiguous mode's block is pre-allocated so this is a no-op.
-        if not self.contiguous and not self._extend_slot(task_id, req_idx, pos):
-            return False
-
-        self._task_len[req_idx] = pos + 1
-        return True
-
-    def _extend_slot(self, task_id: str, req_idx: int, pos: int) -> bool:
-        """Allocate the physical slot for one extended token (paged mode)."""
-        if self.page_size == 1:
-            slots = self._alloc_tokens(1)
-            if slots is None:
-                return False
-            self._task_slots.setdefault(task_id, []).extend(slots)
-            self._req_pool.req_to_token[req_idx, pos] = slots[0]
-            return True
-
-        page_idx = pos // self.page_size
-        existing = self._task_pages.get(task_id, [])
-        if page_idx >= len(existing):
-            p = self._alloc.alloc()
-            if p < 0:
-                return False
-            existing.append(p)
-            self._task_pages[task_id] = existing
-        page_offset = pos % self.page_size
-        page = existing[page_idx]
-        token_slot = page * self.page_size + page_offset
-        self._req_pool.req_to_token[req_idx, pos] = token_slot
-        return True
-
-    def task_cached(self, task_id: str) -> int:
-        return self._task_cached.get(task_id, 0)
-
-    def task_record_hashes(
-        self, task_id: str, prompt_ids: List[int], start_logical_page: int = 0
-    ):
-        if self._prefix is None or self.contiguous:
-            return
-        pages = self._task_pages.get(task_id, [])
-        full_pages = len(prompt_ids) // self.page_size
-        for i in range(start_logical_page, min(full_pages, len(pages))):
-            self._prefix.record(pages[i], prompt_ids, i)
-
-    def task_cacheable_ids(
-        self, task_id: str, prompt_ids: List[int], output_ids: List[int]
-    ):
-        """Return the sequence whose KV entries are already materialized.
-
-        The first sampled output is produced by prompt prefill, and the last
-        sampled output has not been decoded into KV yet.  Therefore the cache
-        can safely retain the prompt plus every output except the last one.
-        """
-        return list(prompt_ids) + list(output_ids[:-1])
-
-    # ---- bind for forward ----
-
-    def bind_tasks(
-        self,
-        task_ids: List[str],
-        workspace: InferenceWorkspace,
-        device: Optional[torch.device] = None,
-        start_pos: Optional[int] = None,
-    ) -> KVCache:
-        if device is None:
-            device = workspace.device
-        req_indices = [self._task_req[tid] for tid in task_ids]
-        # Per-request lengths come from the pool's own tracking (task_alloc
-        # sets len(prompt_ids); task_extend sets pos+1), so callers need not
-        # pass them.
-        seq_lens = [self._task_len[req_idx] for req_idx in req_indices]
-        b = len(task_ids)
-        sig = tuple(task_ids)
-
-        # Write into the caller's workspace buffers (fixed addresses, sized
-        # to max_batch/max_seq at init) — the sole owner of the per-step
-        # KV bind tensors.
-        rpi_buf = workspace.req_pool_indices
-        sl_buf = workspace.seq_lens
-        kvp_buf = workspace.kv_indptr
-        inc_buf = workspace.inc
-        ocl_buf = workspace.out_cache_loc
-
-        incremental = (
-            start_pos is None
-            and self._bind_sig is not None
-            and self._bind_sig == sig
-            and self._bind_seq_lens is not None
-            and len(self._bind_seq_lens) == b
-            and all(s == p + 1 for s, p in zip(seq_lens, self._bind_seq_lens))
-        )
-        if incremental:
-            # Steady-state decode: advance the stable buffers in-place.
-            # Normal-mode buffers keep ``+=`` legal regardless of whether
-            # this runs inside ``torch.inference_mode()``.
-            sl_buf[:b] += 1
-            kvp_buf[: b + 1] += inc_buf[: b + 1]
-            req_pool_indices = rpi_buf[:b]
-            seq_lens_t = sl_buf[:b]
-            kv_indptr = kvp_buf[: b + 1]
-        else:
-            # Cold path: fill the stable buffers from fresh host tensors.
-            rpi_buf[:b].copy_(
-                torch.tensor(req_indices, dtype=torch.long, device=device)
-            )
-            sl_buf[:b].copy_(torch.tensor(seq_lens, dtype=torch.long, device=device))
-            kvp_buf[: b + 1].zero_()
-            kvp_buf[1 : b + 1] = sl_buf[:b].cumsum(0).to(torch.int32)
-            req_pool_indices = rpi_buf[:b]
-            seq_lens_t = sl_buf[:b]
-            kv_indptr = kvp_buf[: b + 1]
-        self._bind_sig = sig
-        self._bind_seq_lens = list(seq_lens)
-
-        if start_pos is not None:
-            seq_len = seq_lens[0]
-            out_cache_loc = self._req_pool.req_to_token[
-                req_pool_indices, start_pos:seq_len
-            ]
-            # Ragged query segmentation for the prefill kernel, computed once
-            # (was rebuilt per layer in CudaBackend.fwd_prefill).
-            q_len = seq_len - start_pos
-            workspace.qo_indptr[: b + 1].copy_(
-                torch.arange(b + 1, dtype=torch.int32, device=device) * q_len
-            )
-            qo_indptr = workspace.qo_indptr[: b + 1]
-        else:
-            write_pos = seq_lens_t - 1
-            loc = self._req_pool.req_to_token[req_pool_indices, write_pos].unsqueeze(-1)
-            ocl_buf[:b].copy_(loc)
-            out_cache_loc = ocl_buf[:b]
-            qo_indptr = None
-
-        return KVCache(
-            k_buffer=self._storage.k_buffer,
-            v_buffer=self._storage.v_buffer,
-            req_to_token=self._req_pool.req_to_token,
-            req_pool_indices=req_pool_indices,
-            seq_lens=seq_lens_t,
-            out_cache_loc=out_cache_loc,
-            max_len=max(seq_lens),
-            kv_indptr=kv_indptr,
-            qo_indptr=qo_indptr,
-        )
-
-    # ---- internals ----
-
-    def _alloc_tokens(self, n: int) -> Optional[List[int]]:
-        if self.page_size != 1:
-            raise RuntimeError("_alloc_tokens is for page_size=1 only")
-        slots = []
-        for _ in range(n):
-            p = self._alloc.alloc()
-            if p < 0:
-                for s in slots:
-                    self._alloc.free(s)
-                return None
-            slots.append(p)
-        return slots
-
-    def _write_req_to_token(self, task_id: str, prompt_ids: List[int], cached: int):
-        req_idx = self._task_req[task_id]
-        total = len(prompt_ids)
-
-        if self.contiguous:
-            return
-
-        if self.page_size == 1:
-            slots = self._task_slots.get(task_id, [])
-            all_slots = slots[: total - cached]
-            if all_slots:
-                self._req_pool.req_to_token[req_idx, cached:total] = torch.tensor(
-                    all_slots, dtype=torch.long, device=self.device
-                )
-        else:
-            pages = self._task_pages.get(task_id, [])
-            for pos in range(cached, total):
-                page_idx = pos // self.page_size
-                page_offset = pos % self.page_size
-                if page_idx < len(pages):
-                    token_slot = pages[page_idx] * self.page_size + page_offset
-                    self._req_pool.req_to_token[req_idx, pos] = token_slot

astrai/inference/core/executor.py

@@ -1,241 +0,0 @@
-import logging
-from dataclasses import dataclass
-from typing import List, Optional
-
-import torch
-from torch import Tensor
-
-from astrai.inference.core.cache import PagePool
-from astrai.inference.core.task import Task
-from astrai.inference.core.workspace import InferenceWorkspace
-from astrai.inference.sample import sample
-from astrai.model.automodel import AutoModel
-from astrai.tokenize.tokenizer import AutoTokenizer
-
-logger = logging.getLogger(__name__)
-
-
-@dataclass
-class SamplingBatchInfo:
-    """Per-batch sampling parameters, cached across decode steps.
-
-    Sampling params are constant for a given ordered task set, so they are
-    built once (pinned-memory async H2D) and reused until the task set
-    changes.  ``top_ks`` is int32 to match the native consumers.
-    """
-
-    temperatures: Tensor  # float32 [B]
-    top_ks: Tensor  # int32  [B]
-    top_ps: Tensor  # float32 [B]
-    freq_penalties: Tensor  # float32 [B]
-    has_freq: bool  # any frequency_penalty != 0 (avoids per-step GPU .any())
-
-
-def _build_sampling_batch_info(tasks: List[Task], device) -> SamplingBatchInfo:
-    pin = str(device).startswith("cuda")
-    freq_penalties = torch.tensor(
-        [t.frequency_penalty for t in tasks], dtype=torch.float32, pin_memory=pin
-    ).to(device, non_blocking=True)
-    return SamplingBatchInfo(
-        temperatures=torch.tensor(
-            [t.temperature for t in tasks], dtype=torch.float32, pin_memory=pin
-        ).to(device, non_blocking=True),
-        top_ks=torch.tensor(
-            [t.top_k for t in tasks], dtype=torch.int32, pin_memory=pin
-        ).to(device, non_blocking=True),
-        top_ps=torch.tensor(
-            [t.top_p for t in tasks], dtype=torch.float32, pin_memory=pin
-        ).to(device, non_blocking=True),
-        freq_penalties=freq_penalties,
-        has_freq=bool((freq_penalties != 0).any()),
-    )
-
-
-class Executor:
-    """Model forward passes for prefill and decode phases."""
-
-    def __init__(
-        self,
-        model: AutoModel,
-        tokenizer: AutoTokenizer,
-        kv_cache: PagePool,
-        device: Optional[str] = None,
-        dtype: Optional[torch.dtype] = None,
-    ):
-        self.model = model
-        self.tokenizer = tokenizer
-        self.kv_cache = kv_cache
-        self.device = device or next(model.parameters()).device
-        self.dtype = dtype or next(model.parameters()).dtype
-
-        # Per-step decode cache for the steady-state case where the same
-        # ordered task set decodes one token per step.  Sampling params are
-        # constant across steps; position_ids grows by exactly 1.  Single-slot:
-        # any task-set change is a cache miss.
-        self._decode_cache: Optional[tuple] = None
-
-        # Pre-allocated fixed-shape buffers for the decode hot path
-        # (input_ids, decode mask, KV bind metadata).  Eagerly sized at init
-        # so the workspace is CUDA-graph-capture friendly — no allocation
-        # during capture.
-        self._workspace = InferenceWorkspace(
-            max_batch_size=kv_cache.max_batch_size,
-            max_seq_len=kv_cache.max_seq_len,
-            device=self.device,
-            dtype=self.dtype,
-        )
-
-    def _sample_logits(
-        self,
-        logits: Tensor,
-        tasks: List[Task],
-        return_logprobs: bool = False,
-        info: Optional[SamplingBatchInfo] = None,
-    ):
-        info = info or _build_sampling_batch_info(tasks, self.device)
-        if info.has_freq:
-            history_lists = [
-                t.prompt_ids[-t.rep_window :] + t.output_ids for t in tasks
-            ]
-            history_lens = [len(ids) for ids in history_lists]
-            max_len = max(history_lens, default=0)
-            padded_ids = torch.zeros(
-                len(tasks), max_len, dtype=torch.long, device=self.device
-            )
-            padded_mask = torch.zeros(
-                len(tasks), max_len, dtype=torch.bool, device=self.device
-            )
-            for i, ids in enumerate(history_lists):
-                length = len(ids)
-                padded_ids[i, :length] = torch.as_tensor(
-                    ids, dtype=torch.long, device=self.device
-                )
-                padded_mask[i, :length] = True
-        else:
-            padded_ids = None
-            padded_mask = None
-
-        result = sample(
-            logits,
-            temperature=info.temperatures,
-            top_k=info.top_ks,
-            top_p=info.top_ps,
-            frequency_penalty=info.freq_penalties,
-            input_ids=padded_ids,
-            input_mask=padded_mask,
-            return_logprobs=return_logprobs,
-        )
-        if not return_logprobs:
-            return result.tolist()
-
-        tokens, logprobs = result
-        tokens_list = tokens.tolist()
-        logprobs_list = logprobs.tolist()
-        for task, logprob in zip(tasks, logprobs_list):
-            task.output_logprobs.append(float(logprob))
-        return list(zip(tokens_list, logprobs_list))
-
-    def execute_prefill(
-        self,
-        tasks: List[Task],
-        prompt_len: int,
-        start_pos: int = 0,
-        return_logprobs: bool = False,
-    ):
-        if start_pos >= prompt_len:
-            return []
-
-        tasks = sorted(tasks, key=lambda t: t.task_id)
-        batch_sz = len(tasks)
-
-        input_ids = torch.tensor(
-            [t.prompt_ids[start_pos:prompt_len] for t in tasks],
-            dtype=torch.long,
-            device=self.device,
-        )
-
-        task_ids = [t.task_id for t in tasks]
-        position_ids = (
-            torch.arange(start_pos, prompt_len, dtype=torch.long, device=self.device)
-            .unsqueeze(0)
-            .expand(batch_sz, -1)
-        )
-        input_mask = position_ids.unsqueeze(-1) >= torch.arange(
-            prompt_len, device=self.device
-        )
-
-        with torch.inference_mode():
-            outputs = self.model(
-                input_ids,
-                input_mask=input_mask,
-                position_ids=position_ids,
-                kv_cache=self.kv_cache.bind_tasks(
-                    task_ids,
-                    self._workspace,
-                    start_pos=start_pos,
-                ),
-            )
-            logits = outputs["logits"][:, -1, :]
-
-        return tasks, self._sample_logits(logits, tasks, return_logprobs)
-
-    def execute_decode(
-        self, tasks: List[Task], return_logprobs: bool = False
-    ) -> List[int]:
-        """Decode next token for each task.
-
-        Args:
-            return_logprobs: When ``True``, also record (and return)
-                the log-probability of each sampled token under the
-                post-strategy sampling distribution.  The logprob is
-                appended to ``task.output_logprobs`` and the return
-                list becomes ``List[Tuple[int, float]]``.
-
-        Returns:
-            ``List[int]`` of sampled token IDs, or
-            ``List[Tuple[int, float]]`` of ``(token_id, logprob)`` when
-            ``return_logprobs`` is ``True``.
-        """
-        if not tasks:
-            return []
-
-        input_ids = self._workspace.fill_input_ids(
-            [t.output_ids[-1] if t.output_ids else t.prompt_ids[-1] for t in tasks]
-        ).unsqueeze(1)
-
-        task_ids = [t.task_id for t in tasks]
-
-        sig = tuple(task_ids)
-        cur_positions = [t.next_pos for t in tasks]
-        cached = self._decode_cache
-        if (
-            cached is not None
-            and cached[0] == sig
-            and cur_positions == [p + 1 for p in cached[1]]
-        ):
-            _, _, info, position_ids = cached
-            position_ids += 1
-            self._decode_cache = (sig, cur_positions, info, position_ids)
-        else:
-            info = _build_sampling_batch_info(tasks, self.device)
-            position_ids = torch.tensor(
-                cur_positions, dtype=torch.long, device=self.device
-            )
-            self._decode_cache = (sig, cur_positions, info, position_ids)
-
-        total_len = max(t.next_pos for t in tasks) + 1
-        input_mask = self._workspace.decode_mask(position_ids, total_len)
-
-        with torch.inference_mode():
-            outputs = self.model(
-                input_ids,
-                input_mask=input_mask,
-                kv_cache=self.kv_cache.bind_tasks(
-                    task_ids,
-                    self._workspace,
-                ),
-                position_ids=position_ids.unsqueeze(1),
-            )
-            logits = outputs["logits"][:, -1, :]
-
-        return self._sample_logits(logits, tasks, return_logprobs, info=info)

astrai/inference/engine.py

@@ -8,9 +8,10 @@ from typing import Any, AsyncGenerator, Dict, Generator, List, Optional, Tuple,
 import torch
 import torch.nn as nn
 
-from astrai.inference.core.cache import PagePool
-from astrai.inference.core.scheduler import InferenceScheduler
-from astrai.inference.core.task import STOP
+from astrai.extension import ATTN_BACKEND, AttentionBackend, get_backend
+from astrai.inference.cache import PagePool
+from astrai.inference.scheduler import InferenceScheduler
+from astrai.inference.task import STOP
 from astrai.tokenize import AutoTokenizer
 
 
@@ -64,44 +65,6 @@ class GenerateResult:
             return self.results.copy()
 
 
-class GenerationRequest:
-    """Request parameters for text generation."""
-
-    def __init__(
-        self,
-        messages: List[Dict[str, str]],
-        top_k: int = 50,
-        top_p: float = 1.0,
-        temperature: float = 1.0,
-        max_tokens: Optional[int] = None,
-        frequency_penalty: float = 0.0,
-        rep_window: int = 64,
-        stream: bool = False,
-    ):
-        if not (isinstance(top_k, int) and top_k >= 0):
-            raise ValueError("top_k must be a non-negative integer")
-        if not (0.0 <= top_p <= 1.0):
-            raise ValueError("top_p must be a float between 0.0 and 1.0")
-        if not (isinstance(temperature, (int, float)) and temperature >= 0):
-            raise ValueError("temperature must be a non-negative number")
-        if not (
-            isinstance(frequency_penalty, (int, float))
-            and -2.0 <= frequency_penalty <= 2.0
-        ):
-            raise ValueError("frequency_penalty must be between -2.0 and 2.0")
-        if not (isinstance(rep_window, int) and rep_window > 0):
-            raise ValueError("rep_window must be a positive integer")
-
-        self.messages = messages
-        self.top_k = top_k
-        self.top_p = top_p
-        self.temperature = temperature
-        self.max_tokens = max_tokens
-        self.frequency_penalty = frequency_penalty
-        self.rep_window = rep_window
-        self.stream = stream
-
-
 class InferenceEngine:
     """Unified inference engine backed by continuous-batching scheduler."""
 
@@ -112,6 +75,8 @@ class InferenceEngine:
         max_batch_size: int = 1,
         max_seq_len: Optional[int] = None,
         cache: Optional[PagePool] = None,
+        enable_cuda_graph: bool = True,
+        backend: Optional[Union[str, ATTN_BACKEND, AttentionBackend, type]] = None,
     ):
         self.model = model
         self.tokenizer = tokenizer
@@ -121,6 +86,8 @@ class InferenceEngine:
             max_batch_size=max_batch_size,
             max_seq_len=max_seq_len,
             cache=cache,
+            enable_cuda_graph=enable_cuda_graph,
+            backend=backend,
         )
 
         self.scheduler.start()
@@ -146,28 +113,23 @@ class InferenceEngine:
         is_batch = isinstance(prompt, list)
         prompts = prompt if is_batch else [prompt]
 
-        if stream:
-            return self._generate_streaming(
-                prompts,
-                is_batch,
-                max_tokens,
-                temperature,
-                top_p,
-                top_k,
-                frequency_penalty,
-                rep_window,
-            )
-        else:
-            return self._generate_non_streaming(
-                prompts,
-                is_batch,
-                max_tokens,
-                temperature,
-                top_p,
-                top_k,
-                frequency_penalty,
-                rep_window,
-            )
+        if max_tokens is not None and max_tokens <= 0:
+            if stream:
+                return iter(())
+            results = [""] * len(prompts)
+            return results if is_batch else results[0]
+
+        return self._generate(
+            prompts,
+            is_batch,
+            stream,
+            max_tokens,
+            temperature,
+            top_p,
+            top_k,
+            frequency_penalty,
+            rep_window,
+        )
 
     def generate_async(
         self,
@@ -179,9 +141,10 @@ class InferenceEngine:
         frequency_penalty: float = 0.0,
         rep_window: int = 64,
     ) -> AsyncGenerator[str, None]:
-        sync_gen = self._generate_streaming(
+        sync_gen = self._generate(
             [prompt],
             False,
+            True,
             max_tokens,
             temperature,
             top_p,
@@ -193,51 +156,30 @@ class InferenceEngine:
         async def _agen():
             loop = asyncio.get_event_loop()
             while True:
-                token = await loop.run_in_executor(None, self._next_token, sync_gen)
+                token = await loop.run_in_executor(None, next, sync_gen, None)
                 if token is None:
                     break
                 yield token
 
         return _agen()
 
-    @staticmethod
-    def _next_token(gen: Generator) -> Optional[str]:
-        try:
-            return next(gen)
-        except StopIteration:
-            return None
-
-    def generate_with_request(
-        self, request: GenerationRequest
-    ) -> Union[Generator[str, None, None], str, List[str]]:
-        prompt = self.tokenizer.apply_chat_template(request.messages, tokenize=False)
-        return self.generate(
-            prompt=prompt,
-            stream=request.stream,
-            max_tokens=request.max_tokens,
-            temperature=request.temperature,
-            top_p=request.top_p,
-            top_k=request.top_k,
-            frequency_penalty=request.frequency_penalty,
-            rep_window=request.rep_window,
-        )
-
-    def _submit_tasks(
+    def _generate(
         self,
         prompts: List[str],
+        is_batch: bool,
+        stream: bool,
         max_tokens: Optional[int],
         temperature: float,
         top_p: float,
         top_k: int,
         frequency_penalty: float,
         rep_window: int,
-    ) -> Tuple[GenerateResult, List[str]]:
+    ) -> Union[Generator, str, List[str]]:
         n = len(prompts)
+        request_backend = get_backend(use_default=False)
         result = GenerateResult(count=n)
-        task_ids = []
-        for i, p in enumerate(prompts):
-            cb = self._make_callback(result, i)
-            task_id = self.scheduler.add_task(
+        task_ids = [
+            self.scheduler.add_task(
                 prompt=p,
                 max_tokens=max_tokens,
                 temperature=temperature,
@@ -245,99 +187,54 @@ class InferenceEngine:
                 top_k=top_k,
                 frequency_penalty=frequency_penalty,
                 rep_window=rep_window,
-                stream_callback=cb,
+                backend=request_backend,
+                stream_callback=lambda token, idx=i: result.append(token, idx),
             )
-            task_ids.append(task_id)
-        return result, task_ids
+            for i, p in enumerate(prompts)
+        ]
 
-    @staticmethod
-    def _make_callback(result: GenerateResult, idx: int):
-        def cb(token):
-            result.append(token, idx)
+        if not stream:
+            try:
+                result.wait_completion()
+            except TimeoutError:
+                for tid in task_ids:
+                    self.scheduler.remove_task(tid)
+                raise
+            for tid in task_ids:
+                self.scheduler.remove_task(tid)
+            res = result.get_results()
+            return res if is_batch else res[0]
 
-        return cb
-
-    def _generate_streaming(
-        self,
-        prompts: List[str],
-        is_batch: bool,
-        max_tokens: Optional[int],
-        temperature: float,
-        top_p: float,
-        top_k: int,
-        frequency_penalty: float,
-        rep_window: int,
-    ) -> Generator:
-        result, task_ids = self._submit_tasks(
-            prompts,
-            max_tokens,
-            temperature,
-            top_p,
-            top_k,
-            frequency_penalty,
-            rep_window,
-        )
-        n = len(prompts)
         remaining = n
         finished = [False] * n
 
         def gen():
             nonlocal remaining
-            try:
-                while remaining > 0:
-                    items = result.pop_all()
-                    for idx, token in items:
-                        if token is STOP:
-                            if not finished[idx]:
-                                finished[idx] = True
-                                remaining -= 1
-                        else:
-                            yield (idx, token) if is_batch else token
-                    if remaining > 0:
-                        result.wait(timeout=0.05)
-            finally:
-                for tid in task_ids:
-                    self.scheduler.remove_task(tid)
+            while remaining > 0:
+                items = result.pop_all()
+                for idx, token in items:
+                    if token is STOP:
+                        if not finished[idx]:
+                            finished[idx] = True
+                            remaining -= 1
+                    else:
+                        yield (idx, token) if is_batch else token
+                if remaining > 0:
+                    result.wait(timeout=0.05)
 
         return gen()
 
-    def _generate_non_streaming(
-        self,
-        prompts: List[str],
-        is_batch: bool,
-        max_tokens: Optional[int],
-        temperature: float,
-        top_p: float,
-        top_k: int,
-        frequency_penalty: float,
-        rep_window: int,
-    ) -> Union[str, List[str]]:
-        result, task_ids = self._submit_tasks(
-            prompts,
-            max_tokens,
-            temperature,
-            top_p,
-            top_k,
-            frequency_penalty,
-            rep_window,
-        )
-
-        try:
-            result.wait_completion()
-        except TimeoutError:
-            for tid in task_ids:
-                self.scheduler.remove_task(tid)
-            raise
-
-        for tid in task_ids:
-            self.scheduler.remove_task(tid)
-
-        res = result.get_results()
-        return res if is_batch else res[0]
-
     def get_stats(self) -> Dict[str, Any]:
         return self.scheduler.get_stats()
 
+    @property
+    def backend_name(self) -> str:
+        return self.scheduler.backend_name
+
+    @property
+    def cuda_graph_enabled(self) -> bool:
+        return self.scheduler.cuda_graph_enabled
+
     def shutdown(self):
         self.scheduler.stop()
         if torch.cuda.is_available():

astrai/inference/metrics.py

@@ -0,0 +1,201 @@
+"""Unified per-task perf/stats: timing records, context-manager scopes, aggregate reporting."""
+
+import time
+from collections import deque
+from contextlib import contextmanager
+from dataclasses import dataclass
+from typing import Any, Deque, Dict, Generator, List, Literal, Optional
+
+
+@dataclass
+class TaskTiming:
+    """Timestamp snapshots and computed metrics for one generation task.
+
+    Created by :class:`MetricsCollector` at task-registration time;
+    updated via ``record`` / ``mark_finished``.
+    """
+
+    task_id: str
+    arrival_time: float
+    prefill_start_time: Optional[float] = None
+    first_token_time: Optional[float] = None
+    finish_time: Optional[float] = None
+    input_tokens: int = 0
+    output_tokens: int = 0
+    _decode_steps: int = 0
+    _decode_total_s: float = 0.0
+
+    # derived metrics
+
+    @property
+    def queue_wait_ms(self) -> Optional[float]:
+        if self.prefill_start_time is not None:
+            return (self.prefill_start_time - self.arrival_time) * 1000
+        return None
+
+    @property
+    def ttft_ms(self) -> Optional[float]:
+        if self.first_token_time is not None:
+            return (self.first_token_time - self.arrival_time) * 1000
+        return None
+
+    @property
+    def prefill_tps(self) -> Optional[float]:
+        if self.prefill_start_time is not None and self.first_token_time is not None:
+            d = self.first_token_time - self.prefill_start_time
+            if d > 0 and self.input_tokens > 0:
+                return self.input_tokens / d
+        return None
+
+    @property
+    def decode_tps(self) -> Optional[float]:
+        if self.first_token_time is not None and self.finish_time is not None:
+            d = self.finish_time - self.first_token_time
+            dt = self.output_tokens - 1
+            if dt > 0 and d > 0:
+                return dt / d
+        return None
+
+    @property
+    def decode_avg_ms(self) -> Optional[float]:
+        if self._decode_steps > 0 and self._decode_total_s > 0:
+            return (self._decode_total_s / self._decode_steps) * 1000
+        return None
+
+    @property
+    def e2e_latency_ms(self) -> Optional[float]:
+        if self.finish_time is not None:
+            return (self.finish_time - self.arrival_time) * 1000
+        return None
+
+    @property
+    def total_tps(self) -> Optional[float]:
+        if self.finish_time is not None:
+            total = self.input_tokens + self.output_tokens
+            d = self.finish_time - self.arrival_time
+            if total > 0 and d > 0:
+                return total / d
+        return None
+
+    def to_dict(self) -> Dict[str, Any]:
+        return {
+            "task_id": self.task_id,
+            "input_tokens": self.input_tokens,
+            "output_tokens": self.output_tokens,
+            "queue_wait_ms": (
+                round(self.queue_wait_ms, 2) if self.queue_wait_ms is not None else None
+            ),
+            "ttft_ms": (round(self.ttft_ms, 2) if self.ttft_ms is not None else None),
+            "prefill_tps": (
+                round(self.prefill_tps, 2) if self.prefill_tps is not None else None
+            ),
+            "decode_tps": (
+                round(self.decode_tps, 2) if self.decode_tps is not None else None
+            ),
+            "decode_avg_ms": (
+                round(self.decode_avg_ms, 2) if self.decode_avg_ms is not None else None
+            ),
+            "total_tps": (
+                round(self.total_tps, 2) if self.total_tps is not None else None
+            ),
+            "e2e_latency_ms": (
+                round(self.e2e_latency_ms, 2)
+                if self.e2e_latency_ms is not None
+                else None
+            ),
+        }
+
+
+class MetricsCollector:
+    """Single-owner perf/stats hub for all generation tasks.
+
+    Usage::
+
+        metrics = MetricsCollector()
+        metrics.register(task_id, arrival_time)
+
+        with metrics.record(task_ids, "prefill"):
+            run_prefill(...)
+
+        metrics.mark_finished(task_id, input_tokens, output_tokens)
+
+        stats = metrics.get_stats()
+    """
+
+    def __init__(self, max_recent: int = 128):
+        self._timings: Dict[str, TaskTiming] = {}
+        self._completed: Deque[TaskTiming] = deque(maxlen=max_recent)
+
+        self._ttft_ms_sum = 0.0
+        self._ttft_ms_count = 0
+        self._decode_tps_sum = 0.0
+        self._decode_tps_count = 0
+        self._e2e_ms_sum = 0.0
+        self._e2e_ms_count = 0
+
+    def register(self, task_id: str):
+        """Create a timing record for a newly-created task."""
+        self._timings[task_id] = TaskTiming(task_id=task_id, arrival_time=time.time())
+
+    def mark_finished(self, task_id: str, input_tokens: int, output_tokens: int):
+        """Close timing for a finished/aborted task and move it to completed."""
+        timing = self._timings.pop(task_id, None)
+        if timing is None:
+            return
+        timing.finish_time = time.time()
+        timing.input_tokens = input_tokens
+        timing.output_tokens = output_tokens
+        self._completed.append(timing)
+        self._accumulate(timing)
+
+    # timing scopes
+
+    @contextmanager
+    def record(
+        self, task_ids: List[str], phase: Literal["prefill", "decode"]
+    ) -> Generator[None, None, None]:
+        tic = time.time()
+        yield
+        toc = time.time()
+        dt = toc - tic
+        for tid in task_ids:
+            t = self._timings.get(tid)
+            if t is None:
+                continue
+            if phase == "prefill":
+                t.prefill_start_time = tic
+                t.first_token_time = toc
+            elif phase == "decode":
+                t._decode_steps += 1
+                t._decode_total_s += dt
+
+    # aggregate stats
+
+    def get_stats(self) -> Dict[str, Any]:
+        stats: Dict[str, Any] = {}
+        if self._ttft_ms_count > 0:
+            stats["avg_ttft_ms"] = round(self._ttft_ms_sum / self._ttft_ms_count, 2)
+        if self._decode_tps_count > 0:
+            stats["avg_decode_tps"] = round(
+                self._decode_tps_sum / self._decode_tps_count, 2
+            )
+        if self._e2e_ms_count > 0:
+            stats["avg_e2e_latency_ms"] = round(
+                self._e2e_ms_sum / self._e2e_ms_count, 2
+            )
+        if self._completed:
+            stats["recent_tasks"] = [t.to_dict() for t in self._completed]
+        return stats
+
+    # internal
+
+    def _accumulate(self, t: TaskTiming):
+        if t.ttft_ms is not None:
+            self._ttft_ms_sum += t.ttft_ms
+            self._ttft_ms_count += 1
+        if t.decode_tps is not None:
+            self._decode_tps_sum += t.decode_tps
+            self._decode_tps_count += 1
+        if t.e2e_latency_ms is not None:
+            self._e2e_ms_sum += t.e2e_latency_ms
+            self._e2e_ms_count += 1

astrai/inference/network/__init__.py

@@ -4,8 +4,7 @@
 lazy singleton FastAPI instance.
 """
 
-from astrai.inference.api.protocol import GenContext, ProtocolHandler, StopChecker
-from astrai.inference.api.server import (
+from astrai.inference.network.app import (
     AnthropicMessage,
     ChatCompletionRequest,
     ChatMessage,
@@ -15,7 +14,8 @@ from astrai.inference.api.server import (
     get_app,
     run_server,
 )
-from astrai.inference.api.tool_parser import (
+from astrai.inference.network.protocol import GenContext, ProtocolHandler, StopChecker
+from astrai.inference.network.tool_parser import (
     BaseToolParser,
     SimpleJsonToolParser,
     ToolParserFactory,

astrai/inference/network/anthropic.py

@@ -6,13 +6,13 @@ from typing import Any, Dict, List, Tuple, Union
 
 from pydantic import BaseModel
 
-from astrai.inference.api.protocol import (
+from astrai.inference.engine import InferenceEngine
+from astrai.inference.network.protocol import (
     GenContext,
     ResponseBuilder,
     StopInfo,
     sse_event,
 )
-from astrai.inference.engine import InferenceEngine
 
 
 def _extract_text(content: Union[str, List[Dict[str, Any]]]) -> str:

astrai/inference/network/app.py

@@ -18,10 +18,10 @@ import uvicorn
 from fastapi import APIRouter, FastAPI, HTTPException
 from pydantic import BaseModel, Field
 
-from astrai.inference.api.anthropic import AnthropicResponseBuilder
-from astrai.inference.api.openai import OpenAIResponseBuilder
-from astrai.inference.api.protocol import ProtocolHandler
 from astrai.inference.engine import InferenceEngine
+from astrai.inference.network.anthropic import AnthropicResponseBuilder
+from astrai.inference.network.openai import OpenAIResponseBuilder
+from astrai.inference.network.protocol import ProtocolHandler
 from astrai.model import AutoModel
 from astrai.tokenize import AutoTokenizer
 

astrai/inference/network/openai.py

@@ -7,14 +7,14 @@ from typing import Any, Dict, List, Optional, Tuple, Union
 
 from pydantic import BaseModel
 
-from astrai.inference.api.protocol import (
+from astrai.inference.engine import InferenceEngine
+from astrai.inference.network.protocol import (
     GenContext,
     ResponseBuilder,
     StopInfo,
     sse_event,
 )
-from astrai.inference.api.tool_parser import BaseToolParser, ToolParserFactory
-from astrai.inference.engine import InferenceEngine
+from astrai.inference.network.tool_parser import BaseToolParser, ToolParserFactory
 
 logger = logging.getLogger(__name__)
 

astrai/inference/network/protocol.py

@@ -181,12 +181,10 @@ class ProtocolHandler:
         self, agen: AsyncGenerator, ctx: GenContext, stop_sequences: List[str]
     ) -> Dict[str, Any]:
         checker = StopChecker(stop_sequences)
-        chunks: List[str] = []
         body = ""
         matched = None
 
         async for token in agen:
-            chunks.append(token)
             body += token
 
             matched = checker.check(body)
@@ -195,6 +193,5 @@ class ProtocolHandler:
 
             ctx.completion_tokens += 1
 
-        content = "".join(chunks)
         stop = StopInfo(matched=matched, body=body)
-        return self.builder.format_response(ctx, content, stop)
+        return self.builder.format_response(ctx, body, stop)

astrai/inference/runtime/__init__.py

@@ -0,0 +1,25 @@
+"""Execution primitives: forward passes, CUDA graphs, and sampling."""
+
+from astrai.inference.runtime.executor import Executor
+from astrai.inference.runtime.graph import CudaGraphContext
+from astrai.inference.runtime.sample import (
+    BaseSamplingStrategy,
+    FrequencyPenaltyStrategy,
+    SamplingPipeline,
+    TemperatureStrategy,
+    TopKStrategy,
+    TopPStrategy,
+    sample,
+)
+
+__all__ = [
+    "Executor",
+    "CudaGraphContext",
+    "BaseSamplingStrategy",
+    "FrequencyPenaltyStrategy",
+    "SamplingPipeline",
+    "TemperatureStrategy",
+    "TopKStrategy",
+    "TopPStrategy",
+    "sample",
+]

astrai/inference/runtime/executor.py

@@ -0,0 +1,443 @@
+import logging
+import time
+from contextlib import contextmanager
+from dataclasses import dataclass
+from typing import List, Optional
+
+import torch
+from torch import Tensor
+
+from astrai.extension.backend.attention import (
+    CudaBackend,
+    get_backend,
+)
+from astrai.inference.cache import PagePool, TaskCacheManager
+from astrai.inference.runtime.graph import CudaGraphContext
+from astrai.inference.runtime.sample import sample
+from astrai.inference.task import Task
+from astrai.inference.workspace import InferenceWorkspace
+from astrai.model.automodel import AutoModel
+
+logger = logging.getLogger(__name__)
+
+
+@contextmanager
+def timed(label: str, log: Optional[logging.Logger] = None):
+    """GPU-precise timer via CUDA events; falls back to perf_counter on CPU."""
+    log = log or logger
+    if not log.isEnabledFor(logging.DEBUG):
+        yield
+        return
+    use_cuda = torch.cuda.is_available()
+    if use_cuda:
+        start = torch.cuda.Event(enable_timing=True)
+        end = torch.cuda.Event(enable_timing=True)
+        start.record()
+    else:
+        tic = time.perf_counter()
+    yield
+    if use_cuda:
+        end.record()
+        torch.cuda.synchronize()
+        elapsed_ms = start.elapsed_time(end)
+    else:
+        elapsed_ms = (time.perf_counter() - tic) * 1000
+    log.debug("%s %.2fms", label, elapsed_ms)
+
+
+@dataclass
+class SamplingBatchInfo:
+    """Per-batch sampling parameters, cached across decode steps.
+
+    Sampling params are constant for a given ordered task set, so they are
+    built once (pinned-memory async H2D) and reused until the task set
+    changes.  ``top_ks`` is int32 to match the native consumers.
+    """
+
+    temperatures: Tensor  # float32 [B]
+    top_ks: Tensor  # int32  [B]
+    top_ps: Tensor  # float32 [B]
+    freq_penalties: Tensor  # float32 [B]
+    has_freq: bool  # any frequency_penalty != 0 (avoids per-step GPU .any())
+
+
+@dataclass
+class DecodeSteadyState:
+    """Cached decode metadata for the steady-state case.
+
+    When the same ordered task set decodes one token per step, sampling
+    params and task signature are reused; only positions advance by 1.
+    ``last_tokens`` keeps that step's sampled ids on-device so the next
+    step with an unchanged signature can fill ``input_ids`` via a
+    device-to-device copy.
+    """
+
+    task_sig: tuple
+    positions: list[int]
+    sampling_info: SamplingBatchInfo
+    last_tokens: Optional[Tensor] = None
+
+
+def _build_sampling_batch_info(tasks: List[Task], device) -> SamplingBatchInfo:
+    pin = str(device).startswith("cuda")
+    freq_penalties = torch.tensor(
+        [t.frequency_penalty for t in tasks], dtype=torch.float32, pin_memory=pin
+    ).to(device, non_blocking=True)
+    return SamplingBatchInfo(
+        temperatures=torch.tensor(
+            [t.temperature for t in tasks], dtype=torch.float32, pin_memory=pin
+        ).to(device, non_blocking=True),
+        top_ks=torch.tensor(
+            [t.top_k for t in tasks], dtype=torch.int32, pin_memory=pin
+        ).to(device, non_blocking=True),
+        top_ps=torch.tensor(
+            [t.top_p for t in tasks], dtype=torch.float32, pin_memory=pin
+        ).to(device, non_blocking=True),
+        freq_penalties=freq_penalties,
+        has_freq=bool((freq_penalties != 0).any()),
+    )
+
+
+def _warmup_cuda_graphs(
+    model: AutoModel,
+    pool: PagePool,
+    task_cache: TaskCacheManager,
+    ws: InferenceWorkspace,
+    gctx: CudaGraphContext,
+    max_batch_size: int,
+    prompt_len: int = 1,
+    device: Optional[str] = None,
+):
+    dev = device or next(model.parameters()).device
+
+    # Prefill warmup: cuBLAS auto-tunes for the actual prompt-length tensor
+    # shapes on first call (F.linear is the dominant cost).  This also warms
+    # up the CUDA context (driver init) and compiles the graph-capture trace
+    # that follows.  Custom .so kernels do NOT need this — they are pre-built.
+    warmup_len = 64
+    tid = "_warmup_prefill"
+    if task_cache.task_alloc(tid, list(range(warmup_len))):
+        with (
+            torch.inference_mode(),
+            timed("warmup prefill", logger),
+        ):
+            kv = task_cache.bind([tid], ws, start_pos=0)
+            ids_in = torch.arange(warmup_len, device=dev)
+            pos_in = ids_in
+            model(
+                ids_in,
+                kv_cache=kv,
+                position_ids=pos_in,
+                fwd="prefill",
+            )
+        task_cache.task_free(tid)
+
+    batch_sizes = [1]
+    n = 2
+    while n <= max_batch_size:
+        batch_sizes.append(n)
+        n *= 2
+    if max_batch_size not in batch_sizes:
+        batch_sizes.append(max_batch_size)
+
+    for b in batch_sizes:
+        task_ids = [f"_warmup_decode_{b}_{i}" for i in range(b)]
+        prompt_tokens = [list(range(prompt_len)) for _ in range(b)]
+        alloc_ok = True
+        for tid, pt in zip(task_ids, prompt_tokens):
+            if not task_cache.task_alloc(tid, pt):
+                alloc_ok = False
+                break
+        if not alloc_ok:
+            for tid in task_ids:
+                task_cache.task_free(tid)
+            continue
+
+        with (
+            torch.inference_mode(),
+            timed(f"warmup decode b={b}", logger),
+        ):
+            for step in range(2):
+                seq_pos = step
+                ws.position_ids[:b] = seq_pos
+                for tid in task_ids:
+                    task_cache.task_extend(tid, seq_pos)
+                kv = task_cache.bind(task_ids, ws)
+                ids_buf = ws.fill_input_ids([step] * b)
+                gctx.forward(
+                    model,
+                    key=(b,),
+                    input_ids=ids_buf,
+                    kv_cache=kv,
+                    position_ids=ws.position_ids[:b],
+                    fwd="decode",
+                )
+
+        for tid in task_ids:
+            task_cache.task_free(tid)
+        torch.cuda.synchronize()
+
+
+class Executor:
+    """Model forward passes for prefill and decode phases."""
+
+    def __init__(
+        self,
+        model: AutoModel,
+        kv_cache: PagePool,
+        task_cache: TaskCacheManager,
+        device: Optional[str] = None,
+        dtype: Optional[torch.dtype] = None,
+        enable_cuda_graph: bool = True,
+    ):
+        self.model = model
+        self.kv_cache = kv_cache
+        self.task_cache = task_cache
+        self.device = device or next(model.parameters()).device
+        self.dtype = dtype or next(model.parameters()).dtype
+
+        # Per-step decode cache for the steady-state case (same ordered
+        # task set decodes one token per step).  Sampling params stay
+        # constant; only positions advance.
+        self._decode_cache: Optional[DecodeSteadyState] = None
+
+        # Pre-allocated fixed-shape buffers for the decode hot path
+        # (input_ids, decode mask, KV bind metadata).  Eagerly sized at init
+        # so the workspace is CUDA-graph-capture friendly — no allocation
+        # during capture.
+        config = model.config
+        max_q_heads = config.num_attention_heads
+        head_dim = config.hidden_size // config.num_attention_heads
+        backend = get_backend()
+        self._graph_supported = backend.supports_graph() and (
+            CudaBackend.available() and head_dim in CudaBackend.HEAD_DIMS
+        )
+        self._workspace = InferenceWorkspace(
+            max_batch_size=kv_cache.max_batch_size,
+            max_seq_len=kv_cache.max_seq_len,
+            max_q_heads=max_q_heads,
+            head_dim=head_dim,
+            device=self.device,
+            dtype=self.dtype,
+        )
+
+        # CUDA-graph capture: one graph per (batch_size,) key.
+        # Enabled at init-time via _warmup_cuda_graphs for CudaBackend
+        # on supported head_dims; left disabled otherwise.
+        self._graph_ctx = CudaGraphContext()
+        if enable_cuda_graph:
+            self._try_enable_cuda_graph()
+
+    def _try_enable_cuda_graph(self):
+        if not self._graph_supported:
+            return
+
+        self._graph_ctx.set_enabled(True)
+        _warmup_cuda_graphs(
+            self.model,
+            self.kv_cache,
+            self.task_cache,
+            self._workspace,
+            self._graph_ctx,
+            max_batch_size=self.kv_cache.max_batch_size,
+            device=self.device,
+        )
+
+    @property
+    def cuda_graph_enabled(self) -> bool:
+        return self._graph_ctx.enabled and self._graph_supported
+
+    def _sample_logits(
+        self,
+        logits: Tensor,
+        tasks: List[Task],
+        return_logprobs: bool = False,
+        info: Optional[SamplingBatchInfo] = None,
+    ):
+        """Sample from ``logits`` and return ``(host_payload, tokens)``.
+
+        ``host_payload`` is the scheduler-facing list (token ids, or
+        ``(token_id, logprob)`` tuples with ``return_logprobs``);
+        ``tokens`` is the ``[B]`` device tensor that produced it, kept
+        for the steady-state decode fast path.
+        """
+        info = info or _build_sampling_batch_info(tasks, self.device)
+        if info.has_freq:
+            history_lists = [
+                t.prompt_ids[-t.rep_window :] + t.output_ids for t in tasks
+            ]
+            history_lens = [len(ids) for ids in history_lists]
+            max_len = max(history_lens, default=0)
+            padded_ids = torch.zeros(
+                len(tasks), max_len, dtype=torch.long, device=self.device
+            )
+            padded_mask = torch.zeros(
+                len(tasks), max_len, dtype=torch.bool, device=self.device
+            )
+            for i, ids in enumerate(history_lists):
+                length = len(ids)
+                padded_ids[i, :length] = torch.as_tensor(
+                    ids, dtype=torch.long, device=self.device
+                )
+                padded_mask[i, :length] = True
+        else:
+            padded_ids = None
+            padded_mask = None
+
+        result = sample(
+            logits,
+            temperature=info.temperatures,
+            top_k=info.top_ks,
+            top_p=info.top_ps,
+            frequency_penalty=info.freq_penalties,
+            input_ids=padded_ids,
+            input_mask=padded_mask,
+            return_logprobs=return_logprobs,
+        )
+        if not return_logprobs:
+            return result.tolist(), result
+
+        tokens, logprobs = result
+        tokens_list = tokens.tolist()
+        logprobs_list = logprobs.tolist()
+        for task, logprob in zip(tasks, logprobs_list):
+            task.output_logprobs.append(float(logprob))
+        return list(zip(tokens_list, logprobs_list)), tokens
+
+    def execute_prefill(
+        self,
+        tasks: List[Task],
+        prompt_len: int,
+        start_pos: int = 0,
+        return_logprobs: bool = False,
+    ):
+        if start_pos >= prompt_len:
+            return []
+
+        tasks = sorted(tasks, key=lambda t: t.task_id)
+        batch_sz = len(tasks)
+
+        input_ids = torch.tensor(
+            [token for t in tasks for token in t.prompt_ids[start_pos:prompt_len]],
+            dtype=torch.long,
+            device=self.device,
+        )
+
+        task_ids = [t.task_id for t in tasks]
+        position_ids = torch.arange(
+            start_pos, prompt_len, dtype=torch.long, device=self.device
+        ).repeat(batch_sz)
+
+        with (
+            torch.inference_mode(),
+            timed(f"execute_prefill b={batch_sz} prompt_len={prompt_len}", logger),
+        ):
+            outputs = self.model(
+                input_ids,
+                position_ids=position_ids,
+                kv_cache=self.task_cache.bind(
+                    task_ids,
+                    self._workspace,
+                    start_pos=start_pos,
+                ),
+                fwd="prefill",
+            )
+            q_len = prompt_len - start_pos
+            logits = outputs["logits"][
+                torch.arange(1, batch_sz + 1, device=self.device) * q_len - 1
+            ]
+
+        step_out, _ = self._sample_logits(logits, tasks, return_logprobs)
+        return tasks, step_out
+
+    def execute_decode(
+        self, tasks: List[Task], return_logprobs: bool = False
+    ) -> List[int]:
+        """Decode next token for each task.
+
+        Args:
+            return_logprobs: When ``True``, also record (and return)
+                the log-probability of each sampled token under the
+                post-strategy sampling distribution.  The logprob is
+                appended to ``task.output_logprobs`` and the return
+                list becomes ``List[Tuple[int, float]]``.
+
+        Returns:
+            ``List[int]`` of sampled token IDs, or
+            ``List[Tuple[int, float]]`` of ``(token_id, logprob)`` when
+            ``return_logprobs`` is ``True``.
+        """
+        if not tasks:
+            return []
+
+        b = len(tasks)
+        ws = self._workspace
+        task_ids = [t.task_id for t in tasks]
+        cur_positions = [t.next_pos for t in tasks]
+        task_sig = tuple(task_ids)
+
+        # ---- pre-replay: update input buffers in-place ----
+
+        # When the previous decode step ran this same ordered task set, its
+        # sampled tokens are still on-device and map 1:1 onto the current
+        # slots — fill input ids device-to-device.  inference_mode guards
+        # the read because the source was produced under sampling's
+        # inference-mode context.
+        cached = self._decode_cache
+        sig_match = cached is not None and cached.task_sig == task_sig
+        if sig_match and cached.last_tokens is not None:
+            with torch.inference_mode():
+                input_ids = ws.fill_input_ids_from_device(cached.last_tokens)
+        else:
+            input_ids = ws.fill_input_ids(
+                [t.output_ids[-1] if t.output_ids else t.prompt_ids[-1] for t in tasks]
+            )
+
+        kv_cache = self.task_cache.bind(task_ids, ws)
+
+        reuse_decode_state = self.task_cache.bind_was_steady and sig_match
+        if reuse_decode_state:
+            info = self._decode_cache.sampling_info
+            ws.position_ids[:b] += 1
+        else:
+            info = _build_sampling_batch_info(tasks, self.device)
+            ws.position_ids[:b].copy_(
+                torch.tensor(cur_positions, dtype=torch.long, device=self.device)
+            )
+        self._decode_cache = DecodeSteadyState(task_sig, cur_positions, info)
+
+        # ---- forward (graph replay or live run + capture) ----
+
+        use_graph = (
+            self._graph_ctx.enabled
+            and self._graph_supported
+            and get_backend().supports_graph()
+        )
+        key = (b,)
+        with (
+            torch.inference_mode(),
+            timed(f"execute_decode forward b={b}", logger),
+        ):
+            if use_graph:
+                outputs = self._graph_ctx.forward(
+                    self.model,
+                    key=key,
+                    input_ids=input_ids,
+                    kv_cache=kv_cache,
+                    position_ids=ws.position_ids[:b],
+                    fwd="decode",
+                )
+            else:
+                outputs = self.model(
+                    input_ids,
+                    kv_cache=kv_cache,
+                    position_ids=ws.position_ids[:b],
+                    fwd="decode",
+                )
+            logits = outputs["logits"]
+
+        step_out, tokens_dev = self._sample_logits(
+            logits, tasks, return_logprobs, info=info
+        )
+        self._decode_cache.last_tokens = tokens_dev
+        return step_out

astrai/inference/runtime/graph.py

@@ -0,0 +1,103 @@
+"""CUDA-graph capture for the decode model-forward step.
+
+Mirrors SGLang's cuda-graph manager: one graph per batch size.  The graph
+pair.  The graph captures ``model.forward()`` with workspace-backed inputs
+(all at fixed addresses).  Before each replay the caller updates the input
+buffer content in-place so the graph sees fresh data at the same tensor
+addresses.
+
+Only the model forward is captured — sampling runs outside the graph
+(via ``torch.multinomial`` which consumes a mutable RNG state).
+"""
+
+import torch
+from torch import Tensor
+
+
+class CudaGraphContext:
+    """CUDA-graph capture/replay for decode steps.
+
+    Parameters:
+        enabled: When ``False``, ``forward()`` always runs the live model
+            forward without capture/replay (graphs are cleared).  Toggle at
+            runtime via the ``set_enabled()`` method.
+
+    Usage::
+
+        gctx = CudaGraphContext()
+        with torch.inference_mode():
+            outputs = gctx.forward(
+                model,
+                key=(batch_size,),
+                input_ids=workspace.input_ids[:b].unsqueeze(1),
+                input_mask=input_mask,
+                kv_cache=kv_cache,
+                position_ids=workspace.position_ids[:b].unsqueeze(1),
+            )
+
+    The first call at a given key runs *without* capture (warmup).  The
+    second call captures the graph.  Subsequent calls replay the captured
+    graph.  A ``torch.cuda.synchronize()`` before capture drains in-flight
+    work so the graph trace is clean.
+    """
+
+    def __init__(self, enabled: bool = False):
+        self._enabled = enabled
+        self._graphs: dict[tuple, torch.cuda.CUDAGraph] = {}
+        self._outputs: dict[tuple, dict[str, Tensor]] = {}
+        self._warmed: set[tuple] = set()
+
+    @property
+    def enabled(self) -> bool:
+        return self._enabled
+
+    def set_enabled(self, flag: bool):
+        """Enable or disable CUDA-graph capture at runtime.
+
+        Disabling clears all captured graphs (frees GPU memory) and warmup
+        state.  Re-enabling after disable starts fresh — graphs are
+        re-captured on the next warmup cycle.
+        """
+        if flag == self._enabled:
+            return
+        self._enabled = flag
+        if not flag:
+            self._graphs.clear()
+            self._outputs.clear()
+            self._warmed.clear()
+
+    def forward(self, model, *, key, **kwargs) -> dict[str, Tensor]:
+        """Run ``model(**kwargs)`` via graph replay or live forward.
+
+        Args:
+            model: callable, e.g. ``self.model.forward``.
+            key: ``(batch_size,)`` — the dispatch key (one graph per batch size).
+            **kwargs: arguments forwarded to ``model``.  All tensor arguments
+                must reside at stable addresses (workspace buffers).
+
+        Returns:
+            The dict produced by ``model(**kwargs)``, e.g.
+            ``{"logits": ..., "h0": ...}``.
+        """
+        if not self._enabled:
+            self._outputs[key] = model(**kwargs)
+            return self._outputs[key]
+
+        if key in self._graphs:
+            self._graphs[key].replay()
+        elif key in self._warmed:
+            cap_output = model(**kwargs)
+            torch.cuda.synchronize()
+            graph = torch.cuda.CUDAGraph()
+            with torch.cuda.graph(graph):
+                self._outputs[key] = model(**kwargs)
+            self._graphs[key] = graph
+            self._warmed.discard(key)
+            return cap_output
+        else:
+            self._warmed.add(key)
+            self._outputs[key] = model(**kwargs)
+        return self._outputs[key]
+
+    def has_graph(self, key: tuple) -> bool:
+        return key in self._graphs

astrai/inference/runtime/sample.py

@@ -266,7 +266,7 @@ class SamplingPipeline(BaseSamplingStrategy):
     @staticmethod
     def _is_greedy(temperature: Union[float, Tensor]) -> bool:
         if isinstance(temperature, Tensor):
-            return temperature.numel() == 1 and temperature.item() == 0
+            return bool((temperature == 0).all())
         return temperature == 0
 
