- double-buffer K/V one tile ahead via cp.async to overlap load with tensor-core math (ncu long_scoreboard 2.12->0.53)
- reorder wait->barrier->prefetch so one __syncthreads/tile covers both cross-warp publish and buffer-reuse (was two)
- add predicated cp_async_16_pred (src-size=0 zero-fills OOB) to unify full/partial tiles, dropping the scalar fallback
- halve BC to 16 to keep 3 blocks/SM despite the doubled smem
- pack adjacent bf16 output into one 32-bit STG, removing the uncoalesced scalar-store penalty (14%->5% sectors)
- result vs torch SDPA: prefill 0.61-0.78x -> 0.70-0.82x, spills eliminated
- add case 32 to decode/prefill dispatch switch
- fix swiz_col out-of-bounds for HEAD_DIM=32: XOR mask now limited to chunk count (3 for 32, 7 for >=64) instead of always 7, which produced column offsets >= LD=32 and corrupted shared memory
- restructure decode dispatch to #ifndef/#else/#endif matching prefill
- split astrai/extension/__init__.py into loader.py (kernel .so discovery) and ops.py (wrapper functions + torch SDPA fallback); __init__.py now re-exports the public API
ViperEkura