     @torch.inference_mode()
@@ -363,24 +363,6 @@ def sample(
         ``True`` — a ``(token_ids, chosen_logprobs)`` tuple where
         ``chosen_logprobs`` has shape ``[batch]``.
     """
-    greedy = (
-        (
-            isinstance(temperature, Tensor)
-            and temperature.numel() == 1
-            and temperature.item() == 0
-        )
-        if isinstance(temperature, Tensor)
-        else temperature == 0
-    )
-
-    if greedy:
-        tokens = logits.argmax(dim=-1)
-        if not return_logprobs:
-            return tokens
-        log_probs = torch.log_softmax(logits.float(), dim=-1)
-        chosen = torch.gather(log_probs, -1, tokens.unsqueeze(-1)).squeeze(-1)
-        return tokens, chosen
-
     has_freq = (
         (isinstance(frequency_penalty, Tensor) and (frequency_penalty != 0).any())
         if isinstance(frequency_penalty, Tensor)

astrai/inference/scheduler.py

@@ -1,13 +1,21 @@
 import logging
 import threading
 import uuid
-from typing import Any, Dict, List, Optional, Tuple
+from contextlib import nullcontext
+from typing import Any, Dict, List, Optional, Tuple, Union
 
 import torch
 
-from astrai.inference.core.cache import PagePool
-from astrai.inference.core.executor import Executor
-from astrai.inference.core.task import STOP, Task, TaskManager, TaskStatus
+from astrai.extension import (
+    ATTN_BACKEND,
+    AttentionBackend,
+    attn_backend,
+    get_backend,
+)
+from astrai.inference.cache import PagePool, TaskCacheManager
+from astrai.inference.metrics import MetricsCollector
+from astrai.inference.runtime.executor import Executor
+from astrai.inference.task import STOP, Task, TaskManager, TaskStatus
 from astrai.model.automodel import AutoModel
 from astrai.tokenize.tokenizer import AutoTokenizer
 
@@ -26,6 +34,8 @@ class InferenceScheduler:
         device: Optional[str] = None,
         dtype: Optional[torch.dtype] = None,
         cache: Optional[PagePool] = None,
+        enable_cuda_graph: bool = True,
+        backend: Optional[Union[str, ATTN_BACKEND, AttentionBackend, type]] = None,
     ):
         config = model.config
 
@@ -56,19 +66,34 @@ class InferenceScheduler:
                 dtype=self.dtype,
             )
 
+        self._metrics = MetricsCollector()
+
+        self._task_cache = TaskCacheManager(self._cache)
+
         self._task_mgr = TaskManager(
             tokenizer=tokenizer,
             max_batch_size=max_batch_size,
             max_seq_len=self.max_seq_len,
+            metrics=self._metrics,
         )
 
-        self._executor = Executor(
-            model=model,
-            tokenizer=tokenizer,
-            kv_cache=self._cache,
-            device=self.device,
-            dtype=self.dtype,
-        )
+        if backend is None:
+            self._backend = None
+            active_backend = get_backend()
+        else:
+            active_backend = backend
+        with attn_backend(active_backend):
+            if backend is not None:
+                self._backend = get_backend()
+            self._backend_name = type(get_backend()).__name__
+            self._executor = Executor(
+                model=model,
+                kv_cache=self._cache,
+                task_cache=self._task_cache,
+                device=self.device,
+                dtype=self.dtype,
+                enable_cuda_graph=enable_cuda_graph,
+            )
 
         self._stop_event = threading.Event()
         self._loop_thread: Optional[threading.Thread] = None
@@ -78,11 +103,31 @@ class InferenceScheduler:
 
     def remove_task(self, task_id: str):
         for task in self._task_mgr.remove_task(task_id):
-            self._cache.task_free(task.task_id)
+            self._task_cache.task_free(task.task_id)
 
     def get_stats(self) -> Dict[str, Any]:
         return self._task_mgr.get_stats()
 
+    @property
+    def backend_name(self) -> str:
+        return self._backend_name
+
+    @property
+    def cuda_graph_enabled(self) -> bool:
+        return self._executor.cuda_graph_enabled
+
+    def _backend_context(self):
+        if self._backend is None:
+            return nullcontext()
+        return attn_backend(self._backend)
+
+    @staticmethod
+    def _task_backend_groups(tasks: List[Task]):
+        groups = {}
+        for task in tasks:
+            groups.setdefault(task.backend, (task.backend, []))[1].append(task)
+        return groups.values()
+
     def _step(
         self, tasks: List[Task], return_logprobs: bool = False
     ) -> Tuple[List[Task], List[Task]]:
@@ -106,32 +151,45 @@ class InferenceScheduler:
             already appended to ``output_ids``) and tasks that hit the
             sequence cap and were marked ``ABORTED``.
         """
-        cache = self._cache
-
-        to_prefill = [t for t in tasks if t.output_tokens == 0 and t.prompt_ids]
+        to_prefill = [t for t in tasks if not t.prefill_done and t.prompt_ids]
         prefilled_ids = set()
         produced: List[Task] = []
         if to_prefill:
             for t in to_prefill:
                 t.input_tokens = len(t.prompt_ids)
 
-            groups: Dict[Tuple[int, int], List[Task]] = {}
+            groups: Dict[Tuple[int, int, Optional[AttentionBackend]], List[Task]] = {}
             for t in to_prefill:
-                start_pos = min(cache.task_cached(t.task_id), len(t.prompt_ids) - 1)
-                groups.setdefault((len(t.prompt_ids), start_pos), []).append(t)
-
-            for (prompt_len, start_pos), group in groups.items():
-                prefilled, step_out = self._executor.execute_prefill(
-                    group, prompt_len, start_pos, return_logprobs=return_logprobs
+                start_pos = min(
+                    self._task_cache.task_cached(t.task_id), len(t.prompt_ids) - 1
                 )
+                groups.setdefault((len(t.prompt_ids), start_pos, t.backend), []).append(
+                    t
+                )
+
+            for (prompt_len, start_pos, _), group in groups.items():
+                backend = group[0].backend
+                backend_context = (
+                    attn_backend(backend) if backend is not None else nullcontext()
+                )
+                with (
+                    backend_context,
+                    self._metrics.record([t.task_id for t in group], "prefill"),
+                ):
+                    prefilled, step_out = self._executor.execute_prefill(
+                        group, prompt_len, start_pos, return_logprobs=return_logprobs
+                    )
+
                 for t, out in zip(prefilled, step_out):
                     t.output_ids.append(out[0] if return_logprobs else out)
                     t.output_tokens += 1
+                    t.mark_prefill_done()
                     prefilled_ids.add(t.task_id)
                     produced.append(t)
-                start_logical_page = start_pos // getattr(cache, "page_size", 64)
+
+                start_logical_page = start_pos // self._cache.page_size
                 for t in group:
-                    cache.task_record_hashes(
+                    self._task_cache.task_record_hashes(
                         t.task_id, t.prompt_ids, start_logical_page
                     )
 
@@ -140,82 +198,84 @@ class InferenceScheduler:
         for t in tasks:
             if t.task_id in prefilled_ids:
                 continue
-            if cache.task_extend(t.task_id, t.next_pos):
+            if self._task_cache.task_extend(t.task_id, t.next_pos):
                 decoded.append(t)
             else:
                 t.status = TaskStatus.ABORTED
                 aborted.append(t)
 
-        if decoded:
-            step_out = self._executor.execute_decode(
-                decoded, return_logprobs=return_logprobs
+        for backend, group in self._task_backend_groups(decoded):
+            backend_context = (
+                attn_backend(backend) if backend is not None else nullcontext()
             )
-            for t, out in zip(decoded, step_out):
+            with (
+                backend_context,
+                self._metrics.record([t.task_id for t in group], "decode"),
+            ):
+                step_out = self._executor.execute_decode(
+                    group, return_logprobs=return_logprobs
+                )
+            for t, out in zip(group, step_out):
                 t.output_ids.append(out[0] if return_logprobs else out)
                 t.output_tokens += 1
+                t.advance_kv()
                 produced.append(t)
 
         return produced, aborted
 
     def _run_generation_loop(self):
         stop_ids = self._task_mgr.tokenizer.stop_ids
-        cache = self._cache
         try:
-            while not self._stop_event.is_set():
-                finished = self._task_mgr.remove_finished_tasks(stop_ids)
-                for task in finished:
-                    if task.status == TaskStatus.FINISHED:
-                        cache.task_record_hashes(
-                            task.task_id,
-                            cache.task_cacheable_ids(
-                                task.task_id, task.prompt_ids, task.output_ids
-                            ),
-                        )
-                    cache.task_free(task.task_id)
+            with self._backend_context():
+                while not self._stop_event.is_set():
+                    finished = self._task_mgr.remove_finished_tasks(stop_ids)
+                    for task in finished:
+                        if task.status == TaskStatus.FINISHED:
+                            self._task_cache.task_record_hashes(
+                                task.task_id,
+                                self._task_cache.task_cacheable_ids(
+                                    task.task_id, task.prompt_ids, task.output_ids
+                                ),
+                            )
+                        self._task_cache.task_free(task.task_id)
 
-                active = self._task_mgr.get_active_tasks()
-                available = self._task_mgr.max_batch_size - len(active)
-                if available > 0:
-                    candidates = self._task_mgr.pull_candidates(available)
-                    failed = []
-                    for task in candidates:
-                        if cache.task_alloc(task.task_id, task.prompt_ids):
-                            self._task_mgr.activate(task)
-                        else:
-                            failed.append(task)
-                    if failed:
-                        self._task_mgr.return_to_waiting(failed)
+                    active = self._task_mgr.get_active_tasks()
+                    available = self._task_mgr.max_batch_size - len(active)
+                    if available > 0:
+                        candidates = self._task_mgr.pull_candidates(available)
+                        failed = []
+                        for task in candidates:
+                            if self._task_cache.task_alloc(
+                                task.task_id, task.prompt_ids
+                            ):
+                                self._task_mgr.activate(task)
+                            else:
+                                failed.append(task)
+                        if failed:
+                            self._task_mgr.return_to_waiting(failed)
 
-                if not self._task_mgr.has_work():
-                    self._task_mgr.wait_for_tasks(timeout=1.0)
-                    continue
+                    if not self._task_mgr.has_work():
+                        self._task_mgr.wait_for_tasks(timeout=1.0)
+                        continue
 
-                active = self._task_mgr.get_active_tasks()
+                    active = self._task_mgr.get_active_tasks()
 
-                decoded, aborted = self._step(active)
+                    decoded, aborted = self._step(active)
 
-                for t in aborted:
-                    self._task_mgr.invoke_callback(t.task_id, STOP)
-
-                for t in decoded:
-                    new_text = t.decode_new_token(self._task_mgr.tokenizer)
-                    if new_text:
-                        self._task_mgr.invoke_callback(t.task_id, new_text)
-                    if t.is_finished(stop_ids):
-                        remaining = t.flush_remaining(self._task_mgr.tokenizer)
-                        if remaining:
-                            self._task_mgr.invoke_callback(t.task_id, remaining)
+                    for t in aborted:
                         self._task_mgr.invoke_callback(t.task_id, STOP)
 
+                    for t in decoded:
+                        new_text = t.decode_new_token(self._task_mgr.tokenizer)
+                        if new_text:
+                            self._task_mgr.invoke_callback(t.task_id, new_text)
+                        if t.is_finished(stop_ids):
+                            self._task_mgr.invoke_callback(t.task_id, STOP)
+
         except Exception as e:
             self._stop_event.set()
             logger.error(f"Scheduler loop crashed: {e}", exc_info=True)
-            for task in self._task_mgr.get_active_tasks():
-                self._task_mgr.invoke_callback(task.task_id, STOP)
-                cache.task_free(task.task_id)
-            for task in self._task_mgr.get_waiting_tasks():
-                self._task_mgr.invoke_callback(task.task_id, STOP)
-            self._task_mgr.clear_queues()
+            self._abort_and_clear(free_waiting=False)
 
     def start(self):
         if self._loop_thread is not None and self._loop_thread.is_alive():
@@ -231,16 +291,21 @@ class InferenceScheduler:
         if self._loop_thread is not None:
             self._loop_thread.join(timeout=2.0)
         self._loop_thread = None
-        for task in self._task_mgr.get_active_tasks():
-            self._task_mgr.invoke_callback(task.task_id, STOP)
-            self._cache.task_free(task.task_id)
-        for task in self._task_mgr.get_waiting_tasks():
-            self._task_mgr.invoke_callback(task.task_id, STOP)
-            self._cache.task_free(task.task_id)
-        self._task_mgr.clear_queues()
+        self._abort_and_clear(free_waiting=True)
         if torch.cuda.is_available():
             torch.cuda.empty_cache()
 
+    def _abort_and_clear(self, free_waiting: bool):
+        """Invoke STOP callbacks, release cache slots, and clear task queues."""
+        for task in self._task_mgr.get_active_tasks():
+            self._task_mgr.invoke_callback(task.task_id, STOP)
+            self._task_cache.task_free(task.task_id)
+        for task in self._task_mgr.get_waiting_tasks():
+            self._task_mgr.invoke_callback(task.task_id, STOP)
+            if free_waiting:
+                self._task_cache.task_free(task.task_id)
+        self._task_mgr.clear_queues()
+
     def run_batch(
         self,
         prompt_ids_list: List[List[int]],
@@ -275,8 +340,8 @@ class InferenceScheduler:
             ``List[Tuple[List[int], List[float]]]``.
         """
         stop_ids = self._task_mgr.tokenizer.stop_ids
-        cache = self._cache
         seq_cap = self.max_seq_len
+        request_backend = get_backend(use_default=False)
 
         tasks: List[Task] = []
         for ids in prompt_ids_list:
@@ -288,6 +353,9 @@ class InferenceScheduler:
                 t_max = seq_cap - len(ids)
             else:
                 t_max = min(t_max, seq_cap - len(ids))
+            if t_max <= 0:
+                tasks.append(None)
+                continue
             task = Task(
                 task_id=f"batch_{uuid.uuid4().hex[:8]}",
                 prompt_ids=list(ids),
@@ -297,23 +365,29 @@ class InferenceScheduler:
                 top_k=top_k,
                 frequency_penalty=frequency_penalty,
                 rep_window=rep_window,
+                backend=request_backend,
             )
-            if not cache.task_alloc(task.task_id, task.prompt_ids):
+            if not self._task_cache.task_alloc(task.task_id, task.prompt_ids):
                 tasks.append(None)
                 continue
             task.input_tokens = len(task.prompt_ids)
+            self._metrics.register(task.task_id)
             tasks.append(task)
 
         try:
             live = [t for t in tasks if t is not None]
 
-            while live:
-                decoded, _ = self._step(live, return_logprobs=return_logprobs)
-                live = [t for t in decoded if not t.is_finished(stop_ids)]
+            with self._backend_context():
+                while live:
+                    decoded, _ = self._step(live, return_logprobs=return_logprobs)
+                    live = [t for t in decoded if not t.is_finished(stop_ids)]
         finally:
             for t in tasks:
                 if t is not None:
-                    cache.task_free(t.task_id)
+                    self._metrics.mark_finished(
+                        t.task_id, t.input_tokens, t.output_tokens
+                    )
+                    self._task_cache.task_free(t.task_id)
 
         results: List[Any] = []
         for t in tasks:

astrai/inference/task.py

@@ -1,16 +1,17 @@
-import logging
 import threading
 import time
 import uuid
 from collections import deque
 from enum import Enum
-from typing import Any, Callable, Deque, Dict, List, Optional
+from typing import TYPE_CHECKING, Any, Callable, Deque, Dict, List, Optional
 
 from tokenizers.decoders import DecodeStream
 
+from astrai.inference.metrics import MetricsCollector
 from astrai.tokenize.tokenizer import AutoTokenizer
 
-logger = logging.getLogger(__name__)
+if TYPE_CHECKING:
+    from astrai.extension import AttentionBackend
 
 STOP = object()
 
@@ -64,6 +65,7 @@ class Task:
         top_k: int = 50,
         frequency_penalty: float = 0.0,
         rep_window: int = 64,
+        backend: Optional["AttentionBackend"] = None,
     ):
         self.task_id = task_id
         self.prompt_ids = prompt_ids
@@ -73,16 +75,25 @@ class Task:
         self.top_k = top_k
         self.frequency_penalty = frequency_penalty
         self.rep_window = rep_window
+        self.backend = backend
 
         self.status = TaskStatus.PENDING
         self.output_ids: List[int] = []
         self.output_logprobs: List[float] = []
         self.input_tokens: int = 0
         self.output_tokens: int = 0
-        self.arrival_time = time.time()
-        self.finish_time: Optional[float] = None
+        self._kv_len: int = 0
         self._decoder: Optional[StreamDecoder] = None
 
+    def mark_prefill_done(self):
+        """Prompt KV is materialized by prefill; first output sampled but
+        not yet written to KV."""
+        self._kv_len = self.input_tokens
+
+    def advance_kv(self):
+        """One more position written to KV (after a decode forward)."""
+        self._kv_len += 1
+
     def decode_new_token(self, tokenizer: AutoTokenizer) -> str:
         """Decode the last appended output token, buffering incomplete
         multi-byte sequences across calls.
@@ -93,20 +104,15 @@ class Task:
             self._decoder = StreamDecoder(tokenizer)
         return self._decoder.push(self.output_ids[-1])
 
-    def flush_remaining(self, tokenizer: AutoTokenizer) -> str:
-        """Emit any text still buffered in the decoder.
-
-        With the Rust-native DecodeStream, the stream is always in a
-        correct state — any completed text was already emitted by the
-        last ``push``.  A trailing incomplete multi-byte sequence has no
-        valid text to emit, so this is a no-op.
-        """
-        return ""
-
     @property
     def next_pos(self) -> int:
-        # The first output is sampled from prefill and enters KV on the next step.
-        return self.input_tokens + max(0, len(self.output_ids) - 1)
+        """KV position where the next decode step will write."""
+        return self._kv_len
+
+    @property
+    def prefill_done(self) -> bool:
+        """True when all prompt KV entries are materialized."""
+        return self._kv_len >= self.input_tokens > 0
 
     def is_finished(self, stop_ids: List[int]) -> bool:
         if self.max_tokens is not None and self.output_tokens >= self.max_tokens:
@@ -124,6 +130,7 @@ class TaskManager:
         tokenizer: AutoTokenizer,
         max_batch_size: int = 16,
         max_seq_len: int = 8192,
+        metrics: Optional["MetricsCollector"] = None,
     ):
         self.tokenizer = tokenizer
         self.max_batch_size = max_batch_size
@@ -139,6 +146,8 @@ class TaskManager:
         self._total_tasks = 0
         self._total_tokens = 0
 
+        self._metrics = metrics
+
     def add_task(
         self,
         prompt: str,
@@ -148,6 +157,7 @@ class TaskManager:
         top_k: int = 50,
         frequency_penalty: float = 0.0,
         rep_window: int = 64,
+        backend: Optional["AttentionBackend"] = None,
         stream_callback: Optional[Callable[[str], None]] = None,
     ) -> str:
         task_id = f"task_{int(time.time())}_{uuid.uuid4().hex[:8]}"
@@ -155,11 +165,6 @@ class TaskManager:
         if len(prompt_ids) > self.max_seq_len:
             prompt_ids = prompt_ids[-self.max_seq_len :]
 
-        if len(prompt_ids) > self.max_seq_len:
-            if stream_callback:
-                stream_callback(STOP)
-            return task_id
-
         if max_tokens is None:
             max_tokens = self.max_seq_len - len(prompt_ids)
         else:
@@ -174,6 +179,7 @@ class TaskManager:
             top_k=top_k,
             frequency_penalty=frequency_penalty,
             rep_window=rep_window,
+            backend=backend,
         )
 
         with self._lock:
@@ -182,6 +188,9 @@ class TaskManager:
             if stream_callback:
                 self._callbacks[task_id] = stream_callback
 
+        if self._metrics is not None:
+            self._metrics.register(task_id)
+
         self._task_event.set()
         return task_id
 
@@ -201,26 +210,33 @@ class TaskManager:
             cb(token)
 
     def get_stats(self) -> Dict[str, Any]:
-        return {
+        stats: Dict[str, Any] = {
             "total_tasks": self._total_tasks,
             "total_tokens": self._total_tokens,
             "active_tasks": len(self.active_tasks),
             "waiting_queue": len(self.waiting_queue),
         }
+        if self._metrics is not None:
+            stats.update(self._metrics.get_stats())
+        return stats
 
     def remove_finished_tasks(self, stop_ids: List[int]) -> List[Task]:
         with self._lock:
             finished = []
             for task in self.active_tasks:
                 if task.status == TaskStatus.ABORTED:
-                    task.finish_time = time.time()
                     finished.append(task)
                 elif task.is_finished(stop_ids):
                     task.status = TaskStatus.FINISHED
-                    task.finish_time = time.time()
                     finished.append(task)
                     self._total_tokens += task.output_tokens
 
+            if self._metrics is not None:
+                for task in finished:
+                    self._metrics.mark_finished(
+                        task.task_id, task.input_tokens, task.output_tokens
+                    )
+
             self.active_tasks = [
                 t
                 for t in self.active_tasks

astrai/inference/workspace.py

@@ -1,20 +1,17 @@
 """Pre-allocated buffers for the inference decode hot path.
 
-Mirrors SGLang's pre-allocated input buffers (``input_buffers.py``): tensors
-are sized once to the server's maximum dimensions and sliced to the live
-batch each step, so the per-token decode loop never calls
-``torch.empty``/``torch.zeros``/``torch.arange`` for the hot shapes.  Fills
-go through ``out=`` variants (``torch.ge``) which write into the stable
-buffers instead of allocating fresh results.
-
-All buffers are allocated eagerly at init (nothing is lazy), so the
-workspace is CUDA-graph-capture friendly: the decode step reads/writes
-fixed-address tensors with no allocation during capture.
+Mirrors FlashInfer / SGLang's global workspace pattern: all per-step tensors
+are allocated eagerly at init (nothing is lazy), so the decode step
+reads/writes fixed-address tensors with zero ``torch.empty`` calls during
+the hot loop — a prerequisite for CUDA-graph capture.
 """
 
 import torch
 from torch import Tensor
 
+_MAX_SPLITS = 32
+Q_TILE_ROWS = 64
+
 
 class InferenceWorkspace:
     """Reusable fixed-shape per-step buffers for decode.
@@ -30,6 +27,11 @@ class InferenceWorkspace:
     - KV-cache bind metadata (``req_pool_indices``, ``seq_lens``,
       ``kv_indptr``, ``inc``, ``out_cache_loc``), written by
       ``PagePool.bind_tasks`` when the Executor passes this workspace.
+    - ``decode_o_part`` / ``decode_ml_part``: split-KV partial result buffers
+      (mirrors FlashInfer's workspace).  One global alloc, reused by every
+      decode step across all layers.  Sliced views are passed to the CUDA
+      attention kernel so its internal ``torch.empty`` hot-path alloc goes
+      through a stable address (CUDA-graph capturable).
 
     No re-allocation while the server's bounds are respected.
     """
@@ -38,11 +40,15 @@ class InferenceWorkspace:
         self,
         max_batch_size: int,
         max_seq_len: int,
+        max_q_heads: int,
+        head_dim: int,
         device: torch.device,
         dtype: torch.dtype,
     ):
         self.max_batch_size = max_batch_size
         self.max_seq_len = max_seq_len
+        self.max_q_heads = max_q_heads
+        self.head_dim = head_dim
         self.device = device
         self.dtype = dtype
 
@@ -69,7 +75,7 @@ class InferenceWorkspace:
         # when the Executor passes this workspace).  Stable addresses make the
         # decode forward CUDA-graph capturable.
         self.req_pool_indices = torch.empty(
-            (max_batch_size,), dtype=torch.long, device=device
+            (max_batch_size,), dtype=torch.int32, device=device
         )
         self.seq_lens = torch.empty((max_batch_size,), dtype=torch.long, device=device)
         self.kv_indptr = torch.empty(
@@ -78,9 +84,44 @@ class InferenceWorkspace:
         self.qo_indptr = torch.empty(
             (max_batch_size + 1,), dtype=torch.int32, device=device
         )
+        max_q_tiles = max_batch_size * ((max_seq_len + Q_TILE_ROWS - 1) // Q_TILE_ROWS)
+        self.q_tile_to_batch = torch.empty(
+            (max_q_tiles,), dtype=torch.int32, device=device
+        )
+        self.q_tile_to_index = torch.empty(
+            (max_q_tiles,), dtype=torch.int32, device=device
+        )
         self.inc = torch.arange(max_batch_size + 1, dtype=torch.int32, device=device)
         self.out_cache_loc = torch.empty(
-            (max_batch_size, 1), dtype=torch.long, device=device
+            (max_batch_size, 1), dtype=torch.int32, device=device
+        )
+
+        # Per-step position IDs (must be at a fixed address for CUDA-graph capture).
+        self.position_ids = torch.empty(
+            (max_batch_size,), dtype=torch.long, device=device
+        )
+
+        # Split-KV partial-result buffers for decode (persistent, one global
+        # alloc per process — mirrors FlashInfer's workspace pattern).
+        # Shape: [max_batch_size, max_q_heads, _MAX_SPLITS, head_dim] (o_part)
+        #        [max_batch_size, max_q_heads, _MAX_SPLITS, 2]     (ml_part)
+        self.decode_o_part = torch.empty(
+            (max_batch_size, max_q_heads, _MAX_SPLITS, head_dim),
+            dtype=torch.float32,
+            device=device,
+        )
+        self.decode_ml_part = torch.empty(
+            (max_batch_size, max_q_heads, _MAX_SPLITS, 2),
+            dtype=torch.float32,
+            device=device,
+        )
+
+        # Decode output buffer (graph-safe pre-alloc).  Shape matches the
+        # decode kernel's output: [batch, q_head, head_dim].
+        self.decode_out = torch.empty(
+            (max_batch_size, max_q_heads, head_dim),
+            dtype=dtype,
+            device=device,
         )
 
     def fill_input_ids(self, ids: "list[int]") -> Tensor:
@@ -98,6 +139,18 @@ class InferenceWorkspace:
         self.input_ids[:b].copy_(pin[:b])
         return self.input_ids[:b]
 
+    def fill_input_ids_from_device(self, tokens: Tensor) -> Tensor:
+        """Copy device-resident ``[B]`` token ids into the device buffer.
+
+        Steady-state decode fast path: when the executor's cached task
+        signature still matches, the previous step's sampled tokens map
+        1:1 onto the current slots, so the ids transfer device-to-device
+        instead of round-tripping through the host staging buffers.
+        """
+        b = tokens.size(0)
+        self.input_ids[:b].copy_(tokens)
+        return self.input_ids[:b]
+
     def decode_mask(self, position_ids: Tensor, total_len: int) -> Tensor:
         """Return the ``[B, 1, total_len]`` validity mask for this step.
 

astrai/logging.py

@@ -0,0 +1,37 @@
+import logging
+import os
+
+from astrai.parallel.setup import get_rank, get_world_size
+
+
+class _DistributedContextFilter(logging.Filter):
+    def filter(self, record: logging.LogRecord) -> bool:
+        record.rank = str(get_rank())
+        record.world_size = str(get_world_size())
+        return True
+
+
+def setup_logging(level: str = "INFO"):
+    """Attach a StreamHandler to the ``astrai`` logger (idempotent).
+
+    Call once per process at the top of CLI scripts.
+    Set ``ASTR_LOG_LEVEL`` env var to override the default level.
+
+    Level names: ``DEBUG``, ``INFO``, ``WARNING``, ``ERROR``, ``CRITICAL``.
+    ``DEBUG`` enables per-step prefill/decode timing logs
+    (:func:`astrai.inference.runtime.executor.timed`).
+    """
+    logger = logging.getLogger("astrai")
+    if logger.handlers:
+        return
+    level_name = os.environ.get("ASTR_LOG_LEVEL", level).upper()
+    logger.setLevel(getattr(logging, level_name, logging.INFO))
+    handler = logging.StreamHandler()
+    handler.addFilter(_DistributedContextFilter())
+    handler.setFormatter(
+        logging.Formatter(
+            "%(asctime)s | %(levelname)-8s | rank=%(rank)2s/%(world_size)-2s | %(name)-32s | %(message)s",
+            datefmt="%Y-%m-%d %H:%M:%S",
+        )
+    )
+    logger.addHandler(handler)

astrai/model/automodel.py

@@ -4,13 +4,21 @@ AutoModel base class for model loading and saving.
 
 from contextlib import contextmanager
 from pathlib import Path
-from typing import Self, Union
+from typing import Union
 
 import torch.nn as nn
 
 from astrai.config.model_config import BaseModelConfig, ConfigFactory
 from astrai.factory import BaseFactory
-from astrai.serialization import load_model_config, load_model_weights, save_model
+from astrai.serialization import (
+    HF_MODEL_TYPES,
+    adapt_config,
+    convert_hf_weights,
+    load_model_config,
+    load_model_weights,
+    looks_like_hf_state_dict,
+    save_model,
+)
 
 
 @contextmanager
@@ -57,7 +65,25 @@ class AutoModel(nn.Module):
         path: Union[str, Path],
         disable_random_init: bool = True,
         strict: bool = True,
+        weights_format: str = "auto",
     ) -> nn.Module:
+        """Load a model directory.
+
+        Args:
+            path: Directory containing ``config.json`` and optionally
+                ``model.safetensors``.
+            disable_random_init: Replace parameter initializers with no-ops
+                while building the model.
+            strict: Passed to ``load_state_dict``.
+            weights_format: ``"auto"`` detects HuggingFace checkpoints
+                (LLaMA-style keys and ``model_type``) and converts them;
+                ``"astrai"`` skips conversion; ``"hf"`` forces it.
+        """
+        if weights_format not in ("auto", "astrai", "hf"):
+            raise ValueError(
+                f"weights_format must be one of 'auto', 'astrai', 'hf', "
+                f"got {weights_format!r}"
+            )
 
         model_path = Path(path)
 
@@ -66,6 +92,12 @@ class AutoModel(nn.Module):
             raise FileNotFoundError(f"Config file not found: {config_path}")
 
         raw = load_model_config(str(model_path))
+        is_hf_config = weights_format == "hf" or (
+            weights_format == "auto" and raw.get("model_type") in HF_MODEL_TYPES
+        )
+        if is_hf_config:
+            raw = adapt_config(raw)
+
         config = ConfigFactory.load(raw)
         model_type = config.model_type or "autoregressive_lm"
 
@@ -75,8 +107,14 @@ class AutoModel(nn.Module):
             model = actual_cls(config)
 
         weights_path = model_path / "model.safetensors"
-        if weights_path.exists():
+        index_path = model_path / "model.safetensors.index.json"
+        if weights_path.exists() or index_path.exists():
             state_dict = load_model_weights(str(model_path))
+            is_hf_weights = is_hf_config or (
+                weights_format == "auto" and looks_like_hf_state_dict(state_dict)
+            )
+            if is_hf_weights:
+                state_dict = convert_hf_weights(state_dict, config)
             model.load_state_dict(state_dict, strict=strict)
 
         return model
@@ -90,7 +128,3 @@ class AutoModel(nn.Module):
             state_dict=self.state_dict(),
             save_directory=str(save_directory),
         )
-
-    def to(self, *args, **kwargs) -> Self:
-        """Move model to device/dtype."""
-        return super().to(*args, **kwargs)

astrai/model/components/__init__.py

@@ -1,4 +1,4 @@
-from astrai.extension.rotary_backend import apply_rotary_emb
+from astrai.extension.backend.rotary import apply_rotary_emb
 from astrai.model.components.attention import GQA, MLA
 from astrai.model.components.decoder_block import DecoderBlock
 from astrai.model.components.embedding import Embedding

astrai/model/components/attention.py

@@ -5,10 +5,9 @@ import torch.nn as nn
 import torch.nn.functional as F
 from torch import Tensor
 
-from astrai.extension import attention
-from astrai.extension.rotary_backend import apply_rotary_emb
+from astrai.extension.backend import apply_rotary_emb, attention
 from astrai.factory import BaseFactory
-from astrai.inference.core.cache import KVCache
+from astrai.inference.cache import KVCache
 from astrai.model.components.linear import Linear
 from astrai.model.components.norm import RMSNorm
 
@@ -56,9 +55,7 @@ class GQA(nn.Module):
             self.gate = Linear(dim, dim)
 
     def _split_heads(self, x: Tensor, n_heads) -> Tensor:
-        batch_size, seq_len, _ = x.shape
-        x = x.reshape(batch_size, seq_len, n_heads, self.head_dim)
-        return x
+        return x.reshape(*x.shape[:-1], n_heads, self.head_dim)
 
     def forward(
         self,
@@ -67,6 +64,7 @@ class GQA(nn.Module):
         attn_mask: Tensor = None,
         kv_cache: Optional[KVCache] = None,
         is_causal: bool = False,
+        fwd: Optional[str] = None,
     ) -> Tensor:
         q = self._split_heads(self.q_proj(x), self.n_heads)
         k = self._split_heads(self.k_proj(x), self.n_kv_heads)
@@ -76,7 +74,9 @@ class GQA(nn.Module):
         if self.use_qk_norm:
             q, k = self.q_norm(q), self.k_norm(k)
 
-        sdqa_out = attention(q, k, v, kv_cache, self.layer_id, attn_mask, is_causal)
+        sdqa_out = attention(
+            q, k, v, kv_cache, self.layer_id, attn_mask, is_causal, fwd
+        ).reshape(*x.shape[:-1], self.dim)
 
         if self.use_gated_attention:
             sdqa_out = sdqa_out * F.sigmoid(self.gate(x))
@@ -141,17 +141,16 @@ class MLA(nn.Module):
         attn_mask: Tensor = None,
         kv_cache: Optional[KVCache] = None,
         is_causal: bool = False,
+        fwd: Optional[str] = None,
     ) -> Tensor:
-        bsz, seq_len, _ = x.size()
-
         q = self.q_proj(x)
-        q = q.view(bsz, seq_len, self.n_heads, self.head_dim)
+        q = q.reshape(*x.shape[:-1], self.n_heads, self.head_dim)
 
         kv_compressed = self.kv_a_proj(x)
         kv_compressed = self.kv_norm(kv_compressed)
 
         kv = self.kv_b_proj(kv_compressed)
-        kv = kv.view(bsz, seq_len, self.n_kv_heads, -1)
+        kv = kv.reshape(*x.shape[:-1], self.n_kv_heads, -1)
 
         k_nope, k_rope, v = torch.split(
             kv, [self.qk_nope_head_dim, self.qk_rope_head_dim, self.head_dim], dim=-1
@@ -171,7 +170,9 @@ class MLA(nn.Module):
             q = self.q_norm(q)
             k = self.k_norm(k)
 
-        attn_out = attention(q, k, v, kv_cache, self.layer_id, attn_mask, is_causal)
+        attn_out = attention(
+            q, k, v, kv_cache, self.layer_id, attn_mask, is_causal, fwd
+        ).reshape(*x.shape[:-1], self.dim)
 
         if self.use_gated_attention:
             attn_out = attn_out * F.sigmoid(self.gate(x))

astrai/model/components/decoder_block.py

@@ -4,7 +4,7 @@ from typing import Optional, TypedDict
 import torch.nn as nn
 from torch import Tensor
 
-from astrai.inference.core.cache import KVCache
+from astrai.inference.cache import KVCache
 from astrai.model.components.attention import AttnFactory
 from astrai.model.components.mlp import FFNFactory, RouterStats
 from astrai.model.components.norm import RMSNorm
@@ -54,6 +54,7 @@ class DecoderBlock(nn.Module):
         attention_mask: Optional[Tensor] = None,
         kv_cache: Optional[KVCache] = None,
         is_causal: bool = False,
+        fwd: Optional[str] = None,
     ) -> DecoderOutput:
         attn_output = self.attention(
             self.input_norm(x),
@@ -61,6 +62,7 @@ class DecoderBlock(nn.Module):
             attention_mask,
             kv_cache,
             is_causal,
+            fwd,
         )
         x = attn_output + x
         normalized = self.post_attention_norm(x)

astrai/model/components/mlp.py

@@ -29,12 +29,6 @@ class FFNOutput(TypedDict):
     router_stats: Optional[RouterStats]
 
 
-class RoutedOutput(TypedDict):
-    hidden_states: Tensor
-    aux_loss: Optional[Tensor]
-    router_stats: Optional[RouterStats]
-
-
 @FFNFactory.register("mlp")
 class MLP(nn.Module):
     def __init__(self, dim: int, dim_ffn: int, down_init_std: float = 0.02):
@@ -100,13 +94,14 @@ class DeepSeekMoE(nn.Module):
 
     def forward(self, x: Tensor) -> FFNOutput:
         include_aux_loss = self.training and torch.is_grad_enabled()
-        bsz, seq_len, dim = x.shape
+        shape = x.shape
+        dim = shape[-1]
         x_flat = x.view(-1, dim)
 
         shared_out = self._shared_forward(x_flat)
         routed_output = self._routed_forward(x_flat, include_aux_loss)
 
-        out = (shared_out + routed_output["hidden_states"]).view(bsz, seq_len, dim)
+        out = (shared_out + routed_output["hidden_states"]).view(shape)
         return {
             "hidden_states": out,
             "aux_loss": routed_output["aux_loss"],
@@ -121,7 +116,7 @@ class DeepSeekMoE(nn.Module):
             / self.n_shared_experts
         )
 
-    def _routed_forward(self, x: Tensor, include_aux_loss: bool) -> RoutedOutput:
+    def _routed_forward(self, x: Tensor, include_aux_loss: bool) -> FFNOutput:
         N, D = x.shape
         K = self.n_activated_experts
         E = self.n_routed_experts

astrai/model/components/rope.py

@@ -65,9 +65,12 @@ class RotaryEmbedding(nn.Module):
             [batch, seq_len, dim/2, 2] (f32) — [cos, sin] pairs.
         """
         if position_ids is None:
-            position_ids = (
-                torch.arange(x.size(1), device=x.device)
-                .unsqueeze(0)
-                .expand(x.size(0), -1)
-            )
+            if x.ndim == 2:
+                position_ids = torch.arange(x.size(0), device=x.device)
+            else:
+                position_ids = (
+                    torch.arange(x.size(1), device=x.device)
+                    .unsqueeze(0)
+                    .expand(x.size(0), -1)
+                )
         return self.freqs_cis[position_ids].float()

astrai/model/transformer.py

@@ -5,7 +5,7 @@ import torch.nn as nn
 from torch import Tensor
 
 from astrai.config.model_config import AutoRegressiveLMConfig
-from astrai.inference.core.cache import KVCache
+from astrai.inference.cache import KVCache
 from astrai.model.automodel import AutoModel, ModelFactory
 from astrai.model.components.decoder_block import DecoderBlock
 from astrai.model.components.embedding import Embedding
@@ -105,8 +105,20 @@ class AutoRegressiveLM(AutoModel):
         input_mask: Optional[Tensor] = None,
         kv_cache: Optional[KVCache] = None,
         position_ids: Optional[Tensor] = None,
+        fwd: Optional[str] = None,
     ) -> Dict[str, Tensor]:
-        assert input_ids.ndim == 2
+        if fwd is None:
+            if input_ids.ndim != 2:
+                raise ValueError("training input_ids must be [batch, seq_len]")
+            if kv_cache is not None:
+                raise ValueError("training forward does not accept a KV cache")
+        elif fwd in ("prefill", "decode"):
+            if input_ids.ndim != 1:
+                raise ValueError("inference input_ids must be packed [tokens]")
+            if kv_cache is None:
+                raise ValueError("inference forward requires a KV cache")
+        else:
+            raise ValueError(f"unsupported forward mode: {fwd}")
 
         x = self.embed_tokens(input_ids)
         rotary_emb = self.rotary_embedding(x, position_ids)
@@ -122,6 +134,7 @@ class AutoRegressiveLM(AutoModel):
                 attn_mask,
                 kv_cache,
                 use_sdpa_causal_mask,
+                fwd,
             )
             x = layer_output["hidden_states"]
             stats = layer_output.get("router_stats")

astrai/parallel/setup.py

@@ -30,15 +30,13 @@ def get_current_device():
 def get_world_size() -> int:
     if dist.is_available() and dist.is_initialized():
         return dist.get_world_size()
-    else:
-        return 1
+    return int(os.environ.get("WORLD_SIZE", "1"))
 
 
 def get_rank() -> int:
     if dist.is_available() and dist.is_initialized():
         return dist.get_rank()
-    else:
-        return 0
+    return int(os.environ.get("RANK", "0"))
 
 
 @contextmanager
@@ -247,18 +245,15 @@ class LocalStrategy(LaunchStrategy):
             ctx.join()
 
 
-def _detect_launcher() -> str:
-    """Detect the distributed launcher from environment.
-
-    Returns one of: "torchelastic", "torchrun", "external", "local".
-    """
+def _is_external_launcher() -> bool:
+    """Whether an external launcher (torchrun/elastic/manual env) started us."""
     if dist.is_torchelastic_launched():
-        return "torchelastic"
+        return True
     if "LOCAL_WORLD_SIZE" in os.environ:
-        return "torchrun"
+        return True
     if "RANK" in os.environ and "WORLD_SIZE" in os.environ:
-        return "external"
-    return "local"
+        return True
+    return False
 
 
 def spawn_parallel_fn(
@@ -273,8 +268,7 @@ def spawn_parallel_fn(
 ):
     if master_port is None:
         master_port = find_free_port()
-    launcher = _detect_launcher()
-    if launcher in ("torchelastic", "torchrun", "external"):
+    if _is_external_launcher():
         strategy = TorchrunStrategy(
             world_size, backend, master_addr, master_port, device_type, start_method
         )

astrai/serialization/__init__.py

@@ -22,9 +22,21 @@ from astrai.serialization.dataset import (
     load_bin_offsets,
     save_bin,
 )
+from astrai.serialization.hf_adapter import (
+    HF_MODEL_TYPES,
+    adapt_config,
+    convert_hf_config,
+    convert_hf_weights,
+    looks_like_hf_state_dict,
+)
 
 __all__ = [
     "Checkpoint",
+    "HF_MODEL_TYPES",
+    "adapt_config",
+    "convert_hf_config",
+    "convert_hf_weights",
+    "looks_like_hf_state_dict",
     "load_json",
     "load_model_config",
     "load_model_weights",

astrai/serialization/checkpoint.py

@@ -5,7 +5,7 @@ import json
 import time
 from dataclasses import dataclass, field
 from pathlib import Path
-from typing import Any, Dict, Optional, Union
+from typing import Any, Callable, Dict, Optional, Union
 
 import safetensors.torch as st
 import torch
@@ -22,39 +22,31 @@ def save_safetensors(state_dict: dict, path: Union[str, Path]):
     st.save_file(state_dict, str(path))
 
 
-def load_safetensors(path: Union[str, Path], broadcast: bool = False) -> dict:
+def _broadcast_load(loader: Callable[[], dict], broadcast: bool) -> dict:
+    """Load on rank 0 and broadcast the object to all ranks."""
     if not broadcast or not dist.is_initialized():
-        return st.load_file(str(path))
-
+        return loader()
     rank = get_rank()
     if rank == 0:
-        state_dict = st.load_file(str(path))
+        data = loader()
     else:
-        state_dict = {}
-    tmp = [state_dict]
+        data = {}
+    tmp = [data]
     dist.broadcast_object_list(tmp, src=0)
     return tmp[0]
 
 
+def load_safetensors(path: Union[str, Path], broadcast: bool = False) -> dict:
+    return _broadcast_load(lambda: st.load_file(str(path)), broadcast)
+
+
 def save_json(data: dict, path: Union[str, Path]):
     with open(str(path), "w") as f:
         json.dump(data, f, indent=2)
 
 
 def load_json(path: Union[str, Path], broadcast: bool = False) -> dict:
-    if not broadcast or not dist.is_initialized():
-        with open(str(path), "r") as f:
-            return json.load(f)
-
-    rank = get_rank()
-    if rank == 0:
-        with open(str(path), "r") as f:
-            data = json.load(f)
-    else:
-        data = {}
-    tmp = [data]
-    dist.broadcast_object_list(tmp, src=0)
-    return tmp[0]
+    return _broadcast_load(lambda: json.loads(Path(path).read_text()), broadcast)
 
 
 def save_torch(obj: Any, path: Union[str, Path]):
@@ -99,7 +91,21 @@ def load_model_config(save_directory: str) -> dict:
 
 
 def load_model_weights(save_directory: str) -> dict:
-    return load_state_dict(Path(save_directory) / _WEIGHTS_FILE)
+    save_path = Path(save_directory)
+    weights_file = save_path / _WEIGHTS_FILE
+    if weights_file.exists():
+        return load_state_dict(weights_file)
+
+    index_path = save_path / "model.safetensors.index.json"
+    if index_path.exists():
+        index = load_json(index_path)
+        weight_map = index.get("weight_map", {})
+        state_dict = {}
+        for shard in sorted(set(weight_map.values())):
+            state_dict.update(load_state_dict(save_path / shard))
+        return state_dict
+
+    raise FileNotFoundError(f"No model weights found in {save_directory}")
 
 
 def load_state_dict(path: Union[str, Path], broadcast: bool = False) -> dict:
@@ -190,8 +196,10 @@ class Checkpoint:
         if meta_path.exists():
             return cls.load(save_dir, broadcast=broadcast)
 
-        if weights_path.exists():
-            state_dict = load_state_dict(weights_path, broadcast=broadcast)
+        weights_path = save_path / _WEIGHTS_FILE
+        index_path = save_path / "model.safetensors.index.json"
+        if weights_path.exists() or index_path.exists():
+            state_dict = load_model_weights(save_dir)
             config = {}
             config_path = save_path / _CONFIG_FILE
             if config_path.exists():

astrai/serialization/hf_adapter.py

@@ -0,0 +1,271 @@
+"""HuggingFace checkpoint adaptation for LLaMA-style decoder models.
+
+AstrAI stores weights with its own key names (``layers.<i>.input_norm``,
+``layers.<i>.mlp.gate``), while HuggingFace decoder-only checkpoints use
+``model.layers.<i>.input_layernorm`` / ``model.layers.<i>.mlp.gate_proj``.
+This module translates HF configs and state dicts so external checkpoints
+can be loaded directly.
+
+Supported families (LLaMA layout, dense and MoE):
+- dense FFN: llama, mistral, qwen2, gemma, gemma2, phi3
+- MoE FFN (Mixtral / Qwen2-MoE / DeepSeek-V3 layout): router
+  ``mlp.gate``, routed experts ``mlp.experts.<j>``, shared experts
+  ``mlp.shared_experts.<j>``
+
+Not supported:
+- MLA attention (DeepSeek-V2/V3 ``kv_a_proj_with_mqa``) uses a different
+  KV factorization and cannot be converted numerically.
+- Attention/MLP bias (``attention_bias`` / ``mlp_bias``) — AstrAI
+  projections are bias-free.
+"""
+
+import logging
+import re
+from typing import Any, Dict, Mapping
+
+import torch
+
+from astrai.config.base import BaseConfig
+
+logger = logging.getLogger(__name__)
+
+HF_MODEL_TYPES = frozenset(
+    {
+        "llama",
+        "mistral",
+        "mixtral",
+        "qwen2",
+        "qwen2_moe",
+        "gemma",
+        "gemma2",
+        "phi3",
+    }
+)
+
+_EMBED = re.compile(r"^model\.embed_tokens\.weight$")
+_ATTN = re.compile(r"^model\.layers\.(\d+)\.self_attn\.(q|k|v|o)_proj\.(weight|bias)$")
+_Q_NORM = re.compile(r"^model\.layers\.(\d+)\.self_attn\.q_norm\.weight$")
+_K_NORM = re.compile(r"^model\.layers\.(\d+)\.self_attn\.k_norm\.weight$")
+_INPUT_NORM = re.compile(r"^model\.layers\.(\d+)\.input_layernorm\.weight$")
+_POST_NORM = re.compile(r"^model\.layers\.(\d+)\.post_attention_layernorm\.weight$")
+_FINAL_NORM = re.compile(r"^model\.norm\.weight$")
+_LM_HEAD = re.compile(r"^lm_head\.weight$")
+_DENSE_MLP = re.compile(
+    r"^model\.layers\.(\d+)\.mlp\.(gate|up|down)_proj\.(weight|bias)$"
+)
+_MOE_ROUTER = re.compile(r"^model\.layers\.(\d+)\.mlp\.gate\.weight$")
+_MOE_EXPERTS = re.compile(
+    r"^model\.layers\.(\d+)\.mlp\.experts\.(\d+)\.(gate|up|down)_proj\.(weight|bias)$"
+)
+_MOE_SHARED = re.compile(
+    r"^model\.layers\.(\d+)\.mlp\.shared_expert(?:s)?\.(\d+)\."
+    r"(gate|up|down)_proj\.(weight|bias)$"
+)
+
+_ASTR_PREFIXES = ("embed_tokens.", "layers.", "norm.", "lm_head.")
+
+
+def looks_like_hf_state_dict(state_dict: Mapping[str, Any]) -> bool:
+    """Return True if *state_dict* uses HuggingFace key names."""
+    return any(
+        key.startswith("model.")
+        or "self_attn." in key
+        or "input_layernorm" in key
+        or "mlp.experts." in key
+        for key in state_dict
+    )
+
+
+def _is_dense_mlp_layer(config: BaseConfig, layer_id: int) -> bool:
+    """Return whether a layer uses dense MLP instead of routed experts."""
+    if getattr(config, "ffn_type", "mlp") != "moe":
+        return True
+    mlp_only = getattr(config, "mlp_only_layers", None) or []
+    if layer_id in mlp_only:
+        return True
+    step = getattr(config, "decoder_sparse_step", 1) or 1
+    return step > 1 and (layer_id + 1) % step != 0
+
+
+def adapt_config(raw: Dict[str, Any]) -> Dict[str, Any]:
+    """Translate *raw* for AstrAI if it looks like an HF model config."""
+    if raw.get("model_type") in HF_MODEL_TYPES:
+        return convert_hf_config(raw)
+    return raw
+
+
+def convert_hf_config(raw: Dict[str, Any]) -> Dict[str, Any]:
+    """Convert an HF LLaMA-style config dict to AstrAI field names."""
+    if raw.get("attention_bias") or raw.get("mlp_bias"):
+        raise NotImplementedError(
+            "attention_bias / mlp_bias checkpoints are not supported; "
+            "AstrAI projections are bias-free"
+        )
+
+    cfg: Dict[str, Any] = {}
+    for key in (
+        "vocab_size",
+        "hidden_size",
+        "num_hidden_layers",
+        "intermediate_size",
+        "rms_norm_eps",
+        "tie_word_embeddings",
+        "max_position_embeddings",
+        "rope_theta",
+        "rope_scaling",
+        "num_attention_heads",
+        "num_key_value_heads",
+        "use_qk_norm",
+        "use_gated_attention",
+        "kv_lora_rank",
+        "qk_nope_head_dim",
+        "qk_rope_head_dim",
+        "moe_intermediate_size",
+        "shared_expert_intermediate_size",
+        "topk_method",
+        "norm_topk_prob",
+        "moe_aux_loss_coef",
+        "decoder_sparse_step",
+        "mlp_only_layers",
+        "neftune_alpha",
+    ):
+        if key in raw:
+            cfg[key] = raw[key]
+
+    if "qk_norm" in raw and "use_qk_norm" not in cfg:
+        cfg["use_qk_norm"] = raw["qk_norm"]
+    if (
+        raw.get("model_type") in ("gemma", "gemma2")
+        and "use_qk_norm" not in cfg
+        and "qk_norm" not in raw
+    ):
+        # Gemma/Gemma2 always apply RMSNorm to Q and K before attention.
+        cfg["use_qk_norm"] = True
+
+    n_heads = raw.get("num_attention_heads")
+    if cfg.get("num_key_value_heads") is None and n_heads is not None:
+        cfg["num_key_value_heads"] = n_heads
+
+    if raw.get("head_dim") is not None and n_heads and raw.get("hidden_size"):
+        expected = raw["hidden_size"] // n_heads
+        if raw["head_dim"] != expected:
+            raise NotImplementedError(
+                f"HF head_dim={raw['head_dim']} differs from the computed "
+                f"head dim {expected}; AstrAI derives head_dim from "
+                "hidden_size / num_attention_heads"
+            )
+
+    if "kv_lora_rank" in raw:
+        cfg["attn_type"] = "mla"
+
+    n_experts = raw.get("num_local_experts") or raw.get("n_routed_experts")
+    if n_experts:
+        cfg["ffn_type"] = "moe"
+        cfg["n_routed_experts"] = n_experts
+        if "num_experts_per_tok" in raw:
+            cfg["n_activated_experts"] = raw["num_experts_per_tok"]
+        if "n_activated_experts" in raw:
+            cfg["n_activated_experts"] = raw["n_activated_experts"]
+        if "n_shared_experts" in raw:
+            cfg["n_shared_experts"] = raw["n_shared_experts"]
+        else:
+            # Mixtral has no shared experts; AstrAI defaults to one.
+            cfg["n_shared_experts"] = 0
+        if cfg.get("moe_intermediate_size") is None and "intermediate_size" in raw:
+            # MoE configs store the per-expert FFN size in intermediate_size.
+            cfg["moe_intermediate_size"] = raw["intermediate_size"]
+        first_k_dense = raw.get("first_k_dense_replace")
+        if isinstance(first_k_dense, int) and first_k_dense > 0:
+            cfg["mlp_only_layers"] = list(range(first_k_dense))
+            cfg["decoder_sparse_step"] = 1
+
+    cfg["model_type"] = "autoregressive_lm"
+    return cfg
+
+
+def convert_hf_weights(
+    state_dict: Mapping[str, Any],
+    config: BaseConfig,
+) -> Dict[str, torch.Tensor]:
+    """Rename HF state dict keys to AstrAI names.
+
+    Keys that are already AstrAI-style pass through unchanged; unmapped
+    HF keys are dropped with a warning. Use with ``strict=True`` to fail
+    loudly when the checkpoint does not match the config.
+    """
+    if getattr(config, "attn_type", "gqa") == "mla":
+        if any("kv_a_proj_with_mqa" in key for key in state_dict):
+            raise NotImplementedError(
+                "MLA attention (DeepSeek-V2/V3 kv_a_proj_with_mqa) uses a "
+                "different KV factorization and cannot be converted"
+            )
+
+    ffn_type = getattr(config, "ffn_type", "mlp")
+    converted: Dict[str, torch.Tensor] = {}
+    skipped: list[str] = []
+    for key, tensor in state_dict.items():
+        if key.startswith(_ASTR_PREFIXES):
+            converted[key] = tensor
+            continue
+
+        new_key = None
+        if ffn_type == "moe":
+            m = _MOE_ROUTER.match(key)
+            if m:
+                new_key = f"layers.{m.group(1)}.mlp.router.weight"
+            else:
+                m = _MOE_EXPERTS.match(key)
+                if m:
+                    new_key = (
+                        f"layers.{m.group(1)}.mlp.routed_experts.{m.group(2)}."
+                        f"{m.group(3)}.{m.group(4)}"
+                    )
+                else:
+                    m = _MOE_SHARED.match(key)
+                    if m:
+                        new_key = (
+                            f"layers.{m.group(1)}.mlp.shared_experts.{m.group(2)}."
+                            f"{m.group(3)}.{m.group(4)}"
+                        )
+            if new_key is None:
+                m = _DENSE_MLP.match(key)
+                if m and _is_dense_mlp_layer(config, int(m.group(1))):
+                    new_key = f"layers.{m.group(1)}.mlp.{m.group(2)}.{m.group(3)}"
+        else:
+            m = _DENSE_MLP.match(key)
+            if m:
+                new_key = f"layers.{m.group(1)}.mlp.{m.group(2)}.{m.group(3)}"
+
+        if new_key is None:
+            m = _ATTN.match(key)
+            if m:
+                new_key = (
+                    f"layers.{m.group(1)}.attention.{m.group(2)}_proj.{m.group(3)}"
+                )
+            elif (m := _Q_NORM.match(key)) is not None:
+                new_key = f"layers.{m.group(1)}.attention.q_norm.weight"
+            elif (m := _K_NORM.match(key)) is not None:
+                new_key = f"layers.{m.group(1)}.attention.k_norm.weight"
+            elif (m := _INPUT_NORM.match(key)) is not None:
+                new_key = f"layers.{m.group(1)}.input_norm.weight"
+            elif (m := _POST_NORM.match(key)) is not None:
+                new_key = f"layers.{m.group(1)}.post_attention_norm.weight"
+            elif (m := _EMBED.match(key)) is not None:
+                new_key = "embed_tokens.weight"
+            elif (m := _FINAL_NORM.match(key)) is not None:
+                new_key = "norm.weight"
+            elif (m := _LM_HEAD.match(key)) is not None:
+                new_key = "lm_head.weight"
+
+        if new_key is None:
+            skipped.append(key)
+        else:
+            converted[new_key] = tensor
+
+    if skipped:
+        logger.warning(
+            "Dropped %d unmapped HuggingFace weight key(s): %s",
+            len(skipped),
+            ", ".join(sorted(skipped)[:10]),
+        )
+    return converted

astrai/trainer/metric_util.py

@@ -1,3 +1,4 @@
+import math
 from typing import Dict
 
 import torch
@@ -27,6 +28,8 @@ class GradSNRTracker:
 
     SNR = E[g]^2 / Var(g) = E[g]^2 / (E[g^2] - E[g]^2)
 
+    The reported value is the power ratio in decibels: ``10 * log10(SNR)``.
+
     The tracker accumulates per-parameter EMA moments across optimizer steps.
     Call ``update`` after backward (before ``optimizer.step``) and read
     ``snr`` to get the aggregate SNR across all parameters.
@@ -64,7 +67,8 @@ class GradSNRTracker:
             noise = (v - m.pow(2)).clamp(min=0).sum().item()
             total_signal += signal
             total_noise += noise
-        return total_signal / (total_noise + self.eps)
+        snr = total_signal / (total_noise + self.eps)
+        return 10.0 * math.log10(max(snr, self.eps))
 
 
 def ctx_get_loss(ctx):
@@ -90,21 +94,5 @@ def ctx_get_grad_snr(ctx):
     return tracker.snr
 
 
-def ctx_get_moe_aux_loss(ctx):
-    return ctx.strategy._moe_metrics.get("aux_loss")
-
-
-def ctx_get_router_entropy(ctx):
-    return ctx.strategy._moe_metrics.get("router_entropy")
-
-
-def ctx_get_dead_expert_fraction(ctx):
-    return ctx.strategy._moe_metrics.get("dead_expert_fraction")
-
-
-def ctx_get_load_imbalance_mean(ctx):
-    return ctx.strategy._moe_metrics.get("load_imbalance_mean")
-
-
-def ctx_get_load_imbalance_max(ctx):
-    return ctx.strategy._moe_metrics.get("load_imbalance_max")
+def ctx_get_moe_metric(ctx, key):
+    return ctx.strategy._moe_metrics.get(key)

astrai/trainer/rollout.py

@@ -6,7 +6,7 @@ Provides:
 - :class:`BaseRewardModel` — pluggable reward interface
 - :class:`RolloutGenerator` — KV-cache-backed generation of grouped
   responses + decoding (no reward); delegates the generation loop to
-  :class:`~astrai.inference.core.scheduler.InferenceScheduler.run_batch`
+  :class:`~astrai.inference.scheduler.InferenceScheduler.run_batch`
   so rollout and the production inference server share one code path
 - :class:`RolloutRunner` — orchestrates generation + scoring with a
   step-driven cache; its ``__call__`` returns ``(RolloutResult, is_fresh)``
@@ -20,7 +20,7 @@ from typing import Dict, List, Optional, Tuple
 import torch
 from torch import Tensor
 
-from astrai.inference.core.scheduler import InferenceScheduler
+from astrai.inference.scheduler import InferenceScheduler
 
 
 @dataclass(kw_only=True)
@@ -101,7 +101,7 @@ class RolloutGenerator:
     """Pure generation + decoding for a group of responses per prompt.
 
     Delegates the prefill/decode loop to
-    :meth:`~astrai.inference.core.scheduler.InferenceScheduler.run_batch`,
+    :meth:`~astrai.inference.scheduler.InferenceScheduler.run_batch`,
     which uses a real KV cache (no O(n²) recompute).  Has no dependency
     on any reward model; can be reused in isolation for offline
     generation, qualitative sampling, or eval pipelines.

astrai/trainer/schedule.py

@@ -2,7 +2,7 @@
 
 import math
 from abc import ABC, abstractmethod
-from typing import Any, Dict, List
+from typing import List
 
 from torch.optim.lr_scheduler import LRScheduler
 
@@ -20,12 +20,6 @@ class BaseScheduler(LRScheduler, ABC):
         """Calculate the current learning rate."""
         raise NotImplementedError
 
-    def state_dict(self) -> Dict[str, Any]:
-        return super().state_dict()
-
-    def load_state_dict(self, state_dict: Dict[str, Any]):
-        super().load_state_dict(state_dict)
-
 
 class SchedulerFactory(BaseFactory["BaseScheduler"]):
     """Factory class for creating learning rate schedulers.

astrai/trainer/strategy.py

@@ -1,6 +1,6 @@
 """Training strategy implementations with factory pattern."""
 
-from abc import ABC, abstractmethod
+from abc import ABC
 from typing import Callable, Dict, List, Optional, TypedDict, Union
 
 import torch
@@ -184,10 +184,9 @@ class BaseStrategy(ABC):
         self.executor = kwargs.pop("executor", None)
         self.moe_aux_loss_coef = kwargs.pop("moe_aux_loss_coef", 0.01)
         self._moe_metrics: Dict[str, float] = {}
-        self.extra_kwargs = kwargs
+        self.strategy_kwargs = kwargs
         self._rollout_runner = None
 
-    @abstractmethod
     def compute_loss(self, batch: Dict[str, Tensor]) -> Tensor:
         """Compute loss for the given batch.
 
@@ -197,7 +196,7 @@ class BaseStrategy(ABC):
         Returns:
             Computed loss tensor
         """
-        raise NotImplementedError
+        return self.compute_loss_output(batch)["loss"]
 
     def compute_loss_output(self, batch: Dict[str, Tensor]) -> LossOutput:
         return self._normalize_output(self.compute_loss(batch))
@@ -328,9 +327,6 @@ class SEQStrategy(BaseStrategy):
         super().__init__(model, device, **kwargs)
         self.label_smoothing = label_smoothing
 
-    def compute_loss(self, batch: Dict[str, Tensor]) -> Tensor:
-        return self.compute_loss_output(batch)["loss"]
-
     def compute_loss_output(self, batch: Dict[str, Tensor]) -> LossOutput:
         batch = move_to_device(batch, self.device)
         input_ids, target_ids = batch["input_ids"], batch["target_ids"]
@@ -369,9 +365,6 @@ class SFTStrategy(BaseStrategy):
         super().__init__(model, device, **kwargs)
         self.label_smoothing = label_smoothing
 
-    def compute_loss(self, batch: Dict[str, Tensor]) -> Tensor:
-        return self.compute_loss_output(batch)["loss"]
-
     def compute_loss_output(self, batch: Dict[str, Tensor]) -> LossOutput:
         batch = move_to_device(batch, self.device)
         input_ids, target_ids, position_ids, loss_mask = (
@@ -426,9 +419,6 @@ class DPOStrategy(BaseStrategy):
         self.beta = beta
         self.reduction = reduction
 
-    def compute_loss(self, batch: Dict[str, Tensor]) -> Tensor:
-        return self.compute_loss_output(batch)["loss"]
-
     def compute_loss_output(self, batch: Dict[str, Tensor]) -> LossOutput:
         batch = move_to_device(batch, self.device)
         chosen_ids, rejected_ids = batch["chosen"], batch["rejected"]
@@ -553,9 +543,6 @@ class GRPOStrategy(BaseStrategy):
         if state_dict is not None:
             self.old_model.load_state_dict(state_dict)
 
-    def compute_loss(self, batch: Dict[str, Tensor]) -> Tensor:
-        return self.compute_loss_output(batch)["loss"]
-
     def compute_loss_output(self, batch: Dict[str, Tensor]) -> LossOutput:
         batch = move_to_device(batch, self.device)
         prompts = batch["prompts"]

astrai/trainer/train_callback.py

@@ -3,6 +3,7 @@ import logging
 import os
 import sys
 import time
+from functools import partial
 from pathlib import Path
 from typing import IO, Callable, List, Optional, Protocol, runtime_checkable
 
@@ -17,15 +18,11 @@ from astrai.parallel import only_on_rank
 from astrai.parallel.setup import get_current_device
 from astrai.serialization import Checkpoint
 from astrai.trainer.metric_util import (
-    ctx_get_dead_expert_fraction,
     ctx_get_grad_norm,
     ctx_get_grad_snr,
-    ctx_get_load_imbalance_max,
-    ctx_get_load_imbalance_mean,
     ctx_get_loss,
     ctx_get_lr,
-    ctx_get_moe_aux_loss,
-    ctx_get_router_entropy,
+    ctx_get_moe_metric,
     ctx_get_val_loss,
 )
 from astrai.trainer.train_context import TrainContext
@@ -119,6 +116,8 @@ class GradientCheckpointingCallback(TrainCallback):
             del module._original_forward
 
     def on_train_begin(self, context: TrainContext):
+        if not self.modules:
+            return
         context.model.apply(self._enable)
         logger.info("Gradient checkpointing enabled")
 
@@ -262,11 +261,15 @@ class MetricCallback(TrainCallback):
             "val_loss": ctx_get_val_loss,
             "grad_norm": ctx_get_grad_norm,
             "grad_snr": ctx_get_grad_snr,
-            "moe_aux_loss": ctx_get_moe_aux_loss,
-            "router_entropy": ctx_get_router_entropy,
-            "dead_expert_fraction": ctx_get_dead_expert_fraction,
-            "load_imbalance_mean": ctx_get_load_imbalance_mean,
-            "load_imbalance_max": ctx_get_load_imbalance_max,
+            "moe_aux_loss": partial(ctx_get_moe_metric, key="aux_loss"),
+            "router_entropy": partial(ctx_get_moe_metric, key="router_entropy"),
+            "dead_expert_fraction": partial(
+                ctx_get_moe_metric, key="dead_expert_fraction"
+            ),
+            "load_imbalance_mean": partial(
+                ctx_get_moe_metric, key="load_imbalance_mean"
+            ),
+            "load_imbalance_max": partial(ctx_get_moe_metric, key="load_imbalance_max"),
         }
 
     def _metrics(self, context: TrainContext, names):

astrai/trainer/train_context.py

@@ -8,14 +8,21 @@ import torch
 import torch.nn as nn
 from torch.utils.data import DataLoader, random_split
 
+from astrai.config.model_config import ConfigFactory
 from astrai.config.train_config import TrainConfig
 from astrai.dataset import RDSampler
-from astrai.inference.core.scheduler import InferenceScheduler
+from astrai.inference.scheduler import InferenceScheduler
 from astrai.model.components.lora import inject_lora
 from astrai.parallel.executor import BaseExecutor, ExecutorFactory, create_ref_model
 from astrai.parallel.setup import get_current_device, get_rank, get_world_size
 from astrai.protocols import OptimizerProtocol, SchedulerProtocol
-from astrai.serialization import Checkpoint, load_json
+from astrai.serialization import (
+    Checkpoint,
+    adapt_config,
+    convert_hf_weights,
+    load_json,
+    looks_like_hf_state_dict,
+)
 from astrai.tokenize import AutoTokenizer
 from astrai.trainer.metric_util import GradSNRTracker
 from astrai.trainer.rollout import RolloutGenerator, RolloutRunner
@@ -66,6 +73,15 @@ class TrainContext:
         )
 
 
+@dataclass
+class _PreloadedState:
+    model_config: dict = field(default_factory=dict)
+    state_dict: Optional[dict] = None
+    epoch: int = 0
+    consumed_samples: int = 0
+    checkpoint: Optional[Checkpoint] = None
+
+
 class TrainContextBuilder:
     def __init__(
         self,
@@ -81,213 +97,241 @@ class TrainContextBuilder:
         return self
 
     def build(self) -> TrainContext:
-        cfg = self.config
-        device = get_current_device()
+        # Resolve persisted state.
+        preloaded_state = self._load_preloaded_state()
 
-        executor = ExecutorFactory.create(
+        # Build the core training components and restore their persisted state.
+        executor = self._create_executor()
+        context = self._create_context(preloaded_state, executor)
+        self._prepare_model(context, executor, preloaded_state)
+        self._restore_optimizer_state(context)
+
+        # Resolve datasets.
+        train_dataset, val_dataset = self._get_datasets()
+        self._create_dataloaders(context, train_dataset, val_dataset)
+
+        # Strategies depend on the prepared model; online rollout depends on both.
+        strategy_kwargs = self._create_strategy(context, executor)
+        self._configure_rollout(context, strategy_kwargs)
+
+        return context
+
+    def _create_executor(self) -> BaseExecutor:
+        cfg = self.config
+        return ExecutorFactory.create(
             cfg.parallel_mode,
             grad_accum_steps=cfg.grad_accum_steps,
             **cfg.executor_kwargs,
         )
 
-        model_config = {}
+    def _load_preloaded_state(self) -> _PreloadedState:
+        cfg = self.config
+        state = _PreloadedState(
+            epoch=cfg.start_epoch,
+            consumed_samples=cfg.start_samples * get_world_size(),
+        )
         if self._param_path:
             config_path = Path(self._param_path) / "config.json"
             if config_path.exists():
-                model_config = load_json(config_path)
-
-        preloaded_state_dict = None
-        preloaded_epoch = cfg.start_epoch
-        preloaded_consumed = cfg.start_samples * get_world_size()
-        preloaded_checkpoint = None
-        if self._param_path:
+                state.model_config = adapt_config(load_json(config_path))
             checkpoint = Checkpoint.load_any(self._param_path)
             if checkpoint is not None:
-                preloaded_state_dict = checkpoint.state_dict
                 if checkpoint.config:
-                    model_config = checkpoint.config
+                    checkpoint.config = adapt_config(checkpoint.config)
+                if checkpoint.state_dict and looks_like_hf_state_dict(
+                    checkpoint.state_dict
+                ):
+                    checkpoint.state_dict = convert_hf_weights(
+                        checkpoint.state_dict,
+                        ConfigFactory.load(checkpoint.config or state.model_config),
+                    )
+                state.state_dict = checkpoint.state_dict
+                state.model_config = checkpoint.config or state.model_config
                 if self._resume:
-                    preloaded_epoch = checkpoint.epoch
+                    state.epoch = checkpoint.epoch
                     per_step = (
                         cfg.batch_per_device * get_world_size() * cfg.grad_accum_steps
                     )
-                    preloaded_consumed = (
-                        checkpoint.consumed_samples // per_step
-                    ) * per_step
-                    preloaded_checkpoint = checkpoint
+                    state.consumed_samples = (
+                        checkpoint.consumed_samples // per_step * per_step
+                    )
+                    state.checkpoint = checkpoint
+        if not state.model_config:
+            model = cfg.model_fn()
+            if hasattr(model, "config"):
+                state.model_config = model.config.to_dict()
+        return state
 
-        if not model_config and hasattr(cfg.model_fn(), "config"):
-            model_config = cfg.model_fn().config.to_dict()
+    def _create_context(
+        self, state: _PreloadedState, executor: BaseExecutor
+    ) -> TrainContext:
+        return TrainContext(
+            world_size=get_world_size(),
+            rank=get_rank(),
+            config=self.config,
+            model_config=state.model_config,
+            executor=executor,
+            epoch=state.epoch,
+            consumed_samples=state.consumed_samples,
+            checkpoint=state.checkpoint,
+        )
 
-        def _before_wrap(m):
-            m = m.to(device=device)
+    def _prepare_model(
+        self, context: TrainContext, executor: BaseExecutor, state: _PreloadedState
+    ) -> None:
+        cfg = self.config
+        device = get_current_device()
+
+        def before_wrap(model):
+            model = model.to(device=device)
             if cfg.lora is not None:
                 inject_lora(
-                    m,
+                    model,
                     r=cfg.lora.r,
                     alpha=cfg.lora.alpha,
                     target_modules=set(cfg.lora.target_modules),
                 )
-            if preloaded_state_dict is not None:
-                m.load_state_dict(preloaded_state_dict, strict=False)
-            return m
+            if state.state_dict is not None:
+                model.load_state_dict(state.state_dict, strict=False)
+            return model
 
-        def _after_wrap(m):
+        def after_wrap(model):
             if cfg.compile_mode is not None:
                 logger.info("torch.compile enabled (mode=%s)", cfg.compile_mode)
-                m = torch.compile(m, mode=cfg.compile_mode)
-            return m
-
-        context = TrainContext(
-            world_size=get_world_size(),
-            rank=get_rank(),
-            config=cfg,
-            model_config=model_config,
-            executor=executor,
-            epoch=preloaded_epoch,
-            consumed_samples=preloaded_consumed,
-            checkpoint=preloaded_checkpoint,
-        )
+                model = torch.compile(model, mode=cfg.compile_mode)
+            return model
 
         context.model, context.optimizer, context.scheduler = executor.prepare(
             cfg.model_fn,
             cfg.optimizer_fn,
             cfg.scheduler_fn,
-            before_wrap=_before_wrap,
-            after_wrap=_after_wrap,
+            before_wrap=before_wrap,
+            after_wrap=after_wrap,
         )
 
-        train_dataset = cfg.dataset
-        val_dataset = cfg.val_dataset
+    def _get_datasets(self):
+        cfg = self.config
+        if cfg.val_dataset is not None or cfg.val_split is None:
+            return cfg.dataset, cfg.val_dataset
+        n_val = max(1, int(len(cfg.dataset) * cfg.val_split))
+        generator = torch.Generator().manual_seed(cfg.random_seed)
+        return random_split(
+            cfg.dataset, [len(cfg.dataset) - n_val, n_val], generator=generator
+        )
 
-        if val_dataset is None and cfg.val_split is not None:
-            n_total = len(cfg.dataset)
-            n_val = max(1, int(n_total * cfg.val_split))
-            n_train = n_total - n_val
-            generator = torch.Generator().manual_seed(cfg.random_seed)
-            train_dataset, val_dataset = random_split(
-                cfg.dataset, [n_train, n_val], generator=generator
+    def _create_dataloaders(
+        self, context: TrainContext, train_dataset, val_dataset
+    ) -> None:
+        sampler_offset = context.consumed_samples // context.world_size
+        if self._resume and sampler_offset > 0:
+            samples_per_replica = (
+                len(train_dataset) + context.world_size - 1
+            ) // context.world_size
+            if samples_per_replica > 0:
+                context.epoch = sampler_offset // samples_per_replica
+        context.dataloader = self._create_dataloader(
+            train_dataset, context.epoch, sampler_offset
+        )
+        if val_dataset is not None:
+            context.val_dataloader = self._create_dataloader(
+                val_dataset, 0, 0, shuffle=False
             )
 
-        sampler_offset = context.consumed_samples // context.world_size
-
-        if self._resume and sampler_offset > 0:
-            offset = context.world_size - 1
-            num_samples_per_replica = (
-                len(train_dataset) + offset
-            ) // context.world_size
-            if num_samples_per_replica > 0:
-                context.epoch = sampler_offset // num_samples_per_replica
-
+    def _create_dataloader(
+        self, dataset, epoch: int, start_iter: int, shuffle: bool = True
+    ):
+        cfg = self.config
         sampler = RDSampler(
-            data_source=train_dataset,
-            start_epoch=context.epoch,
-            start_iter=sampler_offset,
+            dataset,
+            start_epoch=epoch,
+            start_iter=start_iter,
             seed=cfg.random_seed,
+            shuffle=shuffle,
         )
-        context.dataloader = DataLoader(
-            train_dataset,
+        loader_kwargs = dict(
+            dataset=dataset,
             batch_size=cfg.batch_per_device,
             sampler=sampler,
             num_workers=cfg.num_workers,
             pin_memory=cfg.pin_memory,
-            prefetch_factor=cfg.prefetch_factor,
             collate_fn=cfg.collate_fn,
         )
-
-        if val_dataset is not None:
-            val_sampler = RDSampler(
-                data_source=val_dataset,
-                start_epoch=0,
-                start_iter=0,
-                seed=cfg.random_seed,
-                shuffle=False,
-            )
-            context.val_dataloader = DataLoader(
-                val_dataset,
-                batch_size=cfg.batch_per_device,
-                sampler=val_sampler,
-                num_workers=cfg.num_workers,
-                pin_memory=cfg.pin_memory,
-                prefetch_factor=cfg.prefetch_factor,
-                collate_fn=cfg.collate_fn,
-            )
-
-        if context.checkpoint and context.checkpoint.extra:
-            extra = context.checkpoint.extra
-            for name in ("optimizer", "scheduler"):
-                if name in extra:
-                    obj = getattr(context, name, None)
-                    if obj is not None:
-                        obj.load_state_dict(extra[name])
-
-        strategy_kwargs = dict(cfg.extra_kwargs)
-        strategy_kwargs.setdefault("moe_aux_loss_coef", cfg.moe_aux_loss_coef)
-
-        needs_ref = cfg.strategy in (
-            "dpo",
-            "grpo",
-            "online_grpo",
-            "online_dpo",
+        # PyTorch rejects prefetch_factor/persistent_workers when workers=0.
+        if cfg.num_workers > 0:
+            loader_kwargs["persistent_workers"] = cfg.persistent_workers
+            if cfg.prefetch_factor is not None:
+                loader_kwargs["prefetch_factor"] = cfg.prefetch_factor
+        return DataLoader(
+            **loader_kwargs,
         )
-        needs_old = cfg.strategy in ("grpo", "online_grpo")
 
-        if needs_ref:
-            strategy_kwargs["ref_model"] = create_ref_model(
-                cfg.model_fn, executor=executor, model=context.model, device=device
+    def _restore_optimizer_state(self, context: TrainContext) -> None:
+        if context.checkpoint and context.checkpoint.extra:
+            for name in ("optimizer", "scheduler"):
+                if (
+                    name in context.checkpoint.extra
+                    and getattr(context, name, None) is not None
+                ):
+                    getattr(context, name).load_state_dict(
+                        context.checkpoint.extra[name]
+                    )
+
+    def _create_strategy(self, context: TrainContext, executor: BaseExecutor) -> dict:
+        cfg = self.config
+        kwargs = dict(cfg.strategy_kwargs)
+        kwargs.setdefault("moe_aux_loss_coef", cfg.moe_aux_loss_coef)
+        if cfg.strategy in ("dpo", "grpo", "online_grpo", "online_dpo"):
+            kwargs["ref_model"] = create_ref_model(
+                cfg.model_fn,
+                executor=executor,
+                model=context.model,
+                device=get_current_device(),
             )
-
-        if needs_old:
-            strategy_kwargs["old_model"] = create_ref_model(
-                cfg.model_fn, executor=executor, model=context.model, device=device
+        if cfg.strategy in ("grpo", "online_grpo"):
+            kwargs["old_model"] = create_ref_model(
+                cfg.model_fn,
+                executor=executor,
+                model=context.model,
+                device=get_current_device(),
             )
-
         context.strategy = StrategyFactory.create(
             cfg.strategy,
             model=context.model,
-            device=device,
+            device=get_current_device(),
             executor=executor,
-            **strategy_kwargs,
+            **kwargs,
         )
+        return kwargs
 
-        # Enable online rollout when the train_type is an ``online_*`` variant.
-        is_online = cfg.strategy.startswith("online_")
-        if is_online:
-            if not context.strategy.supports_online():
-                raise ValueError(
-                    f"Strategy '{cfg.strategy}' does not support online rollout"
-                )
-            if cfg.reward_model_fn is None:
-                raise ValueError("reward_model_fn is required for online RL strategies")
-
-            tokenizer = AutoTokenizer.from_pretrained(self._param_path)
-            reward_model = cfg.reward_model_fn()
-
-            group_size = strategy_kwargs.get("group_size", 1)
-            rollout_batch_size = group_size * max(1, cfg.batch_per_device)
-            max_seq_len = getattr(context.model.config, "max_position_embeddings", None)
-
-            scheduler = InferenceScheduler(
-                model=context.model,
-                tokenizer=tokenizer,
-                max_batch_size=rollout_batch_size,
-                max_seq_len=max_seq_len,
+    def _configure_rollout(self, context: TrainContext, strategy_kwargs: dict) -> None:
+        cfg = self.config
+        if not cfg.strategy.startswith("online_"):
+            return
+        if not context.strategy.supports_online():
+            raise ValueError(
+                f"Strategy '{cfg.strategy}' does not support online rollout"
             )
-
-            generator = RolloutGenerator(
-                scheduler=scheduler,
-                tokenizer=tokenizer,
-                max_tokens=cfg.rollout_max_tokens,
-                group_size=group_size,
-                temperature=cfg.rollout_temperature,
-                top_k=cfg.rollout_top_k,
-                top_p=cfg.rollout_top_p,
-            )
-            runner = RolloutRunner(
+        tokenizer = AutoTokenizer.from_pretrained(self._param_path)
+        group_size = strategy_kwargs.get("group_size", 1)
+        scheduler = InferenceScheduler(
+            model=context.model,
+            tokenizer=tokenizer,
+            max_batch_size=group_size * max(1, cfg.batch_per_device),
+            max_seq_len=getattr(context.model.config, "max_position_embeddings", None),
+        )
+        generator = RolloutGenerator(
+            scheduler=scheduler,
+            tokenizer=tokenizer,
+            max_tokens=cfg.rollout_max_tokens,
+            group_size=group_size,
+            temperature=cfg.rollout_temperature,
+            top_k=cfg.rollout_top_k,
+            top_p=cfg.rollout_top_p,
+        )
+        context.strategy.set_rollout_runner(
+            RolloutRunner(
                 generator=generator,
-                reward_model=reward_model,
+                reward_model=cfg.reward_model_fn(),
                 rollout_interval=cfg.rollout_interval,
             )
-            context.strategy.set_rollout_runner(runner)
-
-        return context
+        )

csrc/CMakeLists.txt

@@ -48,10 +48,44 @@ set(TORCH_LIBS
 
 set(CMAKE_CUDA_ARCHITECTURES "${ASTRAI_CUDA_ARCH}")
 
-set(KERNELS attn_decode attn_prefill attn_paged_decode attn_paged_prefill rotary_emb)
+# Kernel registry — parallel lists of module names (.so / pybind names,
+# globally unique across families) and their per-family source paths under
+# kernels/. `loader.py` auto-discovers the .so files in astrai/extension/lib/,
+# so this CMake registry is the single place to register a new kernel.
+#
+# FP8 MMA instructions require sm_89+. Keep the target out of the build on
+# older architectures instead of instantiating templates that cannot compile.
+# The remaining kernels are still useful on sm_80+ (including sm_86).
+set(KERNEL_NAMES
+    attn_decode
+    attn_prefill
+    attn_paged_decode
+    attn_paged_prefill
+    rotary_emb
+)
+set(KERNEL_SRCS
+    attention/decode.cu
+    attention/prefill.cu
+    attention/paged_decode.cu
+    attention/paged_prefill.cu
+    rotary/rotary_emb.cu
+)
 
-foreach(name ${KERNELS})
-    add_library(${name} MODULE "${CMAKE_CURRENT_SOURCE_DIR}/kernels/${name}.cu")
+if(ASTRAI_CUDA_ARCH GREATER_EQUAL 89)
+    list(APPEND KERNEL_NAMES fp8_ops)
+    list(APPEND KERNEL_SRCS fp8/ops.cu)
+else()
+    message(WARNING
+        "FP8 operator disabled: ASTRAI_CUDA_ARCH=${ASTRAI_CUDA_ARCH} "
+        "requires compute capability 89 or newer")
+endif()
+
+list(LENGTH KERNEL_NAMES _kernel_count)
+math(EXPR _kernel_last "${_kernel_count} - 1")
+foreach(i RANGE ${_kernel_last})
+    list(GET KERNEL_NAMES ${i} name)
+    list(GET KERNEL_SRCS ${i} src)
+    add_library(${name} MODULE "${CMAKE_CURRENT_SOURCE_DIR}/kernels/${src}")
 
     target_compile_definitions(${name} PRIVATE TORCH_EXTENSION_NAME=${name})
 

csrc/__init__.py

@@ -1,2 +1,2 @@
 # Source directory for CUDA kernels — build-time only.
-# Compiled .so files live in astrAI/_ext/.
+# Compiled .so files live in astrai/extension/lib/ (see csrc/CMakeLists.txt).

csrc/kernels/attention/common.h

@@ -0,0 +1,100 @@
+#pragma once
+
+// Pure POD header
+
+namespace astrai {
+namespace attention {
+
+// Tensor layout for Q/K/V tensors passed to attention kernels.
+// Internally, kernels always operate on BHLD [batch, n_heads, seq_len, head_dim].
+// When the caller passes BLHD, dims 1 and 2 are transposed at entry.
+enum TensorLayout : int {
+    BHLD = 0,  // [batch, n_heads, seq_len, head_dim]
+    BLHD = 1,  // [batch, seq_len, n_heads, head_dim]
+};
+
+// Split-KV workspace cap: max decode splits per (batch, q_head).
+constexpr int MAX_SPLITS = 32;
+
+// Paged-prefill host Q-tile granularity in q rows: one q_tile_to_index unit
+// covers this many query rows of one request.  Must match Q_TILE_ROWS in
+// astrai/inference/workspace.py, which builds the device-side tile maps.
+constexpr int HOST_Q_TILE_ROWS = 64;
+
+
+// Unified attention params covering BOTH addressing modes:
+//   - Contiguous K/V: dense [batch, kv_head, kv_len, head_dim] tensors (k/v).
+//   - Paged (SGLang-style): flat pool [size, kv_head, head_dim] + req_to_token.
+// Each kernel selects the addressing via a KVSource policy (see
+// layout_policies.cuh); a given call only touches the fields of one mode, so
+// this is a POD shared by both paths rather than two parallel structs that
+// drift out of sync.
+//
+// Pointer/flag members carry default member initializers: the pointers gate
+// optional paths via null checks (new_k_ptr, mask, o_part, ...), so a stack
+// `AttentionParams<T> p;` left partially packed must never see garbage
+// non-null pointers or a garbage use_mask/causal_offset — that class of bug
+// reads through wild addresses. NSDMI keeps the struct an aggregate (C++17)
+// and trivially copyable, so `= {}`, memcpy-style packing and by-value kernel
+// params all behave exactly as before.
+template<typename T, typename AT = float>
+struct AttentionParams {
+    // Shape
+    int batch;
+    int q_head;
+    int kv_head;
+    int head_dim;
+    int q_len;   // Per-request in contiguous mode; total_q in paged mode.
+    int kv_len;  // Contiguous mode; paged mode uses kv_indptr.
+
+    // Attention behavior
+    float scale;
+    // -1 = non-causal; >=0 = absolute position of first Q token
+    int causal_offset = -1;
+    int use_mask = 0;
+
+    // pointers
+    const T* __restrict__ q_ptr = nullptr;
+    const T* __restrict__ k_ptr = nullptr;
+    const T* __restrict__ v_ptr = nullptr;
+    const T* __restrict__ new_k_ptr = nullptr;
+    const T* __restrict__ new_v_ptr = nullptr;
+    T* __restrict__ o_ptr = nullptr;
+    const bool* __restrict__ mask = nullptr;
+
+    // strides
+    int q_b_stride;
+    int q_h_stride;
+    int q_l_stride;
+    int q_d_stride;
+
+    int kv_b_stride;
+    int kv_h_stride;
+    int kv_l_stride;
+    int kv_d_stride;
+
+    int new_kv_b_stride;
+    int new_kv_h_stride;
+
+    int mask_b_stride;
+    int mask_h_stride;
+    int mask_l_stride;
+
+    // Paged K/V addressing
+    const int* __restrict__ req_to_token = nullptr;      // [num_reqs, max_context_len]
+    const int* __restrict__ req_pool_indices = nullptr;  // [batch]
+    const int* __restrict__ kv_indptr = nullptr;         // [batch + 1]
+    const int* __restrict__ qo_indptr = nullptr;         // [batch + 1] or nullptr for decode
+    const int* __restrict__ q_tile_to_batch = nullptr;   // [num_q_tiles], prefill only
+    const int* __restrict__ q_tile_to_index = nullptr;   // [num_q_tiles], prefill only
+    int num_q_tiles;
+    int max_context_len; // req_to_token stride (dim 1)
+
+    // Decode split-KV workspace
+    int num_splits;
+    AT* __restrict__ o_part = nullptr;
+    AT* __restrict__ ml_part = nullptr;
+};
+
+}  // namespace attention
+}  // namespace astrai

csrc/kernels/attention/decode.cu

@@ -0,0 +1,65 @@
+#include "dispatchers.cuh"
+#include "entry_utils.cuh"
+
+using namespace astrai::attention;
+
+torch::Tensor attn_decode(
+    torch::Tensor q,
+    torch::Tensor k,
+    torch::Tensor v,
+    c10::optional<torch::Tensor> mask,
+    int64_t causal_offset,
+    double scale,
+    int64_t layout,
+    c10::optional<torch::Tensor> o_part_buf,
+    c10::optional<torch::Tensor> ml_part_buf
+) {
+    const at::cuda::OptionalCUDAGuard device_guard(device_of(q));
+    auto stream = at::cuda::getCurrentCUDAStream();
+
+    AttentionParams<bf16> p;
+    attn_pack_params(q, k, v, mask, causal_offset, scale, layout, p);
+    TORCH_CHECK(p.q_len == 1, "Q seq_len must be 1");
+    TORCH_CHECK(p.head_dim % 32 == 0, "head_dim must be multiple of 32");
+
+    auto O = torch::empty_strided(q.sizes(), q.strides(), q.options());
+    auto O_view = (layout == BLHD) ? O.transpose(1, 2) : O;
+    p.o_ptr = (bf16*)O_view.data_ptr();
+
+    if (o_part_buf.has_value() && ml_part_buf.has_value()
+        && o_part_buf->defined() && ml_part_buf->defined()) {
+        TORCH_CHECK(o_part_buf->scalar_type() == torch::kFloat32, "o_part_buf must be f32");
+        TORCH_CHECK(ml_part_buf->scalar_type() == torch::kFloat32, "ml_part_buf must be f32");
+        int64_t o_needed = (int64_t)p.batch * p.q_head * MAX_SPLITS * p.head_dim;
+        int64_t ml_needed = (int64_t)p.batch * p.q_head * MAX_SPLITS * 2;
+        TORCH_CHECK(o_part_buf->numel() >= o_needed,
+                     "o_part_buf too small: need ", o_needed, " got ", o_part_buf->numel());
+        TORCH_CHECK(ml_part_buf->numel() >= ml_needed,
+                     "ml_part_buf too small: need ", ml_needed, " got ", ml_part_buf->numel());
+        TORCH_CHECK(o_part_buf->is_cuda() && ml_part_buf->is_cuda(),
+                     "split buffers must be CUDA tensors");
+        TORCH_CHECK(o_part_buf->is_contiguous() && ml_part_buf->is_contiguous(),
+                     "split buffers must be contiguous");
+        p.o_part = (float*)o_part_buf->data_ptr();
+        p.ml_part = (float*)ml_part_buf->data_ptr();
+    } else {
+        alloc_split_partials(p);
+    }
+    DISPATCH_HEAD_DIM(p.head_dim, dispatch_decode, p, stream);
+    C10_CUDA_CHECK(cudaGetLastError());
+    return O;
+}
+
+PYBIND11_MODULE(TORCH_EXTENSION_NAME, m) {
+    m.def("attn_decode", &attn_decode,
+        py::arg("q"),
+        py::arg("k"),
+        py::arg("v"),
+        py::arg("mask") = py::none(),
+        py::arg("causal_offset") = -1,
+        py::arg("scale") = 0.0,
+        py::arg("layout") = (int64_t)BHLD,
+        py::arg("o_part_buf") = py::none(),
+        py::arg("ml_part_buf") = py::none(),
+        "GQA decode (tensor-core head-packing on sm_80+, scalar fallback)");
+}

csrc/kernels/attention/decode_split_kv.cuh

@@ -1,9 +1,13 @@
 #pragma once
 #include <cuda_bf16.h>
 #include <float.h>
-#include "attn_common.h"
-#include "attn_kv_source.cuh"
-#include "attn_warp_utils.cuh"
+#include "common.h"
+#include "layout_policies.cuh"
+#include "../common/reduce.cuh"
+
+namespace astrai {
+namespace attention {
+
 constexpr int DC_CHUNK = 64;
 
 // Scalar split-KV decode (fallback for sm < 80, no tensor cores), unified
@@ -27,15 +31,17 @@ __global__ void attn_decode_split_kv_kernel(AttentionParams<bf16> p) {
     // Q: [batch, q_head, q_len=1, head_dim] — stride-based
     float q_reg[8];
     int q_off = KV::q_decode_base(p, batch, q_head)
-              + lane * hd_per_thread * p.q_stride_d;
+              + lane * hd_per_thread * p.q_d_stride;
     for (int i = 0; i < hd_per_thread; i++)
-        q_reg[i] = __bfloat162float(p.q[q_off + i * p.q_stride_d]);
+        q_reg[i] = __bfloat162float(p.q_ptr[q_off + i * p.q_d_stride]);
 
     int mask_base = batch * p.mask_b_stride + q_head * p.mask_h_stride;
 
     float m = -FLT_MAX, d = 0.0f, acc_reg[8] = {0.0f};
 
-    extern __shared__ __align__(16) bf16 k_smem[];
+    extern __shared__ __align__(16) bf16 smem[];
+    bf16* k_smem = smem;
+    bf16* v_smem = smem + DC_CHUNK * p.head_dim;
 
     // Split-KV: each split processes a contiguous subset of chunks
     int chunks_total = (seq_len + DC_CHUNK - 1) / DC_CHUNK;
@@ -47,16 +53,18 @@ __global__ void attn_decode_split_kv_kernel(AttentionParams<bf16> p) {
         int chunk_start = ci * DC_CHUNK;
         int this_chunk = min(DC_CHUNK, seq_len - chunk_start);
 
-        // Load K into shared memory (addressing via KV policy; paged guards
-        // empty slots with zero-fill).
+        // Load K and V into shared memory (addressing via KV policy;
+        // paged guards empty slots with zero-fill).
         int total = this_chunk * p.head_dim;
         for (int i = threadIdx.y * 32 + lane; i < total;
              i += blockDim.x * blockDim.y) {
             int s = i / p.head_dim;
             int d_dim = i % p.head_dim;
             int kc = chunk_start + s;
-            KVAddr a = KV::kv_addr(p, kctx, kc, d_dim, true);
+            KVAddr a = KV::template decode_addr<1>(
+                p, kctx, batch, kv_head, kc, d_dim, true, true);
             k_smem[i] = a.valid ? *reinterpret_cast<const bf16*>(a.k) : (bf16)0.f;
+            v_smem[i] = a.valid ? *reinterpret_cast<const bf16*>(a.v) : (bf16)0.f;
         }
         __syncthreads();
 
@@ -82,13 +90,8 @@ __global__ void attn_decode_split_kv_kernel(AttentionParams<bf16> p) {
             float beta  = __expf(partial - new_m);
             d = d * alpha + beta;
 
-            // V read via KV policy; when masked (beta == 0) or the slot is
-            // empty the term vanishes, so no extra branches are needed.
             for (int i = 0; i < hd_per_thread; i++) {
-                KVAddr a = KV::kv_addr(p, kctx, kv_idx, lane * hd_per_thread + i, true);
-                float vv = a.valid
-                    ? __bfloat162float(*reinterpret_cast<const bf16*>(a.v))
-                    : 0.0f;
+                float vv = __bfloat162float(v_smem[s * p.head_dim + lane * hd_per_thread + i]);
                 acc_reg[i] = fmaf(acc_reg[i], alpha, vv * beta);
             }
             m = new_m;
@@ -140,6 +143,9 @@ __global__ void attn_decode_combine_kernel(AttentionParams<bf16> p) {
     }
 
     float inv = (l > 1e-20f) ? (1.0f / l) : 0.0f;
-    int o_off = KV::q_decode_base(p, batch, q_head) + d * p.q_stride_d;
-    p.o[o_off] = __float2bfloat16(acc * inv);
+    int o_off = KV::q_decode_base(p, batch, q_head) + d * p.q_d_stride;
+    p.o_ptr[o_off] = __float2bfloat16(acc * inv);
 }
+
+}  // namespace attention
+}  // namespace astrai

csrc/kernels/attention/decode_split_kv_mma.cuh

@@ -1,10 +1,12 @@
 #pragma once
 #include <cfloat>
 #include <cuda_bf16.h>
-#include "attn_common.h"
-#include "attn_kv_source.cuh"
-#include "attn_mma_utils.cuh"
-#include "attn_warp_utils.cuh"
+#include "common.h"
+#include "layout_policies.cuh"
+#include "mma_utils.cuh"
+
+namespace astrai {
+namespace attention {
 
 // Split-K (FlashDecoding) tensor-core decode via GQA head-packing, unified
 // across contiguous and paged (SGLang flat-pool) K/V via the KV template
@@ -48,7 +50,7 @@ __global__ void attn_decode_split_kv_mma_kernel(AttentionParams<bf16> p) {
     const int qrb = gid + 8;
     const bool va = qra < G, vb = qrb < G;
     unsigned Qa[Traits::KD][4];
-    load_q_mma_frags<Traits::KD>(p.q + q_base, p.q_stride_h, p.q_stride_d,
+    load_q_mma_frags<Traits::KD>(p.q_ptr + q_base, p.q_h_stride, p.q_d_stride,
                                   qra, qrb, va, vb, tid4, Qa);
 
     float Oacc[Traits::DN8][4];
@@ -73,12 +75,15 @@ __global__ void attn_decode_split_kv_mma_kernel(AttentionParams<bf16> p) {
             int r = i / Traits::HEAD_DIM, d = i % Traits::HEAD_DIM;
             int kc = kv0 + r;
             bool valid = kc < seq_len;
-            KVAddr a = KV::kv_addr(p, kctx, kc, d, valid);
+            // All GQA passes consume new K/V directly. Only the first pass
+            // persists it, so no cross-block synchronization is required.
+            KVAddr a = KV::template decode_addr<Traits::VEC>(
+                p, kctx, batch, kv_head, kc, d, valid, pass == 0);
             int off = r * Traits::LD + swiz_col(d, r, Traits::SWIZ_MASK);
-            cp_async_16_pred(&dK[off], a.k, a.valid);
-            cp_async_16_pred(&dV[off], a.v, a.valid);
+            astrai::cp_async_16(&dK[off], a.k, a.valid);
+            astrai::cp_async_16(&dV[off], a.v, a.valid);
         }
-        cp_async_commit();
+        astrai::cp_async_commit_group();
     };
 
     // ---- Multi-stage cp.async pipeline ----
@@ -107,10 +112,11 @@ __global__ void attn_decode_split_kv_mma_kernel(AttentionParams<bf16> p) {
         int maxc = IsCausal ? KV::decode_attend_len(p, batch) : seq_len;
         mma_softmax_tile<Traits, HasMask>(kv0, maxc, maxc,
                                            0, 0,
-                                           p.mask_b_stride, 0, 0,
-                                           batch, 0,
-                                           p.mask,
-                                           Sacc, Oacc, m0, m1, l0, l1, lane);
+                                            p.mask_b_stride, p.mask_h_stride, p.mask_l_stride,
+                                            batch, q_head0 + gid, q_head0 + gid + 8,
+                                            p.mask,
+                                            va, vb,
+                                            Sacc, Oacc, m0, m1, l0, l1, lane);
 
         mma_pv_accumulate<Traits>(Sacc, bV, lane, Oacc);
     };
@@ -121,7 +127,10 @@ __global__ void attn_decode_split_kv_mma_kernel(AttentionParams<bf16> p) {
             load_tile(ti_begin + i, i);
 
         for (int it = 0; it < ntiles; it++) {
-            cp_async_wait_group<STAGES - 1>();
+            if (it + 1 == ntiles)
+                astrai::cp_async_wait_group<0>();
+            else
+                astrai::cp_async_wait_group<STAGES - 1>();
             __syncwarp();
             process_tile(it, it & (STAGES - 1));
             __syncwarp();
@@ -132,7 +141,7 @@ __global__ void attn_decode_split_kv_mma_kernel(AttentionParams<bf16> p) {
         // Fewer tiles than stages: load all, wait for all, process.
         for (int i = 0; i < ntiles; i++)
             load_tile(ti_begin + i, i);
-        cp_async_wait_group<0>();
+        astrai::cp_async_wait_all();
         __syncwarp();
         for (int it = 0; it < ntiles; it++)
             process_tile(it, it);
@@ -174,3 +183,6 @@ __global__ void attn_decode_split_kv_mma_kernel(AttentionParams<bf16> p) {
         }
     }
 }
+
+}  // namespace attention
+}  // namespace astrai

csrc/kernels/attention/dispatchers.cuh

@@ -3,22 +3,24 @@
 // No torch dependency; pure CUDA.
 //
 // The paged and contiguous kernels are unified by the KVSource policy
-// (ContigKV / PagedKV from attn_kv_source.cuh), so each launcher struct
+// (ContigKV / PagedKV from layout_policies.cuh), so each launcher struct
 // below is templated on KV and the paged dispatch is just the same launcher
 // instantiated with PagedKV.  Only the grid/split math differs, and that is
 // covered by KV::host_q_len / KV::host_kv_len.
 
 #include <cuda_runtime.h>
 #include <algorithm>
-#include "attn_warp_utils.cuh"
-#include "attn_kv_source.cuh"
-#include "attn_prefill_split_q.cuh"
-#include "attn_decode_split_kv.cuh"
+#include "layout_policies.cuh"
+#include "prefill_split_q.cuh"
+#include "decode_split_kv.cuh"
 #ifndef ASTRAI_NO_MMA
-#include "attn_prefill_split_q_mma.cuh"
-#include "attn_decode_split_kv_mma.cuh"
+#include "prefill_split_q_mma.cuh"
+#include "decode_split_kv_mma.cuh"
 #endif
 
+namespace astrai {
+namespace attention {
+
 // Split-KV: compute number of splits to fill all SMs for small-batch decode.
 // Caps splits so each split processes at least `min_tiles_per_split` tiles,
 // avoiding excessive loop/prologue overhead when tiles are small.
@@ -59,32 +61,62 @@ inline int compute_num_splits(int base_blocks, int tiles_total,
 // ======================================================================
 
 #ifndef ASTRAI_NO_MMA
-template <typename KV>
+template <int BC_>
+struct PrefillKernelConfig {
+    static constexpr int BC = BC_;
+    static constexpr int WARPS = 4;
+    static constexpr int STAGES = 2;
+};
+
+// Compile-time configuration map shared by contiguous and paged prefill.
+// Unsupported head dimensions intentionally have no mapping.
+template <int HEAD_DIM, bool IsCausal>
+struct PrefillConfigMap;
+
+template <> struct PrefillConfigMap<32, false>  : PrefillKernelConfig<32> {};
+template <> struct PrefillConfigMap<32, true>   : PrefillKernelConfig<64> {};
+template <> struct PrefillConfigMap<64, false>  : PrefillKernelConfig<32> {};
+template <> struct PrefillConfigMap<64, true>   : PrefillKernelConfig<64> {};
+template <> struct PrefillConfigMap<128, false> : PrefillKernelConfig<32> {};
+template <> struct PrefillConfigMap<128, true>  : PrefillKernelConfig<32> {};
+template <> struct PrefillConfigMap<256, false> : PrefillKernelConfig<16> {};
+template <> struct PrefillConfigMap<256, true>  : PrefillKernelConfig<16> {};
+
+template <typename QSchedule, typename KV>
 struct PrefillLauncherMMA {
     template <int HEAD_DIM, bool IsCausal, bool HasMask>
     static void launch(AttentionParams<bf16>& p, cudaStream_t stream) {
-        constexpr int WARPS = 4;
-        constexpr int BC = (HEAD_DIM <= 128) ? 32 : 16;
-        using Traits = KernelTraits<HEAD_DIM, BC, WARPS, 2>;
-        int q_len = KV::host_q_len(p);
-        dim3 grid((q_len + Traits::BR * WARPS - 1) / (Traits::BR * WARPS),
-                  p.q_head, p.batch);
+        using Config = PrefillConfigMap<HEAD_DIM, IsCausal>;
+        using Traits = KernelTraits<HEAD_DIM, Config::BC, Config::WARPS, Config::STAGES>;
+        // GQA head packing: HB = min(G, WARPS) q-heads of one kv-head group
+        // share each block's K/V stream (~HB× less global K/V traffic).
+        // Each head gets WPH = WARPS/HB 16-row chunks per block, so per-head
+        // rows drop from 64 to BR*WPH while total mma work per K/V byte is
+        // unchanged.  G=1 (MHA) reproduces the historical grid exactly.
+        const int G = p.q_head / p.kv_head;
+        const int HB = std::min(G, Config::WARPS);
+        const int WPH = Config::WARPS / HB;
+        constexpr int BR = Traits::BR;
+        dim3 grid(QSchedule::packed_grid_x(p, BR * WPH),
+                  p.kv_head * ((G + HB - 1) / HB),
+                  QSchedule::host_grid_batch(p));
         dim3 block(Traits::NUM_THREADS);
-        attn_prefill_split_q_mma_kernel<Traits, KV, IsCausal, HasMask>
+        attn_prefill_split_q_mma_kernel<Traits, QSchedule, KV, IsCausal, HasMask>
             <<<grid, block, 0, stream>>>(p);
     }
 };
 #endif
 
-template <typename KV>
+template <typename QSchedule, typename KV>
 struct PrefillLauncherScalar {
     template <int HEAD_DIM, bool IsCausal, bool HasMask>
     static void launch(AttentionParams<bf16>& p, cudaStream_t stream) {
-        constexpr int G = 8, ROWS = 32, P_BC = 32;
-        int q_len = KV::host_q_len(p);
-        dim3 grid((q_len + ROWS - 1) / ROWS, p.q_head, p.batch);
+        constexpr int G = (HEAD_DIM == 32) ? 4 : 8, ROWS = 64, P_BC = 32;
+        dim3 grid(QSchedule::host_q_blocks(p, ROWS), p.q_head,
+                  QSchedule::host_grid_batch(p));
         dim3 block(G, ROWS);
-        attn_prefill_split_q_kernel_t<HEAD_DIM, KV, G, ROWS, P_BC, IsCausal, HasMask>
+        attn_prefill_split_q_kernel_t<HEAD_DIM, QSchedule, KV, G, ROWS, P_BC,
+                                      IsCausal, HasMask>
             <<<grid, block, 0, stream>>>(p);
     }
 };
@@ -95,12 +127,14 @@ static inline void dispatch_prefill(AttentionParams<bf16>& p, cudaStream_t strea
     bool has_mask = (p.use_mask && p.mask);
 
 #ifndef ASTRAI_NO_MMA
+    using Launcher = PrefillLauncherMMA<DenseQSchedule, ContigKV>;
     DISPATCH_CAUSAL_MASK(is_causal, has_mask,
-                         PrefillLauncherMMA<ContigKV>::template launch,
+                         Launcher::template launch,
                          HEAD_DIM, p, stream);
 #else
+    using Launcher = PrefillLauncherScalar<DenseQSchedule, ContigKV>;
     DISPATCH_CAUSAL_MASK(is_causal, has_mask,
-                         PrefillLauncherScalar<ContigKV>::template launch,
+                         Launcher::template launch,
                          HEAD_DIM, p, stream);
 #endif
 }
@@ -111,12 +145,14 @@ static inline void dispatch_paged_prefill(AttentionParams<bf16>& p, cudaStream_t
     bool has_mask = (p.use_mask && p.mask);
 
 #ifndef ASTRAI_NO_MMA
+    using Launcher = PrefillLauncherMMA<PackedQSchedule, PagedKV>;
     DISPATCH_CAUSAL_MASK(is_causal, has_mask,
-                         PrefillLauncherMMA<PagedKV>::template launch,
+                         Launcher::template launch,
                          HEAD_DIM, p, stream);
 #else
+    using Launcher = PrefillLauncherScalar<PackedQSchedule, PagedKV>;
     DISPATCH_CAUSAL_MASK(is_causal, has_mask,
-                         PrefillLauncherScalar<PagedKV>::template launch,
+                         Launcher::template launch,
                          HEAD_DIM, p, stream);
 #endif
 }
@@ -133,7 +169,7 @@ static inline void dispatch_paged_prefill(AttentionParams<bf16>& p, cudaStream_t
 template <typename KV>
 struct DecodeLauncherMMA {
     template <int HEAD_DIM, bool IsCausal, bool HasMask>
-    static void launch(AttentionParams<bf16>& p, int group_size, cudaStream_t stream) {
+    static void launch(AttentionParams<bf16>& p, cudaStream_t stream) {
         int G = p.q_head / p.kv_head;
         constexpr int MAX_G = 16;
         int num_passes = (G + MAX_G - 1) / MAX_G;
@@ -153,14 +189,19 @@ struct DecodeLauncherMMA {
 template <typename KV>
 struct DecodeLauncherScalar {
     template <int HEAD_DIM, bool IsCausal, bool HasMask>
-    static void launch(AttentionParams<bf16>& p, int group_size, cudaStream_t stream) {
+    static void launch(AttentionParams<bf16>& p, cudaStream_t stream) {
         int kv_len = KV::host_kv_len(p);
         int chunks_total = (kv_len + DC_CHUNK - 1) / DC_CHUNK;
         p.num_splits = compute_num_splits(p.batch * p.kv_head, chunks_total);
-        size_t smem = DC_CHUNK * p.head_dim * sizeof(bf16);
+        size_t smem = 2 * DC_CHUNK * p.head_dim * sizeof(bf16);
+        int group_size = p.q_head / p.kv_head;
         int g = min(group_size, 32);  // cap at 32 to respect 1024-thread limit
         dim3 grid(p.batch * p.kv_head, 1, p.num_splits);
         dim3 block(32, g);
+        cudaFuncSetAttribute(
+            attn_decode_split_kv_kernel<HEAD_DIM, KV, IsCausal, HasMask>,
+            cudaFuncAttributeMaxDynamicSharedMemorySize,
+            smem);
         attn_decode_split_kv_kernel<HEAD_DIM, KV, IsCausal, HasMask>
             <<<grid, block, smem, stream>>>(p);
     }
@@ -170,16 +211,15 @@ template <int HEAD_DIM>
 static inline void dispatch_decode(AttentionParams<bf16>& p, cudaStream_t stream) {
     bool is_causal = (p.causal_offset >= 0);
     bool has_mask = (p.use_mask && p.mask);
-    int group_size = p.q_head / p.kv_head;
 
 #ifndef ASTRAI_NO_MMA
     DISPATCH_CAUSAL_MASK(is_causal, has_mask,
                          DecodeLauncherMMA<ContigKV>::template launch,
-                         HEAD_DIM, p, group_size, stream);
+                         HEAD_DIM, p, stream);
 #else
     DISPATCH_CAUSAL_MASK(is_causal, has_mask,
                          DecodeLauncherScalar<ContigKV>::template launch,
-                         HEAD_DIM, p, group_size, stream);
+                         HEAD_DIM, p, stream);
 #endif
 
     attn_decode_combine_kernel<ContigKV><<<p.batch * p.q_head, p.head_dim, 0, stream>>>(p);
@@ -189,17 +229,19 @@ template <int HEAD_DIM>
 static inline void dispatch_paged_decode(AttentionParams<bf16>& p, cudaStream_t stream) {
     bool is_causal = (p.causal_offset >= 0);
     bool has_mask = (p.use_mask && p.mask);
-    int group_size = p.q_head / p.kv_head;
 
 #ifndef ASTRAI_NO_MMA
     DISPATCH_CAUSAL_MASK(is_causal, has_mask,
                          DecodeLauncherMMA<PagedKV>::template launch,
-                         HEAD_DIM, p, group_size, stream);
+                         HEAD_DIM, p, stream);
 #else
     DISPATCH_CAUSAL_MASK(is_causal, has_mask,
                          DecodeLauncherScalar<PagedKV>::template launch,
-                         HEAD_DIM, p, group_size, stream);
+                         HEAD_DIM, p, stream);
 #endif
 
     attn_decode_combine_kernel<PagedKV><<<p.batch * p.q_head, p.head_dim, 0, stream>>>(p);
 }
+
+}  // namespace attention
+}  // namespace astrai

csrc/kernels/attention/entry_utils.cuh

@@ -2,10 +2,7 @@
 #include <float.h>
 #include <torch/extension.h>
 #include <c10/cuda/CUDAGuard.h>
-#include "attn_common.h"
-#include "attn_warp_utils.cuh"
-
-using bf16 = __nv_bfloat16;
+#include "common.h"
 
 // Dispatch head_dim: shared macro — avoids C++20 lambda template syntax.
 // Usage: DISPATCH_HEAD_DIM(hd, fn, args...)
@@ -21,6 +18,11 @@ using bf16 = __nv_bfloat16;
                          " (supported: 32, 64, 128, 256)"); \
     }
 
+namespace astrai {
+namespace attention {
+
+using bf16 = __nv_bfloat16;
+
 // The split kernel unconditionally writes every (batch, q_head, split) slot it
 // owns — including empty split ranges, which store m = -FLT_MAX so the combine
 // skips them. Allocators are therefore left uninitialized (torch::empty); the
@@ -42,10 +44,10 @@ inline void extract_q_dims_and_strides(torch::Tensor& q, int64_t layout, P& p) {
     p.q_head = (int)q.size(1);
     p.q_len = (int)q.size(2);
     p.head_dim = (int)q.size(3);
-    p.q_stride_b = (int)q.stride(0);
-    p.q_stride_h = (int)q.stride(1);
-    p.q_stride_l = (int)q.stride(2);
-    p.q_stride_d = (int)q.stride(3);
+    p.q_b_stride = (int)q.stride(0);
+    p.q_h_stride = (int)q.stride(1);
+    p.q_l_stride = (int)q.stride(2);
+    p.q_d_stride = (int)q.stride(3);
 }
 
 // ---- Shared mask packing ----
@@ -63,17 +65,17 @@ inline void pack_mask(const c10::optional<torch::Tensor>& mask, P& p) {
         if (m.dim() == 2) {
             p.mask_b_stride = (int)m.stride(0);
             p.mask_h_stride = 0;
-            p.mask_q_stride = 0;
+            p.mask_l_stride = 0;
         } else if (m.dim() == 3) {
             TORCH_CHECK(m.size(1) == 1 || m.size(1) == p.q_len, "mask q_len mismatch");
             p.mask_b_stride = (int)m.stride(0);
             p.mask_h_stride = 0;
-            p.mask_q_stride = (m.size(1) == 1) ? 0 : (int)m.stride(1);
+            p.mask_l_stride = (m.size(1) == 1) ? 0 : (int)m.stride(1);
         } else if (m.dim() == 4) {
             TORCH_CHECK(m.size(2) == 1 || m.size(2) == p.q_len, "mask q_len mismatch");
             p.mask_b_stride = (int)m.stride(0);
             p.mask_h_stride = (m.size(1) == 1) ? 0 : (int)m.stride(1);
-            p.mask_q_stride = (m.size(2) == 1) ? 0 : (int)m.stride(2);
+            p.mask_l_stride = (m.size(2) == 1) ? 0 : (int)m.stride(2);
         } else {
             TORCH_CHECK(false, "mask must be 2D, 3D, or 4D");
         }
@@ -82,7 +84,7 @@ inline void pack_mask(const c10::optional<torch::Tensor>& mask, P& p) {
         p.mask = nullptr;
         p.mask_b_stride = 0;
         p.mask_h_stride = 0;
-        p.mask_q_stride = 0;
+        p.mask_l_stride = 0;
     }
 }
 
@@ -106,28 +108,33 @@ inline void attn_pack_params(
     TORCH_CHECK(v.dtype() == torch::kBFloat16);
     TORCH_CHECK(k.sizes() == v.sizes(), "K and V must have identical shapes");
     TORCH_CHECK(q.dim() == 4 && k.dim() == 4, "Q/K/V must be 4D");
-
     extract_q_dims_and_strides(q, layout, p);
 
     if (layout == BLHD) k = k.transpose(1, 2), v = v.transpose(1, 2);
 
     p.kv_head = (int)k.size(1);
     p.kv_len = (int)k.size(2);
+    TORCH_CHECK(p.q_head % p.kv_head == 0,
+                "q_head must be divisible by kv_head");
     TORCH_CHECK(k.size(3) == p.head_dim, "K/V head_dim must match Q");
+    TORCH_CHECK(q.stride(3) == 1 && k.stride(3) == 1 && v.stride(3) == 1,
+                "Q/K/V head_dim must be contiguous");
 
-    p.kv_stride_b = (int)k.stride(0);
-    p.kv_stride_h = (int)k.stride(1);
-    p.kv_stride_l = (int)k.stride(2);
-    p.kv_stride_d = (int)k.stride(3);
+    p.kv_b_stride = (int)k.stride(0);
+    p.kv_h_stride = (int)k.stride(1);
+    p.kv_l_stride = (int)k.stride(2);
+    p.kv_d_stride = (int)k.stride(3);
 
     p.causal_offset = (int)causal_offset;
     p.use_mask = mask.has_value() ? 1 : 0;
     p.scale = (scale > 0.0) ? (float)scale : 1.0f / sqrtf((float)p.head_dim);
 
-    p.q = (const T*)q.data_ptr();
-    p.k = (const T*)k.data_ptr();
-    p.v = (const T*)v.data_ptr();
-    p.o = nullptr;
+    p.q_ptr = (const T*)q.data_ptr();
+    p.k_ptr = (const T*)k.data_ptr();
+    p.v_ptr = (const T*)v.data_ptr();
+    p.new_k_ptr = nullptr;
+    p.new_v_ptr = nullptr;
+    p.o_ptr = nullptr;
     p.o_part = nullptr;
     p.ml_part = nullptr;
 
@@ -145,7 +152,8 @@ inline void attn_pack_paged_decode_params(
     torch::Tensor req_to_token,
     torch::Tensor req_pool_indices,
     torch::Tensor kv_indptr,
-    int64_t max_seq_len,
+    const c10::optional<torch::Tensor>& new_k,
+    const c10::optional<torch::Tensor>& new_v,
     c10::optional<torch::Tensor> mask,
     int64_t causal_offset,
     double scale,
@@ -158,8 +166,9 @@ inline void attn_pack_paged_decode_params(
     TORCH_CHECK(q.dtype() == torch::kBFloat16, "q must be bf16");
     TORCH_CHECK(k_cache.dtype() == torch::kBFloat16, "k_cache must be bf16");
     TORCH_CHECK(v_cache.dtype() == torch::kBFloat16, "v_cache must be bf16");
-    TORCH_CHECK(req_to_token.dtype() == torch::kLong, "req_to_token must be int64");
-    TORCH_CHECK(req_pool_indices.dtype() == torch::kLong, "req_pool_indices must be int64");
+    TORCH_CHECK(req_to_token.dtype() == torch::kInt32, "req_to_token must be int32");
+    TORCH_CHECK(req_pool_indices.dtype() == torch::kInt32,
+                "req_pool_indices must be int32");
     TORCH_CHECK(kv_indptr.dtype() == torch::kInt32, "kv_indptr must be int32");
     TORCH_CHECK(k_cache.sizes() == v_cache.sizes(), "k_cache and v_cache must match");
     TORCH_CHECK(k_cache.dim() == 3, "k_cache must be 3D [size, kv_head, head_dim]");
@@ -170,24 +179,50 @@ inline void attn_pack_paged_decode_params(
     p.head_dim = (int)q.size(2);
     p.kv_head = (int)k_cache.size(1);
     TORCH_CHECK(k_cache.size(2) == p.head_dim, "k_cache head_dim mismatch");
+    TORCH_CHECK(q.stride(2) == 1 && k_cache.stride(2) == 1 && v_cache.stride(2) == 1,
+                "Q/K/V head_dim must be contiguous");
     TORCH_CHECK(p.head_dim % 32 == 0, "head_dim must be multiple of 32");
     TORCH_CHECK(p.q_head % p.kv_head == 0, "q_head must be divisible by kv_head");
 
-    p.q_stride_l = (int)q.stride(0);
-    p.q_stride_h = (int)q.stride(1);
-    p.q_stride_d = (int)q.stride(2);
+    p.q_l_stride = (int)q.stride(0);
+    p.q_h_stride = (int)q.stride(1);
+    p.q_d_stride = (int)q.stride(2);
 
-    p.k_cache = (const T*)k_cache.data_ptr();
-    p.v_cache = (const T*)v_cache.data_ptr();
-    p.q = (const T*)q.data_ptr();
-    p.req_to_token = req_to_token.data_ptr<int64_t>();
-    p.req_pool_indices = req_pool_indices.data_ptr<int64_t>();
+    p.k_ptr = (const T*)k_cache.data_ptr();
+    p.v_ptr = (const T*)v_cache.data_ptr();
+    p.q_ptr = (const T*)q.data_ptr();
+    p.req_to_token = req_to_token.data_ptr<int>();
+    p.req_pool_indices = req_pool_indices.data_ptr<int>();
     p.kv_indptr = kv_indptr.data_ptr<int>();
     p.qo_indptr = nullptr;
     p.max_context_len = (int)req_to_token.size(1);
-    p.max_seq_len = (int)max_seq_len;
-    p.total_q = p.batch;  // decode: 1 Q token per request
-    p.max_q_len = 1;
+
+    TORCH_CHECK(new_k.has_value() == new_v.has_value(),
+                "new_k and new_v must be provided together");
+    if (new_k.has_value()) {
+        auto nk = new_k.value();
+        auto nv = new_v.value();
+        TORCH_CHECK(nk.is_cuda() && nv.is_cuda(), "new K/V must be CUDA tensors");
+        TORCH_CHECK(nk.dtype() == torch::kBFloat16 && nv.dtype() == torch::kBFloat16,
+                    "new K/V must be bf16");
+        TORCH_CHECK(nk.dim() == 3 && nv.dim() == 3,
+                    "new K/V must be 3D [batch, kv_head, head_dim]");
+        TORCH_CHECK(nk.sizes() == nv.sizes(), "new K and V must have identical shapes");
+        TORCH_CHECK(nk.strides() == nv.strides(),
+                    "new K and V must have identical strides");
+        TORCH_CHECK(nk.size(0) == p.batch && nk.size(1) == p.kv_head
+                    && nk.size(2) == p.head_dim, "new K/V shape mismatch");
+        TORCH_CHECK(nk.stride(2) == 1 && nv.stride(2) == 1,
+                    "new K/V head_dim must be contiguous");
+        p.new_k_ptr = (const T*)nk.data_ptr();
+        p.new_v_ptr = (const T*)nv.data_ptr();
+        p.new_kv_b_stride = (int)nk.stride(0);
+        p.new_kv_h_stride = (int)nk.stride(1);
+    } else {
+        p.new_k_ptr = nullptr;
+        p.new_v_ptr = nullptr;
+        p.new_kv_b_stride = p.new_kv_h_stride = 0;
+    }
 
     p.causal_offset = (int)causal_offset;
     p.use_mask = (mask.has_value() && mask.value().defined()) ? 1 : 0;
@@ -199,16 +234,16 @@ inline void attn_pack_paged_decode_params(
         TORCH_CHECK(m.size(0) == p.batch, "mask batch mismatch");
         p.mask_b_stride = (int)m.stride(0);
         p.mask_h_stride = 0;
-        p.mask_q_stride = 0;
+        p.mask_l_stride = 0;
         p.mask = m.data_ptr<bool>();
     } else {
         p.mask = nullptr;
         p.mask_b_stride = 0;
         p.mask_h_stride = 0;
-        p.mask_q_stride = 0;
+        p.mask_l_stride = 0;
     }
 
-    p.o = nullptr;
+    p.o_ptr = nullptr;
     p.o_part = nullptr;
     p.ml_part = nullptr;
 }
@@ -225,8 +260,9 @@ inline void attn_pack_paged_prefill_params(
     torch::Tensor req_pool_indices,
     torch::Tensor kv_indptr,
     torch::Tensor qo_indptr,
+    torch::Tensor q_tile_to_batch,
+    torch::Tensor q_tile_to_index,
     c10::optional<torch::Tensor> mask,
-    int64_t max_q_len,
     int64_t causal_offset,
     double scale,
     AttentionParams<T>& p
@@ -236,44 +272,57 @@ inline void attn_pack_paged_prefill_params(
     TORCH_CHECK(q.is_cuda() && k_cache.is_cuda() && v_cache.is_cuda());
     TORCH_CHECK(req_to_token.is_cuda() && req_pool_indices.is_cuda());
     TORCH_CHECK(kv_indptr.is_cuda() && qo_indptr.is_cuda());
+    TORCH_CHECK(q_tile_to_batch.is_cuda() && q_tile_to_index.is_cuda());
     TORCH_CHECK(q.dtype() == torch::kBFloat16, "q must be bf16");
     TORCH_CHECK(k_cache.dtype() == torch::kBFloat16, "k_cache must be bf16");
     TORCH_CHECK(v_cache.dtype() == torch::kBFloat16, "v_cache must be bf16");
-    TORCH_CHECK(req_to_token.dtype() == torch::kLong, "req_to_token must be int64");
-    TORCH_CHECK(req_pool_indices.dtype() == torch::kLong, "req_pool_indices must be int64");
+    TORCH_CHECK(req_to_token.dtype() == torch::kInt32, "req_to_token must be int32");
+    TORCH_CHECK(req_pool_indices.dtype() == torch::kInt32,
+                "req_pool_indices must be int32");
     TORCH_CHECK(kv_indptr.dtype() == torch::kInt32, "kv_indptr must be int32");
     TORCH_CHECK(qo_indptr.dtype() == torch::kInt32, "qo_indptr must be int32");
+    TORCH_CHECK(q_tile_to_batch.dtype() == torch::kInt32,
+                "q_tile_to_batch must be int32");
+    TORCH_CHECK(q_tile_to_index.dtype() == torch::kInt32,
+                "q_tile_to_index must be int32");
     TORCH_CHECK(k_cache.sizes() == v_cache.sizes(), "k_cache and v_cache must match");
     TORCH_CHECK(k_cache.dim() == 3, "k_cache must be 3D [size, kv_head, head_dim]");
     TORCH_CHECK(q.dim() == 3, "q must be 3D [total_q, q_head, head_dim]");
 
     p.q_head = (int)q.size(1);
     p.head_dim = (int)q.size(2);
+    p.q_len = (int)q.size(0);
     p.kv_head = (int)k_cache.size(1);
     p.batch = (int)req_pool_indices.size(0);
     TORCH_CHECK(k_cache.size(2) == p.head_dim, "k_cache head_dim mismatch");
+    TORCH_CHECK(q.stride(2) == 1 && k_cache.stride(2) == 1 && v_cache.stride(2) == 1,
+                "Q/K/V head_dim must be contiguous");
     TORCH_CHECK(p.head_dim % 16 == 0, "head_dim must be multiple of 16");
     TORCH_CHECK(p.q_head % p.kv_head == 0, "q_head must be divisible by kv_head");
     TORCH_CHECK(kv_indptr.size(0) == p.batch + 1, "kv_indptr must be [batch+1]");
     TORCH_CHECK(qo_indptr.size(0) == p.batch + 1, "qo_indptr must be [batch+1]");
+    TORCH_CHECK(q_tile_to_batch.dim() == 1 && q_tile_to_index.dim() == 1,
+                "Q tile mappings must be 1D");
+    TORCH_CHECK(q_tile_to_batch.size(0) == q_tile_to_index.size(0),
+                "Q tile mappings must have equal length");
 
-    p.q_stride_l = (int)q.stride(0);
-    p.q_stride_h = (int)q.stride(1);
-    p.q_stride_d = (int)q.stride(2);
+    p.q_l_stride = (int)q.stride(0);
+    p.q_h_stride = (int)q.stride(1);
+    p.q_d_stride = (int)q.stride(2);
 
-    p.k_cache = (const T*)k_cache.data_ptr();
-    p.v_cache = (const T*)v_cache.data_ptr();
-    p.q = (const T*)q.data_ptr();
-    p.req_to_token = req_to_token.data_ptr<int64_t>();
-    p.req_pool_indices = req_pool_indices.data_ptr<int64_t>();
+    p.k_ptr = (const T*)k_cache.data_ptr();
+    p.v_ptr = (const T*)v_cache.data_ptr();
+    p.new_k_ptr = nullptr;
+    p.new_v_ptr = nullptr;
+    p.q_ptr = (const T*)q.data_ptr();
+    p.req_to_token = req_to_token.data_ptr<int>();
+    p.req_pool_indices = req_pool_indices.data_ptr<int>();
     p.kv_indptr = kv_indptr.data_ptr<int>();
     p.qo_indptr = qo_indptr.data_ptr<int>();
+    p.q_tile_to_batch = q_tile_to_batch.data_ptr<int>();
+    p.q_tile_to_index = q_tile_to_index.data_ptr<int>();
+    p.num_q_tiles = (int)q_tile_to_batch.size(0);
     p.max_context_len = (int)req_to_token.size(1);
-    p.total_q = (int)q.size(0);  // prefill: flattened Q across all requests
-    p.max_q_len = (int)max_q_len;
-    // max_seq_len is unused by the prefill path (decode uses it for split
-    // computation); fill with max_q_len only to keep the POD struct defined.
-    p.max_seq_len = p.max_q_len;
 
     p.causal_offset = (int)causal_offset;
     p.use_mask = (mask.has_value() && mask.value().defined()) ? 1 : 0;
@@ -285,14 +334,14 @@ inline void attn_pack_paged_prefill_params(
             TORCH_CHECK(m.size(1) <= p.max_context_len, "mask kv_len mismatch");
             p.mask_b_stride = (int)m.stride(0);
             p.mask_h_stride = 0;
-            p.mask_q_stride = 0;
+            p.mask_l_stride = 0;
         } else if (m.dim() == 4) {
             TORCH_CHECK(m.size(1) == 1 || m.size(1) == p.q_head, "mask head mismatch");
-            TORCH_CHECK(m.size(2) == 1 || m.size(2) == p.max_q_len, "mask q_len mismatch");
+            TORCH_CHECK(m.size(2) > 0 && m.size(2) <= p.q_len, "mask q_len mismatch");
             TORCH_CHECK(m.size(3) <= p.max_context_len, "mask kv_len mismatch");
             p.mask_b_stride = (int)m.stride(0);
             p.mask_h_stride = (m.size(1) == 1) ? 0 : (int)m.stride(1);
-            p.mask_q_stride = (m.size(2) == 1) ? 0 : (int)m.stride(2);
+            p.mask_l_stride = (m.size(2) == 1) ? 0 : (int)m.stride(2);
         } else {
             TORCH_CHECK(false, "mask must be 2D or 4D");
         }
@@ -301,11 +350,14 @@ inline void attn_pack_paged_prefill_params(
         p.mask = nullptr;
         p.mask_b_stride = 0;
         p.mask_h_stride = 0;
-        p.mask_q_stride = 0;
+        p.mask_l_stride = 0;
     }
     p.scale = (scale > 0.0) ? (float)scale : 1.0f / sqrtf((float)p.head_dim);
 
-    p.o = nullptr;
+    p.o_ptr = nullptr;
     p.o_part = nullptr;
     p.ml_part = nullptr;
 }
+
+}  // namespace attention
+}  // namespace astrai

csrc/kernels/attention/layout_policies.cuh

@@ -0,0 +1,292 @@
+#pragma once
+#include <cuda_bf16.h>
+#include "common.h"
+
+// ============================================================================
+// Attention layout policies keep Q scheduling independent from K/V storage.
+// DenseQSchedule / PackedQSchedule map blocks to Q tiles; ContigKV / PagedKV
+// resolve logical K/V positions to physical addresses. This lets the shared
+// kernels compose Q layout and K/V storage without coupling the two concerns.
+//
+//   ContigKV:  K/V are dense [batch, kv_head, kv_len, head_dim] tensors.
+//              Params fields used: k, v, kv_stride_*, kv_len, q_len,
+//              q_b_stride, causal_offset.
+//   PagedKV:   K/V live in a flat pool [size, kv_head, head_dim] indexed via
+//              req_to_token.  Params fields used: k_cache, v_cache,
+//              req_to_token, req_pool_indices, kv_indptr, qo_indptr,
+//              max_context_len, q_l_stride.
+//
+// Addressing state that is constant across a whole kernel invocation for one
+// (batch, kv_head) pair is captured once by make_ctx<HEAD_DIM>() and passed
+// to kv_addr, so the load loops never redo the hoistable base computation
+// (e.g. the req_pool_indices global read) element-by-element.
+// ============================================================================
+
+#define HOST_FORCEINLINE static __host__ __forceinline__
+#define DEVICE_FORCEINLINE static __device__ __forceinline__
+#define HOST_DEV_FORCEINLINE static __host__ __device__ __forceinline__
+
+namespace astrai {
+namespace attention {
+
+using bf16 = __nv_bfloat16;
+
+// ============================================================================
+// Q scheduling policies
+//
+// Map CUDA blocks to request-local Q tiles independently of K/V storage.
+// Dense tensors encode the request in blockIdx.z; packed ragged tensors use
+// a compact precomputed work map indexed by blockIdx.x.
+// ============================================================================
+
+struct DenseQSchedule {
+    HOST_FORCEINLINE int host_q_blocks(
+        const AttentionParams<bf16>& p, int rows) {
+        return (p.q_len + rows - 1) / rows;
+    }
+
+    HOST_FORCEINLINE int host_grid_batch(
+        const AttentionParams<bf16>& p) {
+        return p.batch;
+    }
+
+    DEVICE_FORCEINLINE void map_block(
+        const AttentionParams<bf16>&, int& batch, int& q_tile) {
+        batch = blockIdx.z;
+        q_tile = blockIdx.x;
+    }
+
+    // GQA-packed prefill mapping: HB q-heads of one kv-head group share a
+    // block's K/V stream, each head owning `rows` = BR*WPH consecutive q rows
+    // per block.  Dense tensors tile q_len directly, one block per range.
+    HOST_FORCEINLINE int packed_grid_x(
+        const AttentionParams<bf16>& p, int rows) {
+        return (p.q_len + rows - 1) / rows;
+    }
+
+    DEVICE_FORCEINLINE void map_packed_block(
+        const AttentionParams<bf16>&, int rows, int& batch, int& row_base) {
+        batch = blockIdx.z;
+        row_base = blockIdx.x * rows;
+    }
+
+    DEVICE_FORCEINLINE int q_len(
+        const AttentionParams<bf16>& p, int) {
+        return p.q_len;
+    }
+
+    DEVICE_FORCEINLINE int q_base(
+        const AttentionParams<bf16>& p, int batch, int q_head) {
+        return batch * p.q_b_stride + q_head * p.q_h_stride;
+    }
+};
+
+struct PackedQSchedule {
+    HOST_FORCEINLINE int host_q_blocks(
+        const AttentionParams<bf16>& p, int) {
+        return p.num_q_tiles;
+    }
+
+    HOST_FORCEINLINE int host_grid_batch(
+        const AttentionParams<bf16>&) {
+        return 1;
+    }
+
+    DEVICE_FORCEINLINE void map_block(
+        const AttentionParams<bf16>& p, int& batch, int& q_tile) {
+        batch = p.q_tile_to_batch[blockIdx.x];
+        q_tile = p.q_tile_to_index[blockIdx.x];
+    }
+
+    // GQA-packed prefill mapping: the host tile maps are built in
+    // HOST_Q_TILE_ROWS granularity, so each host tile splits into
+    // HOST_Q_TILE_ROWS / rows packed blocks along blockIdx.x.
+    HOST_FORCEINLINE int packed_grid_x(
+        const AttentionParams<bf16>& p, int rows) {
+        return p.num_q_tiles * (HOST_Q_TILE_ROWS / rows);
+    }
+
+    DEVICE_FORCEINLINE void map_packed_block(
+        const AttentionParams<bf16>& p, int rows, int& batch, int& row_base) {
+        const int hb = HOST_Q_TILE_ROWS / rows;
+        const int host_tile = blockIdx.x / hb;
+        batch = p.q_tile_to_batch[host_tile];
+        row_base = p.q_tile_to_index[host_tile] * HOST_Q_TILE_ROWS
+            + (blockIdx.x - host_tile * hb) * rows;
+    }
+
+    DEVICE_FORCEINLINE int q_len(
+        const AttentionParams<bf16>& p, int batch) {
+        return p.qo_indptr[batch + 1] - p.qo_indptr[batch];
+    }
+
+    DEVICE_FORCEINLINE int q_base(
+        const AttentionParams<bf16>& p, int batch, int q_head) {
+        return p.qo_indptr[batch] * p.q_l_stride + q_head * p.q_h_stride;
+    }
+};
+
+// Hoisted per-(batch, kv_head) addressing context.
+struct KVContext {
+    int kv_base;          // contig: batch*kv_b_stride + kv_head*kv_h_stride
+    int req_idx;          // paged: req_pool_indices[batch]
+    int64_t rtt_stride;   // paged: max_context_len
+    int64_t pool_stride;  // paged: kv_head * HEAD_DIM
+    int64_t head_off;     // paged: kv_head * HEAD_DIM
+};
+
+// Per-element K/V global addresses for one (kc, d) position of a K/V tile.
+// The pointers are ALWAYS the computed addresses (never nullptr) — callers
+// gate on `valid` (cp.async src_size=0, or a guarded scalar deref).  `valid`
+// starts as "within the request's seq_len"; the paged policy further degrades
+// it when req_to_token maps the position to a negative slot (empty padding).
+// This matches the original hand-rolled load loops, where the address was
+// always formed and the predicate decided whether anything was read.
+struct KVAddr {
+    const void* k;
+    const void* v;
+    bool valid;
+};
+
+// ---- Contiguous K/V ----
+struct ContigKV {
+    static constexpr bool kPaged = false;
+
+    HOST_FORCEINLINE int host_kv_len(const AttentionParams<bf16>& p) {
+        return p.kv_len;
+    }
+
+    // decode: same offset (q_len == 1, so there is no row stride component)
+    DEVICE_FORCEINLINE int q_decode_base(
+        const AttentionParams<bf16>& p, int batch, int q_head) {
+        return batch * p.q_b_stride + q_head * p.q_h_stride;
+    }
+
+    DEVICE_FORCEINLINE int kv_len(const AttentionParams<bf16>& p, int) {
+        return p.kv_len;
+    }
+    DEVICE_FORCEINLINE int causal_offset(
+        const AttentionParams<bf16>& p, int, int) {
+        return p.causal_offset;
+    }
+    // decode: exclusive bound of the single query's attend range
+    DEVICE_FORCEINLINE int decode_attend_len(const AttentionParams<bf16>& p, int) {
+        return (p.kv_len < p.causal_offset + 1) ? p.kv_len : (p.causal_offset + 1);
+    }
+
+    template <int HEAD_DIM>
+    DEVICE_FORCEINLINE KVContext make_ctx(
+        const AttentionParams<bf16>& p, int batch, int kv_head) {
+        KVContext c = {};
+        c.kv_base = batch * p.kv_b_stride + kv_head * p.kv_h_stride;
+        return c;
+    }
+    DEVICE_FORCEINLINE int resolve_token(
+        const AttentionParams<bf16>& p, const KVContext& c, int kc, bool valid) {
+        return valid ? kc : -1;
+    }
+    DEVICE_FORCEINLINE KVAddr kv_addr_from_token(
+        const AttentionParams<bf16>& p, const KVContext& c, int token, int d) {
+        const bool valid = token >= 0;
+        const int safe_token = valid ? token : 0;
+        const int64_t gmem_off = (int64_t)c.kv_base
+            + (int64_t)safe_token * p.kv_l_stride
+            + (int64_t)d * p.kv_d_stride;
+        return {&p.k_ptr[gmem_off], &p.v_ptr[gmem_off], valid};
+    }
+
+    template <int VEC>
+    DEVICE_FORCEINLINE KVAddr decode_addr(
+        const AttentionParams<bf16>& p, const KVContext& c,
+        int, int, int kc, int d, bool valid, bool) {
+        int token = resolve_token(p, c, kc, valid);
+        return kv_addr_from_token(p, c, token, d);
+    }
+};
+
+// ---- Paged (SGLang-style flat pool) K/V ----
+struct PagedKV {
+    static constexpr bool kPaged = true;
+
+    HOST_FORCEINLINE int host_kv_len(const AttentionParams<bf16>& p) {
+        return p.max_context_len;
+    }
+
+    // decode: Q is [batch, q_head, head_dim], so batch is the outer row
+    DEVICE_FORCEINLINE int q_decode_base(
+        const AttentionParams<bf16>& p, int batch, int q_head) {
+        return batch * p.q_l_stride + q_head * p.q_h_stride;
+    }
+
+    DEVICE_FORCEINLINE int kv_len(const AttentionParams<bf16>& p, int batch) {
+        return p.kv_indptr[batch + 1] - p.kv_indptr[batch];
+    }
+    DEVICE_FORCEINLINE int causal_offset(
+        const AttentionParams<bf16>& p, int batch, int q_len) {
+        return kv_len(p, batch) - q_len;
+    }
+    // decode: the query is the last token, so [0, seq_len) IS its causal range
+    DEVICE_FORCEINLINE int decode_attend_len(const AttentionParams<bf16>& p, int batch) {
+        return kv_len(p, batch);
+    }
+
+    template <int HEAD_DIM>
+    DEVICE_FORCEINLINE KVContext make_ctx(
+        const AttentionParams<bf16>& p, int batch, int kv_head) {
+        KVContext c = {};
+        c.req_idx = p.req_pool_indices[batch];
+        c.rtt_stride = (int64_t)p.max_context_len;
+        c.pool_stride = (int64_t)p.kv_head * HEAD_DIM;
+        c.head_off = (int64_t)kv_head * HEAD_DIM;
+        return c;
+    }
+    DEVICE_FORCEINLINE int resolve_token(
+        const AttentionParams<bf16>& p, const KVContext& c, int kc, bool valid) {
+        return valid ? p.req_to_token[c.req_idx * c.rtt_stride + kc] : -1;
+    }
+    DEVICE_FORCEINLINE KVAddr kv_addr_from_token(
+        const AttentionParams<bf16>& p, const KVContext& c, int slot, int d) {
+        const bool valid = slot >= 0;
+        const int safe_slot = valid ? slot : 0;
+        const int64_t gmem_off = (int64_t)safe_slot * c.pool_stride + c.head_off + d;
+        return {&p.k_ptr[gmem_off], &p.v_ptr[gmem_off], valid};
+    }
+
+    DEVICE_FORCEINLINE KVAddr new_kv_addr(
+        const AttentionParams<bf16>& p, int batch, int kv_head, int d) {
+        const int64_t off = (int64_t)batch * p.new_kv_b_stride
+            + (int64_t)kv_head * p.new_kv_h_stride + d;
+        return {&p.new_k_ptr[off], &p.new_v_ptr[off], true};
+    }
+
+    DEVICE_FORCEINLINE void store_new_kv(
+        const AttentionParams<bf16>& p, const KVContext& c,
+        int seq_len, int d, const KVAddr& src) {
+        int slot = resolve_token(p, c, seq_len - 1, true);
+        const int64_t off = (int64_t)slot * c.pool_stride + c.head_off + d;
+        const_cast<bf16*>(p.k_ptr)[off] = *reinterpret_cast<const bf16*>(src.k);
+        const_cast<bf16*>(p.v_ptr)[off] = *reinterpret_cast<const bf16*>(src.v);
+    }
+
+    template <int VEC>
+    DEVICE_FORCEINLINE KVAddr decode_addr(
+        const AttentionParams<bf16>& p, const KVContext& c,
+        int batch, int kv_head, int kc, int d, bool valid, bool persist) {
+        if (p.new_k_ptr && valid && kc == kv_len(p, batch) - 1) {
+            KVAddr src = new_kv_addr(p, batch, kv_head, d);
+            if (persist) {
+                #pragma unroll
+                for (int j = 0; j < VEC; j++) {
+                    KVAddr value = new_kv_addr(p, batch, kv_head, d + j);
+                    store_new_kv(p, c, kc + 1, d + j, value);
+                }
+            }
+            return src;
+        }
+        int token = resolve_token(p, c, kc, valid);
+        return kv_addr_from_token(p, c, token, d);
+    }
+};
+
+}  // namespace attention
+}  // namespace astrai

csrc/kernels/attention/mma_utils.cuh

@@ -3,12 +3,18 @@
 #include <cuda_fp16.h>
 #include <cuda_runtime.h>
 
+#include "../common/cp_async.cuh"
+#include "../common/mma.cuh"
+
 // Predicated cp.async (4-operand form) requires CUDA 11.2+.
 // bf16 mma.sync requires sm_80+ (guarded at build time by ASTRAI_NO_MMA).
 #if CUDART_VERSION < 11020
 #error "AstrAI CUDA kernels require CUDA 11.2 or later (CUDART_VERSION >= 11020)."
 #endif
 
+namespace astrai {
+namespace attention {
+
 // ============================================================================
 // KernelTraits — FlashAttention-v2 style compile-time configuration bundle.
 //
@@ -24,10 +30,10 @@ struct KernelTraits {
 
     static constexpr int BR = 16;             // Q rows per warp (mma M=16)
 
-    // Derived: mma.sync.m16n8k16 tile counts
-    static constexpr int KD  = HEAD_DIM / 16;  // Q/K k-slides
+    // Derived: mma tile counts from the shared mma_shape (m16n8k16 for bf16)
+    static constexpr int KD  = HEAD_DIM / astrai::mma_shape<bf16>::k;  // Q/K k-slides
     static constexpr int NC8 = BC / 8;          // S n-tiles (N=8)
-    static constexpr int KT2 = BC / 16;         // P k-tiles (K=16)
+    static constexpr int KT2 = BC / astrai::mma_shape<bf16>::k;        // P k-tiles (K=16)
     static constexpr int DN8 = HEAD_DIM / 8;    // O n-tiles (N=8)
 
     static constexpr int LD = HEAD_DIM;         // smem leading dim
@@ -43,16 +49,7 @@ struct KernelTraits {
 
 // ---- PTX wrappers ----
 using bf16 = __nv_bfloat16;
-
-__device__ __forceinline__ void mma16816(float* d, const unsigned* a,
-                                          const unsigned* b, const float* c) {
-    asm volatile(
-        "mma.sync.aligned.m16n8k16.row.col.f32.bf16.bf16.f32 "
-        "{%0,%1,%2,%3}, {%4,%5,%6,%7}, {%8,%9}, {%10,%11,%12,%13};"
-        : "=f"(d[0]), "=f"(d[1]), "=f"(d[2]), "=f"(d[3])
-        : "r"(a[0]), "r"(a[1]), "r"(a[2]), "r"(a[3]), "r"(b[0]), "r"(b[1]),
-          "f"(c[0]), "f"(c[1]), "f"(c[2]), "f"(c[3]));
-}
+// bf16 mma.sync lives in the shared astrai::mma_sync template (common/mma.cuh).
 
 // read two adjacent bf16 from smem as one packed .b32 (elem0 low, elem1 high)
 __device__ __forceinline__ unsigned ld2(const bf16* p) {
@@ -73,68 +70,24 @@ __device__ __forceinline__ unsigned pkb(bf16 a, bf16 b) {
     return *reinterpret_cast<unsigned*>(&v);
 }
 
-// ldmatrix: cooperatively load mma fragments from smem (one instruction per
-// 16x16 / 16x8 tile) with the exact register layout mma expects.
-__device__ __forceinline__ void ldmatrix_x4(unsigned* r, const bf16* p) {
-    unsigned a = __cvta_generic_to_shared(p);
-    asm volatile("ldmatrix.sync.aligned.m8n8.x4.shared.b16 {%0,%1,%2,%3}, [%4];"
-                 : "=r"(r[0]), "=r"(r[1]), "=r"(r[2]), "=r"(r[3])
-                 : "r"(a));
-}
-__device__ __forceinline__ void ldmatrix_x2(unsigned* r, const bf16* p) {
-    unsigned a = __cvta_generic_to_shared(p);
-    asm volatile("ldmatrix.sync.aligned.m8n8.x2.shared.b16 {%0,%1}, [%2];"
-                 : "=r"(r[0]), "=r"(r[1])
-                 : "r"(a));
-}
-__device__ __forceinline__ void ldmatrix_x2_trans(unsigned* r, const bf16* p) {
-    unsigned a = __cvta_generic_to_shared(p);
-    asm volatile("ldmatrix.sync.aligned.m8n8.x2.trans.shared.b16 {%0,%1}, [%2];"
-                 : "=r"(r[0]), "=r"(r[1])
-                 : "r"(a));
-}
+// ldmatrix lives in the shared template (common/mma.cuh):
+// `astrai::ldmatrix_x2<bf16>` / `<bf16, /*Trans=*/true>` load the K/V
+// fragments with the exact register layout mma expects.
 
 // XOR swizzle for shared-memory column at 8-bf16 chunk granularity.
 __device__ __forceinline__ int swiz_col(int d, int r, int mask = 7) {
     return ((d >> 3) ^ (r & mask)) << 3 | (d & 7);
 }
 
-// cp.async: copy 16 bytes (8 bf16) from global to shared memory directly.
-__device__ __forceinline__ void cp_async_16(bf16* smem_ptr, const void* gmem_ptr) {
-    unsigned smem_addr = __cvta_generic_to_shared(smem_ptr);
-    asm volatile("cp.async.ca.shared.global [%0], [%1], 16;"
-                 :: "r"(smem_addr), "l"(gmem_ptr));
-}
-
-// Predicated cp.async: copy 16 bytes when `pred`, otherwise zero-fill.
-// src_size=0 → no bytes read from src, so out-of-bounds src address is safe.
-__device__ __forceinline__ void cp_async_16_pred(bf16* smem_ptr,
-                                                  const void* gmem_ptr,
-                                                  bool pred) {
-    unsigned smem_addr = __cvta_generic_to_shared(smem_ptr);
-    int src_size = pred ? 16 : 0;
-    asm volatile("cp.async.ca.shared.global [%0], [%1], 16, %2;"
-                 :: "r"(smem_addr), "l"(gmem_ptr), "r"(src_size));
-}
-
-__device__ __forceinline__ void cp_async_commit() {
-    asm volatile("cp.async.commit_group;");
-}
-
-__device__ __forceinline__ void cp_async_wait_all() {
-    asm volatile("cp.async.wait_all;");
-}
-
-template <int N>
-__device__ __forceinline__ void cp_async_wait_group() {
-    asm volatile("cp.async.wait_group %0;" :: "n"(N));
-}
+// cp.async primitives live in the shared template (common/cp_async.cuh):
+// `astrai::cp_async_16` (predicated), `astrai::cp_async_commit_group`,
+// `astrai::cp_async_wait_group<N>` / `_wait_all` stage the K/V tiles.
 
 // ---------------------------------------------------------------------------
 // Q-load: load query rows directly from global memory into mma A-operand
 // register layout. One call replaces ~15 duplicated lines in each MMA kernel.
-// stride_row is p.q_stride_h for decode (q_len=1, G heads) or
-//              p.q_stride_l for prefill (multi-q rows).
+// stride_row is p.q_h_stride for decode (q_len=1, G heads) or
+//              p.q_l_stride for prefill (multi-q rows).
 // ---------------------------------------------------------------------------
 template <int KD>
 __device__ inline void load_q_mma_frags(
@@ -180,9 +133,9 @@ __device__ inline void mma_compute_scores(
         #pragma unroll
         for (int kt = 0; kt < Traits::KD; kt++) {
             unsigned b[2];
-            ldmatrix_x2(b, &sK[krow_l * Traits::LD
+            astrai::ldmatrix_x2<bf16>(b, &sK[krow_l * Traits::LD
                 + swiz_col(kt * 16 + kcol_h, krow_l, Traits::SWIZ_MASK)]);
-            mma16816(Sacc[n8], Qa[kt], b, Sacc[n8]);
+            astrai::mma_sync<bf16>(Sacc[n8], Qa[kt], b, Sacc[n8]);
         }
     }
 }
@@ -198,9 +151,10 @@ __device__ inline void mma_softmax_tile(
     int kv0,
     int maxc0, int maxc1,
     int qrow0, int qrow1,
-    int mask_b_stride, int mask_h_stride, int mask_q_stride,
-    int mask_batch, int mask_head,
+    int mask_b_stride, int mask_h_stride, int mask_l_stride,
+    int mask_batch, int mask_head0, int mask_head1,
     const bool* __restrict__ mask,
+    bool valid0, bool valid1,
     float Sacc[Traits::NC8][4],
     float Oacc[Traits::DN8][4],
     float& m0, float& m1,
@@ -210,16 +164,16 @@ __device__ inline void mma_softmax_tile(
     int tid4 = lane & 3;
 
     float rmax0 = -FLT_MAX, rmax1 = -FLT_MAX;
-    int mask_base0 = mask_batch * mask_b_stride + mask_head * mask_h_stride + qrow0 * mask_q_stride;
-    int mask_base1 = mask_batch * mask_b_stride + mask_head * mask_h_stride + qrow1 * mask_q_stride;
+    int mask_base0 = mask_batch * mask_b_stride + mask_head0 * mask_h_stride + qrow0 * mask_l_stride;
+    int mask_base1 = mask_batch * mask_b_stride + mask_head1 * mask_h_stride + qrow1 * mask_l_stride;
     #pragma unroll
     for (int n8 = 0; n8 < Traits::NC8; n8++) {
         int cc = kv0 + n8 * 8 + 2 * tid4;
         int c1 = cc + 1;
-        bool b0 = (cc >= maxc0) || (HasMask && !mask[mask_base0 + cc]);
-        bool b1 = (c1 >= maxc0) || (HasMask && !mask[mask_base0 + c1]);
-        bool b2 = (cc >= maxc1) || (HasMask && !mask[mask_base1 + cc]);
-        bool b3 = (c1 >= maxc1) || (HasMask && !mask[mask_base1 + c1]);
+        bool b0 = !valid0 || (cc >= maxc0) || (HasMask && !mask[mask_base0 + cc]);
+        bool b1 = !valid0 || (c1 >= maxc0) || (HasMask && !mask[mask_base0 + c1]);
+        bool b2 = !valid1 || (cc >= maxc1) || (HasMask && !mask[mask_base1 + cc]);
+        bool b3 = !valid1 || (c1 >= maxc1) || (HasMask && !mask[mask_base1 + c1]);
         float s0 = b0 ? -FLT_MAX : Sacc[n8][0];
         float s1 = b1 ? -FLT_MAX : Sacc[n8][1];
         float s2 = b2 ? -FLT_MAX : Sacc[n8][2];
@@ -289,9 +243,12 @@ __device__ inline void mma_pv_accumulate(
         #pragma unroll
         for (int dn8 = 0; dn8 < Traits::DN8; dn8++) {
             unsigned b[2];
-            ldmatrix_x2_trans(b, &sV[vrow_l * Traits::LD
+            astrai::ldmatrix_x2<bf16, true>(b, &sV[vrow_l * Traits::LD
                 + swiz_col(dn8 * 8, vrow_l, Traits::SWIZ_MASK)]);
-            mma16816(Oacc[dn8], Pa, b, Oacc[dn8]);
+            astrai::mma_sync<bf16>(Oacc[dn8], Pa, b, Oacc[dn8]);
         }
     }
 }
+
+}  // namespace attention
+}  // namespace astrai

csrc/kernels/attention/paged_decode.cu

@@ -0,0 +1,88 @@
+#include "dispatchers.cuh"
+#include "entry_utils.cuh"
+
+using namespace astrai::attention;
+
+torch::Tensor attn_paged_decode(
+    torch::Tensor q,
+    torch::Tensor k_cache,
+    torch::Tensor v_cache,
+    torch::Tensor req_to_token,
+    torch::Tensor req_pool_indices,
+    torch::Tensor kv_indptr,
+    c10::optional<torch::Tensor> new_k,
+    c10::optional<torch::Tensor> new_v,
+    c10::optional<torch::Tensor> mask,
+    int64_t causal_offset,
+    double scale,
+    c10::optional<torch::Tensor> o_part_buf,
+    c10::optional<torch::Tensor> ml_part_buf,
+    c10::optional<torch::Tensor> out_buf
+) {
+    const at::cuda::OptionalCUDAGuard device_guard(device_of(q));
+    auto stream = at::cuda::getCurrentCUDAStream();
+
+    AttentionParams<bf16> p;
+    attn_pack_paged_decode_params(q, k_cache, v_cache,
+                                   req_to_token, req_pool_indices, kv_indptr,
+                                   new_k, new_v,
+                                   mask, causal_offset, scale, p);
+
+    torch::Tensor O;
+    if (out_buf.has_value() && out_buf->defined()) {
+        TORCH_CHECK(out_buf->dtype() == q.dtype(), "out_buf dtype must match q");
+        TORCH_CHECK(out_buf->is_cuda() && out_buf->is_contiguous(),
+                    "out_buf must be a contiguous CUDA tensor");
+        TORCH_CHECK(out_buf->size(0) >= q.size(0), "out_buf batch too small");
+        TORCH_CHECK(out_buf->size(1) == q.size(1), "out_buf heads must match q");
+        TORCH_CHECK(out_buf->size(2) == q.size(2), "out_buf head_dim must match q");
+        TORCH_CHECK(q.is_contiguous(),
+                    "q must be contiguous when out_buf is provided");
+        O = out_buf.value().slice(0, 0, q.size(0));
+    } else {
+        O = torch::empty({q.size(0), q.size(1), q.size(2)}, q.options());
+    }
+    p.o_ptr = (bf16*)O.data_ptr();
+
+    if (o_part_buf.has_value() && ml_part_buf.has_value()
+        && o_part_buf->defined() && ml_part_buf->defined()) {
+        TORCH_CHECK(o_part_buf->scalar_type() == torch::kFloat32, "o_part_buf must be f32");
+        TORCH_CHECK(ml_part_buf->scalar_type() == torch::kFloat32, "ml_part_buf must be f32");
+        int64_t o_needed = (int64_t)p.batch * p.q_head * MAX_SPLITS * p.head_dim;
+        int64_t ml_needed = (int64_t)p.batch * p.q_head * MAX_SPLITS * 2;
+        TORCH_CHECK(o_part_buf->numel() >= o_needed,
+                     "o_part_buf too small: need ", o_needed, " got ", o_part_buf->numel());
+        TORCH_CHECK(ml_part_buf->numel() >= ml_needed,
+                     "ml_part_buf too small: need ", ml_needed, " got ", ml_part_buf->numel());
+        TORCH_CHECK(o_part_buf->is_cuda() && ml_part_buf->is_cuda(),
+                    "split buffers must be CUDA tensors");
+        TORCH_CHECK(o_part_buf->is_contiguous() && ml_part_buf->is_contiguous(),
+                    "split buffers must be contiguous");
+        p.o_part = (float*)o_part_buf->data_ptr();
+        p.ml_part = (float*)ml_part_buf->data_ptr();
+    } else {
+        alloc_split_partials(p);
+    }
+    DISPATCH_HEAD_DIM(p.head_dim, dispatch_paged_decode, p, stream);
+    C10_CUDA_CHECK(cudaGetLastError());
+    return O;
+}
+
+PYBIND11_MODULE(TORCH_EXTENSION_NAME, m) {
+    m.def("attn_paged_decode", &attn_paged_decode,
+        py::arg("q"),
+        py::arg("k_cache"),
+        py::arg("v_cache"),
+        py::arg("req_to_token"),
+        py::arg("req_pool_indices"),
+        py::arg("kv_indptr"),
+        py::arg("new_k") = py::none(),
+        py::arg("new_v") = py::none(),
+        py::arg("mask") = py::none(),
+        py::arg("causal_offset") = -1,
+        py::arg("scale") = 0.0,
+        py::arg("o_part_buf") = py::none(),
+        py::arg("ml_part_buf") = py::none(),
+        py::arg("out_buf") = py::none(),
+        "SGLang-style paged decode: flat KV pool + req_to_token + kv_indptr.");
+}

csrc/kernels/attention/paged_prefill.cu

@@ -1,5 +1,7 @@
-#include "attn_dispatchers.cuh"
-#include "attn_entry_utils.cuh"
+#include "dispatchers.cuh"
+#include "entry_utils.cuh"
+
+using namespace astrai::attention;
 
 torch::Tensor attn_paged_prefill(
     torch::Tensor q,
@@ -9,8 +11,9 @@ torch::Tensor attn_paged_prefill(
     torch::Tensor req_pool_indices,
     torch::Tensor kv_indptr,
     torch::Tensor qo_indptr,
+    torch::Tensor q_tile_to_batch,
+    torch::Tensor q_tile_to_index,
     c10::optional<torch::Tensor> mask,
-    int64_t max_q_len,
     int64_t causal_offset,
     double scale
 ) {
@@ -19,12 +22,13 @@ torch::Tensor attn_paged_prefill(
 
     AttentionParams<bf16> p;
     attn_pack_paged_prefill_params(q, k_cache, v_cache,
-                                    req_to_token, req_pool_indices,
-                                    kv_indptr, qo_indptr, mask,
-                                    max_q_len, causal_offset, scale, p);
+                                     req_to_token, req_pool_indices,
+                                     kv_indptr, qo_indptr,
+                                     q_tile_to_batch, q_tile_to_index, mask,
+                                    causal_offset, scale, p);
 
     auto O = torch::empty({q.size(0), q.size(1), q.size(2)}, q.options());
-    p.o = (bf16*)O.data_ptr();
+    p.o_ptr = (bf16*)O.data_ptr();
 
     DISPATCH_HEAD_DIM(p.head_dim, dispatch_paged_prefill, p, stream);
     C10_CUDA_CHECK(cudaGetLastError());
@@ -40,8 +44,9 @@ PYBIND11_MODULE(TORCH_EXTENSION_NAME, m) {
         py::arg("req_pool_indices"),
         py::arg("kv_indptr"),
         py::arg("qo_indptr"),
+        py::arg("q_tile_to_batch"),
+        py::arg("q_tile_to_index"),
         py::arg("mask") = py::none(),
-        py::arg("max_q_len"),
         py::arg("causal_offset") = -1,
         py::arg("scale") = 0.0,
         "SGLang-style paged prefill: flat KV pool + ragged batch.");

csrc/kernels/attention/prefill.cu

@@ -1,5 +1,7 @@
-#include "attn_dispatchers.cuh"
-#include "attn_entry_utils.cuh"
+#include "dispatchers.cuh"
+#include "entry_utils.cuh"
+
+using namespace astrai::attention;
 
 torch::Tensor attn_prefill(
     torch::Tensor q,
@@ -19,7 +21,7 @@ torch::Tensor attn_prefill(
 
     auto O = torch::empty_strided(q.sizes(), q.strides(), q.options());
     auto O_view = (layout == BLHD) ? O.transpose(1, 2) : O;
-    p.o = (bf16*)O_view.data_ptr();
+    p.o_ptr = (bf16*)O_view.data_ptr();
 
     DISPATCH_HEAD_DIM(p.head_dim, dispatch_prefill, p, stream);
     C10_CUDA_CHECK(cudaGetLastError());

csrc/kernels/attention/prefill_split_q.cuh

@@ -1,8 +1,12 @@
 #pragma once
 #include <cfloat>
 #include <cuda_bf16.h>
-#include "attn_common.h"
-#include "attn_kv_source.cuh"
+#include "common.h"
+#include "layout_policies.cuh"
+#include "../common/reduce.cuh"
+
+namespace astrai {
+namespace attention {
 
 using bf16 = __nv_bfloat16;
 
@@ -11,14 +15,7 @@ using bf16 = __nv_bfloat16;
 // compile-time bools — the compiler eliminates dead branches.
 // Unified across contiguous and paged (SGLang flat-pool) K/V via KV.
 // Templated on <HEAD_DIM, KV, G, ROWS, P_BC, IsCausal, HasMask>.
-
-template <int G>
-__device__ __forceinline__ float group_reduce_sum(float v, unsigned mask) {
-#pragma unroll
-    for (int o = G / 2; o > 0; o >>= 1)
-        v += __shfl_xor_sync(mask, v, o);
-    return v;
-}
+// group_reduce_sum<G> lives in common/reduce.cuh (astrai::).
 
 // load 8 contiguous bf16 from (16-byte aligned) smem as one float4
 __device__ __forceinline__ void ld8(const bf16* p, float* o) {
@@ -32,21 +29,23 @@ __device__ __forceinline__ void ld8(const bf16* p, float* o) {
     }
 }
 
-template <int HEAD_DIM, typename KV, int G, int ROWS, int P_BC, bool IsCausal, bool HasMask>
+template <int HEAD_DIM, typename QSchedule, typename KV, int G, int ROWS, int P_BC,
+          bool IsCausal, bool HasMask>
 __global__ void attn_prefill_split_q_kernel_t(AttentionParams<bf16> p) {
     constexpr int DPT = HEAD_DIM / G;
 
-    int q_tile = blockIdx.x;
+    int batch, q_tile;
+    QSchedule::map_block(p, batch, q_tile);
+
     int q_head = blockIdx.y;
-    int batch  = blockIdx.z;
     int gpos   = threadIdx.x;  // 0..G-1  (which d-chunk)
     int row    = threadIdx.y;  // 0..ROWS-1
     int q_row  = q_tile * ROWS + row;
 
     // Per-request dims (from KV policy — paged reads kv_indptr/qo_indptr).
     const int seq_len    = KV::kv_len(p, batch);
-    const int q_len      = KV::q_len(p, batch);
-    const int causal_off = KV::causal_offset(p, batch);
+    const int q_len      = QSchedule::q_len(p, batch);
+    const int causal_off = KV::causal_offset(p, batch, q_len);
     const int kv_head = q_head / (p.q_head / p.kv_head);
     const KVContext kctx = KV::template make_ctx<HEAD_DIM>(p, batch, kv_head);
 
@@ -54,13 +53,13 @@ __global__ void attn_prefill_split_q_kernel_t(AttentionParams<bf16> p) {
     __shared__ __align__(16) bf16 sV[P_BC * HEAD_DIM];
 
     // Q: stride-based load [batch, q_head, q_len, head_dim]
-    const int q_base = KV::q_base(p, batch, q_head);
+    const int q_base = QSchedule::q_base(p, batch, q_head);
     float qreg[DPT];
     if (q_row < q_len) {
-        int q_off = q_base + q_row * p.q_stride_l + gpos * DPT * p.q_stride_d;
+        int q_off = q_base + q_row * p.q_l_stride + gpos * DPT * p.q_d_stride;
 #pragma unroll
         for (int i = 0; i < DPT; i++)
-            qreg[i] = __bfloat162float(p.q[q_off + i * p.q_stride_d]);
+            qreg[i] = __bfloat162float(p.q_ptr[q_off + i * p.q_d_stride]);
     }
 
     float m = -FLT_MAX, l = 0.0f;
@@ -88,7 +87,8 @@ __global__ void attn_prefill_split_q_kernel_t(AttentionParams<bf16> p) {
             int s = i / HEAD_DIM;
             int d_dim = i % HEAD_DIM;
             int kc = kv0 + s;
-            KVAddr a = KV::kv_addr(p, kctx, kc, d_dim, true);
+            int token = KV::resolve_token(p, kctx, kc, true);
+            KVAddr a = KV::kv_addr_from_token(p, kctx, token, d_dim);
             sK[i] = a.valid ? *reinterpret_cast<const bf16*>(a.k) : (bf16)0.f;
             sV[i] = a.valid ? *reinterpret_cast<const bf16*>(a.v) : (bf16)0.f;
         }
@@ -105,7 +105,7 @@ __global__ void attn_prefill_split_q_kernel_t(AttentionParams<bf16> p) {
             }
         }
 
-        int mask_row_base = mask_batch_base + q_row * p.mask_q_stride;
+        int mask_row_base = mask_batch_base + q_row * p.mask_l_stride;
         for (int s = 0; s < lim; s++) {
             const bf16* kr = sK + s * HEAD_DIM + gpos * DPT;
             float part = 0.0f;
@@ -145,10 +145,13 @@ __global__ void attn_prefill_split_q_kernel_t(AttentionParams<bf16> p) {
     }
 
     if (q_row < q_len) {
-        int o_off = q_base + q_row * p.q_stride_l + gpos * DPT * p.q_stride_d;
+        int o_off = q_base + q_row * p.q_l_stride + gpos * DPT * p.q_d_stride;
         float rl = (l > 1e-20f) ? (1.0f / l) : 0.0f;
 #pragma unroll
         for (int i = 0; i < DPT; i++)
-            p.o[o_off + i * p.q_stride_d] = __float2bfloat16(acc[i] * rl);
+            p.o_ptr[o_off + i * p.q_d_stride] = __float2bfloat16(acc[i] * rl);
     }
 }
+
+}  // namespace attention
+}  // namespace astrai

csrc/kernels/attention/prefill_split_q_mma.cuh

@@ -1,37 +1,60 @@
 #pragma once
 #include <cfloat>
 #include <cuda_bf16.h>
-#include "attn_common.h"
-#include "attn_kv_source.cuh"
-#include "attn_mma_utils.cuh"
+#include "common.h"
+#include "layout_policies.cuh"
+#include "mma_utils.cuh"
+
+namespace astrai {
+namespace attention {
 
 // Tensor-core prefill flash attention (raw mma.sync PTX), unified across
 // contiguous and paged (SGLang flat-pool) K/V via the KV template parameter.
 // One warp owns BR=16 query rows. S = Q@K^T and O = P@V run on bf16 tensor
 // cores via mma.sync.m16n8k16 (f32 accumulate).
 //
+// GQA head packing (FA2/FA3-style): HB = min(G, WARPS) query heads of one
+// kv-head group share a block's K/V tiles, so each K/V element is read from
+// global memory once per block instead of once per q head (~HB× less K/V
+// traffic).  WARPS = WPH × HB: warp w handles head slot w/WPH, chunk w%WPH;
+// all warps of a block cover the same token range, keeping the causal sweep
+// end block-uniform.  G=1 (MHA) degenerates to the unpadded layout.
+//
 // KV = ContigKV (dense [batch, kv_head, kv_len, head_dim]) or PagedKV
 //      (flat pool + req_to_token, ragged batches via qo_indptr/kv_indptr).
 // IsCausal and HasMask are compile-time bools — the compiler eliminates all
 // dead branches in the inner compute loop (FA2-style).
 //
 // Traits = KernelTraits<HEAD_DIM, BC, WARPS=4, STAGES=2>.
-template <typename Traits, typename KV, bool IsCausal, bool HasMask>
+template <typename Traits, typename QSchedule, typename KV, bool IsCausal, bool HasMask>
 __global__ void attn_prefill_split_q_mma_kernel(AttentionParams<bf16> p) {
     const int warp = threadIdx.x / 32;
     const int lane = threadIdx.x % 32;
     const int gid = lane >> 2;   // 0..7
     const int tid4 = lane & 3;   // 0..3
 
-    const int q_head = blockIdx.y;
-    const int batch = blockIdx.z;
-    const int kv_head = q_head / (p.q_head / p.kv_head);
-    const int qrow0 = (blockIdx.x * Traits::WARPS + warp) * Traits::BR;
+    const int G = p.q_head / p.kv_head;
+    const int HB = min(G, Traits::WARPS);   // q heads packed per block
+    const int WPH = Traits::WARPS / HB;     // 16-row chunks per head
+    const int BPG = (G + HB - 1) / HB;      // blocks per GQA group
+    const int chunk = warp % WPH;
+
+    int batch, row_base;
+    QSchedule::map_packed_block(p, Traits::BR * WPH, batch, row_base);
+    const int kv_head = blockIdx.y / BPG;
+    const int slot = blockIdx.y - kv_head * BPG;
+    const int head_idx = slot * HB + warp / WPH;
+    // G % HB tail blocks have idle head slots: clamp to the last head so all
+    // warps do valid work (cp.async + __syncthreads stay block-uniform) and
+    // just skip the O store via `active`.
+    const bool active = head_idx < G;
+    const int q_head = kv_head * G + min(head_idx, G - 1);
+    const int qrow0 = row_base + chunk * Traits::BR;
 
     // Per-request dims (from KV policy — paged reads kv_indptr/qo_indptr).
     const int seq_len    = KV::kv_len(p, batch);
-    const int q_len      = KV::q_len(p, batch);
-    const int causal_off = KV::causal_offset(p, batch);
+    const int q_len      = QSchedule::q_len(p, batch);
+    const int causal_off = KV::causal_offset(p, batch, q_len);
     const KVContext kctx = KV::template make_ctx<Traits::HEAD_DIM>(p, batch, kv_head);
 
     // Static shared memory: double-buffered K/V (no sQ — Q goes direct
@@ -40,12 +63,12 @@ __global__ void attn_prefill_split_q_mma_kernel(AttentionParams<bf16> p) {
     __shared__ __align__(16) bf16 sV[Traits::STAGES * Traits::BC * Traits::LD];
 
     // Load Q fragments straight from global into mma A-operand layout.
-    const int q_base = KV::q_base(p, batch, q_head);
+    const int q_base = QSchedule::q_base(p, batch, q_head);
     const int qra = qrow0 + gid;
     const int qrb = qrow0 + gid + 8;
     const bool va = qra < q_len, vb = qrb < q_len;
     unsigned Qa[Traits::KD][4];
-    load_q_mma_frags<Traits::KD>(p.q + q_base, p.q_stride_l, p.q_stride_d,
+    load_q_mma_frags<Traits::KD>(p.q_ptr + q_base, p.q_l_stride, p.q_d_stride,
                                   qra, qrb, va, vb, tid4, Qa);
 
     float Oacc[Traits::DN8][4];
@@ -58,11 +81,11 @@ __global__ void attn_prefill_split_q_mma_kernel(AttentionParams<bf16> p) {
     const int qr0 = qrow0 + gid;
     const int qr1 = qrow0 + gid + 8;
 
-    // Causal tile-skip bounds (dead code when IsCausal == false)
+    // Causal tile-skip bounds (dead code when IsCausal == false).
+    // max_kv is per-warp (its own 16 rows); block_max_kv is the last row of
+    // the whole block's range and must be uniform for the shared sweep loop.
     const int max_kv = qrow0 + Traits::BR - 1 + causal_off;
-    const int block_max_kv =
-        blockIdx.x * Traits::WARPS * Traits::BR + Traits::WARPS * Traits::BR - 1
-        + causal_off;
+    const int block_max_kv = row_base + WPH * Traits::BR - 1 + causal_off;
 
     int t_end = tiles - 1;
     if constexpr (IsCausal) {
@@ -81,12 +104,13 @@ __global__ void attn_prefill_split_q_mma_kernel(AttentionParams<bf16> p) {
             int r = i / Traits::HEAD_DIM, d = i % Traits::HEAD_DIM;
             int kc = kv0 + r;
             bool valid = kc < seq_len;
-            KVAddr a = KV::kv_addr(p, kctx, kc, d, valid);
+            int token = KV::resolve_token(p, kctx, kc, valid);
+            KVAddr a = KV::kv_addr_from_token(p, kctx, token, d);
             int off = r * Traits::LD + swiz_col(d, r, Traits::SWIZ_MASK);
-            cp_async_16_pred(&dK[off], a.k, a.valid);
-            cp_async_16_pred(&dV[off], a.v, a.valid);
+            astrai::cp_async_16(&dK[off], a.k, a.valid);
+            astrai::cp_async_16(&dV[off], a.v, a.valid);
         }
-        cp_async_commit();
+        astrai::cp_async_commit_group();
     };
 
     // ---- Prologue: issue first tile load ----
@@ -96,7 +120,7 @@ __global__ void attn_prefill_split_q_mma_kernel(AttentionParams<bf16> p) {
         int buf = ti & 1;
 
         // Wait for current tile, then publish cross-warp + guard buffer reuse.
-        cp_async_wait_group<0>();
+        astrai::cp_async_wait_group<0>();
         __syncthreads();
         if (ti < t_end) load_tile(ti + 1, (ti + 1) & 1);
 
@@ -122,9 +146,10 @@ __global__ void attn_prefill_split_q_mma_kernel(AttentionParams<bf16> p) {
                                  : seq_len;
             mma_softmax_tile<Traits, HasMask>(kv0, maxc0, maxc1,
                                                qr0, qr1,
-                                               p.mask_b_stride, p.mask_h_stride, p.mask_q_stride,
-                                               batch, q_head,
+                                               p.mask_b_stride, p.mask_h_stride, p.mask_l_stride,
+                                               batch, q_head, q_head,
                                                p.mask,
+                                               va, vb,
                                                Sacc, Oacc, m0, m1, l0, l1, lane);
 
             mma_pv_accumulate<Traits>(Sacc, bV, lane, Oacc);
@@ -134,21 +159,24 @@ __global__ void attn_prefill_split_q_mma_kernel(AttentionParams<bf16> p) {
     // ---- write output: packed bf16x2 stores ----
     float rl0 = (l0 > 1e-20f) ? (1.0f / l0) : 0.0f;
     float rl1 = (l1 > 1e-20f) ? (1.0f / l1) : 0.0f;
-    const int o_base = KV::q_base(p, batch, q_head);
+    const int o_base = QSchedule::q_base(p, batch, q_head);
     #pragma unroll
     for (int dn8 = 0; dn8 < Traits::DN8; dn8++) {
         int d = dn8 * 8 + 2 * tid4;
-        if (qr0 < q_len) {
+        if (active && qr0 < q_len) {
             __nv_bfloat162 v = __floats2bfloat162_rn(Oacc[dn8][0] * rl0,
                                                       Oacc[dn8][1] * rl0);
             *reinterpret_cast<__nv_bfloat162*>(
-                &p.o[o_base + qr0 * p.q_stride_l + d * p.q_stride_d]) = v;
+                &p.o_ptr[o_base + qr0 * p.q_l_stride + d * p.q_d_stride]) = v;
         }
-        if (qr1 < q_len) {
+        if (active && qr1 < q_len) {
             __nv_bfloat162 v = __floats2bfloat162_rn(Oacc[dn8][2] * rl1,
-                                                      Oacc[dn8][3] * rl1);
+                                                     Oacc[dn8][3] * rl1);
             *reinterpret_cast<__nv_bfloat162*>(
-                &p.o[o_base + qr1 * p.q_stride_l + d * p.q_stride_d]) = v;
+                &p.o_ptr[o_base + qr1 * p.q_l_stride + d * p.q_d_stride]) = v;
         }
     }
 }
+
+}  // namespace attention
+}  // namespace astrai

csrc/kernels/attn_common.h

@@ -1,66 +0,0 @@
-#pragma once
-
-// Tensor layout for Q/K/V tensors passed to attention kernels.
-// Internally, kernels always operate on BHLD [batch, n_heads, seq_len, head_dim].
-// When the caller passes BLHD, dims 1 and 2 are transposed at entry.
-enum TensorLayout : int {
-    BHLD = 0,  // [batch, n_heads, seq_len, head_dim]
-    BLHD = 1,  // [batch, seq_len, n_heads, head_dim]
-};
-
-
-// Unified attention params covering BOTH addressing modes:
-//   - Contiguous K/V: dense [batch, kv_head, kv_len, head_dim] tensors (k/v).
-//   - Paged (SGLang-style): flat pool [size, kv_head, head_dim] + req_to_token.
-// Each kernel selects the addressing via a KVSource policy (see
-// attn_kv_source.cuh); a given call only touches the fields of one mode, so
-// this is a POD shared by both paths rather than two parallel structs that
-// drift out of sync.
-template<typename T, typename AT = float>
-struct AttentionParams {
-    // ---- shared across all paths ----
-    int batch;
-    int q_head;
-    int kv_head;
-    int head_dim;
-    int use_mask;
-    int causal_offset;   // -1 = non-causal; >=0 = absolute position of first Q token
-    int num_splits;
-    float scale;
-
-    // Q strides (element offsets for each dim — layout-agnostic)
-    int q_stride_b, q_stride_h, q_stride_l, q_stride_d;
-
-    // Mask: 2D [batch, kv_len], 3D [batch, q_len, kv_len],
-    // or 4D [batch, n_heads, q_len, kv_len] (head dim broadcasts when stride=0)
-    int mask_b_stride;   // batch stride
-    int mask_h_stride;   // head stride (0 = broadcast across heads)
-    int mask_q_stride;   // q stride (0 = all q rows share)
-    const bool* __restrict__ mask;
-
-    const T* __restrict__ q;
-    T* __restrict__ o;
-    AT* __restrict__ o_part;
-    AT* __restrict__ ml_part;
-
-    // ---- contiguous K/V mode ----
-    int q_len;
-    int kv_len;
-    int kv_stride_b, kv_stride_h, kv_stride_l, kv_stride_d;
-    const T* __restrict__ k;
-    const T* __restrict__ v;
-
-    // ---- paged (SGLang flat pool) mode ----
-    const T* __restrict__ k_cache;
-    const T* __restrict__ v_cache;
-
-    // Indexing
-    const int64_t* __restrict__ req_to_token;      // [num_reqs, max_context_len]
-    const int64_t* __restrict__ req_pool_indices;   // [batch]
-    const int* __restrict__ kv_indptr;               // [batch+1]
-    const int* __restrict__ qo_indptr;               // [batch+1] or nullptr (decode)
-    int max_context_len;  // req_to_token stride (dim 1)
-    int max_seq_len;      // max per-request seq_len (host-side, for split computation)
-    int total_q;          // total Q tokens across all requests (host-side, for grid)
-    int max_q_len;        // max per-request q_len (host-side, for prefill grid)
-};

csrc/kernels/attn_decode.cu

@@ -1,41 +0,0 @@
-#include "attn_dispatchers.cuh"
-#include "attn_entry_utils.cuh"
-
-torch::Tensor attn_decode(
-    torch::Tensor q,
-    torch::Tensor k,
-    torch::Tensor v,
-    c10::optional<torch::Tensor> mask,
-    int64_t causal_offset,
-    double scale,
-    int64_t layout
-) {
-    const at::cuda::OptionalCUDAGuard device_guard(device_of(q));
-    auto stream = at::cuda::getCurrentCUDAStream();
-
-    AttentionParams<bf16> p;
-    attn_pack_params(q, k, v, mask, causal_offset, scale, layout, p);
-    TORCH_CHECK(p.q_len == 1, "Q seq_len must be 1");
-    TORCH_CHECK(p.head_dim % 32 == 0, "head_dim must be multiple of 32");
-
-    auto O = torch::empty_strided(q.sizes(), q.strides(), q.options());
-    auto O_view = (layout == BLHD) ? O.transpose(1, 2) : O;
-    p.o = (bf16*)O_view.data_ptr();
-
-    alloc_split_partials(p);
-    DISPATCH_HEAD_DIM(p.head_dim, dispatch_decode, p, stream);
-    C10_CUDA_CHECK(cudaGetLastError());
-    return O;
-}
-
-PYBIND11_MODULE(TORCH_EXTENSION_NAME, m) {
-    m.def("attn_decode", &attn_decode,
-        py::arg("q"),
-        py::arg("k"),
-        py::arg("v"),
-        py::arg("mask") = py::none(),
-        py::arg("causal_offset") = -1,
-        py::arg("scale") = 0.0,
-        py::arg("layout") = (int64_t)BHLD,
-        "GQA decode (tensor-core head-packing on sm_80+, scalar fallback)");
-}

csrc/kernels/attn_kv_source.cuh

@@ -1,159 +0,0 @@
-#pragma once
-#include <cuda_bf16.h>
-#include "attn_common.h"
-
-// ============================================================================
-// KVSource policies — the single dimension along which the paged and
-// non-paged attention kernels differ.  Each kernel is templated on one of
-// these (ContigKV / PagedKV) and stays fully generic: the policy owns every
-// place where "where does K/V live" and "what is this request's seq_len"
-// are answered.  All methods are __host__ __device__ so the same policy
-// serves both the device kernels (addressing, seq_len) and the host-side
-// launchers (grid / split computation).
-//
-//   ContigKV:  K/V are dense [batch, kv_head, kv_len, head_dim] tensors.
-//              Params fields used: k, v, kv_stride_*, kv_len, q_len,
-//              q_stride_b, causal_offset.
-//   PagedKV:   K/V live in a flat pool [size, kv_head, head_dim] indexed via
-//              req_to_token.  Params fields used: k_cache, v_cache,
-//              req_to_token, req_pool_indices, kv_indptr, qo_indptr,
-//              max_context_len, q_stride_l.
-//
-// Addressing state that is constant across a whole kernel invocation for one
-// (batch, kv_head) pair is captured once by make_ctx<HEAD_DIM>() and passed
-// to kv_addr, so the load loops never redo the hoistable base computation
-// (e.g. the req_pool_indices global read) element-by-element.
-// ============================================================================
-
-// Every policy method is static + callable from both host and device code.
-#define HOST_DEV_FORCEINLINE static __host__ __device__ __forceinline__
-
-using bf16 = __nv_bfloat16;
-
-// Hoisted per-(batch, kv_head) addressing context.
-struct KVContext {
-    int kv_base;          // contig: batch*kv_stride_b + kv_head*kv_stride_h
-    int64_t req_idx;      // paged: req_pool_indices[batch]
-    int64_t rtt_stride;   // paged: max_context_len
-    int64_t pool_stride;  // paged: kv_head * HEAD_DIM
-    int64_t head_off;     // paged: kv_head * HEAD_DIM
-};
-
-// Per-element K/V global addresses for one (kc, d) position of a K/V tile.
-// The pointers are ALWAYS the computed addresses (never nullptr) — callers
-// gate on `valid` (cp.async src_size=0, or a guarded scalar deref).  `valid`
-// starts as "within the request's seq_len"; the paged policy further degrades
-// it when req_to_token maps the position to a negative slot (empty padding).
-// This matches the original hand-rolled load loops, where the address was
-// always formed and the predicate decided whether anything was read.
-struct KVAddr {
-    const void* k;
-    const void* v;
-    bool valid;
-};
-
-// ---- Contiguous K/V ----
-struct ContigKV {
-    static constexpr bool kPaged = false;
-
-    // host-side length hooks (grid + split computation in the launchers)
-    HOST_DEV_FORCEINLINE int host_q_len(const AttentionParams<bf16>& p) {
-        return p.q_len;
-    }
-    HOST_DEV_FORCEINLINE int host_kv_len(const AttentionParams<bf16>& p) {
-        return p.kv_len;
-    }
-
-    // prefill: element offset of the request's Q rows (kernel adds qrow*q_stride_l)
-    HOST_DEV_FORCEINLINE int q_base(
-        const AttentionParams<bf16>& p, int batch, int q_head) {
-        return batch * p.q_stride_b + q_head * p.q_stride_h;
-    }
-    // decode: same offset (q_len == 1, so there is no row stride component)
-    HOST_DEV_FORCEINLINE int q_decode_base(
-        const AttentionParams<bf16>& p, int batch, int q_head) {
-        return batch * p.q_stride_b + q_head * p.q_stride_h;
-    }
-
-    HOST_DEV_FORCEINLINE int kv_len(const AttentionParams<bf16>& p, int batch) {
-        return p.kv_len;
-    }
-    HOST_DEV_FORCEINLINE int q_len(const AttentionParams<bf16>& p, int batch) {
-        return p.q_len;
-    }
-    HOST_DEV_FORCEINLINE int causal_offset(const AttentionParams<bf16>& p, int batch) {
-        return p.causal_offset;
-    }
-    // decode: exclusive bound of the single query's attend range
-    HOST_DEV_FORCEINLINE int decode_attend_len(const AttentionParams<bf16>& p, int batch) {
-        return (p.kv_len < p.causal_offset + 1) ? p.kv_len : (p.causal_offset + 1);
-    }
-
-    template <int HEAD_DIM>
-    HOST_DEV_FORCEINLINE KVContext make_ctx(
-        const AttentionParams<bf16>& p, int batch, int kv_head) {
-        KVContext c = {};
-        c.kv_base = batch * p.kv_stride_b + kv_head * p.kv_stride_h;
-        return c;
-    }
-    HOST_DEV_FORCEINLINE KVAddr kv_addr(
-        const AttentionParams<bf16>& p, const KVContext& c, int kc, int d, bool valid) {
-        const int g_off = c.kv_base + kc * p.kv_stride_l + d * p.kv_stride_d;
-        return {&p.k[g_off], &p.v[g_off], valid};
-    }
-};
-
-// ---- Paged (SGLang-style flat pool) K/V ----
-struct PagedKV {
-    static constexpr bool kPaged = true;
-
-    HOST_DEV_FORCEINLINE int host_q_len(const AttentionParams<bf16>& p) {
-        return p.max_q_len;
-    }
-    HOST_DEV_FORCEINLINE int host_kv_len(const AttentionParams<bf16>& p) {
-        return p.max_seq_len;
-    }
-
-    // prefill: Q rows start at qo_indptr[batch] (ragged batch base)
-    HOST_DEV_FORCEINLINE int q_base(
-        const AttentionParams<bf16>& p, int batch, int q_head) {
-        return p.qo_indptr[batch] * p.q_stride_l + q_head * p.q_stride_h;
-    }
-    // decode: Q is [batch, q_head, head_dim], so batch is the outer row
-    HOST_DEV_FORCEINLINE int q_decode_base(
-        const AttentionParams<bf16>& p, int batch, int q_head) {
-        return batch * p.q_stride_l + q_head * p.q_stride_h;
-    }
-
-    HOST_DEV_FORCEINLINE int kv_len(const AttentionParams<bf16>& p, int batch) {
-        return p.kv_indptr[batch + 1] - p.kv_indptr[batch];
-    }
-    HOST_DEV_FORCEINLINE int q_len(const AttentionParams<bf16>& p, int batch) {
-        return p.qo_indptr[batch + 1] - p.qo_indptr[batch];
-    }
-    HOST_DEV_FORCEINLINE int causal_offset(const AttentionParams<bf16>& p, int batch) {
-        return kv_len(p, batch) - q_len(p, batch);
-    }
-    // decode: the query is the last token, so [0, seq_len) IS its causal range
-    HOST_DEV_FORCEINLINE int decode_attend_len(const AttentionParams<bf16>& p, int batch) {
-        return kv_len(p, batch);
-    }
-
-    template <int HEAD_DIM>
-    HOST_DEV_FORCEINLINE KVContext make_ctx(
-        const AttentionParams<bf16>& p, int batch, int kv_head) {
-        KVContext c = {};
-        c.req_idx = p.req_pool_indices[batch];
-        c.rtt_stride = (int64_t)p.max_context_len;
-        c.pool_stride = (int64_t)p.kv_head * HEAD_DIM;
-        c.head_off = (int64_t)kv_head * HEAD_DIM;
-        return c;
-    }
-    HOST_DEV_FORCEINLINE KVAddr kv_addr(
-        const AttentionParams<bf16>& p, const KVContext& c, int kc, int d, bool valid) {
-        const int64_t slot = valid ? p.req_to_token[c.req_idx * c.rtt_stride + kc] : 0;
-        const bool ok = valid && (slot >= 0);
-        const int64_t gmem_off = slot * c.pool_stride + c.head_off + d;
-        return {&p.k_cache[gmem_off], &p.v_cache[gmem_off], ok};
-    }
-};

csrc/kernels/attn_paged_decode.cu

@@ -1,46 +0,0 @@
-#include "attn_dispatchers.cuh"
-#include "attn_entry_utils.cuh"
-
-torch::Tensor attn_paged_decode(
-    torch::Tensor q,
-    torch::Tensor k_cache,
-    torch::Tensor v_cache,
-    torch::Tensor req_to_token,
-    torch::Tensor req_pool_indices,
-    torch::Tensor kv_indptr,
-    int64_t max_seq_len,
-    c10::optional<torch::Tensor> mask,
-    int64_t causal_offset,
-    double scale
-) {
-    const at::cuda::OptionalCUDAGuard device_guard(device_of(q));
-    auto stream = at::cuda::getCurrentCUDAStream();
-
-    AttentionParams<bf16> p;
-    attn_pack_paged_decode_params(q, k_cache, v_cache,
-                                   req_to_token, req_pool_indices, kv_indptr,
-                                   max_seq_len, mask, causal_offset, scale, p);
-
-    auto O = torch::empty({q.size(0), q.size(1), q.size(2)}, q.options());
-    p.o = (bf16*)O.data_ptr();
-
-    alloc_split_partials(p);
-    DISPATCH_HEAD_DIM(p.head_dim, dispatch_paged_decode, p, stream);
-    C10_CUDA_CHECK(cudaGetLastError());
-    return O;
-}
-
-PYBIND11_MODULE(TORCH_EXTENSION_NAME, m) {
-    m.def("attn_paged_decode", &attn_paged_decode,
-        py::arg("q"),
-        py::arg("k_cache"),
-        py::arg("v_cache"),
-        py::arg("req_to_token"),
-        py::arg("req_pool_indices"),
-        py::arg("kv_indptr"),
-        py::arg("max_seq_len"),
-        py::arg("mask") = py::none(),
-        py::arg("causal_offset") = -1,
-        py::arg("scale") = 0.0,
-        "SGLang-style paged decode: flat KV pool + req_to_token + kv_indptr.");
-}

csrc/kernels/attn_warp_utils.cuh

@@ -1,13 +0,0 @@
-#pragma once
-#include <cuda_bf16.h>
-
-using bf16 = __nv_bfloat16;
-
-static constexpr int MAX_SPLITS = 32;
-
-__device__ inline float warp_reduce_sum(float val) {
-    #pragma unroll
-    for (int offset = 16; offset > 0; offset >>= 1)
-        val += __shfl_xor_sync(0xFFFFFFFF, val, offset);
-    return val;
-}

csrc/kernels/common/cp_async.cuh

@@ -0,0 +1,82 @@
+// Shared cp.async primitives — pure CUDA, no torch.
+//
+// One header for the async-copy pipeline used by both the attention kernels
+// (predicated 16-byte K/V tile staging) and the fp8 GEMM (predicated operand
+// staging + the fixed-depth wait_group). The emitter is split from its
+// policies: cp_async_16_raw owns the single PTX site, and each wrapper states
+// one destination contract (generic pointer vs loop-carried shared offset)
+// and one predication contract (unconditional vs zero-fill-when-false), so
+// call sites never pass a dead `true` predicate or re-convert a carried
+// offset. PTX requires wait_group's operand to be an immediate, hence the
+// template form below.
+
+#pragma once
+
+#include <cuda_runtime.h>
+
+namespace astrai {
+
+// Raw emitter: read src_size bytes (<= 16) from gmem into the shared
+// offset. src_size = 0 reads nothing, so a predicated-off call zero-fills
+// its destination without touching the (possibly out-of-range) source.
+// BypassL1 selects .cg (L2 only, default) vs .ca (L1 + L2).
+template <bool BypassL1 = true>
+__device__ __forceinline__ void cp_async_16_raw(unsigned smem_addr,
+                                                const void* gmem_ptr,
+                                                int src_size) {
+    if constexpr (BypassL1) {
+        asm volatile("cp.async.cg.shared.global [%0], [%1], 16, %2;"
+                     :: "r"(smem_addr), "l"(gmem_ptr), "r"(src_size));
+    } else {
+        asm volatile("cp.async.ca.shared.global [%0], [%1], 16, %2;"
+                     :: "r"(smem_addr), "l"(gmem_ptr), "r"(src_size));
+    }
+}
+
+// Unconditional 16-byte copy to a generic shared pointer.
+// `T` is the smem element type; only the destination pointer's type matters.
+template <typename T, bool BypassL1 = true>
+__device__ __forceinline__ void cp_async_16(T* smem_ptr,
+                                            const void* gmem_ptr) {
+    cp_async_16_raw<BypassL1>(__cvta_generic_to_shared(smem_ptr), gmem_ptr,
+                              16);
+}
+
+// Predicated: full copy when `pred`, zero-fill otherwise.
+template <typename T, bool BypassL1 = true>
+__device__ __forceinline__ void cp_async_16(T* smem_ptr, const void* gmem_ptr,
+                                            bool pred) {
+    cp_async_16_raw<BypassL1>(__cvta_generic_to_shared(smem_ptr), gmem_ptr,
+                              pred ? 16 : 0);
+}
+
+// Predicated raw-offset form: the destination is an already-converted
+// shared-memory offset (e.g. a loop-carried swizzled stage address), so
+// steady-state prefetch sites issue one LDGSTS straight from the register.
+template <bool BypassL1 = true>
+__device__ __forceinline__ void cp_async_16(unsigned smem_addr,
+                                            const void* gmem_ptr, bool pred) {
+    cp_async_16_raw<BypassL1>(smem_addr, gmem_ptr, pred ? 16 : 0);
+}
+
+// Commit all outstanding cp.async ops of this thread as one group.
+__device__ __forceinline__ void cp_async_commit_group() {
+    asm volatile("cp.async.commit_group;");
+}
+
+// Wait for every committed group (pipeline drain).
+__device__ __forceinline__ void cp_async_wait_all() {
+    asm volatile("cp.async.wait_all;");
+}
+
+// Wait until at most KeepGroups committed groups are still in flight.
+// PTX requires an immediate operand; keep it as a template argument so the
+// stage policy stays compile-time configurable.
+template <int KeepGroups>
+__device__ __forceinline__ void cp_async_wait_group() {
+    static_assert(KeepGroups >= 0 && KeepGroups <= 7,
+                  "cp.async.wait_group supports immediates in [0, 7]");
+    asm volatile("cp.async.wait_group %0;" :: "n"(KeepGroups));
+}
+
+}  // namespace astrai

csrc/kernels/common/device.cuh

@@ -0,0 +1,23 @@
+// Pure-CUDA device helpers shared across kernel families (no torch).
+//
+// Family-local headers under kernels/<family>/ own their POD params and
+// strategy traits; anything cross-cutting (compute-capability checks, device
+// constants) lives here.
+
+#pragma once
+
+namespace astrai {
+
+// Compute-capability comparison: is the device at least (major, minor)?
+inline bool sm_at_least(int device_major, int device_minor, int major,
+                        int minor) {
+    return device_major > major ||
+           (device_major == major && device_minor >= minor);
+}
+
+// FP8 tensor-core MMA (`mma.sync.aligned.m16n8k32` with fp8 inputs) exists on
+// Ada (sm_89) and Hopper (sm_90+); sm_80 has no fp8 instructions.
+inline constexpr int kMinSmForFp8Major = 8;
+inline constexpr int kMinSmForFp8Minor = 9;
+
+}  // namespace astrai

csrc/kernels/common/mma.cuh

@@ -0,0 +1,165 @@
+// Shared mma.sync wrappers — pure CUDA, no torch.
+//
+// One template for every tensor-core MMA used by the kernel families. The
+// instruction shape follows from the input element type:
+//   __nv_bfloat16        -> mma.sync.aligned.m16n8k16 (sm_80+), A = 4x b32, B = 2x b32
+//   __nv_fp8_e4m3/e5m2   -> mma.sync.aligned.m16n8k32 (sm_89+), A = 4x b32, B = 2x b32
+// All variants accumulate into fp32: d = a*b + c, with the PTX mnemonic and
+// the K dimension differing per type. `d` may alias `c` (in-place accumulate,
+// as the FP8 GEMM does).
+
+#pragma once
+
+#include <cuda_bf16.h>
+#include <cuda_fp8.h>
+#include <cuda_runtime.h>
+#include <type_traits>
+
+
+#define DEVICE_FORCEINLINE static __device__ __forceinline__
+
+namespace astrai {
+
+// Compute capability of the current compilation pass: 0 in the host pass,
+// the numeric CC (e.g. 890) in device passes where __CUDA_ARCH__ is defined.
+// Defined() cannot appear in expressions, so this macro lets mma_sync use
+// the arch in a static_assert instead of per-branch #if guards.
+#ifndef __CUDA_ARCH__
+#define ASTRAI_DEVICE_ARCH 0
+#else
+#define ASTRAI_DEVICE_ARCH __CUDA_ARCH__
+#endif
+
+// Compile-time shape of the MMA instruction for an input element type.
+// `min_arch` is the numeric compute capability the instruction requires —
+// the single place that encodes the hardware floor for each type.
+template <typename InT>
+struct mma_shape {
+    static constexpr int k = 16;         // m16n8k16
+    static constexpr int a_regs = 4;     // A fragment: 4x b32
+    static constexpr int b_regs = 2;     // B fragment: 2x b32
+    static constexpr int min_arch = 800; // bf16 mma.sync, sm_80+
+};
+
+template <>
+struct mma_shape<__nv_fp8_e4m3> {
+    static constexpr int k = 32;         // m16n8k32
+    static constexpr int a_regs = 4;
+    static constexpr int b_regs = 2;
+    static constexpr int min_arch = 890; // fp8 mma.sync, sm_89+ (Ada/Hopper)
+};
+
+template <>
+struct mma_shape<__nv_fp8_e5m2> {
+    static constexpr int k = 32;
+    static constexpr int a_regs = 4;
+    static constexpr int b_regs = 2;
+    static constexpr int min_arch = 890;
+};
+
+// d[4] = a[4] x b[2] + c[4], row-major A, col-major B, fp32 accumulator.
+// The PTX mnemonic is selected from InT. Building for a compute capability
+// below `mma_shape<InT>::min_arch` is a **compile error** — the instruction
+// does not exist there, and a silent no-op would produce wrong results.
+template <typename InT>
+DEVICE_FORCEINLINE void mma_sync(float d[4], const unsigned a[4],
+                                 const unsigned b[2],
+                                 const float c[4]) {
+    static_assert(ASTRAI_DEVICE_ARCH == 0 ||
+                      ASTRAI_DEVICE_ARCH >= mma_shape<InT>::min_arch,
+                  "mma_sync: this MMA shape requires a newer compute "
+                  "capability than the build target");
+    if constexpr (std::is_same_v<InT, __nv_bfloat16>) {
+        asm volatile(
+            "mma.sync.aligned.m16n8k16.row.col.f32.bf16.bf16.f32 "
+            "{%0,%1,%2,%3}, {%4,%5,%6,%7}, {%8,%9}, {%10,%11,%12,%13};"
+            : "=f"(d[0]), "=f"(d[1]), "=f"(d[2]), "=f"(d[3])
+            : "r"(a[0]), "r"(a[1]), "r"(a[2]), "r"(a[3]), "r"(b[0]), "r"(b[1]),
+              "f"(c[0]), "f"(c[1]), "f"(c[2]), "f"(c[3]));
+    } else if constexpr (std::is_same_v<InT, __nv_fp8_e5m2>) {
+        asm volatile(
+            "mma.sync.aligned.m16n8k32.row.col.f32.e5m2.e5m2.f32 "
+            "{%0,%1,%2,%3}, {%4,%5,%6,%7}, {%8,%9}, {%10,%11,%12,%13};"
+            : "=f"(d[0]), "=f"(d[1]), "=f"(d[2]), "=f"(d[3])
+            : "r"(a[0]), "r"(a[1]), "r"(a[2]), "r"(a[3]), "r"(b[0]), "r"(b[1]),
+              "f"(c[0]), "f"(c[1]), "f"(c[2]), "f"(c[3]));
+    } else {
+        asm volatile(
+            "mma.sync.aligned.m16n8k32.row.col.f32.e4m3.e4m3.f32 "
+            "{%0,%1,%2,%3}, {%4,%5,%6,%7}, {%8,%9}, {%10,%11,%12,%13};"
+            : "=f"(d[0]), "=f"(d[1]), "=f"(d[2]), "=f"(d[3])
+            : "r"(a[0]), "r"(a[1]), "r"(a[2]), "r"(a[3]), "r"(b[0]), "r"(b[1]),
+              "f"(c[0]), "f"(c[1]), "f"(c[2]), "f"(c[3]));
+    }
+}
+
+#undef ASTRAI_DEVICE_ARCH
+
+// ---------------------------------------------------------------------------
+// ldmatrix — cooperatively load 8x8 b16 matrices from smem into registers.
+//
+// The instruction is identical for every 16-bit-storage element type: bf16
+// maps 1:1 onto b16 slots; fp8 is stored packed two-per-slot (see
+// fp8/gemm.cuh), so one b16 slot holds two fp8 values. `T` is the element
+// type and only serves as a semantic tag.
+//
+//   x2 (single address): matrix0 = p (8 rows), matrix1 = p + 8*16 bytes
+//   x4:                  four matrices at p, +128, +256, +384 bytes
+//   Trans:               transpose variant (V fragments of attention)
+//
+// ldmatrix takes a *single* smem address per thread, but the addresses of
+// the 32 lanes are *not* all the same: lane i supplies the start address of
+// matrix-row i (modulo 8) for matrix (i/8) — lanes 0-7 feed matrix 0's rows,
+// lanes 8-15 matrix 1's rows (x2/x4), lanes 16-23 / 24-31 matrix 2 / 3's rows
+// (x4 only; their addresses are ignored by x2). Each matrix is 8 rows x 16
+// bytes, and consecutive matrices of one instruction are contiguous at
+// 128-byte strides. fp8 fragment layouts in fp8/gemm.cuh are arranged around
+// this constraint.
+// ---------------------------------------------------------------------------
+
+template <typename T, bool Trans = false>
+DEVICE_FORCEINLINE void ldmatrix_x2(unsigned r[2], const T* p) {
+    const unsigned a = __cvta_generic_to_shared(p);
+    if constexpr (Trans) {
+        asm volatile(
+            "ldmatrix.sync.aligned.m8n8.x2.trans.shared.b16 {%0,%1}, [%2];"
+            : "=r"(r[0]), "=r"(r[1])
+            : "r"(a));
+    } else {
+        asm volatile(
+            "ldmatrix.sync.aligned.m8n8.x2.shared.b16 {%0,%1}, [%2];"
+            : "=r"(r[0]), "=r"(r[1])
+            : "r"(a));
+    }
+}
+
+// Four matrices at p, p+128, p+256, p+384 bytes (16-byte row stride).
+template <typename T>
+DEVICE_FORCEINLINE void ldmatrix_x4(unsigned r[4], const T* p) {
+    const unsigned a = __cvta_generic_to_shared(p);
+    asm volatile(
+        "ldmatrix.sync.aligned.m8n8.x4.shared.b16 {%0,%1,%2,%3}, [%4];"
+        : "=r"(r[0]), "=r"(r[1]), "=r"(r[2]), "=r"(r[3])
+        : "r"(a));
+}
+
+// Per-lane-address variants: the caller supplies a raw shared-memory address
+// per lane instead of one common pointer. Use when the fragment tiles are
+// XOR-swizzled per 16B chunk so each lane must compute its own row and chunk
+// address (see fp8/gemm.cuh's frag_addr + lane selectors for the m16n8k32
+// operand layouts).
+DEVICE_FORCEINLINE void ldmatrix_x2_lane(unsigned r[2],
+                                          unsigned addr) {
+    asm volatile("ldmatrix.sync.aligned.m8n8.x2.shared.b16 {%0,%1}, [%2];"
+                 : "=r"(r[0]), "=r"(r[1])
+                 : "r"(addr));
+}
+
+DEVICE_FORCEINLINE void ldmatrix_x4_lane(unsigned r[4],
+                                          unsigned addr) {
+    asm volatile("ldmatrix.sync.aligned.m8n8.x4.shared.b16 {%0,%1,%2,%3}, [%4];"
+                 : "=r"(r[0]), "=r"(r[1]), "=r"(r[2]), "=r"(r[3])
+                 : "r"(addr));
+}
+
+}  // namespace astrai

csrc/kernels/common/reduce.cuh

@@ -0,0 +1,48 @@
+// Shared warp/block reduction + atomic helpers — pure CUDA, no torch.
+//
+// Extracted from the attention and fp8 families so both share one
+// implementation: warp_reduce_sum (decode scalar kernel), warp_reduce_max +
+// atomic_max_float (fp8 quantize amax), group_reduce_sum<G> (prefill scalar
+// kernel).
+
+#pragma once
+
+namespace astrai {
+
+// Full-warp butterfly sum reduction (32 lanes).
+__device__ __forceinline__ float warp_reduce_sum(float val) {
+#pragma unroll
+    for (int offset = 16; offset > 0; offset >>= 1)
+        val += __shfl_xor_sync(0xFFFFFFFF, val, offset);
+    return val;
+}
+
+// Full-warp butterfly max reduction (32 lanes).
+__device__ __forceinline__ float warp_reduce_max(float value) {
+#pragma unroll
+    for (int offset = 16; offset > 0; offset >>= 1)
+        value = fmaxf(value, __shfl_xor_sync(0xffffffffu, value, offset));
+    return value;
+}
+
+// Sub-warp group reduction over G consecutive lanes (G a power of two).
+// `mask` is the full participating-lane mask of the group (see the
+// prefill scalar kernel's gmask computation).
+template <int G>
+__device__ __forceinline__ float group_reduce_sum(float v, unsigned mask) {
+#pragma unroll
+    for (int o = G / 2; o > 0; o >>= 1)
+        v += __shfl_xor_sync(mask, v, o);
+    return v;
+}
+
+// Unsigned-bit-pattern atomicMax for non-negative floats; a null
+// destination disables the update (kernels with optional amax slots).
+__device__ __forceinline__ void atomic_max_float(float* destination,
+                                                 float value) {
+    if (destination)
+        atomicMax(reinterpret_cast<unsigned*>(destination),
+                  __float_as_uint(value));
+}
+
+}  // namespace astrai

csrc/kernels/fp8/common.h

@@ -0,0 +1,130 @@
+#pragma once
+
+#include <cuda_bf16.h>
+#include <cuda_fp8.h>
+#include <cuda_runtime.h>
+#include <cstdint>
+
+// Pure POD/traits header — no .cuh/CUDA-kernel includes; raw __nv_* type
+// spellings only.
+
+namespace astrai {
+namespace fp8 {
+
+// Compile-time FP8 format: E4M3 (forward, max 448) or E5M2 (gradients,
+// max 57344).
+enum class FP8Format : int {
+    E4M3 = 0,
+    E5M2 = 1,
+};
+
+// Operand storage tags (CUTLASS-style) relative to the canonical matrices
+// A [M][K] / B [K][N]: A RowMajor = [M][K] (default), A ColMajor = [K][M],
+// B RowMajor = [K][N], B ColMajor = [N][K] (the nn.Linear weight). Selection
+// is by type at compile time (see gemm.cuh's stage loads).
+struct RowMajor {};
+struct ColMajor {};
+
+// Compile-time tile configuration, mirroring KernelTraits in the attention
+// kernels: CTA tile, warp tile (WarpM x WarpN — e.g. 64x32 on the 128x128
+// CTA, 32x32 on the 64x64 small CTA) and cp.async pipeline depth.
+template <FP8Format Fmt, int BlockM, int BlockN, int K, int Stages,
+          int WarpM = 64, int WarpN = 32>
+struct Fp8GemmTraits {
+    static constexpr FP8Format kFormat = Fmt;
+    static constexpr int kBlockM = BlockM;
+    static constexpr int kBlockN = BlockN;
+    static constexpr int kK = K;
+    static constexpr int kStages = Stages;
+    static constexpr int kWarpM = WarpM;
+    static constexpr int kWarpN = WarpN;
+    static constexpr bool kIsE5M2 = (Fmt == FP8Format::E5M2);
+    static constexpr __nv_fp8_interpretation_t kNvFormat =
+        kIsE5M2 ? __NV_E5M2 : __NV_E4M3;
+    static constexpr float kFp8Max = kIsE5M2 ? 57344.0f : 448.0f;
+
+    // Derived geometry: warp tiles tile the CTA. The smem budget is
+    // layout-aware, so it lives in Fp8GemmSmem (gemm.cuh).
+    static constexpr int kWarpsM = BlockM / WarpM;
+    static constexpr int kWarpsN = BlockN / WarpN;
+    static constexpr int kCtaThreads = kWarpsM * kWarpsN * 32;
+    static_assert(kWarpsM * WarpM == BlockM && kWarpsN * WarpN == BlockN,
+                  "warp tiles must exactly tile the CTA");
+    static_assert(WarpM % 16 == 0 && WarpN % 8 == 0,
+                  "warp tile must be a multiple of the m16n8 MMA shape");
+};
+
+// Quantize output orientation: RowMajor = x8 only; Transposed = the
+// [cols][rows] x8T only; Dual = both from a single read. Transposed/Dual
+// produce K-contiguous operands so crosswise consumers (backward
+// grad_x / grad_w) route through the NT fast path.
+enum class QuantLayout : int {
+    RowMajor = 0,
+    Transposed = 1,
+    Dual = 2,
+};
+
+// Quantize-kernel parameter POD: float input -> FP8 with fused amax.
+struct FP8QuantizeParams {
+    const void* __restrict__ input_ptr = nullptr;
+    void* __restrict__ output_ptr = nullptr;
+    void* __restrict__ output_transposed_ptr = nullptr;  // [cols][rows]
+    QuantLayout out_layout = QuantLayout::RowMajor;
+
+    const float* __restrict__ scale = nullptr;  // device multiplier
+    float* __restrict__ amax = nullptr;         // raw-domain max out
+
+    // Optional delayed-scaling ring fold: when fold_ring is set, the kernel's
+    // last-finishing block folds the final amax into hist[hist_idx], reduces
+    // the window and publishes the next scale — replacing the host-side
+    // update chain. amax then points at a persistent self-cleaning slot
+    // (zeroed by the same last block) inside the caller's ring state.
+    bool fold_ring = false;
+    float* __restrict__ hist = nullptr;  // [hist_len] amax history window
+    float* __restrict__ scale_out = nullptr;
+    unsigned int* __restrict__ done = nullptr;  // block-completion counter
+    int hist_len = 0;
+    int hist_idx = 0;
+    float fp8_max = 448.0f;   // scale = max(hist) / fp8_max / pow2_margin
+    float pow2_margin = 1.0f;
+
+    // Element count (elementwise kernel); the tiled kernel views the same
+    // buffer as [rows][cols] row-major.
+    int total = 0;
+    int rows = 0;
+    int cols = 0;
+};
+
+// Unified GEMM parameter POD, mirroring AttentionParams: one struct flows
+// through the kernels; each kernel touches only the fields it needs.
+struct FP8Params {
+    // FP8 operands + output; scales are quantization steps (device
+    // scalars). Optional bf16 bias fuses into the epilogue (fp32 add before
+    // the single bf16 rounding); null disables.
+    const void* __restrict__ a_ptr = nullptr;
+    const void* __restrict__ b_ptr = nullptr;
+    const void* __restrict__ bias_ptr = nullptr;
+    void* __restrict__ out_ptr = nullptr;
+
+    const float* __restrict__ scale = nullptr;
+    // NN-swap mode (canonicalize_gemm): the kernel computes the transposed
+    // problem and the epilogue scatters D[row][col] to out[col * p.m + row]
+    // in the caller's [M][N] buffer. Zero in the plain orientation.
+    int out_transposed = 0;
+    int m, n, k;  // int covers LLM shapes; kernels promote to int64
+
+    // Batched (bmm) geometry: grid.z steps these element strides (0
+    // broadcasts the operand across batches).
+    int batch = 1;
+    int64_t a_batch_stride = 0;
+    int64_t b_batch_stride = 0;
+    int64_t out_batch_stride = 0;
+
+    // Physical leading dims (row strides) of A and B; the binding packs
+    // them so the kernel reads each buffer naturally or transposed per the
+    // LayoutA/LayoutB tags.
+    int a_ld, b_ld;
+};
+
+}  // namespace fp8
+}  // namespace astrai

csrc/kernels/fp8/gemm.cuh

@@ -0,0 +1,271 @@
+#pragma once
+// FP8 GEMM umbrella: the kernel orchestrator and the host-side launch
+// planning. Device layers live in gemm/ (policy / load / scheduler /
+// mainloop / epilogue) — pure CUDA, no torch; launchers are plain functions
+// shared by the torch binding and the C tests. Layout tags and the NN swap
+// semantics are documented in common.h and the design notes
+// (docs/developer/cuda_kernels.md).
+
+#include <cuda_bf16.h>
+#include <cuda_fp8.h>
+#include <cuda_runtime.h>
+#include <type_traits>
+
+#include "../common/cp_async.cuh"
+#include "common.h"
+#include "gemm/epilogue.cuh"
+#include "gemm/load.cuh"
+#include "gemm/mainloop.cuh"
+#include "gemm/policy.cuh"
+#include "gemm/scheduler.cuh"
+
+namespace astrai {
+namespace fp8 {
+
+template <typename Policy>
+__global__ void __launch_bounds__(Policy::kCtaThreads, Policy::kMinCtas)
+    fp8_gemm_kernel(FP8Params p) {
+    using Traits = typename Policy::Traits;
+    using Mainloop = Fp8CollectiveMainloop<Policy>;
+    using Epilogue = Fp8CollectiveEpilogue<Policy>;
+    // Stages live in dynamic shared memory so deep pipelines (> 48KB
+    // static limit) opt in via cudaFuncSetAttribute in the launcher.
+    extern __shared__ __align__(16) char fp8_gemm_smem[];
+
+    // Batch slice (grid.z): broadcast operands carry a 0 stride, so the
+    // same pointer serves every batch.
+    using T8 = typename Mainloop::T8;
+    const T8* a = reinterpret_cast<const T8*>(p.a_ptr) +
+                  (int64_t)blockIdx.z * p.a_batch_stride;
+    const T8* b = reinterpret_cast<const T8*>(p.b_ptr) +
+                  (int64_t)blockIdx.z * p.b_batch_stride;
+    auto* out_bf16 = reinterpret_cast<__nv_bfloat16*>(p.out_ptr) +
+                     (int64_t)blockIdx.z * p.out_batch_stride;
+
+    static_assert(Mainloop::kBlockM * Mainloop::kBlockN * 2 <=
+                      Mainloop::kARing * Mainloop::kBlockM * Mainloop::kK +
+                          Mainloop::kBRing * Mainloop::kBlockN * Mainloop::kK,
+                  "output tile must fit the reclaimed operand smem");
+    const int2 bn = Fp8GemmTileScheduler<Policy::kGroupRaster>::tile(blockIdx, gridDim);
+    Mainloop mainloop(fp8_gemm_smem, a, b, p.m, p.n, p.k, p.a_ld, p.b_ld,
+                      threadIdx.x, bn);
+    float acc[Mainloop::kNt][Mainloop::kMt][4] = {};  // [nt][mt][acc]
+    mainloop.prologue();
+    mainloop.accumulate(acc);
+    // Drain the pipeline before the epilogue reclaims the operand rings.
+    astrai::cp_async_wait_all();
+    Epilogue(fp8_gemm_smem, p, bn.x, bn.y, threadIdx.x).run(acc, out_bf16);
+}
+
+// ---------------------------------------------------------------------------
+// Launchers — pure CUDA (no torch), usable from the binding and pure C tests.
+// ---------------------------------------------------------------------------
+
+// SM count of the current device (cached per device; benign init race —
+// every writer stores the same value).
+inline int device_sm_count() {
+    static int cached[64] = {};
+    int dev = 0;
+    cudaGetDevice(&dev);
+    const bool cacheable = dev >= 0 && dev < 64;
+    int sms = cacheable ? cached[dev] : 0;
+    if (!sms) {
+        cudaDeviceGetAttribute(&sms, cudaDevAttrMultiProcessorCount, dev);
+        sms = sms > 0 ? sms : 1;
+        if (cacheable) cached[dev] = sms;
+    }
+    return sms;
+}
+
+// Launch one kernel instantiation with its shared-memory budget: budgets
+// beyond the 48KB static limit opt in once per instantiation via
+// cudaFuncSetAttribute. Templated on the kernel *value* (auto NTTP) so
+// every instantiation owns its own armed flag — same-signature kernels
+// must not share it. A failed opt-in arms nothing, so the launch below
+// fails loudly through the caller's error checks.
+template <auto Kernel, typename... Args>
+void launch_with_smem(int smem_bytes, dim3 grid, dim3 block,
+                      cudaStream_t stream, Args... args) {
+    if (smem_bytes > 48 * 1024) {
+        static bool armed = false;  // per instantiation
+        if (!armed) {
+            const cudaError_t err = cudaFuncSetAttribute(
+                Kernel, cudaFuncAttributeMaxDynamicSharedMemorySize,
+                smem_bytes);
+            armed = (err == cudaSuccess);
+        }
+    }
+    Kernel<<<grid, block, smem_bytes, stream>>>(args...);
+}
+
+// Padding-driven small-CTA rule: m or n <= 64 wastes half a 128-row CTA's
+// MMA work, and a non-128-divisible shape drags its edge tiles through the
+// predicated generic path — when 64 divides both dims, the 64x64 CTA tiles
+// exactly and wins that band.
+inline bool small_cta_padding(int64_t m, int64_t n) {
+    if (m <= 64 || n <= 64) return true;
+    const bool big_div = (m % 128 == 0) && (n % 128 == 0);
+    const bool small_div = (m % 64 == 0) && (n % 64 == 0);
+    return !big_div && small_div;
+}
+
+// Launch configuration — a pure function of the problem (unit-testable
+// without a GPU). Raster order is not a plan field: every canonical layout
+// runs grouped raster; the plain-raster knob stays available through
+// launch_plan's GroupRaster parameter for experiments.
+struct Fp8GemmPlan {
+    enum class Cta { kSmall64, kNarrow128x64, kBig128 };
+    Cta cta;
+    bool small_s3;  // kSmall64 only: cp.async pipeline depth (2 vs 3 stages)
+};
+
+// crosswise_ops counts the operands taking the direct crosswise load
+// (A ColMajor / B RowMajor storage): 0 = dual-congruous NT, 1 = TN and the
+// NN swap, 2 = TT. The layout shifts the crossovers (measured tables in
+// the design notes): the small CTA hides the crosswise LDG+PRMT latency
+// far better, while the big CTA's operand reuse buys back load bandwidth
+// the crosswise path does not traffic in.
+inline Fp8GemmPlan plan_gemm(const FP8Params& p, int crosswise_ops = 0) {
+    const int64_t sm = device_sm_count();
+    const int64_t tiles_128 =
+        (int64_t)p.batch * ((p.m + 127) / 128) * ((p.n + 127) / 128);
+    const auto small = [&](bool s3) {
+        return Fp8GemmPlan{Fp8GemmPlan::Cta::kSmall64, s3};
+    };
+    const auto big = [] {
+        return Fp8GemmPlan{Fp8GemmPlan::Cta::kBig128, false};
+    };
+    const auto narrow = [] {
+        return Fp8GemmPlan{Fp8GemmPlan::Cta::kNarrow128x64, false};
+    };
+    // Padding rules first: predication waste beats any wave-fill effect.
+    if (small_cta_padding(p.m, p.n)) return small(crosswise_ops > 0);
+    if (crosswise_ops > 0) {
+        // Crosswise ladder (L20 measured): the small s3 CTA holds ~3/4 of
+        // the big CTA's per-SM throughput but tiles 4x finer, so it owns
+        // the whole sub-wave band and past it; the big CTA takes over once
+        // its grid fills ~1.5 waves.
+        if (tiles_128 >= sm * 3 / 2) return big();
+        return small(true);
+    }
+    if (tiles_128 >= sm) {
+        // Wave band: pick by the wave-quantization cost ceil(tiles/sm) *
+        // T_tile. The narrow tile carries half the big tile's MMA work at
+        // ~94% of its per-SM efficiency (T_narrow ~= 0.53 * T_big,
+        // integer-scaled by 100 below) — reproduces every measured
+        // crossover.
+        const int64_t tiles_narrow =
+            (int64_t)p.batch * ((p.m + 127) / 128) * ((p.n + 63) / 64);
+        const auto waves = [sm](int64_t tiles) { return (tiles + sm - 1) / sm; };
+        if (waves(tiles_narrow) * 53 < waves(tiles_128) * 100) return narrow();
+        return big();
+    }
+    // Sub-wave band: the narrow CTA fills the wave with N-tiles at full
+    // warp depth once its grid passes ~3/8 of a wave; below that the plain
+    // 64x64 CTA's extra parallelism wins, and past ~5/8 of a wave of
+    // 128x128 tiles the big CTA's operand reuse wins instead.
+    if (tiles_128 >= sm * 5 / 8) return big();
+    const int64_t tiles_narrow =
+        (int64_t)p.batch * ((p.m + 127) / 128) * ((p.n + 63) / 64);
+    if (tiles_narrow >= sm * 3 / 8) return narrow();
+    // Full-ring small CTAs: the 24KB s2 variant keeps 4 CTAs/SM while the
+    // whole grid stays resident; past that the 32KB s3 variant's deeper
+    // pipeline wins on multi-wave grids.
+    const int64_t tiles_64 =
+        (int64_t)p.batch * ((p.m + 63) / 64) * ((p.n + 63) / 64);
+    return small(tiles_64 > sm * 3);
+}
+
+// Grid + launch for one concrete Policy — the only place a GEMM kernel goes
+// to the wire.
+template <typename Policy>
+void launch_policy(const FP8Params& p, cudaStream_t stream) {
+    using Traits = typename Policy::Traits;
+    dim3 grid((p.n + Traits::kBlockN - 1) / Traits::kBlockN,
+              (p.m + Traits::kBlockM - 1) / Traits::kBlockM, p.batch);
+    launch_with_smem<fp8_gemm_kernel<Policy>>(
+        Policy::kSmemBytes, grid, dim3(Traits::kCtaThreads), stream, p);
+}
+
+// Plan -> Policy: the production-tuned configs. Big CTA: 128x128 of 8 warps
+// x 64x32, kK=64, 2-stage full ring, fast loop only for dual-congruous
+// layouts. Narrow: 128x64. Small CTA: 64x64 of 4 warps x 32x32, kK=64,
+// kFastLoop always on.
+template <FP8Format Fmt, typename LayoutA, typename LayoutB, int GroupRaster>
+void launch_plan(const FP8Params& p, const Fp8GemmPlan& plan,
+                 cudaStream_t stream) {
+    constexpr bool kBigFast = !std::is_same_v<LayoutA, ColMajor> &&
+                              !std::is_same_v<LayoutB, RowMajor>;
+    switch (plan.cta) {
+    case Fp8GemmPlan::Cta::kBig128: {
+        using Policy =
+            Fp8GemmPolicy<Fmt, 128, 128, LayoutA, LayoutB, 64, 32, 64, 2,
+                          GroupRaster, false, kBigFast>;
+        launch_policy<Policy>(p, stream);
+        break;
+    }
+    case Fp8GemmPlan::Cta::kNarrow128x64: {
+        using Policy =
+            Fp8GemmPolicy<Fmt, 128, 64, LayoutA, LayoutB, 32, 32, 64, 2,
+                          GroupRaster, false, true>;
+        launch_policy<Policy>(p, stream);
+        break;
+    }
+    case Fp8GemmPlan::Cta::kSmall64: {
+        if (plan.small_s3) {
+            using Policy = Fp8GemmPolicy<Fmt, 64, 64, LayoutA, LayoutB, 32, 32,
+                                         64, 3, GroupRaster, false, true>;
+            launch_policy<Policy>(p, stream);
+        } else {
+            using Policy = Fp8GemmPolicy<Fmt, 64, 64, LayoutA, LayoutB, 32, 32,
+                                         64, 2, GroupRaster, false, true>;
+            launch_policy<Policy>(p, stream);
+        }
+        break;
+    }
+    }
+}
+
+// Pure problem rewrite: the dual-N-contiguous problem (trans_a/trans_b both
+// false) has no dedicated instantiation — it runs as its transpose
+// E[N][M] = B^T @ A^T (CUTLASS-sm90's is_swapAB) over swapped operands,
+// with p.out_transposed making the epilogue scatter into the caller's
+// [M][N] row-major buffer. The rewritten trans flags become the layout tags
+// the launcher instantiates; the NN path pays a scalar-store scatter, which
+// its rare usage makes the right trade.
+inline void canonicalize_gemm(FP8Params& p, bool& trans_a, bool& trans_b) {
+    if (!trans_a && !trans_b) {
+        FP8Params s = p;  // E = B^T * A^T: swap roles, M <-> N
+        s.m = p.n;
+        s.n = p.m;
+        s.a_ptr = p.b_ptr;
+        s.b_ptr = p.a_ptr;
+        s.a_ld = p.b_ld;
+        s.b_ld = p.a_ld;
+        s.a_batch_stride = p.b_batch_stride;
+        s.b_batch_stride = p.a_batch_stride;
+        s.out_transposed = 1;
+        p = s;
+        trans_a = trans_b = true;
+    }
+}
+
+// Entry point: canonicalize the problem, plan the launch, wire the layout
+// tags through.
+template <FP8Format Fmt>
+void gemm(FP8Params p, cudaStream_t stream, bool trans_a, bool trans_b) {
+    canonicalize_gemm(p, trans_a, trans_b);
+    // Crosswise operand count for the plan: transposed-A storage (ColMajor)
+    // and plain-B storage (RowMajor) both take the direct crosswise load.
+    const int crosswise = (trans_a ? 1 : 0) + (trans_b ? 0 : 1);
+    const Fp8GemmPlan plan = plan_gemm(p, crosswise);
+    if (trans_a && trans_b)
+        launch_plan<Fmt, ColMajor, ColMajor, 8>(p, plan, stream);
+    else if (trans_b)
+        launch_plan<Fmt, RowMajor, ColMajor, 8>(p, plan, stream);
+    else
+        launch_plan<Fmt, ColMajor, RowMajor, 8>(p, plan, stream);
+}
+
+}  // namespace fp8
+}  // namespace astrai

csrc/kernels/fp8/gemm/epilogue.cuh

@@ -0,0 +1,180 @@
+#pragma once
+// Collective epilogue: fused bias, the bf16 scatter of the fp32 accumulators
+// through the reclaimed operand shared memory, and the coalesced copy-out.
+
+#include "../common.h"
+#include "policy.cuh"
+
+namespace astrai {
+namespace fp8 {
+
+template <typename Policy>
+struct Fp8CollectiveEpilogue {
+    using Traits = typename Policy::Traits;
+    static constexpr bool kStreamOut = Policy::kStreamOut;
+    static constexpr int kBlockM = Traits::kBlockM;
+    static constexpr int kBlockN = Traits::kBlockN;
+    static constexpr int kMt = Traits::kWarpM / 16;
+    static constexpr int kNt = Traits::kWarpN / 8;
+
+    __nv_bfloat16* const tile_out;
+    const float output_scale;
+    const __nv_bfloat16* const bias;
+    const int64_t m, n;
+    const bool t_out;
+    const int row_elems, row_chunks;
+    const int warp_m, warp_n, group, thread_in_group;
+    const int64_t block_m, block_n;
+
+    __device__ Fp8CollectiveEpilogue(char* smem, const FP8Params& p,
+                                     int64_t block_m, int64_t block_n, int tid)
+        : tile_out(reinterpret_cast<__nv_bfloat16*>(smem)),
+          output_scale(*p.scale),
+          bias(reinterpret_cast<const __nv_bfloat16*>(p.bias_ptr)),
+          m(p.m), n(p.n), t_out(p.out_transposed != 0),
+          row_elems(t_out ? kBlockM : kBlockN),
+          row_chunks(row_elems / 8),
+          warp_m((tid >> 5) / Traits::kWarpsN),
+          warp_n((tid >> 5) % Traits::kWarpsN),
+          group((tid & 31) >> 2),
+          thread_in_group(tid & 3),
+          block_m(block_m), block_n(block_n) {}
+
+    // Swizzled address of one 16B chunk (row r, chunk c) of the staged
+    // tile. Plain orientation: kBlockM rows of kBlockN elems; out-
+    // transposed (swap dispatch): rows and row length trade places. Both
+    // row-chunk counts are powers of two, keeping the XOR swizzle
+    // well-defined.
+    __device__ __forceinline__ __nv_bfloat16* out_chunk(int r, int c) const {
+        return tile_out + (size_t)r * row_elems +
+               ((c ^ (r & (row_chunks - 1))) * 8);
+    }
+    __device__ __forceinline__ __nv_bfloat16* out_elem(int r, int v) const {
+        return out_chunk(r, v >> 3) + (v & 7);
+    }
+
+    // Scatter the accumulators into the staging tile: the operand rings are
+    // dead once the mainloop ends, so their space stages the bf16 output
+    // tile. Threads scatter (STS.32 of bf16x2 pairs), a barrier makes the
+    // tile coherent, then the whole CTA copies it out in fully-coalesced
+    // 16B chunks. The 16B-chunk XOR swizzle keeps both the scatter and the
+    // gather conflict-free.
+    __device__ __forceinline__ void stage(float acc[kNt][kMt][4]) const {
+        // Fused bias: added to the fp32 accumulator before the single bf16
+        // rounding. The per-lane loads are L1 broadcasts; rows past the
+        // edge skip the load (their smem slots never copy out). Under
+        // out_transposed the bias indexes D-cols = the kernel's rows.
+        const int local_col0 = warp_n * Traits::kWarpN + thread_in_group * 2;
+        const int64_t bias_col0 = block_n * kBlockN;
+        const int64_t bias_row0 = block_m * kBlockM;
+        if (!t_out) {
+#pragma unroll
+            for (int nt = 0; nt < kNt; ++nt) {
+                const int col = local_col0 + nt * 8;
+                const int64_t gcol = bias_col0 + col;
+                const float b0 =
+                    bias && gcol < n ? __bfloat162float(bias[gcol]) : 0.0f;
+                const float b1 =
+                    bias && gcol + 1 < n ? __bfloat162float(bias[gcol + 1])
+                                         : 0.0f;
+#pragma unroll
+                for (int mt = 0; mt < kMt; ++mt) {
+                    const int r0 = warp_m * Traits::kWarpM + group + mt * 16;
+                    const float* tile_acc = acc[nt][mt];
+                    // Two bf16x2 stores per accumulator tile: rows g and
+                    // g+8 of the m16n8 output, columns tig*2/tig*2+1 inside
+                    // one 16B chunk.
+                    const int off = col & 7;  // element offset in the chunk
+                    *reinterpret_cast<__nv_bfloat162*>(
+                        out_chunk(r0, col >> 3) + off) =
+                        __floats2bfloat162_rn(tile_acc[0] * output_scale + b0,
+                                              tile_acc[1] * output_scale + b1);
+                    *reinterpret_cast<__nv_bfloat162*>(
+                        out_chunk(r0 + 8, col >> 3) + off) =
+                        __floats2bfloat162_rn(tile_acc[2] * output_scale + b0,
+                                              tile_acc[3] * output_scale + b1);
+                }
+            }
+        } else {
+            // Transposed scatter: accumulator (kernel row r0, col) is
+            // D[col0_global + col][row0_global + r0], staged at T[col][r0].
+            // The acc pair spans two staged rows, so these are scalar
+            // stores (the swap path is the rare NN layout). OOB elements
+            // store dead lanes of the tile, never copied out.
+#pragma unroll
+            for (int nt = 0; nt < kNt; ++nt) {
+                const int col = local_col0 + nt * 8;
+#pragma unroll
+                for (int mt = 0; mt < kMt; ++mt) {
+                    const int r0 = warp_m * Traits::kWarpM + group + mt * 16;
+                    const int64_t grow = bias_row0 + r0;
+                    const float b =
+                        bias && grow < m ? __bfloat162float(bias[grow]) : 0.0f;
+                    const float* tile_acc = acc[nt][mt];
+                    *out_elem(col, r0) =
+                        __float2bfloat16(tile_acc[0] * output_scale + b);
+                    *out_elem(col + 1, r0) =
+                        __float2bfloat16(tile_acc[1] * output_scale + b);
+                    *out_elem(col, r0 + 8) =
+                        __float2bfloat16(tile_acc[2] * output_scale + b);
+                    *out_elem(col + 1, r0 + 8) =
+                        __float2bfloat16(tile_acc[3] * output_scale + b);
+                }
+            }
+        }
+    }
+
+    // Coalesced copy-out: thread -> one 16B chunk; consecutive threads walk
+    // a row so each global transaction covers a full 128B line. Under the
+    // swap the staged rows are D-rows counted from block_n's stripe while
+    // the row length is kernel m', so row/stride flip to the swapped dims.
+    __device__ __forceinline__ void store(__nv_bfloat16* out_bf16) const {
+        constexpr int kTotalChunks =
+            kBlockM * (kBlockN / 8);  // == kBlockN * (kBlockM/8)
+        const int64_t row0_global = block_m * kBlockM;
+        const int64_t col0_global = block_n * kBlockN;
+        for (int idx = threadIdx.x; idx < kTotalChunks; idx += kCtaThreads) {
+            const int r = idx / row_chunks;
+            const int c = idx % row_chunks;
+            const uint4 v = *reinterpret_cast<const uint4*>(out_chunk(r, c));
+            const int64_t row = t_out ? (int64_t)block_n * kBlockN + r
+                                      : row0_global + r;
+            const int64_t col = t_out ? row0_global + (int64_t)c * 8
+                                      : col0_global + (int64_t)c * 8;
+            const int64_t rows_total = t_out ? n : m;
+            const int64_t row_stride = t_out ? m : n;
+            if (row >= rows_total) break;  // rows are consecutive: nothing left
+            auto* dst = out_bf16 + row * row_stride + col;
+            if (col + 8 <= row_stride &&
+                (reinterpret_cast<uintptr_t>(dst) & 15) == 0) {
+                if constexpr (kStreamOut) {
+                    // Evict-first streaming store knob: neutral on L20
+                    // squares, -3..4% on rects; kept for other SKUs.
+                    __stcs(reinterpret_cast<uint4*>(dst), v);
+                } else {
+                    *reinterpret_cast<uint4*>(dst) = v;
+                }
+            } else {
+                // Row-edge chunk or an odd-stride row base: spill the
+                // elements that survive the row edge.
+                const __nv_bfloat16* elems =
+                    reinterpret_cast<const __nv_bfloat16*>(&v);
+                for (int e = 0; e < 8 && col + e < row_stride; ++e)
+                    dst[e] = elems[e];
+            }
+        }
+    }
+
+    __device__ __forceinline__ void run(float acc[kNt][kMt][4],
+                                        __nv_bfloat16* out_bf16) {
+        stage(acc);
+        __syncthreads();
+        store(out_bf16);
+    }
+
+  private:
+    static constexpr int kCtaThreads = Traits::kCtaThreads;
+};
+
+}  // namespace fp8
+}  // namespace astrai

csrc/kernels/fp8/gemm/load.cuh

@@ -0,0 +1,224 @@
+#pragma once
+// Operand loaders: swizzled shared-memory staging for congruous operands
+// (cp.async, predicated and interior variants, plus the loop-carried
+// prefetch state) and the direct LDG+PRMT path for crosswise operands.
+// The staging invariants and the swizzle derivation live in
+// docs/developer/cuda_kernels.md.
+
+#include "../../common/cp_async.cuh"
+#include "../common.h"
+#include "policy.cuh"
+
+namespace astrai {
+namespace fp8 {
+
+// log2 of a compile-time power of two (for the swizzle shifts).
+template <int N, int Acc = 0>
+struct log2_const : log2_const<(N >> 1), Acc + 1> {};
+template <int Acc>
+struct log2_const<1, Acc> {
+    static constexpr int value = Acc;
+};
+
+// Swizzled address inside a flat [rows * K] staging tile: the 16B chunk
+// index is XORed with the row bits at [3, 3+log2(kChunks)) so a warp's
+// ldmatrix fragment load (8 consecutive rows x 16B) hits all 32 banks
+// exactly once; chunks stay contiguous, so cp.async staging is unaffected.
+template <int K, typename T8>
+__device__ __forceinline__ T8* tile_at(T8* tile, int row, int col) {
+    constexpr int kChunks = K / 16;  // 16B chunks per row
+    static_assert(kChunks >= 1 && (kChunks & (kChunks - 1)) == 0,
+                  "swizzle needs a power-of-two 16B-chunk count");
+    constexpr int kShift = 3 - log2_const<kChunks>::value;
+    return tile + row * K +
+           ((((col >> 4) ^ ((row >> kShift) & (kChunks - 1))) << 4) + (col & 15));
+}
+
+// Stage-load a CONGRUOUS operand (contract-contiguous storage — the only
+// cp.async-able shape) into the flat [rows * K] swizzled tile. kInterior
+// drops all predication: valid only for a fully interior CTA (whole rows,
+// 16B-aligned base|ld, k_base + K <= contract); the address math then folds
+// to one immediate XOR per chunk (see the design notes). Crosswise operands
+// go through load_crosswise_direct instead.
+template <typename T8, int K, int RowsTile, int kThreads,
+          bool kInterior = false>
+__device__ __forceinline__ void
+load_operand_tile(T8* tile, const T8* __restrict__ operand, int64_t rows,
+                  int64_t contract, int64_t ld, int tid, int64_t k_base,
+                  int64_t block_row) {
+    constexpr int kChunks = K / 16;
+    static_assert(RowsTile * kChunks % kThreads == 0,
+                  "tile chunks must divide evenly across threads");
+    constexpr int kCpt = RowsTile * kChunks / kThreads;  // chunks per thread
+    constexpr int kCpr = kChunks / kCpt;  // chunks per row slice
+    const int r = tid / kCpr;
+    const int c0 = (tid % kCpr) * kCpt * 16;
+    if constexpr (kInterior) {
+        const char* src = reinterpret_cast<const char*>(
+            operand + (block_row + r) * ld + k_base + c0);
+        const uintptr_t dst =
+            reinterpret_cast<uintptr_t>(tile_at<K>(tile, r, c0));
+#pragma unroll
+        for (int j = 0; j < kCpt; ++j)
+            astrai::cp_async_16(reinterpret_cast<T8*>(dst ^ (j << 4)),
+                                src + j * 16);
+    } else {
+        const int64_t row = block_row + r;
+        const bool row_ok = row < rows;
+        // k_base and every c are multiples of 16, so all chunks share the
+        // row base's alignment verdict.
+        const auto* src = operand + row * ld + k_base;
+        const bool chunk_aligned = (reinterpret_cast<uintptr_t>(src) & 15) == 0;
+#pragma unroll
+        for (int j = 0; j < kCpt; ++j) {
+            const int c = c0 + j * 16;
+            T8* dst = tile_at<K>(tile, r, c);
+            if (row_ok && chunk_aligned && k_base + c + 15 < contract) {
+                astrai::cp_async_16(dst, src + c);
+            } else {
+                // Tail chunk / misaligned base / OOB row: scalar fill.
+#pragma unroll
+                for (int i = 0; i < 16; ++i)
+                    dst[i] =
+                        row_ok && k_base + c + i < contract ? src[c + i] : T8(0.0f);
+            }
+        }
+    }
+}
+
+// Loop-carried prefetch state for one congruous operand ring: per-thread
+// (r, c0) mapping with the swizzled stage destination and global source
+// pointer carried across k-tiles, so each prefetch chunk is one LDGSTS
+// issued straight from registers. The guard is a property of the operand's
+// layout, so it lives in the type: the false specialization (crosswise
+// operand) is an empty no-op.
+template <bool kAsync, typename T8, int kK, int kRowsTile, int kThreads>
+struct PrefetchCarry;
+
+template <typename T8, int kK, int kRowsTile, int kThreads>
+struct PrefetchCarry<true, T8, kK, kRowsTile, kThreads> {
+    static constexpr int kCpt = kRowsTile * (kK / 16) / kThreads;
+    static constexpr int kCpr = (kK / 16) / kCpt;
+    unsigned wr = 0;    // current stage's swizzled destination offset
+    unsigned wr0 = 0;   // slot-0 wrap base
+    unsigned wrEnd = 0; // one-past-the-ring sentinel
+    const char* src = nullptr;  // current tile's global source bytes
+
+    __device__ __forceinline__ PrefetchCarry(
+        const T8* ring, int ringSlots, int stageElems, const T8* operand,
+        int64_t ld, int64_t blockRow, int tid, int firstTile) {
+        const int r = tid / kCpr;
+        const int c0 = (tid % kCpr) * kCpt * 16;
+        const T8* slot0 = ring + (firstTile % ringSlots) * stageElems;
+        const unsigned laneOff = static_cast<unsigned>(
+            (const char*)tile_at<kK>(slot0, r, c0) - (const char*)slot0);
+        const unsigned base = __cvta_generic_to_shared(ring) + laneOff;
+        wr = base + (unsigned)((firstTile % ringSlots) * stageElems);
+        wr0 = base;
+        wrEnd = base + (unsigned)(ringSlots * stageElems);
+        src = reinterpret_cast<const char*>(
+                  operand + (blockRow + r) * ld + c0) +
+              (int64_t)firstTile * kK;
+    }
+
+    // Emit this thread's chunks for the current tile; pf false (loop tail)
+    // zero-fills into the slot compute(i-1) already released.
+    __device__ __forceinline__ void emit(bool pf) const {
+#pragma unroll
+        for (int j = 0; j < kCpt; ++j)
+            astrai::cp_async_16(wr ^ (unsigned)(j << 4), src + j * 16, pf);
+    }
+
+    __device__ __forceinline__ void advance(int stageElems) {
+        wr += (unsigned)stageElems;
+        if (wr == wrEnd) wr = wr0;
+        src += kK;
+    }
+};
+
+template <typename T8, int kK, int kRowsTile, int kThreads>
+struct PrefetchCarry<false, T8, kK, kRowsTile, kThreads> {
+    __device__ __forceinline__ PrefetchCarry(
+        const T8*, int, int, const T8*, int64_t, int64_t, int, int) {}
+    __device__ __forceinline__ void emit(bool) const {}
+    __device__ __forceinline__ void advance(int) {}
+};
+
+// Direct (synchronous) crosswise load into a canonical rotating stage:
+// LDG.128 x4 (4 consecutive contract bytes x 16 rows) + in-register PRMT
+// transpose + 16 STS.32. Crosswise operands cannot cp.async into the
+// canonical tile (a 16B global run holds one contract byte for each of 16
+// rows), so they take this path; a staged smem->smem variant measured
+// 15-20% slower and was removed (see git history).
+template <typename T8, int K, int RowsTile, int kThreads>
+__device__ __forceinline__ void
+load_crosswise_direct(T8* tile, const T8* __restrict__ operand, int64_t rows,
+                      int64_t contract, int64_t ld, int tid, int64_t k_base,
+                      int64_t block_row) {
+    constexpr int kQuads = K / 4;    // 4-byte contract quads per tile
+    constexpr int kGroups = RowsTile / 16;
+    constexpr int kTChunks = kQuads * kGroups;  // 64B chunks per tile
+    // r0 is a multiple of 16 and p*ld preserves alignment whenever ld has
+    // it, so every run of a chunk shares one alignment verdict.
+    const bool run_aligned =
+        ((reinterpret_cast<uintptr_t>(operand) | ld) & 15) == 0;
+    for (int chunk = tid; chunk < kTChunks; chunk += kThreads) {
+        const int quad = chunk / kGroups;
+        const int rg = chunk % kGroups;
+        const int64_t r0 = block_row + rg * 16;
+        const bool rows_full = r0 + 15 < rows;
+        if (rows_full && run_aligned) {
+            const int64_t p0 = k_base + quad * 4;
+            uint4 v[4];
+#pragma unroll
+            for (int s = 0; s < 4; ++s) {
+                // Contract tail: a run past k carries zero bytes; they flow
+                // through the PRMT transpose like any other value.
+                if (p0 + s < contract)
+                    v[s] = *reinterpret_cast<const uint4*>(
+                        operand + (p0 + s) * ld + r0);
+                else
+                    v[s] = make_uint4(0u, 0u, 0u, 0u);
+            }
+            const unsigned* bytes = reinterpret_cast<const unsigned*>(v);
+#pragma unroll
+            for (int i = 0; i < 16; ++i) {
+                // word i = row r0+i's quad: byte i of each of the four runs
+                // [v0.b(i), v1.b(i), v2.b(i), v3.b(i)].
+                const unsigned nib = i & 3;
+                const unsigned sel = nib | ((nib + 4) << 4);
+                const unsigned w01 =
+                    __byte_perm(bytes[0 + (i >> 2)], bytes[4 + (i >> 2)], sel);
+                const unsigned w23 =
+                    __byte_perm(bytes[8 + (i >> 2)], bytes[12 + (i >> 2)], sel);
+                *reinterpret_cast<unsigned*>(tile_at<K>(tile, rg * 16 + i,
+                                                        quad * 4)) =
+                    __byte_perm(w01, w23, 0x5410u);
+            }
+        } else {
+            // Row-tail or misaligned chunk: byte-granular gather with
+            // per-row predication; contract-tail columns zero-fill.
+#pragma unroll
+            for (int s = 0; s < 4; ++s) {
+                const int col = quad * 4 + s;
+                if (k_base + col >= contract) {
+#pragma unroll
+                    for (int i = 0; i < 16; ++i)
+                        *tile_at<K>(tile, rg * 16 + i, col) = T8(0.0f);
+                    continue;
+                }
+#pragma unroll
+                for (int i = 0; i < 16; ++i) {
+                    const int64_t r_idx = r0 + i;
+                    *tile_at<K>(tile, rg * 16 + i, col) =
+                        r_idx < rows
+                            ? operand[(k_base + col) * ld + r_idx]
+                            : T8(0.0f);
+                }
+            }
+        }
+    }
+}
+
+}  // namespace fp8
+}  // namespace astrai

csrc/kernels/fp8/gemm/mainloop.cuh

@@ -0,0 +1,336 @@
+#pragma once
+// Collective mainloop: shared-memory stage rings, the gmem->smem stage loads
+// (congruous cp.async / crosswise LDG+PRMT), the per-lane ldmatrix fragment
+// addressing and the software-pipelined mma.sync loop. The fragment
+// addressing scheme and the fast-loop peel rationale live in
+// docs/developer/cuda_kernels.md.
+
+#include <type_traits>
+
+#include "../../common/mma.cuh"
+#include "../common.h"
+#include "load.cuh"
+#include "policy.cuh"
+
+namespace astrai {
+namespace fp8 {
+
+template <typename Policy>
+struct Fp8CollectiveMainloop {
+    using Traits = typename Policy::Traits;
+    using LayoutA = typename Policy::LayoutTagA;
+    using LayoutB = typename Policy::LayoutTagB;
+    using Smem = Fp8GemmSmem<Traits, LayoutA, LayoutB>;
+    static constexpr bool kFastLoop = Policy::kFastLoop;
+    using T8 = std::conditional_t<Traits::kIsE5M2, __nv_fp8_e5m2, __nv_fp8_e4m3>;
+    static constexpr int kBlockM = Traits::kBlockM;
+    static constexpr int kBlockN = Traits::kBlockN;
+    static constexpr int kK = Traits::kK;
+    static constexpr int kStages = Traits::kStages;
+    static constexpr int kCtaThreads = Traits::kCtaThreads;
+    static constexpr bool kDirectA = Smem::kDirectA;
+    static constexpr bool kDirectB = Smem::kDirectB;
+    static_assert(kStages >= 1 && kStages <= 8,
+                  "FP8 GEMM stages must be in [1, 8]");
+    // CTA = (BlockM/WarpM) x (BlockN/WarpN) warps, each warp computing
+    // kMt x kNt m16n8k32 MMAs. Rings rotate kStages+1 buffers (see
+    // Fp8GemmSmem) — one __syncthreads per k-tile.
+    static constexpr int kMt = Traits::kWarpM / 16;  // 16-row MMA tiles per warp
+    static constexpr int kNt = Traits::kWarpN / 8;   // 8-col MMA tiles per warp
+    static constexpr int kSegs = kK / kMmaK;  // mma-sized k segments per tile
+    static constexpr int kARing = Smem::kRingDepth;
+    static constexpr int kBRing = Smem::kRingDepth;
+    static constexpr int kAStageBytes = kBlockM * kK;
+    static constexpr int kBStageBytes = kBlockN * kK;
+
+    T8* const a_base;
+    T8* const b_base;
+    const T8* const a;
+    const T8* const b;
+    const int64_t m, n, k, a_ld, b_ld;
+    const int tid;
+    const int64_t block_m, block_n;
+    const int warp_m, warp_n;
+    const int a_row0;  // + mt * 16 in the loop
+    const int b_row0;  // + nt * 8
+    const int64_t tile_count;
+    // Interior-CTA peel (kFastLoop instantiations only): whole-CTA,
+    // 16B-aligned, K without tail — the mainloop then runs a compile-time
+    // specialized copy with no per-chunk predication (measured +4.5..10% on
+    // the issue-bound small CTA; the 128x128 CTA regressed, so only the
+    // small CTA opts in). The verdict is uniform per CTA.
+    const bool fast_cta;
+
+    __device__ Fp8CollectiveMainloop(char* smem, const T8* a, const T8* b,
+                                     int64_t m, int64_t n, int64_t k,
+                                     int64_t a_ld, int64_t b_ld, int tid,
+                                     int2 block)
+        : a_base(reinterpret_cast<T8*>(smem)),
+          b_base(reinterpret_cast<T8*>(smem + kARing * kAStageBytes)),
+          a(a), b(b), m(m), n(n), k(k), a_ld(a_ld), b_ld(b_ld), tid(tid),
+          block_m(block.x), block_n(block.y),
+          warp_m((tid >> 5) / Traits::kWarpsN),
+          warp_n((tid >> 5) % Traits::kWarpsN),
+          a_row0(warp_m * Traits::kWarpM),
+          b_row0(warp_n * Traits::kWarpN),
+          tile_count((k + kK - 1) / kK),
+          fast_cta(kFastLoop && !kDirectA && !kDirectB &&
+                   ((int64_t)block.x * kBlockM + kBlockM <= m) &&
+                   ((int64_t)block.y * kBlockN + kBlockN <= n) &&
+                   ((reinterpret_cast<uintptr_t>(a) | (uint64_t)a_ld) & 15) == 0 &&
+                   ((reinterpret_cast<uintptr_t>(b) | (uint64_t)b_ld) & 15) == 0 &&
+                   (k % kK) == 0) {}
+
+    // Stage-slot helpers: rings rotate one slot per k-tile, so callers
+    // either compute the slot from the tile index (prologue, generic loop)
+    // or carry an advancing pointer (steady-state fast loop).
+    __device__ __forceinline__ T8* a_stage_of(int64_t tile) const {
+        return a_base + (size_t)(tile % kARing) * kAStageBytes;
+    }
+    __device__ __forceinline__ T8* b_stage_of(int64_t tile) const {
+        return b_base + (size_t)(tile % kBRing) * kBStageBytes;
+    }
+    // Asynchronous congruous loads for one k-tile: cp.async into the
+    // canonical rings; kFast selects the predication-free interior copy
+    // (fast_cta admits only congruous operands). Called after the
+    // post-compute barrier, alongside the commit.
+    template <bool kFast = false>
+    __device__ __forceinline__ void load_async(T8* a_stage, T8* b_stage,
+                                               int64_t k_base) const {
+        if constexpr (!kDirectA)
+            load_operand_tile<T8, kK, kBlockM, kCtaThreads, kFast>(
+                a_stage, a, m, k, a_ld, tid, k_base, block_m * kBlockM);
+        if constexpr (!kDirectB)
+            load_operand_tile<T8, kK, kBlockN, kCtaThreads, kFast>(
+                b_stage, b, n, k, b_ld, tid, k_base, block_n * kBlockN);
+    }
+    // Synchronous direct-crosswise loads for one k-tile. In the steady
+    // state this runs right after barrier 1, so the LDG latency and the
+    // PRMT transpose overlap the MMA phase instead of stalling the
+    // inter-barrier window.
+    __device__ __forceinline__ void load_direct(T8* a_stage, T8* b_stage,
+                                                int64_t k_base) const {
+        if constexpr (kDirectA)
+            load_crosswise_direct<T8, kK, kBlockM, kCtaThreads>(
+                a_stage, a, m, k, a_ld, tid, k_base, block_m * kBlockM);
+        if constexpr (kDirectB)
+            load_crosswise_direct<T8, kK, kBlockN, kCtaThreads>(
+                b_stage, b, n, k, b_ld, tid, k_base, block_n * kBlockN);
+    }
+
+    // Prime the pipeline: kStages committed groups, one per stage slot.
+    // The commit is unconditional — when K is shorter than the pipeline the
+    // skipped stages commit empty groups, so the group sequence stays
+    // tile-indexed and the steady-state wait count never needs a runtime
+    // dispatch.
+    __device__ __forceinline__ void prologue() const {
+#pragma unroll
+        for (int stage = 0; stage < kStages; ++stage) {
+            if (stage < tile_count) {
+                if (fast_cta)
+                    load_async<true>(a_stage_of(stage), b_stage_of(stage),
+                                     (int64_t)stage * kK);
+                else
+                    load_async(a_stage_of(stage), b_stage_of(stage),
+                               (int64_t)stage * kK);
+                load_direct(a_stage_of(stage), b_stage_of(stage),
+                            (int64_t)stage * kK);
+            }
+            astrai::cp_async_commit_group();
+        }
+    }
+
+    // Steady-state mainloop, compile-time specialized on kFast: the fast
+    // copy runs predication-free loads with loop-carried read/write
+    // pointers; the generic copy keeps full predication. kFastLoop=false
+    // instantiates only the generic copy.
+    template <bool kFast>
+    __device__ __forceinline__ void run_loop(float acc[kNt][kMt][4]) const {
+        const int lane = tid & 31;
+        // Fast-path write carries: one per congruous operand (crosswise
+        // operands get the empty no-op type), targeting the first
+        // prefetched tile (kStages). Steady-state read carries: the LDSM
+        // base of the current k-tile's stage with the lane offset folded
+        // in, advanced one stage per iteration with an equality wrap —
+        // replaces the per-k-tile (tile % ring) * stage_bytes
+        // recomputation (a UIMAD.WIDE magic-division ladder in SASS).
+        PrefetchCarry<!kDirectA, T8, kK, kBlockM, kCtaThreads> carry_a(
+            a_base, kARing, kAStageBytes, a, a_ld, block_m * kBlockM, tid,
+            kStages);
+        PrefetchCarry<!kDirectB, T8, kK, kBlockN, kCtaThreads> carry_b(
+            b_base, kBRing, kBStageBytes, b, b_ld, block_n * kBlockN, tid,
+            kStages);
+        const unsigned a_rd0 = __cvta_generic_to_shared(a_base) + a_lane_off(lane);
+        const unsigned b_rd0 =
+            __cvta_generic_to_shared(b_base) +
+            (kPairB ? b4_lane_off(lane) : b_lane_off(lane));
+        const unsigned a_rd_end = a_rd0 + (unsigned)(kARing * kAStageBytes);
+        const unsigned b_rd_end = b_rd0 + (unsigned)(kBRing * kBStageBytes);
+        unsigned a_rd = a_rd0, b_rd = b_rd0;
+        for (int64_t tile_index = 0; tile_index < tile_count; ++tile_index) {
+        // In the steady state exactly kStages-1 younger groups are in flight
+        // when this fires; the tail's unconditional (possibly empty)
+        // commits keep that invariant true for every iteration.
+        const bool prefetch = tile_index + kStages < tile_count;
+        astrai::cp_async_wait_group<kStages - 1>();
+        // Barrier 1: every thread's cp.async for this stage is complete
+        // before any thread reads tiles written by other threads.
+        __syncthreads();
+
+        // Direct chunks for tile i+kStages: issue LDG+PRMT+STS now so the
+        // global-load latency hides behind the MMA phase below.
+        if (prefetch)
+            load_direct(a_stage_of(tile_index + kStages),
+                        b_stage_of(tile_index + kStages),
+                        (tile_index + kStages) * kK);
+
+        const unsigned a_addr = a_rd;
+        const unsigned b_addr = b_rd;
+        // Per-k_seg base pair (cuBLAS's scheme): seg s lives at the seg-0
+        // base XOR (s<<5) — one LOP3 per extra seg per k-tile, never per
+        // fragment. Every LDSM below addresses [base + immediate].
+        unsigned a_seg[kSegs], b_seg[kSegs];
+#pragma unroll
+        for (int s = 0; s < kSegs; ++s) {
+            a_seg[s] = a_addr ^ (unsigned)(s * kSegXor);
+            b_seg[s] = b_addr ^ (unsigned)(s * kSegXor);
+        }
+
+        // kNt ldmatrix.x2 (B) + kMt ldmatrix.x4 (A) feed kMt*kNt*2 mma.sync
+        // per k_seg — 0.5 load instructions per MMA. B fragments
+        // double-buffer across k_segs; kPairB folds the two adjacent nt
+        // fragments of one pair into a single x4 (see b4_lane_off).
+        unsigned b_frag[2][kNt][2];
+        unsigned b_frag4[2][kNt / 2][4];
+        load_b_frags(b_frag[0][0], b_frag4[0][0], b_seg[0]);
+#pragma unroll
+        for (int k_seg = 0; k_seg < kSegs; ++k_seg) {
+            const int bcur = k_seg & 1, bnext = bcur ^ 1;
+            if (k_seg + 1 < kSegs)
+                load_b_frags(b_frag[bnext][0], b_frag4[bnext][0],
+                             b_seg[k_seg + 1]);
+        // Software-pipelined A fragments: the ldmatrix.x4 for row mt+1 is
+        // issued before the MMAs consuming row mt, so the LDS latency hides
+        // behind tensor-pipe work. Costs 4 extra registers.
+        unsigned a_frag[kMt + 1][4];
+        astrai::ldmatrix_x4_lane(a_frag[0], a_seg[k_seg]);
+#pragma unroll
+        for (int mt = 0; mt < kMt; ++mt) {
+            if (mt + 1 < kMt)
+                astrai::ldmatrix_x4_lane(a_frag[mt + 1],
+                                         a_seg[k_seg] + (mt + 1) * kMtStep);
+#pragma unroll
+            for (int nt = 0; nt < kNt; ++nt) {
+                const unsigned* bops =
+                    kPairB ? (b_frag4[bcur][nt >> 1] + (nt & 1) * 2)
+                           : b_frag[bcur][nt];
+                astrai::mma_sync<T8>(acc[nt][mt], a_frag[mt], bops,
+                                     acc[nt][mt]);
+            }
+        }
+        // Next tile's LDGSTS chunks inside the MMA phase: A's after the
+        // first k_seg's MMA batch, B's after the last.
+        if constexpr (kFast) {
+            if (k_seg == 0) carry_a.emit(prefetch);
+            if (k_seg == kSegs - 1) carry_b.emit(prefetch);
+        }
+        }
+        // Generic loop (no interleaved prefetch): the next tile's predicated
+        // loads run after the MMA phase.
+        if constexpr (!kFast) {
+            if (prefetch) {
+                load_async(a_stage_of(tile_index + kStages),
+                           b_stage_of(tile_index + kStages),
+                           (tile_index + kStages) * kK);
+            }
+        }
+        // Unconditional commit: empty in the tail, it pads the group
+        // sequence so the fixed wait above stays correct.
+        astrai::cp_async_commit_group();
+        a_rd += (unsigned)kAStageBytes;
+        if (a_rd == a_rd_end) a_rd = a_rd0;
+        b_rd += (unsigned)kBStageBytes;
+        if (b_rd == b_rd_end) b_rd = b_rd0;
+        if constexpr (kFast) {
+            carry_a.advance(kAStageBytes);
+            carry_b.advance(kBStageBytes);
+        }
+        }
+    }
+
+    __device__ __forceinline__ void accumulate(float acc[kNt][kMt][4]) const {
+        if constexpr (kFastLoop) {
+            if (fast_cta)
+                run_loop<true>(acc);
+            else
+                run_loop<false>(acc);
+        } else {
+            run_loop<false>(acc);
+        }
+    }
+
+  private:
+    // Per-lane ldmatrix fragment addressing (base-pair scheme, mirrored
+    // from the cuBLAS SASS; derivation in the design notes): one base
+    // register per operand per k_seg, every fragment offset an LDSM
+    // immediate — zero address arithmetic inside the MMA phase.
+    __device__ __forceinline__ unsigned a_lane_off(int lane) const {
+        const int r7 = lane & 7;          // row within the 8-row matrix
+        const int rh8 = (lane >> 3) & 1;  // +8 rows (A: lanes 8-15, 24-31)
+        const int rh16 = lane >> 4;       // +1 chunk (A: lanes 16-31)
+        constexpr int kChunks = kK / 16;
+        constexpr int kShift = 3 - log2_const<kChunks>::value;  // tile_at's shift
+        const unsigned lswz =
+            static_cast<unsigned>((r7 >> kShift) & (kChunks - 1));
+        // Stage-relative, loop-invariant per-lane base; A's fragment row
+        // carries the +8-row (rh8) and +1-chunk (rh16) halves.
+        return static_cast<unsigned>((a_row0 + rh8 * 8 + r7) * kK +
+                                     ((rh16 ^ lswz) << 4));
+    }
+    __device__ __forceinline__ unsigned b_lane_off(int lane) const {
+        const int r7 = lane & 7;
+        const int rh8 = (lane >> 3) & 1;  // +8 rows (B uses rh8 as its chunk half)
+        constexpr int kChunks = kK / 16;
+        constexpr int kShift = 3 - log2_const<kChunks>::value;
+        const unsigned lswz =
+            static_cast<unsigned>((r7 >> kShift) & (kChunks - 1));
+        return static_cast<unsigned>((b_row0 + r7) * kK + ((rh8 ^ lswz) << 4));
+    }
+    // x4-paired B loads: one ldmatrix.x4 feeds the two adjacent nt
+    // fragments. Lane contract: lanes 0-7 address rows n0..n7 chunk c,
+    // lanes 8-15 rows n0..n7 chunk c+1, lanes 16-23 rows n8..n15 chunk c,
+    // lanes 24-31 rows n8..n15 chunk c+1. The +8-row step never reaches
+    // the swizzle source bits for kK <= 64; kK=128 swizzles on row[2:0]
+    // where +8 flips bits, so that config keeps the x2 loads.
+    static constexpr unsigned kMtStep = 16 * kK;  // bytes per m-tile row step
+    static constexpr unsigned kNtStep = 8 * kK;   // bytes per n-tile row step
+    static constexpr unsigned kSegXor = 32;       // chunk-index +2 per k_seg
+    static constexpr bool kPairB = kK / 16 <= 4;
+    static_assert(!kPairB || kNt % 2 == 0, "B pairing needs even kNt");
+    static constexpr unsigned kPairStep = 16 * kK;  // bytes per nt-pair row step
+    __device__ __forceinline__ unsigned b4_lane_off(int lane) const {
+        return b_lane_off(lane) + (lane >> 4) * kPairStep / 2;
+    }
+
+    // One k_seg's B-fragment loads, shared by the initial fill and the
+    // double-buffer's next-seg fill. frag2/frag4 are the flat bases of one
+    // b_frag / b_frag4 buffer (the unused one is never touched).
+    __device__ __forceinline__ void
+    load_b_frags(unsigned* frag2, unsigned* frag4, unsigned seg_base) const {
+#pragma unroll
+        for (int p = 0; p < kNt / 2; ++p) {
+            if constexpr (kPairB) {
+                astrai::ldmatrix_x4_lane(frag4 + p * 4,
+                                         seg_base + p * kPairStep);
+            } else {
+                astrai::ldmatrix_x2_lane(frag2 + p * 4,
+                                         seg_base + p * 2 * kNtStep);
+                astrai::ldmatrix_x2_lane(frag2 + p * 4 + 2,
+                                         seg_base + (p * 2 + 1) * kNtStep);
+            }
+        }
+    }
+};
+
+}  // namespace fp8
+}  // namespace astrai

csrc/kernels/fp8/gemm/policy.cuh

@@ -0,0 +1,53 @@
+#pragma once
+// Kernel policy layer: shared-memory budget, occupancy hint and the
+// single Policy type the kernel and collectives take (CUTLASS-style
+// consolidation of traits + layout tags + scheduling knobs).
+
+#include <type_traits>
+
+#include "../common.h"
+
+namespace astrai {
+namespace fp8 {
+
+// m16n8k32 (see astrai::mma_shape<fp8 type>::k in common/mma.cuh)
+constexpr int kMmaK = 32;
+
+// Layout-aware shared-memory budget and occupancy hint. Every operand ring
+// holds kStages+1 buffers: the load for tile i+kStages targets slot
+// (i-1)%(kStages+1) — already consumed — so neither load path needs a
+// post-compute barrier (one __syncthreads per k-tile; see the design notes
+// in docs/developer/cuda_kernels.md). The 48KB static watermark picks the
+// resident-CTA hint for __launch_bounds__.
+template <typename Traits, typename LayoutA, typename LayoutB>
+struct Fp8GemmSmem {
+    // Crosswise (direct-load) operands: A ColMajor storage, B RowMajor
+    // storage (B's tag is relative to the canonical [K][N]).
+    static constexpr bool kDirectA = std::is_same_v<LayoutA, ColMajor>;
+    static constexpr bool kDirectB = std::is_same_v<LayoutB, RowMajor>;
+    static constexpr int kRingDepth = Traits::kStages + 1;
+    static constexpr int kBytes =
+        kRingDepth * (Traits::kBlockM + Traits::kBlockN) * Traits::kK;
+    static constexpr int kMinCtas = kBytes <= 48 * 1024 ? 2 : 1;
+};
+
+template <FP8Format Fmt_, int BlockM_, int BlockN_, typename LayoutA_,
+          typename LayoutB_, int WarpM_, int WarpN_, int kK_, int Stages_,
+          int GroupRaster_, bool StreamOut_ = false, bool FastLoop_ = false>
+struct Fp8GemmPolicy {
+    using Traits =
+        Fp8GemmTraits<Fmt_, BlockM_, BlockN_, kK_, Stages_, WarpM_, WarpN_>;
+    using LayoutTagA = LayoutA_;
+    using LayoutTagB = LayoutB_;
+    static constexpr int kGroupRaster = GroupRaster_;
+    static constexpr bool kStreamOut = StreamOut_;
+    static constexpr bool kFastLoop = FastLoop_;
+    using Smem = Fp8GemmSmem<Traits, LayoutA_, LayoutB_>;
+    // Flattened for __launch_bounds__, which takes no dependent type names.
+    static constexpr int kCtaThreads = Traits::kCtaThreads;
+    static constexpr int kMinCtas = Smem::kMinCtas;
+    static constexpr int kSmemBytes = Smem::kBytes;
+};
+
+}  // namespace fp8
+}  // namespace astrai

csrc/kernels/fp8/gemm/scheduler.cuh

@@ -0,0 +1,28 @@
+#pragma once
+// Tile scheduler: the linear CTA id maps to (block_m, block_n) in grouped
+// (L2-friendly) raster — consecutive CTAs share one B column stripe — or
+// plain N-fastest raster (kRasterGroup=0, the measured best for dX's
+// crosswise-B layouts where grouping was neutral).
+
+namespace astrai {
+namespace fp8 {
+
+template <int kRasterGroup>
+struct Fp8GemmTileScheduler {
+    static __device__ int2 tile(const uint3& block, const dim3& blocks) {
+        if constexpr (kRasterGroup > 0) {
+            constexpr int kGroupM = kRasterGroup;
+            const int bid = int(block.y) * int(blocks.x) + int(block.x);
+            const int group_first_m = (bid / (kGroupM * int(blocks.x))) * kGroupM;
+            const int group_rows =
+                min(int(blocks.y) - group_first_m, kGroupM);  // M-tail group is short
+            return int2{group_first_m + bid % group_rows,
+                        (bid % (kGroupM * int(blocks.x))) / group_rows};
+        } else {
+            return int2{int(block.y), int(block.x)};
+        }
+    }
+};
+
+}  // namespace fp8
+}  // namespace astrai

csrc/kernels/fp8/ops.cu

@@ -0,0 +1,307 @@
+// CUDA bindings for the stateless FP8 quantize/GEMM primitives.
+
+#include <ATen/cuda/CUDAContext.h>
+#include <c10/cuda/CUDAGuard.h>
+#include <torch/extension.h>
+
+#include <cstdint>
+#include <mutex>
+#include <unordered_map>
+
+#include "../common/device.cuh"
+#include "gemm.cuh"
+#include "quantize.cuh"
+
+using namespace astrai::fp8;
+
+namespace {
+
+void check_fp8_device(const torch::Tensor& tensor) {
+    static std::mutex mutex;
+    static std::unordered_map<int, bool> supported;
+    const int device = tensor.device().index();
+    {
+        std::lock_guard<std::mutex> lock(mutex);
+        auto it = supported.find(device);
+        if (it != supported.end()) {
+            TORCH_CHECK(it->second, "FP8 MMA requires compute capability 8.9+");
+            return;
+        }
+    }
+    const auto* properties = at::cuda::getDeviceProperties(device);
+    const bool ok = astrai::sm_at_least(
+        properties->major, properties->minor, astrai::kMinSmForFp8Major,
+        astrai::kMinSmForFp8Minor);
+    {
+        std::lock_guard<std::mutex> lock(mutex);
+        supported.emplace(device, ok);
+    }
+    TORCH_CHECK(ok, "FP8 MMA requires compute capability 8.9+");
+}
+
+void check_scale(const torch::Tensor& scale, const torch::Tensor& input) {
+    TORCH_CHECK(scale.is_cuda() && scale.device() == input.device() &&
+                    scale.scalar_type() == torch::kFloat32 && scale.numel() == 1,
+                "scale must be a CUDA float32 scalar on the input device");
+}
+
+// Inner-layout resolution for one GEMM operand. The user flag names the
+// math (0 = last two dims are [rows][contract], 1 = transposed); the
+// storage may independently be a col-major view (.t() of a contiguous
+// buffer), which folds into the returned dispatch flag at zero copy — the
+// kernel's LayoutA/LayoutB tags cover both storages. m/n/k derive from the
+// user flag only. Tensors whose inner dims are neither natural layout fall
+// back to .contiguous().
+bool resolve_operand(const torch::Tensor& t_in, bool flag, int64_t& ld,
+                     int64_t& batch_stride, torch::Tensor& storage) {
+    torch::Tensor t = t_in;
+    bool col_major = false;
+    if (t.stride(-1) != 1) {
+        if (t.stride(-2) == 1) {
+            col_major = true;
+        } else {
+            t = t.contiguous();
+        }
+    }
+    storage = t;
+    ld = col_major ? t.stride(-1) : t.stride(-2);
+    batch_stride = t.dim() == 3 ? t.stride(0) : 0;
+    return flag ^ col_major;
+}
+
+// Dtype dispatch over the unified quantize launcher.
+template <bool Tiled, FP8Format Fmt>
+void launch_for_dtype(const torch::Tensor& x, const FP8QuantizeParams& p,
+                      cudaStream_t stream) {
+    switch (x.scalar_type()) {
+    case torch::kHalf:
+        launch_fp8_quantize<Fmt, __half, Tiled>(p, stream);
+        break;
+    case torch::kFloat32:
+        launch_fp8_quantize<Fmt, float, Tiled>(p, stream);
+        break;
+    default:
+        launch_fp8_quantize<Fmt, __nv_bfloat16, Tiled>(p, stream);
+    }
+}
+
+template <bool Tiled>
+void launch_quantize_for(const torch::Tensor& x, const FP8QuantizeParams& p,
+                         bool e5m2, cudaStream_t stream) {
+    if (e5m2)
+        launch_for_dtype<Tiled, FP8Format::E5M2>(x, p, stream);
+    else
+        launch_for_dtype<Tiled, FP8Format::E4M3>(x, p, stream);
+}
+
+// Shared binding body for the two quantize entry points: RowMajor /
+// Transposed (single output) serve quantize(), Dual (both orientations from
+// one read) serves quantize_dual(). A ring tensor switches
+// on the in-kernel delayed-scaling fold: state layout
+// [hist n | scale | legacy | amax | done-as-int], and the returned amax is
+// the (self-cleaned) persistent slot. Without it, amax is reduced into a
+// fresh buffer armed by a driver memset — cheaper than the zeros() fill
+// kernel.
+py::object quantize_impl(torch::Tensor x, torch::Tensor scale, int64_t fmt,
+                         QuantLayout layout, py::object ring, int64_t hist_idx,
+                         double fp8_max, double pow2_margin) {
+    TORCH_CHECK(x.is_cuda(), "CUDA tensors required");
+    TORCH_CHECK(x.scalar_type() == torch::kBFloat16 ||
+                    x.scalar_type() == torch::kHalf ||
+                    x.scalar_type() == torch::kFloat32,
+                "x must be bf16, fp16 or fp32");
+    TORCH_CHECK(fmt == static_cast<int64_t>(FP8Format::E4M3) ||
+                    fmt == static_cast<int64_t>(FP8Format::E5M2),
+                "unsupported quantization type: expected E4M3 (0) or E5M2 (1)");
+    TORCH_CHECK(layout == QuantLayout::RowMajor || x.dim() >= 2,
+                "transposed quantize layouts need a 2D+ tensor");
+    check_scale(scale, x);
+    check_fp8_device(x);
+    const at::cuda::OptionalCUDAGuard guard(x.device());
+    auto stream = at::cuda::getCurrentCUDAStream();
+    auto input = x.contiguous();
+    auto out_opts = input.options().dtype(
+        fmt ? torch::kFloat8_e5m2 : torch::kFloat8_e4m3fn);
+    torch::Tensor amax;
+    float *ring_hist = nullptr, *ring_scale_out = nullptr;
+    unsigned int* ring_done = nullptr;
+    int ring_len = 0;
+    if (!ring.is_none()) {
+        auto st = ring.cast<torch::Tensor>();
+        TORCH_CHECK(st.is_cuda() && st.dim() == 1 &&
+                        st.scalar_type() == torch::kFloat32,
+                    "ring state must be a 1D float32 CUDA tensor");
+        const int64_t n = st.numel() - 4;
+        TORCH_CHECK(n > 0 && hist_idx >= 0 && hist_idx < n,
+                    "ring state too small or hist_idx out of range");
+        float* base = st.data_ptr<float>();
+        amax = st.narrow(0, n + 2, 1);
+        ring_hist = base;
+        ring_scale_out = base + n;
+        ring_done = reinterpret_cast<unsigned int*>(base + n + 3);
+        ring_len = static_cast<int>(n);
+    } else {
+        amax = torch::empty({1}, input.options().dtype(torch::kFloat32));
+        cudaMemsetAsync(amax.data_ptr(), 0, sizeof(float), stream.stream());
+    }
+
+    FP8QuantizeParams p;
+    p.input_ptr = input.data_ptr();
+    p.scale = scale.data_ptr<float>();
+    p.amax = amax.data_ptr<float>();
+    if (ring_hist) {
+        p.fold_ring = true;
+        p.hist = ring_hist;
+        p.scale_out = ring_scale_out;
+        p.done = ring_done;
+        p.hist_len = ring_len;
+        p.hist_idx = static_cast<int>(hist_idx);
+        p.fp8_max = static_cast<float>(fp8_max);
+        p.pow2_margin = static_cast<float>(pow2_margin);
+    }
+    p.total = static_cast<int>(input.numel());
+    p.out_layout = layout;
+    p.rows = static_cast<int>(input.size(-2));
+    p.cols = static_cast<int>(input.size(-1));
+    torch::Tensor output, output_t;
+    if (layout != QuantLayout::Transposed) {
+        output = torch::empty_like(input, out_opts);
+        p.output_ptr = output.data_ptr();
+    }
+    if (layout != QuantLayout::RowMajor) {
+        output_t = torch::empty({input.size(-1), input.size(-2)}, out_opts);
+        p.output_transposed_ptr = output_t.data_ptr();
+    }
+    const bool e5m2 = fmt == static_cast<int64_t>(FP8Format::E5M2);
+    if (layout == QuantLayout::RowMajor)
+        launch_quantize_for<false>(input, p, e5m2, stream.stream());
+    else
+        launch_quantize_for<true>(input, p, e5m2, stream.stream());
+    C10_CUDA_CHECK(cudaGetLastError());
+    if (layout == QuantLayout::Dual)
+        return py::make_tuple(output, output_t, amax);
+    return py::make_tuple(
+        layout == QuantLayout::Transposed ? output_t : output, amax);
+}
+
+}  // namespace
+
+// Single-orientation quantize binding: row-major x8, or its [cols][rows]
+// transpose when transposed is set — the K-contiguous operand orientation
+// NT GEMMs want. Returns (x8|x8T, amax).
+py::object quantize(torch::Tensor x, torch::Tensor scale, int64_t fmt,
+                    bool transposed, py::object ring, int64_t hist_idx,
+                    double fp8_max, double pow2_margin) {
+    const QuantLayout layout =
+        transposed ? QuantLayout::Transposed : QuantLayout::RowMajor;
+    return quantize_impl(x, scale, fmt, layout, ring, hist_idx, fp8_max,
+                         pow2_margin);
+}
+
+// Dual-orientation quantize binding: one read of x produces both the
+// row-major x8 and its transpose (plus amax), for tensors consumed by GEMMs
+// in both orientations (backward g). Returns (x8, x8T, amax).
+py::object quantize_dual(torch::Tensor x, torch::Tensor scale, int64_t fmt,
+                         py::object ring, int64_t hist_idx, double fp8_max,
+                         double pow2_margin) {
+    return quantize_impl(x, scale, fmt, QuantLayout::Dual, ring, hist_idx,
+                         fp8_max, pow2_margin);
+}
+
+torch::Tensor mm_fp8(torch::Tensor a, torch::Tensor b, torch::Tensor scale,
+                     bool trans_a, bool trans_b, py::object bias) {
+    TORCH_CHECK(a.is_cuda() && b.is_cuda(), "CUDA tensors required");
+    TORCH_CHECK(a.scalar_type() == torch::kFloat8_e4m3fn ||
+                    a.scalar_type() == torch::kFloat8_e5m2,
+                "a and b must be fp8");
+    TORCH_CHECK(a.scalar_type() == b.scalar_type(), "a and b must share format");
+    TORCH_CHECK((a.dim() == 2 || a.dim() == 3) &&
+                    (b.dim() == 2 || b.dim() == 3),
+                "a and b must be 2D or 3D (batched)");
+    TORCH_CHECK(a.device() == b.device(), "a and b must share device");
+    // Python None and an omitted argument both mean "no bias" — an undefined
+    // tensor below. (py::isinstance<torch::Tensor> is false for real tensors
+    // here — torch's caster registers no pybind type info — so validate by
+    // attempting the cast itself.)
+    torch::Tensor bias_t;
+    if (!bias.is_none()) {
+        try {
+            bias_t = bias.cast<torch::Tensor>();
+        } catch (const py::cast_error&) {
+            TORCH_CHECK(false, "bias must be a torch.Tensor or None");
+        }
+    }
+    check_scale(scale, a);
+    check_fp8_device(a);
+    const at::cuda::OptionalCUDAGuard guard(a.device());
+    auto stream = at::cuda::getCurrentCUDAStream();
+
+    // Batched operands follow matmul broadcast rules: 2D acts as a batch
+    // of 1; a size-1 batch broadcasts across the other side (stride 0).
+    const int64_t batch_a = a.dim() == 3 ? a.size(0) : 1;
+    const int64_t batch_b = b.dim() == 3 ? b.size(0) : 1;
+    TORCH_CHECK(batch_a == batch_b || batch_a == 1 || batch_b == 1,
+                "batch dim mismatch (got ", batch_a, " and ", batch_b, ")");
+    const int64_t batch = std::max(batch_a, batch_b);
+    TORCH_CHECK(batch <= 65535, "batch dim exceeds the grid.z launch limit");
+
+    torch::Tensor a_st, b_st;
+    int64_t a_ld, b_ld, a_bstride, b_bstride;
+    const bool tag_a = resolve_operand(a, trans_a, a_ld, a_bstride, a_st);
+    const bool tag_b = resolve_operand(b, trans_b, b_ld, b_bstride, b_st);
+    // GEMM dims from the user flags; storage layout never swaps them.
+    const int64_t m = trans_a ? a.size(-1) : a.size(-2);
+    const int64_t k = trans_a ? a.size(-2) : a.size(-1);
+    const int64_t n = trans_b ? b.size(-2) : b.size(-1);
+    TORCH_CHECK(k == (trans_b ? b.size(-1) : b.size(-2)), "inner dim mismatch");
+
+    const bool batched_out = a.dim() == 3 || b.dim() == 3;
+    torch::Tensor output =
+        batched_out
+            ? torch::empty({batch, m, n}, a.options().dtype(torch::kBFloat16))
+            : torch::empty({m, n}, a.options().dtype(torch::kBFloat16));
+    FP8Params p;
+    p.a_ptr = a_st.data_ptr();
+    p.b_ptr = b_st.data_ptr();
+    p.out_ptr = output.data_ptr();
+    p.scale = scale.data_ptr<float>();
+    p.m = static_cast<int>(m);
+    p.n = static_cast<int>(n);
+    p.k = static_cast<int>(k);
+    p.a_ld = static_cast<int>(a_ld);
+    p.b_ld = static_cast<int>(b_ld);
+    // Fused epilogue bias (bf16, broadcast over rows and batches). An
+    // undefined or 0-element tensor keeps the plain scaled output.
+    if (bias_t.defined() && bias_t.numel() > 0) {
+        TORCH_CHECK(bias_t.is_cuda() && bias_t.scalar_type() == torch::kBFloat16,
+                    "fp8 gemm bias must be a CUDA bf16 tensor");
+        TORCH_CHECK(bias_t.dim() == 1 && bias_t.size(0) == n,
+                    "fp8 gemm bias must be 1D of length n=", n);
+        TORCH_CHECK(bias_t.is_contiguous(), "fp8 gemm bias must be contiguous");
+        p.bias_ptr = bias_t.data_ptr();
+    }
+    p.batch = static_cast<int>(batch);
+    p.a_batch_stride = (batch_a == 1 && batch > 1) ? 0 : a_bstride;
+    p.b_batch_stride = (batch_b == 1 && batch > 1) ? 0 : b_bstride;
+    p.out_batch_stride = m * n;
+    if (a.scalar_type() == torch::kFloat8_e4m3fn)
+        gemm<FP8Format::E4M3>(p, stream.stream(), tag_a, tag_b);
+    else
+        gemm<FP8Format::E5M2>(p, stream.stream(), tag_a, tag_b);
+    C10_CUDA_CHECK(cudaGetLastError());
+    return output;
+}
+
+PYBIND11_MODULE(TORCH_EXTENSION_NAME, m) {
+    m.def("quantize", &quantize, py::arg("x"), py::arg("scale"),
+          py::arg("fmt"), py::arg("transposed") = false,
+          py::arg("ring") = py::none(), py::arg("hist_idx") = 0,
+          py::arg("fp8_max") = 448.0, py::arg("pow2_margin") = 1.0);
+    m.def("quantize_dual", &quantize_dual, py::arg("x"), py::arg("scale"),
+          py::arg("fmt"), py::arg("ring") = py::none(),
+          py::arg("hist_idx") = 0, py::arg("fp8_max") = 448.0,
+          py::arg("pow2_margin") = 1.0);
+    m.def("mm_fp8", &mm_fp8, py::arg("a"), py::arg("b"), py::arg("scale"),
+          py::arg("trans_a") = false, py::arg("trans_b") = false,
+          py::arg("bias") = py::none());
+}

csrc/kernels/fp8/quantize.cuh

@@ -0,0 +1,311 @@
+#pragma once
+// FP8 quantize device code — pure CUDA, no torch: kernels take the
+// FP8QuantizeParams POD, format and input type ride on template parameters,
+// and the launcher is shared by the torch binding and the C tests.
+
+#include <cuda_bf16.h>
+#include <cuda_fp16.h>
+#include <cuda_fp8.h>
+#include <cuda_runtime.h>
+#include <cstdint>
+
+#include "common.h"
+#include "../common/reduce.cuh"
+
+namespace astrai {
+namespace fp8 {
+
+// Input element type traits: one element -> float, the unpack of one
+// 16-byte load into kVecElems floats, and a native 2-element pair load.
+template <typename InT>
+struct quant_in_traits;
+
+template <>
+struct quant_in_traits<__nv_bfloat16> {
+    static constexpr int kVecElems = 8;
+    static __device__ __forceinline__ float to_float(__nv_bfloat16 v) {
+        return __bfloat162float(v);
+    }
+    static __device__ __forceinline__ void load_vec(const uint4& raw,
+                                                    float* f) {
+        const __nv_bfloat162* b2 =
+            reinterpret_cast<const __nv_bfloat162*>(&raw);
+#pragma unroll
+        for (int j = 0; j < 4; ++j) {
+            const float2 p = __bfloat1622float2(b2[j]);
+            f[2 * j] = p.x;
+            f[2 * j + 1] = p.y;
+        }
+    }
+    static __device__ __forceinline__ void load_pair(const __nv_bfloat16* p,
+                                                     float* f) {
+        const float2 v = __bfloat1622float2(
+            *reinterpret_cast<const __nv_bfloat162*>(p));
+        f[0] = v.x;
+        f[1] = v.y;
+    }
+};
+
+template <>
+struct quant_in_traits<__half> {
+    static constexpr int kVecElems = 8;
+    static __device__ __forceinline__ float to_float(__half v) {
+        return __half2float(v);
+    }
+    static __device__ __forceinline__ void load_vec(const uint4& raw,
+                                                    float* f) {
+        const __half2* h2 = reinterpret_cast<const __half2*>(&raw);
+#pragma unroll
+        for (int j = 0; j < 4; ++j) {
+            const float2 p = __half22float2(h2[j]);
+            f[2 * j] = p.x;
+            f[2 * j + 1] = p.y;
+        }
+    }
+    static __device__ __forceinline__ void load_pair(const __half* p,
+                                                     float* f) {
+        const float2 v =
+            __half22float2(*reinterpret_cast<const __half2*>(p));
+        f[0] = v.x;
+        f[1] = v.y;
+    }
+};
+
+template <>
+struct quant_in_traits<float> {
+    static constexpr int kVecElems = 4;
+    static __device__ __forceinline__ float to_float(float v) { return v; }
+    static __device__ __forceinline__ void load_vec(const uint4& raw,
+                                                    float* f) {
+        const unsigned* w = reinterpret_cast<const unsigned*>(&raw);
+#pragma unroll
+        for (int j = 0; j < 4; ++j) f[j] = __uint_as_float(w[j]);
+    }
+    static __device__ __forceinline__ void load_pair(const float* p,
+                                                     float* f) {
+        f[0] = p[0];
+        f[1] = p[1];
+    }
+};
+
+// One float -> one fp8 byte (round-nearest-even + satfinite).
+template <FP8Format Fmt>
+__device__ __forceinline__ uint8_t cvt_fp8(float v) {
+    if constexpr (Fmt == FP8Format::E5M2)
+        return __nv_fp8_e5m2(v).__x;
+    else
+        return __nv_fp8_e4m3(v).__x;
+}
+
+// One float pair -> one packed fp8x2 word (round-nearest-even + satfinite).
+template <FP8Format Fmt>
+__device__ __forceinline__ unsigned cvt_fp8x2(float a, float b) {
+    constexpr __nv_fp8_interpretation_t kFmt =
+        Fmt == FP8Format::E5M2 ? __NV_E5M2 : __NV_E4M3;
+    return static_cast<unsigned>(__nv_cvt_float2_to_fp8x2(
+        make_float2(a, b), __NV_SATFINITE, kFmt));
+}
+
+// Block-wide amax reduce -> one atomic per block: warp-reduce, park one
+// value per warp, thread 0 folds. kWarps must cover the block's warp count.
+// With p.fold_ring, the last-finishing block additionally folds the final
+// amax into the history window and publishes the next scale (atomicAdd
+// ticket + fences), re-zeroing the amax slot and the counter for the next
+// launch — the host-side delayed-scaling update chain disappears.
+template <int kWarps>
+__device__ __forceinline__ void publish_amax(const FP8QuantizeParams& p,
+                                             float v) {
+    v = warp_reduce_max(v);
+    __shared__ float slots[kWarps];
+    const int tid = threadIdx.y * blockDim.x + threadIdx.x;
+    if ((tid & 31) == 0) slots[tid >> 5] = v;
+    __syncthreads();
+    if (tid == 0) {
+#pragma unroll
+        for (int w = 1; w < kWarps; ++w) v = fmaxf(v, slots[w]);
+        atomic_max_float(p.amax, v);
+        if (!p.fold_ring) return;
+        __threadfence();
+        const unsigned int ticket = atomicAdd(p.done, 1u);
+        __threadfence();
+        if (ticket != gridDim.x - 1u) return;
+        p.hist[p.hist_idx] = *p.amax;
+        float peak = p.hist[0];
+        for (int i = 1; i < p.hist_len; ++i) peak = fmaxf(peak, p.hist[i]);
+        *p.scale_out = fmaxf(peak / p.fp8_max / p.pow2_margin, 1e-12f);
+        *p.amax = 0.0f;
+        *p.done = 0u;
+    }
+}
+
+// Elementwise quantize kernel (QuantLayout::RowMajor): vectorized 16B loads
+// -> fp8 stores, fused amax over raw values.
+template <FP8Format Fmt, typename InT>
+__global__ void fp8_quantize_kernel(FP8QuantizeParams p) {
+    const float mult = *p.scale;
+    const auto* x = static_cast<const InT*>(p.input_ptr);
+    uint8_t* x8 = static_cast<uint8_t*>(p.output_ptr);
+    float local_amax = 0.0f;
+    const int64_t stride = (int64_t)blockDim.x * gridDim.x;
+
+    // One 16B load -> kVecElems bytes per step. Torch allocations are >=16B
+    // aligned, so element 0 keeps the uint4 access natural; a misaligned
+    // base (odd storage offset view) falls to the scalar tail via
+    // total_vec = 0.
+    constexpr int kVecElems = quant_in_traits<InT>::kVecElems;
+    const bool aligned =
+        ((reinterpret_cast<uintptr_t>(x) |
+          reinterpret_cast<uintptr_t>(x8)) &
+         15) == 0;
+    const int64_t total_vec = aligned ? p.total / kVecElems : 0;
+    const uint4* xv = reinterpret_cast<const uint4*>(x);
+    for (int64_t i = blockIdx.x * blockDim.x + threadIdx.x; i < total_vec;
+         i += stride) {
+        float f[kVecElems];
+        quant_in_traits<InT>::load_vec(xv[i], f);
+        // One 32-bit word packs two fp8x2 pairs (4 elements).
+        unsigned packed[kVecElems / 4];
+#pragma unroll
+        for (int j = 0; j < kVecElems / 4; ++j) {
+            local_amax = fmaxf(
+                local_amax,
+                fmaxf(fmaxf(fabsf(f[4 * j]), fabsf(f[4 * j + 1])),
+                      fmaxf(fabsf(f[4 * j + 2]), fabsf(f[4 * j + 3]))));
+            const unsigned lo =
+                cvt_fp8x2<Fmt>(f[4 * j] * mult, f[4 * j + 1] * mult);
+            const unsigned hi =
+                cvt_fp8x2<Fmt>(f[4 * j + 2] * mult, f[4 * j + 3] * mult);
+            packed[j] = (lo & 0xffffu) | (hi << 16);
+        }
+        if constexpr (kVecElems == 8)
+            reinterpret_cast<uint2*>(x8)[i] = make_uint2(packed[0], packed[1]);
+        else
+            reinterpret_cast<unsigned*>(x8)[i] = packed[0];
+    }
+    // Scalar tail (and full fallback for misaligned bases).
+    for (int64_t i = total_vec * kVecElems + blockIdx.x * blockDim.x +
+                      threadIdx.x;
+         i < p.total; i += stride) {
+        const float v = quant_in_traits<InT>::to_float(x[i]);
+        local_amax = fmaxf(local_amax, fabsf(v));
+        x8[i] = cvt_fp8<Fmt>(v * mult);
+    }
+    if (p.amax) publish_amax<8>(p, local_amax);
+}
+
+// Tiled transpose quantize (QuantLayout::Transposed/Dual): reads the
+// [rows][cols] input
+// once and writes the fp8 bytes transposed ([cols][rows], so the contract
+// dim lands K-contiguous for NT GEMM operands) and, in mode 2, the row-major
+// copy too. 64x32 tiles, one native pair load per row (a full 128B warp
+// read); rows whose pair is unaligned or ragged (odd widths, misaligned
+// bases) fall back to element loads in place. Staging goes through a byte
+// tile whose pitch keeps the store stride coprime with the 32 banks.
+// (+25-35% over the former 32x32 scalar kernel on sub-4M tensors; ~5%
+// slower once DRAM-saturated — accepted for the single-kernel shape.)
+template <FP8Format Fmt, typename InT>
+__global__ void fp8_quantize_tiled_kernel(FP8QuantizeParams p) {
+    constexpr int kTileC = 64, kTileR = 32;
+    // 34B pitch: staging stride is 17 words (coprime with the 32 banks) so
+    // the pair-byte stores stay conflict-free, and the byte-wise consume
+    // reads still span distinct words.
+    __shared__ uint8_t tile[kTileC][kTileR + 2];
+    const float mult = *p.scale;
+    const auto* x = static_cast<const InT*>(p.input_ptr);
+    const int r0 = blockIdx.y * kTileR;
+    const int c0 = blockIdx.x * kTileC;
+    const int r = r0 + threadIdx.y * 4;
+    const int c = c0 + threadIdx.x * 2;  // cols even => the pair is in-bounds
+
+    uint8_t q[4][2];
+    float local_amax = 0.0f;
+    // Vectorize the pair when both elements are in-bounds and the native
+    // 2-element load is aligned; odd widths, misaligned bases and ragged
+    // edges fall back to element loads row by row.
+    constexpr int kPairAlign = 2 * (int)sizeof(InT);
+#pragma unroll
+    for (int j = 0; j < 4; ++j) {
+        q[j][0] = 0;
+        q[j][1] = 0;
+        if (r + j < p.rows && c < p.cols) {
+            const InT* a = x + (int64_t)(r + j) * p.cols + c;
+            if (c + 1 < p.cols &&
+                (reinterpret_cast<uintptr_t>(a) & (kPairAlign - 1)) == 0) {
+                float f[2];
+                quant_in_traits<InT>::load_pair(a, f);
+#pragma unroll
+                for (int k = 0; k < 2; ++k) {
+                    local_amax = fmaxf(local_amax, fabsf(f[k]));
+                    q[j][k] = cvt_fp8<Fmt>(f[k] * mult);
+                }
+            } else {
+                const float v0 = quant_in_traits<InT>::to_float(a[0]);
+                local_amax = fmaxf(local_amax, fabsf(v0));
+                q[j][0] = cvt_fp8<Fmt>(v0 * mult);
+                if (c + 1 < p.cols) {
+                    const float v1 = quant_in_traits<InT>::to_float(a[1]);
+                    local_amax = fmaxf(local_amax, fabsf(v1));
+                    q[j][1] = cvt_fp8<Fmt>(v1 * mult);
+                }
+            }
+        }
+    }
+    if (p.out_layout == QuantLayout::Dual) {
+        uint8_t* out = static_cast<uint8_t*>(p.output_ptr);
+#pragma unroll
+        for (int j = 0; j < 4; ++j)
+            if (r + j < p.rows && c < p.cols) {
+                uint8_t* o = out + (int64_t)(r + j) * p.cols + c;
+                const int64_t off = (int64_t)(r + j) * p.cols + c;
+                if (c + 1 < p.cols && (off & 1) == 0)
+                    *reinterpret_cast<unsigned short*>(o) =
+                        (unsigned short)(q[j][0] | (q[j][1] << 8));
+                else {
+                    o[0] = q[j][0];
+                    if (c + 1 < p.cols) o[1] = q[j][1];
+                }
+            }
+    }
+#pragma unroll
+    for (int j = 0; j < 4; ++j)
+#pragma unroll
+        for (int k = 0; k < 2; ++k)
+            tile[threadIdx.x * 2 + k][threadIdx.y * 4 + j] = q[j][k];
+    __syncthreads();
+    // Transposed scatter: output element (c, r) lives at c * rows + r;
+    // threadIdx.x tracks r so each warp writes one contiguous run. tile is
+    // [col][row]; warp y walks 8 columns, threads read down one column.
+    uint8_t* out_t = static_cast<uint8_t*>(p.output_transposed_ptr);
+#pragma unroll
+    for (int i = 0; i < 8; ++i) {
+        const int oc = c0 + threadIdx.y * 8 + i;
+        if (oc < p.cols && r0 + threadIdx.x < p.rows)
+            out_t[(int64_t)oc * p.rows + r0 + threadIdx.x] =
+                tile[threadIdx.y * 8 + i][threadIdx.x];
+    }
+    if (p.amax) publish_amax<8>(p, local_amax);
+}
+
+// Unified quantize launcher: Tiled selects the transpose kernel
+// (QuantLayout::Transposed/Dual) over the vectorized elementwise one. The
+// transpose kernel vectorizes
+// pair loads in-kernel and falls back to scalar loads at unaligned/ragged
+// rows, so the host side picks only the grid.
+template <FP8Format Fmt, typename InT, bool Tiled = false>
+void launch_fp8_quantize(const FP8QuantizeParams& p, cudaStream_t stream) {
+    if constexpr (Tiled) {
+        const dim3 grid((p.cols + 63) / 64, (p.rows + 31) / 32);
+        if (grid.x == 0 || grid.y == 0) return;
+        fp8_quantize_tiled_kernel<Fmt, InT><<<grid, dim3(32, 8), 0, stream>>>(p);
+    } else {
+        constexpr int kThreads = 256;
+        constexpr int kVecElems = quant_in_traits<InT>::kVecElems;
+        // Grid-stride loops: any grid >= 1 is correct; one block per 256
+        // vectors plus the tail block covers tiny and misaligned tensors.
+        const int64_t blocks = 1 + p.total / (kVecElems * kThreads);
+        fp8_quantize_kernel<Fmt, InT><<<blocks, kThreads, 0, stream>>>(p);
+    }
+}
+
+}  // namespace fp8
+}  // namespace astrai

csrc/kernels/rotary/rotary_emb.cu

@@ -7,13 +7,12 @@ __global__ void rotary_emb_kernel(
     const __nv_bfloat16* __restrict__ x,
     const float* __restrict__ freqs_cis,
     __nv_bfloat16* __restrict__ out,
-    int batch,
-    int seq_len,
+    int n_tokens,
     int n_heads,
     int head_dim
 ) {
     const int half_dim = head_dim >> 1;
-    const int total = batch * seq_len * n_heads * half_dim;
+    const int total = n_tokens * n_heads * half_dim;
 
     for (int idx = blockIdx.x * blockDim.x + threadIdx.x;
          idx < total;
@@ -23,11 +22,10 @@ __global__ void rotary_emb_kernel(
         int tmp = idx / half_dim;
         int head = tmp % n_heads;
         tmp /= n_heads;
-        int seq = tmp % seq_len;
-        int b = tmp / seq_len;
+        int token = tmp;
 
-        int x_offset = ((b * seq_len + seq) * n_heads + head) * head_dim + (pair << 1);
-        int cs_offset = ((b * seq_len + seq) * half_dim + pair) * 2;
+        int x_offset = (token * n_heads + head) * head_dim + (pair << 1);
+        int cs_offset = (token * half_dim + pair) * 2;
 
         __nv_bfloat162 x_pair = *reinterpret_cast<const __nv_bfloat162*>(x + x_offset);
         float x_even = __bfloat162float(__low2bfloat16(x_pair));
@@ -54,27 +52,28 @@ torch::Tensor rotary_emb(
     TORCH_CHECK(x.is_cuda(), "x must be on CUDA");
     TORCH_CHECK(freqs_cis.is_cuda(), "freqs_cis must be on CUDA");
     TORCH_CHECK(x.scalar_type() == torch::kBFloat16, "x must be bf16");
-    TORCH_CHECK(x.dim() == 4, "x must be 4D [batch, seq_len, n_heads, head_dim]");
+    TORCH_CHECK(x.dim() == 3 || x.dim() == 4,
+                "x must be [tokens, n_heads, head_dim] or "
+                "[batch, seq_len, n_heads, head_dim]");
     TORCH_CHECK(x.is_contiguous(), "x must be contiguous");
-    TORCH_CHECK(freqs_cis.dim() == 4, "freqs_cis must be 4D [batch, seq_len, dim/2, 2]");
+    TORCH_CHECK(freqs_cis.dim() == x.dim(), "freqs_cis rank must match x rank");
     TORCH_CHECK(freqs_cis.is_contiguous(), "freqs_cis must be contiguous");
     TORCH_CHECK(freqs_cis.scalar_type() == torch::kFloat32, "freqs_cis must be f32");
 
-    int batch = x.size(0);
-    int seq_len = x.size(1);
-    int n_heads = x.size(2);
-    int head_dim = x.size(3);
+    int n_tokens = x.dim() == 3 ? x.size(0) : x.size(0) * x.size(1);
+    int n_heads = x.size(x.dim() - 2);
+    int head_dim = x.size(x.dim() - 1);
 
     TORCH_CHECK(head_dim % 2 == 0, "head_dim must be even");
-    TORCH_CHECK(freqs_cis.size(0) == batch, "freqs_cis batch mismatch");
-    TORCH_CHECK(freqs_cis.size(1) == seq_len, "freqs_cis seq_len mismatch");
-    TORCH_CHECK(freqs_cis.size(2) == head_dim / 2, "freqs_cis dim/2 mismatch");
-    TORCH_CHECK(freqs_cis.size(3) == 2, "freqs_cis last dim must be 2 [cos, sin]");
+    TORCH_CHECK(freqs_cis.numel() == (int64_t)n_tokens * head_dim,
+                "freqs_cis token or rotary dimension mismatch");
+    TORCH_CHECK(freqs_cis.size(-2) == head_dim / 2, "freqs_cis dim/2 mismatch");
+    TORCH_CHECK(freqs_cis.size(-1) == 2, "freqs_cis last dim must be 2 [cos, sin]");
 
     auto out = torch::empty_like(x);
 
     int half_dim = head_dim / 2;
-    int total = batch * seq_len * n_heads * half_dim;
+    int total = n_tokens * n_heads * half_dim;
     int block = 256;
     int grid = std::min((total + block - 1) / block, 1024);
 
@@ -82,7 +81,7 @@ torch::Tensor rotary_emb(
         reinterpret_cast<const __nv_bfloat16*>(x.data_ptr()),
         freqs_cis.data_ptr<float>(),
         reinterpret_cast<__nv_bfloat16*>(out.data_ptr()),
-        batch, seq_len, n_heads, head_dim
+        n_tokens, n_heads, head_dim
     );
     C10_CUDA_CHECK(cudaGetLastError());
 
@@ -93,6 +92,6 @@ PYBIND11_MODULE(TORCH_EXTENSION_NAME, m) {
     m.def("rotary_emb", &rotary_emb,
         py::arg("x"),
         py::arg("freqs_cis"),
-        "Fused rotary embedding (bf16 x, f32 freqs_cis [b,s,d/2,2], bf16 out)"
+        "Fused rotary embedding for packed 3D or dense 4D tensors"
     );
 }

csrc/tests/attn_paged_test.cu

@@ -7,7 +7,32 @@
 #include <cstring>
 #include <vector>
 #include "test_utils.cuh"
-#include "../kernels/attn_dispatchers.cuh"
+#include "../kernels/attention/dispatchers.cuh"
+
+using namespace astrai::attention;
+
+struct PagedDecodeDispatch { AttentionParams<bf16>& p; template<int H> void operator()() { dispatch_paged_decode<H>(p, 0); } };
+struct PagedPrefillDispatch { AttentionParams<bf16>& p; template<int H> void operator()() { dispatch_paged_prefill<H>(p, 0); } };
+
+static int make_q_tile_mapping(const std::vector<int>& q_lens,
+                               int** d_batch, int** d_tile) {
+    constexpr int ROWS = 64;
+    std::vector<int> h_batch;
+    std::vector<int> h_tile;
+    for (int b = 0; b < (int)q_lens.size(); ++b) {
+        int n_tiles = (q_lens[b] + ROWS - 1) / ROWS;
+        for (int tile = 0; tile < n_tiles; ++tile) {
+            h_batch.push_back(b);
+            h_tile.push_back(tile);
+        }
+    }
+    size_t bytes = h_batch.size() * sizeof(int);
+    cudaMalloc(d_batch, bytes);
+    cudaMalloc(d_tile, bytes);
+    cudaMemcpy(*d_batch, h_batch.data(), bytes, cudaMemcpyHostToDevice);
+    cudaMemcpy(*d_tile, h_tile.data(), bytes, cudaMemcpyHostToDevice);
+    return (int)h_batch.size();
+}
 
 // ---- CPU reference: paged decode with variable seq_lens ----
 // Q: [B, Hq, D], K/V pool: [pool_size, Hkv, D]
@@ -15,7 +40,7 @@
 // kv_indptr: [B+1].  mask: [B, max_seq_len] bool (True=keep) or NULL.
 static void cpu_paged_decode_ref(
     const float* Q, const float* K_pool, const float* V_pool,
-    const int64_t* req_to_token, const int64_t* req_pool_indices,
+    const int* req_to_token, const int* req_pool_indices,
     const int* kv_indptr, const bool* mask, int mask_b_stride,
     int B, int Hq, int Hkv, int D, int max_ctx_len,
     float* O)
@@ -24,7 +49,7 @@ static void cpu_paged_decode_ref(
     int n_rep = Hq / Hkv;
     for (int b = 0; b < B; b++) {
         int seq_len = kv_indptr[b + 1] - kv_indptr[b];
-        int64_t req_idx = req_pool_indices[b];
+        int req_idx = req_pool_indices[b];
         #pragma omp parallel for schedule(dynamic)
         for (int h = 0; h < Hq; h++) {
             int kv_h = h / n_rep;
@@ -32,7 +57,7 @@ static void cpu_paged_decode_ref(
             float accum[256] = {0.0f};
             for (int kj = 0; kj < seq_len; kj++) {
                 if (mask && !mask[b * mask_b_stride + kj]) continue;
-                int64_t slot = req_to_token[req_idx * max_ctx_len + kj];
+                int slot = req_to_token[req_idx * max_ctx_len + kj];
                 float dot = 0.0f;
                 for (int d = 0; d < D; d++)
                     dot += Q[(b * Hq + h) * D + d] *
@@ -63,9 +88,9 @@ static void cpu_paged_decode_ref(
 //   attention mask on top of the (unused) causal logic.
 static void cpu_paged_prefill_ref(
     const float* Q, const float* K_pool, const float* V_pool,
-    const int64_t* req_to_token, const int64_t* req_pool_indices,
+    const int* req_to_token, const int* req_pool_indices,
     const int* kv_indptr, const int* qo_indptr,
-    const bool* mask, int mask_q_stride, int mask_kv_stride,
+    const bool* mask, int mask_l_stride, int mask_kv_stride,
     int B, int Hq, int Hkv, int D, int max_ctx_len, int causal,
     float* O)
 {
@@ -75,7 +100,7 @@ static void cpu_paged_prefill_ref(
         int seq_len = kv_indptr[b + 1] - kv_indptr[b];
         int q_len = qo_indptr[b + 1] - qo_indptr[b];
         int causal_off = seq_len - q_len;
-        int64_t req_idx = req_pool_indices[b];
+        int req_idx = req_pool_indices[b];
         #pragma omp parallel for collapse(2) schedule(dynamic)
         for (int h = 0; h < Hq; h++) {
             for (int qi = 0; qi < q_len; qi++) {
@@ -84,9 +109,9 @@ static void cpu_paged_prefill_ref(
                 float accum[256] = {0.0f};
                 int lim = causal ? min(seq_len, causal_off + qi + 1) : seq_len;
                 for (int kj = 0; kj < lim; kj++) {
-                    if (mask && !mask[b * mask_q_stride * mask_kv_stride
+                    if (mask && !mask[b * mask_l_stride * mask_kv_stride
                                      + qi * mask_kv_stride + kj]) continue;
-                    int64_t slot = req_to_token[req_idx * max_ctx_len + kj];
+                    int slot = req_to_token[req_idx * max_ctx_len + kj];
                     float dot = 0.0f;
                     for (int d = 0; d < D; d++)
                         dot += Q[(qo_indptr[b] + qi) * Hq * D + h * D + d] *
@@ -127,14 +152,15 @@ inline void print_paged_row(const char* cfg, float max_err, bool pass) {
 // ======================================================================
 template <int HEAD_DIM>
 static int run_decode_test(int B, int Hq, int Hkv, int max_seq,
-                            int causal, int seed) {
+                            int causal, int seed, int context_capacity = 0,
+                            int fixed_seq_len = 0) {
     // Variable seq_lens per request
     srand(seed);
     std::vector<int> seq_lens(B);
     for (int b = 0; b < B; b++)
-        seq_lens[b] = 8 + rand() % (max_seq - 8);
+        seq_lens[b] = fixed_seq_len ? fixed_seq_len : 8 + rand() % (max_seq - 8);
     int max_sl = *std::max_element(seq_lens.begin(), seq_lens.end());
-    int max_ctx = max_sl + 16;
+    int max_ctx = context_capacity ? context_capacity : max_sl + 16;
 
     int pool_size = B * max_ctx;
     int num_reqs = B + 4;
@@ -145,14 +171,14 @@ static int run_decode_test(int B, int Hq, int Hkv, int max_seq,
 
     size_t sz_q  = (size_t)B * Hq * HEAD_DIM * sizeof(bf16);
     size_t sz_kv = (size_t)pool_size * Hkv * HEAD_DIM * sizeof(bf16);
-    size_t sz_rtt = (size_t)num_reqs * max_ctx * sizeof(int64_t);
-    size_t sz_rpi = (size_t)B * sizeof(int64_t);
+    size_t sz_rtt = (size_t)num_reqs * max_ctx * sizeof(int);
+    size_t sz_rpi = (size_t)B * sizeof(int);
     size_t sz_kvi = (size_t)(B + 1) * sizeof(int);
     size_t sz_op = (size_t)B * Hq * MAX_SPLITS * HEAD_DIM * sizeof(float);
     size_t sz_ml = (size_t)B * Hq * MAX_SPLITS * 2 * sizeof(float);
 
     bf16 *d_q, *d_o, *d_k_pool, *d_v_pool;
-    int64_t *d_rtt, *d_rpi;
+    int *d_rtt, *d_rpi;
     int *d_kvi;
     float *d_op, *d_ml;
     cudaMalloc(&d_q, sz_q); cudaMalloc(&d_o, sz_q);
@@ -177,7 +203,7 @@ static int run_decode_test(int B, int Hq, int Hkv, int max_seq,
     cudaMemcpy(d_v_pool, h_v_pool, sz_kv, cudaMemcpyHostToDevice);
 
     // req_to_token: assign unique slots per request (scattered, not contiguous)
-    int64_t* h_rtt = (int64_t*)malloc(sz_rtt);
+    int* h_rtt = (int*)malloc(sz_rtt);
     int next_slot = 0;
     for (int r = 0; r < num_reqs; r++)
         for (int p = 0; p < max_ctx; p++) {
@@ -187,7 +213,7 @@ static int run_decode_test(int B, int Hq, int Hkv, int max_seq,
     cudaMemcpy(d_rtt, h_rtt, sz_rtt, cudaMemcpyHostToDevice);
 
     // req_pool_indices: pick B random request rows
-    int64_t* h_rpi = (int64_t*)malloc(sz_rpi);
+    int* h_rpi = (int*)malloc(sz_rpi);
     for (int b = 0; b < B; b++) h_rpi[b] = b;
     cudaMemcpy(d_rpi, h_rpi, sz_rpi, cudaMemcpyHostToDevice);
 
@@ -212,21 +238,21 @@ static int run_decode_test(int B, int Hq, int Hkv, int max_seq,
                             B, Hq, Hkv, HEAD_DIM, max_ctx, h_o_ref);
 
     // Kernel launch
-    AttentionParams<bf16> p;
+    AttentionParams<bf16> p = {};
     p.batch = B; p.q_head = Hq; p.kv_head = Hkv;
-    p.head_dim = HEAD_DIM; p.total_q = B;
-    p.q_stride_l = Hq * HEAD_DIM; p.q_stride_h = HEAD_DIM; p.q_stride_d = 1;
-    p.max_context_len = max_ctx; p.max_seq_len = max_sl;
+    p.head_dim = HEAD_DIM;
+    p.q_l_stride = Hq * HEAD_DIM; p.q_h_stride = HEAD_DIM; p.q_d_stride = 1;
+    p.max_context_len = max_ctx;
     p.causal_offset = causal ? 0 : -1; p.use_mask = 0;
     p.mask = nullptr; p.mask_b_stride = 0;
-    p.mask_h_stride = 0; p.mask_q_stride = 0;
+    p.mask_h_stride = 0; p.mask_l_stride = 0;
     p.scale = 1.0f / sqrtf((float)HEAD_DIM);
-    p.q = d_q; p.k_cache = d_k_pool; p.v_cache = d_v_pool;
+    p.q_ptr = d_q; p.k_ptr = d_k_pool; p.v_ptr = d_v_pool;
     p.req_to_token = d_rtt; p.req_pool_indices = d_rpi;
     p.kv_indptr = d_kvi; p.qo_indptr = nullptr;
-    p.o = d_o; p.o_part = d_op; p.ml_part = d_ml;
+    p.o_ptr = d_o; p.o_part = d_op; p.ml_part = d_ml;
 
-    dispatch_by_head_dim(HEAD_DIM, [&]<int H>() { dispatch_paged_decode<H>(p, 0); });
+    dispatch_by_head_dim(HEAD_DIM, PagedDecodeDispatch{p});
     cudaDeviceSynchronize();
 
     bf16* h_o_bf = (bf16*)malloc(sz_q);
@@ -234,7 +260,7 @@ static int run_decode_test(int B, int Hq, int Hkv, int max_seq,
     float* h_o_got = (float*)malloc(B * Hq * HEAD_DIM * sizeof(float));
     for (int i = 0; i < B * Hq * HEAD_DIM; i++) h_o_got[i] = bf2f(h_o_bf[i]);
 
-    const float atol = 0.02f, rtol = 0.02f;
+    const float atol = 0.01f, rtol = 0.01f;
     bool pass = true;
     float max_err = 0.0f;
     for (int i = 0; i < B * Hq * HEAD_DIM; i++) {
@@ -274,15 +300,15 @@ static int run_decode_mask_test(int B, int Hq, int Hkv, int max_seq,
 
     size_t sz_q  = (size_t)B * Hq * HEAD_DIM * sizeof(bf16);
     size_t sz_kv = (size_t)pool_size * Hkv * HEAD_DIM * sizeof(bf16);
-    size_t sz_rtt = (size_t)num_reqs * max_ctx * sizeof(int64_t);
-    size_t sz_rpi = (size_t)B * sizeof(int64_t);
+    size_t sz_rtt = (size_t)num_reqs * max_ctx * sizeof(int);
+    size_t sz_rpi = (size_t)B * sizeof(int);
     size_t sz_kvi = (size_t)(B + 1) * sizeof(int);
     size_t sz_mask = (size_t)B * max_sl * sizeof(bool);
     size_t sz_op = (size_t)B * Hq * MAX_SPLITS * HEAD_DIM * sizeof(float);
     size_t sz_ml = (size_t)B * Hq * MAX_SPLITS * 2 * sizeof(float);
 
     bf16 *d_q, *d_o, *d_k_pool, *d_v_pool;
-    int64_t *d_rtt, *d_rpi;
+    int *d_rtt, *d_rpi;
     int *d_kvi;
     bool *d_mask;
     float *d_op, *d_ml;
@@ -308,7 +334,7 @@ static int run_decode_mask_test(int B, int Hq, int Hkv, int max_seq,
     cudaMemcpy(d_k_pool, h_k_pool, sz_kv, cudaMemcpyHostToDevice);
     cudaMemcpy(d_v_pool, h_v_pool, sz_kv, cudaMemcpyHostToDevice);
 
-    int64_t* h_rtt = (int64_t*)malloc(sz_rtt);
+    int* h_rtt = (int*)malloc(sz_rtt);
     int next_slot = 0;
     for (int r = 0; r < num_reqs; r++)
         for (int p = 0; p < max_ctx; p++) {
@@ -317,7 +343,7 @@ static int run_decode_mask_test(int B, int Hq, int Hkv, int max_seq,
         }
     cudaMemcpy(d_rtt, h_rtt, sz_rtt, cudaMemcpyHostToDevice);
 
-    int64_t* h_rpi = (int64_t*)malloc(sz_rpi);
+    int* h_rpi = (int*)malloc(sz_rpi);
     for (int b = 0; b < B; b++) h_rpi[b] = b;
     cudaMemcpy(d_rpi, h_rpi, sz_rpi, cudaMemcpyHostToDevice);
 
@@ -347,21 +373,21 @@ static int run_decode_mask_test(int B, int Hq, int Hkv, int max_seq,
                             h_mask, max_sl,
                             B, Hq, Hkv, HEAD_DIM, max_ctx, h_o_ref);
 
-    AttentionParams<bf16> p;
+    AttentionParams<bf16> p = {};
     p.batch = B; p.q_head = Hq; p.kv_head = Hkv;
-    p.head_dim = HEAD_DIM; p.total_q = B;
-    p.q_stride_l = Hq * HEAD_DIM; p.q_stride_h = HEAD_DIM; p.q_stride_d = 1;
-    p.max_context_len = max_ctx; p.max_seq_len = max_sl;
+    p.head_dim = HEAD_DIM;
+    p.q_l_stride = Hq * HEAD_DIM; p.q_h_stride = HEAD_DIM; p.q_d_stride = 1;
+    p.max_context_len = max_ctx;
     p.causal_offset = -1; p.use_mask = 1;
     p.mask = d_mask; p.mask_b_stride = max_sl;
-    p.mask_h_stride = 0; p.mask_q_stride = 0;
+    p.mask_h_stride = 0; p.mask_l_stride = 0;
     p.scale = 1.0f / sqrtf((float)HEAD_DIM);
-    p.q = d_q; p.k_cache = d_k_pool; p.v_cache = d_v_pool;
+    p.q_ptr = d_q; p.k_ptr = d_k_pool; p.v_ptr = d_v_pool;
     p.req_to_token = d_rtt; p.req_pool_indices = d_rpi;
     p.kv_indptr = d_kvi; p.qo_indptr = nullptr;
-    p.o = d_o; p.o_part = d_op; p.ml_part = d_ml;
+    p.o_ptr = d_o; p.o_part = d_op; p.ml_part = d_ml;
 
-    dispatch_by_head_dim(HEAD_DIM, [&]<int H>() { dispatch_paged_decode<H>(p, 0); });
+    dispatch_by_head_dim(HEAD_DIM, PagedDecodeDispatch{p});
     cudaDeviceSynchronize();
 
     bf16* h_o_bf = (bf16*)malloc(sz_q);
@@ -369,7 +395,7 @@ static int run_decode_mask_test(int B, int Hq, int Hkv, int max_seq,
     float* h_o_got = (float*)malloc(B * Hq * HEAD_DIM * sizeof(float));
     for (int i = 0; i < B * Hq * HEAD_DIM; i++) h_o_got[i] = bf2f(h_o_bf[i]);
 
-    const float atol = 0.02f, rtol = 0.02f;
+    const float atol = 0.01f, rtol = 0.01f;
     bool pass = true;
     float max_err = 0.0f;
     for (int i = 0; i < B * Hq * HEAD_DIM; i++) {
@@ -413,13 +439,13 @@ static int run_prefill_test(int B, int Hq, int Hkv,
 
     size_t sz_q  = (size_t)total_q * Hq * HEAD_DIM * sizeof(bf16);
     size_t sz_kv = (size_t)pool_size * Hkv * HEAD_DIM * sizeof(bf16);
-    size_t sz_rtt = (size_t)num_reqs * max_ctx * sizeof(int64_t);
-    size_t sz_rpi = (size_t)B * sizeof(int64_t);
+    size_t sz_rtt = (size_t)num_reqs * max_ctx * sizeof(int);
+    size_t sz_rpi = (size_t)B * sizeof(int);
     size_t sz_kvi = (size_t)(B + 1) * sizeof(int);
     size_t sz_qoi = (size_t)(B + 1) * sizeof(int);
 
     bf16 *d_q, *d_o, *d_k_pool, *d_v_pool;
-    int64_t *d_rtt, *d_rpi;
+    int *d_rtt, *d_rpi;
     int *d_kvi, *d_qoi;
     cudaMalloc(&d_q, sz_q); cudaMalloc(&d_o, sz_q);
     cudaMalloc(&d_k_pool, sz_kv); cudaMalloc(&d_v_pool, sz_kv);
@@ -442,7 +468,7 @@ static int run_prefill_test(int B, int Hq, int Hkv,
     cudaMemcpy(d_k_pool, h_k_pool, sz_kv, cudaMemcpyHostToDevice);
     cudaMemcpy(d_v_pool, h_v_pool, sz_kv, cudaMemcpyHostToDevice);
 
-    int64_t* h_rtt = (int64_t*)malloc(sz_rtt);
+    int* h_rtt = (int*)malloc(sz_rtt);
     int next_slot = 0;
     for (int r = 0; r < num_reqs; r++)
         for (int p = 0; p < max_ctx; p++) {
@@ -451,7 +477,7 @@ static int run_prefill_test(int B, int Hq, int Hkv,
         }
     cudaMemcpy(d_rtt, h_rtt, sz_rtt, cudaMemcpyHostToDevice);
 
-    int64_t* h_rpi = (int64_t*)malloc(sz_rpi);
+    int* h_rpi = (int*)malloc(sz_rpi);
     for (int b = 0; b < B; b++) h_rpi[b] = b;
     cudaMemcpy(d_rpi, h_rpi, sz_rpi, cudaMemcpyHostToDevice);
 
@@ -479,25 +505,28 @@ static int run_prefill_test(int B, int Hq, int Hkv,
                              nullptr, 0, 0,
                              B, Hq, Hkv, HEAD_DIM, max_ctx, causal, h_o_ref);
 
+    int *d_qtb, *d_qti;
+    int num_q_tiles = make_q_tile_mapping(q_lens, &d_qtb, &d_qti);
+
     // Kernel launch
-    AttentionParams<bf16> p;
+    AttentionParams<bf16> p = {};
     p.batch = B; p.q_head = Hq; p.kv_head = Hkv;
-    p.head_dim = HEAD_DIM; p.total_q = total_q;
-    p.q_stride_l = Hq * HEAD_DIM; p.q_stride_h = HEAD_DIM; p.q_stride_d = 1;
-    p.max_context_len = max_ctx; p.max_seq_len = max_sl;
-    int max_ql = 0;
-    for (int b = 0; b < B; b++) max_ql = max(max_ql, q_lens[b]);
-    p.max_q_len = max_ql;
+    p.head_dim = HEAD_DIM;
+    p.q_l_stride = Hq * HEAD_DIM; p.q_h_stride = HEAD_DIM; p.q_d_stride = 1;
+    p.max_context_len = max_ctx;
+    p.q_len = total_q;
     p.causal_offset = causal ? 0 : -1; p.use_mask = 0;
     p.mask = nullptr; p.mask_b_stride = 0;
-    p.mask_h_stride = 0; p.mask_q_stride = 0;
+    p.mask_h_stride = 0; p.mask_l_stride = 0;
     p.scale = 1.0f / sqrtf((float)HEAD_DIM);
-    p.q = d_q; p.k_cache = d_k_pool; p.v_cache = d_v_pool;
+    p.q_ptr = d_q; p.k_ptr = d_k_pool; p.v_ptr = d_v_pool;
     p.req_to_token = d_rtt; p.req_pool_indices = d_rpi;
     p.kv_indptr = d_kvi; p.qo_indptr = d_qoi;
-    p.o = d_o; p.o_part = nullptr; p.ml_part = nullptr;
+    p.q_tile_to_batch = d_qtb; p.q_tile_to_index = d_qti;
+    p.num_q_tiles = num_q_tiles;
+    p.o_ptr = d_o; p.o_part = nullptr; p.ml_part = nullptr;
 
-    dispatch_by_head_dim(HEAD_DIM, [&]<int H>() { dispatch_paged_prefill<H>(p, 0); });
+    dispatch_by_head_dim(HEAD_DIM, PagedPrefillDispatch{p});
     cudaDeviceSynchronize();
 
     bf16* h_o_bf = (bf16*)malloc(sz_q);
@@ -505,7 +534,7 @@ static int run_prefill_test(int B, int Hq, int Hkv,
     float* h_o_got = (float*)malloc(total_q * Hq * HEAD_DIM * sizeof(float));
     for (int i = 0; i < total_q * Hq * HEAD_DIM; i++) h_o_got[i] = bf2f(h_o_bf[i]);
 
-    const float atol = 0.02f, rtol = 0.02f;
+    const float atol = 0.01f, rtol = 0.01f;
     bool pass = true;
     float max_err = 0.0f;
     for (int i = 0; i < total_q * Hq * HEAD_DIM; i++) {
@@ -521,6 +550,7 @@ static int run_prefill_test(int B, int Hq, int Hkv,
     free(h_o_ref); free(h_o_bf); free(h_o_got);
     cudaFree(d_q); cudaFree(d_o); cudaFree(d_k_pool); cudaFree(d_v_pool);
     cudaFree(d_rtt); cudaFree(d_rpi); cudaFree(d_kvi); cudaFree(d_qoi);
+    cudaFree(d_qtb); cudaFree(d_qti);
     return pass ? 0 : 1;
 }
 
@@ -544,14 +574,14 @@ static int run_prefill_mask_test(int Hq, int Hkv, int q_len, int seed) {
 
     size_t sz_q  = (size_t)total_q * Hq * HEAD_DIM * sizeof(bf16);
     size_t sz_kv = (size_t)pool_size * Hkv * HEAD_DIM * sizeof(bf16);
-    size_t sz_rtt = (size_t)num_reqs * max_ctx * sizeof(int64_t);
-    size_t sz_rpi = (size_t)B * sizeof(int64_t);
+    size_t sz_rtt = (size_t)num_reqs * max_ctx * sizeof(int);
+    size_t sz_rpi = (size_t)B * sizeof(int);
     size_t sz_kvi = (size_t)(B + 1) * sizeof(int);
     size_t sz_qoi = (size_t)(B + 1) * sizeof(int);
     size_t sz_mask = (size_t)B * q_len * q_len * sizeof(bool);
 
     bf16 *d_q, *d_o, *d_k_pool, *d_v_pool;
-    int64_t *d_rtt, *d_rpi;
+    int *d_rtt, *d_rpi;
     int *d_kvi, *d_qoi;
     bool *d_mask;
     cudaMalloc(&d_q, sz_q); cudaMalloc(&d_o, sz_q);
@@ -575,7 +605,7 @@ static int run_prefill_mask_test(int Hq, int Hkv, int q_len, int seed) {
     cudaMemcpy(d_k_pool, h_k_pool, sz_kv, cudaMemcpyHostToDevice);
     cudaMemcpy(d_v_pool, h_v_pool, sz_kv, cudaMemcpyHostToDevice);
 
-    int64_t* h_rtt = (int64_t*)malloc(sz_rtt);
+    int* h_rtt = (int*)malloc(sz_rtt);
     int next_slot = 0;
     for (int r = 0; r < num_reqs; r++)
         for (int p = 0; p < max_ctx; p++) {
@@ -584,7 +614,7 @@ static int run_prefill_mask_test(int Hq, int Hkv, int q_len, int seed) {
         }
     cudaMemcpy(d_rtt, h_rtt, sz_rtt, cudaMemcpyHostToDevice);
 
-    int64_t* h_rpi = (int64_t*)malloc(sz_rpi);
+    int* h_rpi = (int*)malloc(sz_rpi);
     h_rpi[0] = 0;
     cudaMemcpy(d_rpi, h_rpi, sz_rpi, cudaMemcpyHostToDevice);
 
@@ -617,22 +647,28 @@ static int run_prefill_mask_test(int Hq, int Hkv, int q_len, int seed) {
                              h_mask, q_len, q_len,
                              B, Hq, Hkv, HEAD_DIM, max_ctx, 0, h_o_ref);
 
-    AttentionParams<bf16> p;
+    std::vector<int> q_lens(B, q_len);
+    int *d_qtb, *d_qti;
+    int num_q_tiles = make_q_tile_mapping(q_lens, &d_qtb, &d_qti);
+
+    AttentionParams<bf16> p = {};
     p.batch = B; p.q_head = Hq; p.kv_head = Hkv;
-    p.head_dim = HEAD_DIM; p.total_q = total_q;
-    p.q_stride_l = Hq * HEAD_DIM; p.q_stride_h = HEAD_DIM; p.q_stride_d = 1;
-    p.max_context_len = max_ctx; p.max_seq_len = q_len;
-    p.max_q_len = q_len;
+    p.head_dim = HEAD_DIM;
+    p.q_l_stride = Hq * HEAD_DIM; p.q_h_stride = HEAD_DIM; p.q_d_stride = 1;
+    p.max_context_len = max_ctx;
+    p.q_len = B * q_len;
     p.causal_offset = -1; p.use_mask = 1;
     p.mask = d_mask; p.mask_b_stride = q_len * q_len;
-    p.mask_h_stride = 0; p.mask_q_stride = q_len;
+    p.mask_h_stride = 0; p.mask_l_stride = q_len;
     p.scale = 1.0f / sqrtf((float)HEAD_DIM);
-    p.q = d_q; p.k_cache = d_k_pool; p.v_cache = d_v_pool;
+    p.q_ptr = d_q; p.k_ptr = d_k_pool; p.v_ptr = d_v_pool;
     p.req_to_token = d_rtt; p.req_pool_indices = d_rpi;
     p.kv_indptr = d_kvi; p.qo_indptr = d_qoi;
-    p.o = d_o; p.o_part = nullptr; p.ml_part = nullptr;
+    p.q_tile_to_batch = d_qtb; p.q_tile_to_index = d_qti;
+    p.num_q_tiles = num_q_tiles;
+    p.o_ptr = d_o; p.o_part = nullptr; p.ml_part = nullptr;
 
-    dispatch_by_head_dim(HEAD_DIM, [&]<int H>() { dispatch_paged_prefill<H>(p, 0); });
+    dispatch_by_head_dim(HEAD_DIM, PagedPrefillDispatch{p});
     cudaDeviceSynchronize();
 
     bf16* h_o_bf = (bf16*)malloc(sz_q);
@@ -640,7 +676,7 @@ static int run_prefill_mask_test(int Hq, int Hkv, int q_len, int seed) {
     float* h_o_got = (float*)malloc(total_q * Hq * HEAD_DIM * sizeof(float));
     for (int i = 0; i < total_q * Hq * HEAD_DIM; i++) h_o_got[i] = bf2f(h_o_bf[i]);
 
-    const float atol = 0.02f, rtol = 0.02f;
+    const float atol = 0.01f, rtol = 0.01f;
     bool pass = true;
     float max_err = 0.0f;
     for (int i = 0; i < total_q * Hq * HEAD_DIM; i++) {
@@ -657,6 +693,7 @@ static int run_prefill_mask_test(int Hq, int Hkv, int q_len, int seed) {
     cudaFree(d_q); cudaFree(d_o); cudaFree(d_k_pool); cudaFree(d_v_pool);
     cudaFree(d_rtt); cudaFree(d_rpi); cudaFree(d_kvi); cudaFree(d_qoi);
     cudaFree(d_mask);
+    cudaFree(d_qtb); cudaFree(d_qti);
     return pass ? 0 : 1;
 }
 
@@ -665,20 +702,20 @@ static int run_prefill_mask_test(int Hq, int Hkv, int q_len, int seed) {
 // ======================================================================
 template <int HEAD_DIM>
 static void bench_decode(int B, int Hq, int Hkv, int seq_len) {
-    int max_ctx = seq_len + 16;
-    int pool_size = B * max_ctx;
+    int max_ctx = max(16384, seq_len + 16);
+    int pool_size = B * (seq_len + 16);
     int num_reqs = B;
 
     size_t sz_q  = (size_t)B * Hq * HEAD_DIM * sizeof(bf16);
     size_t sz_kv = (size_t)pool_size * Hkv * HEAD_DIM * sizeof(bf16);
-    size_t sz_rtt = (size_t)num_reqs * max_ctx * sizeof(int64_t);
-    size_t sz_rpi = (size_t)B * sizeof(int64_t);
+    size_t sz_rtt = (size_t)num_reqs * max_ctx * sizeof(int);
+    size_t sz_rpi = (size_t)B * sizeof(int);
     size_t sz_kvi = (size_t)(B + 1) * sizeof(int);
     size_t sz_op = (size_t)B * Hq * MAX_SPLITS * HEAD_DIM * sizeof(float);
     size_t sz_ml = (size_t)B * Hq * MAX_SPLITS * 2 * sizeof(float);
 
     bf16 *d_q, *d_o, *d_k_pool, *d_v_pool;
-    int64_t *d_rtt, *d_rpi;
+    int *d_rtt, *d_rpi;
     int *d_kvi;
     float *d_op, *d_ml;
     cudaMalloc(&d_q, sz_q); cudaMalloc(&d_o, sz_q);
@@ -694,12 +731,12 @@ static void bench_decode(int B, int Hq, int Hkv, int seq_len) {
     cudaMemcpy(d_k_pool, tmp, sz_kv, cudaMemcpyHostToDevice);
     cudaMemcpy(d_v_pool, tmp, sz_kv, cudaMemcpyHostToDevice);
 
-    int64_t* h_rtt = (int64_t*)malloc(sz_rtt);
+    int* h_rtt = (int*)malloc(sz_rtt);
     for (int r = 0; r < num_reqs; r++)
         for (int p = 0; p < max_ctx; p++)
             h_rtt[r * max_ctx + p] = (r * max_ctx + p) % pool_size;
     cudaMemcpy(d_rtt, h_rtt, sz_rtt, cudaMemcpyHostToDevice);
-    int64_t* h_rpi = (int64_t*)malloc(sz_rpi);
+    int* h_rpi = (int*)malloc(sz_rpi);
     for (int b = 0; b < B; b++) h_rpi[b] = b;
     cudaMemcpy(d_rpi, h_rpi, sz_rpi, cudaMemcpyHostToDevice);
     int* h_kvi = (int*)malloc(sz_kvi);
@@ -707,21 +744,21 @@ static void bench_decode(int B, int Hq, int Hkv, int seq_len) {
     for (int b = 0; b < B; b++) h_kvi[b + 1] = h_kvi[b] + seq_len;
     cudaMemcpy(d_kvi, h_kvi, sz_kvi, cudaMemcpyHostToDevice);
 
-    AttentionParams<bf16> p;
+    AttentionParams<bf16> p = {};
     p.batch = B; p.q_head = Hq; p.kv_head = Hkv;
-    p.head_dim = HEAD_DIM; p.total_q = B;
-    p.q_stride_l = Hq * HEAD_DIM; p.q_stride_h = HEAD_DIM; p.q_stride_d = 1;
-    p.max_context_len = max_ctx; p.max_seq_len = seq_len;
+    p.head_dim = HEAD_DIM;
+    p.q_l_stride = Hq * HEAD_DIM; p.q_h_stride = HEAD_DIM; p.q_d_stride = 1;
+    p.max_context_len = max_ctx;
     p.causal_offset = 0; p.use_mask = 0;
     p.mask = nullptr; p.mask_b_stride = 0;
     p.scale = 1.0f / sqrtf((float)HEAD_DIM);
-    p.q = d_q; p.k_cache = d_k_pool; p.v_cache = d_v_pool;
+    p.q_ptr = d_q; p.k_ptr = d_k_pool; p.v_ptr = d_v_pool;
     p.req_to_token = d_rtt; p.req_pool_indices = d_rpi;
     p.kv_indptr = d_kvi; p.qo_indptr = nullptr;
-    p.o = d_o; p.o_part = d_op; p.ml_part = d_ml;
+    p.o_ptr = d_o; p.o_part = d_op; p.ml_part = d_ml;
 
     auto launch = [&]() {
-        dispatch_by_head_dim(HEAD_DIM, [&]<int H>() { dispatch_paged_decode<H>(p, 0); });
+        dispatch_by_head_dim(HEAD_DIM, PagedDecodeDispatch{p});
     };
     // Decode: q_len=1, query is the last token → attends to all [0, seq_len).
     // FLOPs = 2 * (QK^T + PV) = 4 * B * Hq * seq_len * D.
@@ -747,13 +784,13 @@ static void bench_prefill(int B, int Hq, int Hkv, int q_len, int kv_len, int cau
 
     size_t sz_q  = (size_t)total_q * Hq * HEAD_DIM * sizeof(bf16);
     size_t sz_kv = (size_t)pool_size * Hkv * HEAD_DIM * sizeof(bf16);
-    size_t sz_rtt = (size_t)num_reqs * max_ctx * sizeof(int64_t);
-    size_t sz_rpi = (size_t)B * sizeof(int64_t);
+    size_t sz_rtt = (size_t)num_reqs * max_ctx * sizeof(int);
+    size_t sz_rpi = (size_t)B * sizeof(int);
     size_t sz_kvi = (size_t)(B + 1) * sizeof(int);
     size_t sz_qoi = (size_t)(B + 1) * sizeof(int);
 
     bf16 *d_q, *d_o, *d_k_pool, *d_v_pool;
-    int64_t *d_rtt, *d_rpi;
+    int *d_rtt, *d_rpi;
     int *d_kvi, *d_qoi;
     cudaMalloc(&d_q, sz_q); cudaMalloc(&d_o, sz_q);
     cudaMalloc(&d_k_pool, sz_kv); cudaMalloc(&d_v_pool, sz_kv);
@@ -767,12 +804,12 @@ static void bench_prefill(int B, int Hq, int Hkv, int q_len, int kv_len, int cau
     cudaMemcpy(d_k_pool, tmp, sz_kv, cudaMemcpyHostToDevice);
     cudaMemcpy(d_v_pool, tmp, sz_kv, cudaMemcpyHostToDevice);
 
-    int64_t* h_rtt = (int64_t*)malloc(sz_rtt);
+    int* h_rtt = (int*)malloc(sz_rtt);
     for (int r = 0; r < num_reqs; r++)
         for (int p = 0; p < max_ctx; p++)
             h_rtt[r * max_ctx + p] = (r * max_ctx + p) % pool_size;
     cudaMemcpy(d_rtt, h_rtt, sz_rtt, cudaMemcpyHostToDevice);
-    int64_t* h_rpi = (int64_t*)malloc(sz_rpi);
+    int* h_rpi = (int*)malloc(sz_rpi);
     for (int b = 0; b < B; b++) h_rpi[b] = b;
     cudaMemcpy(d_rpi, h_rpi, sz_rpi, cudaMemcpyHostToDevice);
     int* h_kvi = (int*)malloc(sz_kvi);
@@ -784,22 +821,28 @@ static void bench_prefill(int B, int Hq, int Hkv, int q_len, int kv_len, int cau
     for (int b = 0; b < B; b++) h_qoi[b + 1] = h_qoi[b] + q_len;
     cudaMemcpy(d_qoi, h_qoi, sz_qoi, cudaMemcpyHostToDevice);
 
-    AttentionParams<bf16> p;
+    std::vector<int> q_lens(B, q_len);
+    int *d_qtb, *d_qti;
+    int num_q_tiles = make_q_tile_mapping(q_lens, &d_qtb, &d_qti);
+
+    AttentionParams<bf16> p = {};
     p.batch = B; p.q_head = Hq; p.kv_head = Hkv;
-    p.head_dim = HEAD_DIM; p.total_q = total_q;
-    p.q_stride_l = Hq * HEAD_DIM; p.q_stride_h = HEAD_DIM; p.q_stride_d = 1;
-    p.max_context_len = max_ctx; p.max_seq_len = kv_len;
-    p.total_q = total_q; p.max_q_len = q_len;
+    p.head_dim = HEAD_DIM;
+    p.q_l_stride = Hq * HEAD_DIM; p.q_h_stride = HEAD_DIM; p.q_d_stride = 1;
+    p.max_context_len = max_ctx;
+    p.q_len = B * q_len;
     p.causal_offset = causal ? 0 : -1; p.use_mask = 0;
     p.mask = nullptr; p.mask_b_stride = 0;
     p.scale = 1.0f / sqrtf((float)HEAD_DIM);
-    p.q = d_q; p.k_cache = d_k_pool; p.v_cache = d_v_pool;
+    p.q_ptr = d_q; p.k_ptr = d_k_pool; p.v_ptr = d_v_pool;
     p.req_to_token = d_rtt; p.req_pool_indices = d_rpi;
     p.kv_indptr = d_kvi; p.qo_indptr = d_qoi;
-    p.o = d_o; p.o_part = nullptr; p.ml_part = nullptr;
+    p.q_tile_to_batch = d_qtb; p.q_tile_to_index = d_qti;
+    p.num_q_tiles = num_q_tiles;
+    p.o_ptr = d_o; p.o_part = nullptr; p.ml_part = nullptr;
 
     auto launch = [&]() {
-        dispatch_by_head_dim(HEAD_DIM, [&]<int H>() { dispatch_paged_prefill<H>(p, 0); });
+        dispatch_by_head_dim(HEAD_DIM, PagedPrefillDispatch{p});
     };
     // FLOPs = 2 * (QK^T + PV) = 4 * effective_qk_pairs * Hq * D.
     // Non-causal: effective = q_len * kv_len.
@@ -825,6 +868,7 @@ static void bench_prefill(int B, int Hq, int Hkv, int q_len, int kv_len, int cau
     free(tmp); free(h_rtt); free(h_rpi); free(h_kvi); free(h_qoi);
     cudaFree(d_q); cudaFree(d_o); cudaFree(d_k_pool); cudaFree(d_v_pool);
     cudaFree(d_rtt); cudaFree(d_rpi); cudaFree(d_kvi); cudaFree(d_qoi);
+    cudaFree(d_qtb); cudaFree(d_qti);
 }
 
 int main() {
@@ -844,6 +888,9 @@ int main() {
     fail += run_decode_test<256>(1, 2, 1, 256, 0, 9);
     fail += run_decode_test<128>(16, 32, 4, 2048, 0, 10);
     fail += run_decode_test<128>(32, 32, 4, 1024, 0, 11);
+    // Production keeps a fixed 32768-wide request table.  This forces 32
+    // splits, so seq_len > 512 gives each split multiple cp.async tiles.
+    fail += run_decode_test<64>(1, 24, 4, 1100, 0, 12, 32768, 1100);
 
     // Decode with 2D mask (regression: mixed seq_lens + HasMask)
     fail += run_decode_mask_test<128>(2, 8, 2, 256, 30);
@@ -928,9 +975,9 @@ int main() {
     bench_decode<128>(1, 32, 4, 1024);
     bench_decode<128>(1, 32, 4, 2048);
     bench_decode<128>(1, 32, 4, 4096);
+    bench_decode<128>(1, 32, 4, 16384);
     bench_decode<128>(4, 32, 4, 2048);
     bench_decode<128>(16, 32, 4, 2048);
-    bench_decode<128>(32, 32, 4, 1024);
 
     printf("\n===== PAGED PREFILL BENCH =====\n");
     print_bench_header();

csrc/tests/attn_test.cu

@@ -7,7 +7,12 @@ nvcc -I csrc -arch=sm_89 -O3 \
 */
 
 #include "test_utils.cuh"
-#include "../kernels/attn_dispatchers.cuh"
+#include "../kernels/attention/dispatchers.cuh"
+
+using namespace astrai::attention;
+
+struct DecodeDispatch { AttentionParams<bf16>& p; template<int H> void operator()() { dispatch_decode<H>(p, 0); } };
+struct PrefillDispatch { AttentionParams<bf16>& p; template<int H> void operator()() { dispatch_prefill<H>(p, 0); } };
 
 // Split-K scratch (torch-free)
 struct DecodeScratch {
@@ -30,8 +35,6 @@ static void free_scratch(DecodeScratch& sc) {
 // ======================================================================
 
 static int run_decode_test(int B, int Hq, int Hk, int sl, int D, int causal) {
-    int gs = Hq / Hk;
-
     size_t nQ = B*Hq*1*D, nKV = B*Hk*sl*D;
     float *hQ=new float[nQ], *hK=new float[nKV], *hV=new float[nKV];
     for (size_t i=0;i<nQ;i++) hQ[i]=randf();
@@ -55,19 +58,19 @@ static int run_decode_test(int B, int Hq, int Hk, int sl, int D, int causal) {
     cudaMemcpy(dV,tmp,nKV*2,cudaMemcpyHostToDevice);
     cudaMemcpy(dMask,hMask,B*sl,cudaMemcpyHostToDevice);
 
-    AttentionParams<bf16> p;
+    AttentionParams<bf16> p = {};
     p.batch=B; p.q_head=Hq; p.kv_head=Hk; p.q_len=1; p.kv_len=sl; p.head_dim=D;
     p.use_mask=0; p.causal_offset=causal?0:-1;
     p.scale=1.0f/sqrtf((float)D);
     set_default_strides(p);
-    p.q=dQ; p.k=dK; p.v=dV; p.mask=nullptr; p.o=dO;
+    p.q_ptr=dQ; p.k_ptr=dK; p.v_ptr=dV; p.mask=nullptr; p.o_ptr=dO;
 
     DecodeScratch sc;
     setup_scratch(p, sc);
     p.o_part = sc.o_part; p.ml_part = sc.ml_part;
 
     double t0=now_ms();
-    dispatch_by_head_dim(D, [&]<int H>() { dispatch_decode<H>(p, 0); });
+    dispatch_by_head_dim(D, DecodeDispatch{p});
     cudaDeviceSynchronize();
     (void)t0;
     cudaError_t err=cudaGetLastError();
@@ -117,7 +120,8 @@ static void bench_decode() {
     printf("\n===== DECODE BENCH (warmup=%d iters=%d) =====\n", WARMUP, ITERS);
     print_bench_header();
 
-    for (int ci = 0; ci < 6; ci++) {
+    int n = sizeof(cfgs) / sizeof(cfgs[0]);
+    for (int ci = 0; ci < n; ci++) {
         int B = cfgs[ci][0], Hq = cfgs[ci][1], Hk = cfgs[ci][2];
         int sl = cfgs[ci][3], D = cfgs[ci][4];
         size_t nQ = (size_t)B * Hq * D;
@@ -135,18 +139,18 @@ static void bench_decode() {
         cudaMemcpy(dV, tmp, nKV*2, cudaMemcpyHostToDevice);
         delete[] tmp;
 
-        AttentionParams<bf16> p;
+        AttentionParams<bf16> p = {};
         p.batch = B; p.q_head = Hq; p.kv_head = Hk; p.q_len = 1; p.kv_len = sl;
         p.head_dim = D; p.use_mask = 0; p.causal_offset = -1;
         p.scale = 1.0f / sqrtf((float)D);
         set_default_strides(p);
-        p.q = dQ; p.k = dK; p.v = dV; p.mask = nullptr; p.o = dO;
+        p.q_ptr = dQ; p.k_ptr = dK; p.v_ptr = dV; p.mask = nullptr; p.o_ptr = dO;
 
         DecodeScratch sc;
         setup_scratch(p, sc);
         p.o_part = sc.o_part; p.ml_part = sc.ml_part;
 
-        auto launch = [&]() { dispatch_by_head_dim(D, [&]<int H>() { dispatch_decode<H>(p, 0); }); };
+        auto launch = [&]() { dispatch_by_head_dim(D, DecodeDispatch{p}); };
         double flops = 4.0 * B * Hq * (double)sl * D;
         BenchResult r = bench_kernel(launch, WARMUP, ITERS, flops);
 
@@ -182,15 +186,15 @@ static int run_prefill_test(int B, int Hq, int Hk, int ql, int kl, int D, int ca
     for (size_t i=0;i<nKV;i++) tmp[i]=f2bf(hV[i]);
     cudaMemcpy(dV,tmp,nKV*2,cudaMemcpyHostToDevice);
 
-    AttentionParams<bf16> p;
+    AttentionParams<bf16> p = {};
     p.batch=B; p.q_head=Hq; p.kv_head=Hk; p.q_len=ql; p.kv_len=kl; p.head_dim=D;
     p.use_mask=0; p.causal_offset=causal?0:-1;
     set_default_strides(p);
     p.scale=1.0f/sqrtf((float)D);
-    p.q=dQ; p.k=dK; p.v=dV; p.mask=nullptr; p.o=dO;
+    p.q_ptr=dQ; p.k_ptr=dK; p.v_ptr=dV; p.mask=nullptr; p.o_ptr=dO;
 
     double t0=now_ms();
-    dispatch_by_head_dim(D, [&]<int H>() { dispatch_prefill<H>(p, 0); });
+    dispatch_by_head_dim(D, PrefillDispatch{p});
     cudaDeviceSynchronize();
     (void)t0;
     cudaError_t err=cudaGetLastError();
@@ -228,6 +232,12 @@ static int run_prefill_test(int B, int Hq, int Hk, int ql, int kl, int D, int ca
 
 static void bench_prefill() {
     const int cfgs[][7] = {
+        {1,32,4,1024,1024,32,0},
+        {1,32,4,1024,1024,32,1},
+        {1,32,4,4096,4096,32,1},
+        {1,32,4,1024,1024,64,0},
+        {1,32,4,1024,1024,64,1},
+        {1,32,4,4096,4096,64,1},
         {1,32,4,512,512,128,0},
         {1,32,4,1024,1024,128,0},
         {1,32,4,2048,2048,128,0},
@@ -256,14 +266,14 @@ static void bench_prefill() {
         for (size_t i=0;i<nKV;i++) tmp[i]=f2bf(randf());
         cudaMemcpy(dV,tmp,nKV*2,cudaMemcpyHostToDevice);
 
-        AttentionParams<bf16> p;
+        AttentionParams<bf16> p = {};
         p.batch=B; p.q_head=Hq; p.kv_head=Hk; p.q_len=ql; p.kv_len=kl; p.head_dim=D;
         p.use_mask=0; p.causal_offset=causal?0:-1;
         set_default_strides(p);
         p.scale=1.0f/sqrtf((float)D);
-        p.q=dQ; p.k=dK; p.v=dV; p.mask=nullptr; p.o=dO;
+        p.q_ptr=dQ; p.k_ptr=dK; p.v_ptr=dV; p.mask=nullptr; p.o_ptr=dO;
 
-        auto launch = [&]() { dispatch_by_head_dim(D, [&]<int H>() { dispatch_prefill<H>(p, 0); }); };
+        auto launch = [&]() { dispatch_by_head_dim(D, PrefillDispatch{p}); };
         for (int i=0;i<WARMUP;i++) launch();
         cudaDeviceSynchronize();
         cudaError_t err=cudaGetLastError();
@@ -322,7 +332,10 @@ int main() {
     // ---- PREFILL ----
     {
         const int configs[][7] = {
+            {1,2,1,64,128,32,0},     // scalar fallback D=32
+            {1,4,2,256,256,32,1},     // causal D=32 dispatch
             {1,2,1,64,128,64,0},     // tiny: B,Hq,Hk,q,kv,D,causal
+            {1,4,2,256,256,64,1},     // causal D=64 dispatch
             {1,32,4,512,512,128,0},  // standard
             {1,32,4,128,256,128,0},  // medium
             {1,4,2,256,256,128,1},   // causal

csrc/tests/fp8_test.cu

@@ -0,0 +1,344 @@
+/*
+FP8 family tests: single-warp MMA demo + full GEMM correctness.
+
+Part 1 exercises one bf16 -> fp8 -> mma.sync m16n8k32 instruction pair
+(sanity for astrai::mma_sync + the fragment layout contract).
+Part 2 checks launch_fp8_gemm across all four operand layouts, both K
+tiles, and ragged shapes against an fp32 CPU reference.
+
+nvcc -I csrc -arch=sm_89 -std=c++17 -O3 csrc/tests/fp8_test.cu -o /tmp/fp8_test \
+    && /tmp/fp8_test
+*/
+
+#include "test_utils.cuh"
+
+#include <cuda_fp8.h>
+#include <algorithm>
+#include <cmath>
+#include <cstdio>
+#include <cstdlib>
+#include <cuda_runtime.h>
+#include <type_traits>
+#include <vector>
+
+#include "../kernels/common/mma.cuh"
+#include "../kernels/fp8/gemm.cuh"
+
+using namespace astrai::fp8;
+
+// ---------------------------------------------------------------------------
+// Part 1: single-kernel BF16 -> FP8 MMA -> BF16 demo (m16n8k32)
+// ---------------------------------------------------------------------------
+
+namespace {
+
+constexpr int kMmaM = 16;
+constexpr int kMmaN = 8;
+constexpr int kMmaK = 32;
+
+__device__ __forceinline__ unsigned pack_fp8x4(float x0, float x1, float x2,
+                                                float x3) {
+    __nv_fp8_e4m3 q0(x0);
+    __nv_fp8_e4m3 q1(x1);
+    __nv_fp8_e4m3 q2(x2);
+    __nv_fp8_e4m3 q3(x3);
+    return static_cast<unsigned>(q0.__x) |
+           (static_cast<unsigned>(q1.__x) << 8) |
+           (static_cast<unsigned>(q2.__x) << 16) |
+           (static_cast<unsigned>(q3.__x) << 24);
+}
+
+__device__ __forceinline__ unsigned load_quantize_fp8x4(
+    const bf16* src, float scale_inv) {
+    return pack_fp8x4(__bfloat162float(src[0]) * scale_inv,
+                      __bfloat162float(src[1]) * scale_inv,
+                      __bfloat162float(src[2]) * scale_inv,
+                      __bfloat162float(src[3]) * scale_inv);
+}
+
+__global__ void fused_bf16_fp8_mma_kernel(
+    const bf16* __restrict__ a, const bf16* __restrict__ b,
+    bf16* __restrict__ out, float scale_a, float scale_b) {
+    const int lane = threadIdx.x;
+    const int group = lane >> 2;
+    const int thread_in_group = lane & 3;
+    const int k0 = thread_in_group * 4;
+
+    // PTX m16n8k32 A fragment: two rows, two 16-column K partitions.
+    unsigned a_frag[4];
+    a_frag[0] = load_quantize_fp8x4(&a[group * kMmaK + k0], 1.0f / scale_a);
+    a_frag[1] =
+        load_quantize_fp8x4(&a[(group + 8) * kMmaK + k0], 1.0f / scale_a);
+    a_frag[2] =
+        load_quantize_fp8x4(&a[group * kMmaK + k0 + 16], 1.0f / scale_a);
+    a_frag[3] = load_quantize_fp8x4(&a[(group + 8) * kMmaK + k0 + 16],
+                                    1.0f / scale_a);
+
+    // B is supplied as row-major [N,K], equivalent to the col-major [K,N]
+    // operand required by the MMA instruction.
+    unsigned b_frag[2];
+    b_frag[0] = load_quantize_fp8x4(&b[group * kMmaK + k0], 1.0f / scale_b);
+    b_frag[1] =
+        load_quantize_fp8x4(&b[group * kMmaK + k0 + 16], 1.0f / scale_b);
+
+    float acc[4] = {0.0f, 0.0f, 0.0f, 0.0f};
+    astrai::mma_sync<__nv_fp8_e4m3>(acc, a_frag, b_frag, acc);
+
+    const int col = thread_in_group * 2;
+    const float output_scale = scale_a * scale_b;
+    *reinterpret_cast<__nv_bfloat162*>(&out[group * kMmaN + col]) =
+        __floats2bfloat162_rn(acc[0] * output_scale, acc[1] * output_scale);
+    *reinterpret_cast<__nv_bfloat162*>(&out[(group + 8) * kMmaN + col]) =
+        __floats2bfloat162_rn(acc[2] * output_scale, acc[3] * output_scale);
+}
+
+static float quantize_e4m3(float value) {
+    return static_cast<float>(__nv_fp8_e4m3(value));
+}
+
+static bool test_single_mma() {
+    srand(0);
+    std::vector<float> a(kMmaM * kMmaK), b(kMmaN * kMmaK),
+        reference(kMmaM * kMmaN, 0.0f);
+    std::vector<bf16> a_bf16(kMmaM * kMmaK), b_bf16(kMmaN * kMmaK),
+        output(kMmaM * kMmaN);
+    for (float& value : a) value = randf() * 4.0f;
+    for (float& value : b) value = randf() * 4.0f;
+    for (int i = 0; i < kMmaM * kMmaK; ++i) {
+        a_bf16[i] = f2bf(a[i]);
+        a[i] = bf2f(a_bf16[i]);
+    }
+    for (int i = 0; i < kMmaN * kMmaK; ++i) {
+        b_bf16[i] = f2bf(b[i]);
+        b[i] = bf2f(b_bf16[i]);
+    }
+
+    const float amax = *std::max_element(
+        a.begin(), a.end(),
+        [](float x, float y) { return fabsf(x) < fabsf(y); });
+    const float bmax = *std::max_element(
+        b.begin(), b.end(),
+        [](float x, float y) { return fabsf(x) < fabsf(y); });
+    const float scale_a = fabsf(amax) / 448.0f;
+    const float scale_b = fabsf(bmax) / 448.0f;
+
+    for (int row = 0; row < kMmaM; ++row) {
+        for (int col = 0; col < kMmaN; ++col) {
+            float sum = 0.0f;
+            for (int k = 0; k < kMmaK; ++k) {
+                float qa = quantize_e4m3(a[row * kMmaK + k] / scale_a);
+                float qb = quantize_e4m3(b[col * kMmaK + k] / scale_b);
+                sum = fmaf(qa, qb, sum);
+            }
+            reference[row * kMmaN + col] = sum * scale_a * scale_b;
+        }
+    }
+
+    bf16 *d_a, *d_b, *d_out;
+    CUDA_CHECK(cudaMalloc(&d_a, a_bf16.size() * sizeof(bf16)));
+    CUDA_CHECK(cudaMalloc(&d_b, b_bf16.size() * sizeof(bf16)));
+    CUDA_CHECK(cudaMalloc(&d_out, output.size() * sizeof(bf16)));
+    CUDA_CHECK(cudaMemcpy(d_a, a_bf16.data(), a_bf16.size() * sizeof(bf16),
+                          cudaMemcpyHostToDevice));
+    CUDA_CHECK(cudaMemcpy(d_b, b_bf16.data(), b_bf16.size() * sizeof(bf16),
+                          cudaMemcpyHostToDevice));
+
+    fused_bf16_fp8_mma_kernel<<<1, 32>>>(d_a, d_b, d_out, scale_a, scale_b);
+    CUDA_CHECK(cudaDeviceSynchronize());
+    CUDA_CHECK(cudaMemcpy(output.data(), d_out, output.size() * sizeof(bf16),
+                          cudaMemcpyDeviceToHost));
+
+    float max_abs_error = 0.0f;
+    float max_rel_error = 0.0f;
+    for (int i = 0; i < kMmaM * kMmaN; ++i) {
+        float error = fabsf(bf2f(output[i]) - reference[i]);
+        max_abs_error = fmaxf(max_abs_error, error);
+        max_rel_error = fmaxf(
+            max_rel_error, error / fmaxf(fabsf(reference[i]), 1e-4f));
+    }
+    const bool pass = max_abs_error < 0.05f;
+    print_test_row("M=16 N=8 K=32 fused BF16->E4M3 MMA", max_abs_error,
+                   max_rel_error, pass);
+
+    cudaFree(d_a);
+    cudaFree(d_b);
+    cudaFree(d_out);
+    return pass;
+}
+
+// ---------------------------------------------------------------------------
+// Part 2: GEMM correctness — layouts x K-tiles vs fp32 CPU reference
+// ---------------------------------------------------------------------------
+
+// Naive fp32 reference on the GPU: same layout interpretation as the CPU
+// loop it replaces (O(m*n) to check instead of O(m*n*k) to compute).
+__global__ static void
+naive_gemm_ref(const __nv_fp8_e4m3* a, const __nv_fp8_e4m3* b, float* out,
+               int m, int n, int k, int a_ld, int b_ld, int a_rm, int b_rm) {
+    const int i = blockIdx.y * 32 + threadIdx.y;
+    const int j = blockIdx.x * 32 + threadIdx.x;
+    if (i >= m || j >= n) return;
+    float acc = 0.f;
+    for (int kk = 0; kk < k; ++kk) {
+        float av = a_rm ? (float)a[i * a_ld + kk] : (float)a[kk * a_ld + i];
+        float bv = b_rm ? (float)b[kk * b_ld + j] : (float)b[j * b_ld + kk];
+        acc += av * bv;
+    }
+    out[i * n + j] = acc;
+}
+
+// Big-CTA policies for the direct-layout cases: kK/Stages vary per case;
+// the fast interior loop follows the dual-congruous rule, grouped raster 8
+// matches the production dispatch.
+template <typename LA, typename LB>
+constexpr bool kCaseFast =
+    !std::is_same_v<LA, ColMajor> && !std::is_same_v<LB, RowMajor>;
+template <typename LA, typename LB, int kK, int Stages>
+using CasePolicy =
+    Fp8GemmPolicy<FP8Format::E4M3, 128, 128, LA, LB, 64, 32, kK, Stages, 8,
+                  false, kCaseFast<LA, LB>>;
+
+template <typename LA, typename LB, int kK, int Stages>
+static bool run_gemm_case(const float* ha, const float* hb, int m, int n,
+                          int k, int a_ld, int b_ld, int dispatch = 0) {
+    __nv_fp8_e4m3 *da, *db;
+    __nv_bfloat16* dout;
+    float* dscale;
+    cudaMalloc(&da, (size_t)m * k);
+    cudaMalloc(&db, (size_t)n * k);
+    cudaMalloc(&dout, (size_t)m * n * 2);
+    cudaMalloc(&dscale, 4);
+    float one = 1.0f;
+    cudaMemcpy(dscale, &one, 4, cudaMemcpyHostToDevice);
+    // quantize inputs to e4m3 on host and upload byte-by-byte
+    std::vector<unsigned char> qa(m * k), qb(n * k);
+    for (int i = 0; i < m * k; ++i) {
+        __nv_fp8_e4m3 q(ha[i]);
+        qa[i] = *(unsigned char*)&q;
+    }
+    for (int i = 0; i < n * k; ++i) {
+        __nv_fp8_e4m3 q(hb[i]);
+        qb[i] = *(unsigned char*)&q;
+    }
+    cudaMemcpy(da, qa.data(), qa.size(), cudaMemcpyHostToDevice);
+    cudaMemcpy(db, qb.data(), qb.size(), cudaMemcpyHostToDevice);
+
+    FP8Params p = {};
+    p.a_ptr = da;
+    p.b_ptr = db;
+    p.out_ptr = dout;
+    p.scale = dscale;
+    p.m = m;
+    p.n = n;
+    p.k = k;
+    p.a_ld = a_ld;
+    p.b_ld = b_ld;
+    float* d_ref;
+    cudaMalloc(&d_ref, (size_t)m * n * 4);
+    naive_gemm_ref<<<dim3((n + 31) / 32, (m + 31) / 32), dim3(32, 32)>>>(
+        da, db, d_ref, m, n, k, a_ld, b_ld,
+        !std::is_same_v<LA, ColMajor>, !std::is_same_v<LB, ColMajor>);
+    std::vector<float> href((size_t)m * n);
+    cudaMemcpy(href.data(), d_ref, href.size() * 4, cudaMemcpyDeviceToHost);
+    cudaFree(d_ref);
+
+    if (dispatch == 1)
+        // Production route, NN: the dual-N-contiguous problem has no
+        // dedicated instantiation — canonicalize_gemm swaps to the
+        // transposed <ColMajor, ColMajor> kernel with its out-transposed
+        // epilogue (see gemm.cuh).
+        gemm<FP8Format::E4M3>(p, 0, false, false);
+    else if (dispatch == 2)
+        // Production route, NT: exercises plan_gemm's small/narrow/big
+        // selection for this shape.
+        gemm<FP8Format::E4M3>(p, 0, false, true);
+    else
+        launch_policy<CasePolicy<LA, LB, kK, Stages>>(p, 0);
+    cudaError_t e = cudaDeviceSynchronize();
+    if (e != cudaSuccess) {
+        printf("  CUDA err: %s\n", cudaGetErrorString(e));
+        return false;
+    }
+    std::vector<unsigned short> hb16(m * n);
+    cudaMemcpy(hb16.data(), dout, (size_t)m * n * 2, cudaMemcpyDeviceToHost);
+    const float tol = 0.06f;
+    double max_rel = 0;
+    bool ok = true;
+    for (int i = 0; i < m && ok; ++i) {
+        for (int j = 0; j < n && ok; ++j) {
+            const float ref = href[(size_t)i * n + j];
+            float got =
+                __bfloat162float(__ushort_as_bfloat16(hb16[i * n + j]));
+            float err = fabsf(got - ref);
+            float rel = err / fmaxf(fabsf(ref), 0.5f);
+            if (rel > max_rel) max_rel = rel;
+            if (err > tol * fmaxf(fabsf(ref), 1.0f)) ok = false;
+        }
+    }
+    printf("  max_rel=%.4f %s\n", max_rel, ok ? "PASS" : "FAIL");
+    cudaFree(da);
+    cudaFree(db);
+    cudaFree(dout);
+    cudaFree(dscale);
+    return ok;
+}
+
+static bool test_gemm() {
+    struct {
+        int m, n, k;
+    } cfgs[] = {
+        {128, 128, 128}, {256, 128, 256}, {128, 256, 64},
+        {100, 130, 96},  {64, 64, 160},   {300, 200, 320},
+        {2048, 256, 512}, {1024, 1024, 512},
+    };
+    bool all = true;
+    for (auto& c : cfgs) {
+        float* ha = new float[c.m * c.k];
+        float* hb_rowmajor = new float[c.k * c.n];  // [K][N] for B RowMajor
+        float* hb_colmajor = new float[c.n * c.k];  // [N][K] for B ColMajor
+        for (int i = 0; i < c.m * c.k; ++i) ha[i] = randf();
+        for (int i = 0; i < c.k * c.n; ++i) hb_rowmajor[i] = randf();
+        for (int i = 0; i < c.k * c.n; ++i)
+            hb_colmajor[i / c.k * c.k + i % c.k] = hb_rowmajor[i];
+        float* ha_t = new float[c.k * c.m];  // [K][M] for A ColMajor
+        for (int i = 0; i < c.m; ++i)
+            for (int p = 0; p < c.k; ++p) ha_t[p * c.m + i] = ha[i * c.k + p];
+        printf("%dx%dx%d:\n", c.m, c.n, c.k);
+        printf(" NT K32:");
+        all &= run_gemm_case<RowMajor, ColMajor, 32, 3>(ha, hb_colmajor, c.m,
+                                                        c.n, c.k, c.k, c.k);
+        printf(" NT K64:");
+        all &= run_gemm_case<RowMajor, ColMajor, 64, 2>(ha, hb_colmajor, c.m,
+                                                        c.n, c.k, c.k, c.k);
+        printf(" NN swap:");
+        all &= run_gemm_case<RowMajor, RowMajor, 64, 2>(
+            ha, hb_rowmajor, c.m, c.n, c.k, c.k, c.n, /*dispatch=*/1);
+        printf(" NT disp:");
+        all &= run_gemm_case<RowMajor, ColMajor, 64, 2>(
+            ha, hb_colmajor, c.m, c.n, c.k, c.k, c.k, /*dispatch=*/2);
+        printf(" TN K32:");
+        all &= run_gemm_case<ColMajor, ColMajor, 32, 3>(ha_t, hb_colmajor, c.m,
+                                                        c.n, c.k, c.m, c.k);
+        printf(" TN K64:");
+        all &= run_gemm_case<ColMajor, ColMajor, 64, 2>(ha_t, hb_colmajor, c.m,
+                                                        c.n, c.k, c.m, c.k);
+        printf(" TT K64:");
+        all &= run_gemm_case<ColMajor, RowMajor, 64, 2>(ha_t, hb_rowmajor, c.m,
+                                                        c.n, c.k, c.m, c.n);
+        delete[] ha;
+        delete[] hb_rowmajor;
+        delete[] hb_colmajor;
+        delete[] ha_t;
+    }
+    return all;
+}
+
+}  // namespace
+
+int main() {
+    print_test_header();
+    bool ok = test_single_mma();
+    ok &= test_gemm();
+    printf(ok ? "All PASS\n" : "FAILURES\n");
+    return ok ? 0 : 1;
+}

csrc/tests/test_utils.cuh

@@ -107,29 +107,29 @@ void dispatch_by_head_dim(int head_dim, Fn&& fn) {
 // Set default strides for contiguous b h l d layout on AttentionParams.
 template<typename P>
 inline void set_default_strides(P& p) {
-    p.q_stride_b  = p.q_head * p.q_len * p.head_dim;
-    p.q_stride_h  = p.q_len * p.head_dim;
-    p.q_stride_l  = p.head_dim;
-    p.q_stride_d  = 1;
-    p.kv_stride_b = p.kv_head * p.kv_len * p.head_dim;
-    p.kv_stride_h = p.kv_len * p.head_dim;
-    p.kv_stride_l = p.head_dim;
-    p.kv_stride_d = 1;
+    p.q_b_stride  = p.q_head * p.q_len * p.head_dim;
+    p.q_h_stride  = p.q_len * p.head_dim;
+    p.q_l_stride  = p.head_dim;
+    p.q_d_stride  = 1;
+    p.kv_b_stride = p.kv_head * p.kv_len * p.head_dim;
+    p.kv_h_stride = p.kv_len * p.head_dim;
+    p.kv_l_stride = p.head_dim;
+    p.kv_d_stride = 1;
     p.mask_b_stride = p.kv_len;
     p.mask_h_stride = 0;
-    p.mask_q_stride = 0;
+    p.mask_l_stride = 0;
 }
 
 // Set default Q strides for a paged decode params struct.
 template<typename P>
 inline void set_default_paged_strides(P& p) {
-    p.q_stride_b  = p.q_head * p.q_len * p.head_dim;
-    p.q_stride_h  = p.q_len * p.head_dim;
-    p.q_stride_l  = p.head_dim;
-    p.q_stride_d  = 1;
+    p.q_b_stride  = p.q_head * p.q_len * p.head_dim;
+    p.q_h_stride  = p.q_len * p.head_dim;
+    p.q_l_stride  = p.head_dim;
+    p.q_d_stride  = 1;
     p.mask_b_stride = p.kv_len;
     p.mask_h_stride = 0;
-    p.mask_q_stride = 0;
+    p.mask_l_stride = 0;
 }
 
 // Generic CPU reference for multi-query / grouped-query attention.

docker-compose.yml

@@ -1,22 +1,27 @@
 services:
   server:
+    image: astrai:latest
     build:
       context: .
       dockerfile: Dockerfile
       args:
         CUDA_TAG: ${CUDA_TAG:-cu128}
-    user: "${UID:-1000}:${GID:-1000}"
+        USER_UID: ${ASTRAI_UID:-1000}
+        USER_GID: ${ASTRAI_GID:-1000}
+    user: "${ASTRAI_UID:-1000}:${ASTRAI_GID:-1000}"
     ports:
-      - "8000:8000"
+      - "${SERVE_PORT:-8000}:${SERVE_CONTAINER_PORT:-8000}"
     volumes:
-      - ./params:/app/params:ro
+      - ${SERVE_PARAM_DIR:-./params}:/app/params:ro
+    environment:
+      - CUDA_VISIBLE_DEVICES
     command: python -m scripts.tools.server --port 8000 --device cuda
     deploy:
       resources:
         reservations:
           devices:
             - driver: nvidia
-              count: 1
+              count: all
               capabilities: [gpu]
     healthcheck:
       test: ["CMD", "curl", "-f", "http://localhost:8000/health"]
@@ -27,17 +32,20 @@ services:
     restart: unless-stopped
 
   server-cpu:
+    image: astrai:latest
     profiles: [cpu]
     build:
       context: .
       dockerfile: Dockerfile
       args:
         CUDA_TAG: ${CUDA_TAG:-cu128}
-    user: "${UID:-1000}:${GID:-1000}"
+        USER_UID: ${ASTRAI_UID:-1000}
+        USER_GID: ${ASTRAI_GID:-1000}
+    user: "${ASTRAI_UID:-1000}:${ASTRAI_GID:-1000}"
     ports:
-      - "8000:8000"
+      - "${SERVE_PORT:-8000}:${SERVE_CONTAINER_PORT:-8000}"
     volumes:
-      - ./params:/app/params:ro
+      - ${SERVE_PARAM_DIR:-./params}:/app/params:ro
     command: python -m scripts.tools.server --port 8000 --device cpu
     healthcheck:
       test: ["CMD", "curl", "-f", "http://localhost:8000/health"]
@@ -46,3 +54,44 @@ services:
       retries: 3
       start_period: 120s
     restart: unless-stopped
+
+  trainer:
+    image: astrai:latest
+    profiles: [train]
+    build:
+      context: .
+      dockerfile: Dockerfile
+      args:
+        CUDA_TAG: ${CUDA_TAG:-cu128}
+        USER_UID: ${ASTRAI_UID:-1000}
+        USER_GID: ${ASTRAI_GID:-1000}
+    init: true
+    user: "${ASTRAI_UID:-1000}:${ASTRAI_GID:-1000}"
+    volumes:
+      - ${TRAIN_DATA_DIR:-./data}:/data:ro
+      - ${TRAIN_MODEL_DIR:-./params}:/models/base:ro
+      - ${TRAIN_CHECKPOINT_DIR:-./checkpoints}:/checkpoints
+    environment:
+      - TRAIN_JOB_NAME=${TRAIN_JOB_NAME:-astrai-train}
+      - TRAIN_CONFIG=${TRAIN_CONFIG:-}
+      - BASE_MODEL=${BASE_MODEL:-/models/base}
+      - CHECKPOINT_ROOT=/checkpoints
+      - TRAIN_GPU_COUNT=${TRAIN_GPU_COUNT:-all}
+      - TRAIN_PARALLEL_MODE=${TRAIN_PARALLEL_MODE:-auto}
+      - CUDA_VISIBLE_DEVICES
+    entrypoint: ["bash", "/app/scripts/docker/train-entrypoint.sh"]
+    ipc: ${TRAIN_IPC_MODE:-host}
+    stop_grace_period: ${TRAIN_STOP_GRACE_PERIOD:-10m}
+    restart: "no"
+    logging:
+      driver: json-file
+      options:
+        max-size: ${TRAIN_LOG_MAX_SIZE:-100m}
+        max-file: ${TRAIN_LOG_MAX_FILES:-5}
+    deploy:
+      resources:
+        reservations:
+          devices:
+            - driver: nvidia
+              count: all
+              capabilities: [gpu]