Studio currently only installs causal-conv1d for qwen3.5 / qwen3.6 /
qwen3-next models. Without flash-linear-attention installed alongside
it, transformers' Qwen3.5 fast-path gate stays False and the model
falls back to a pure-PyTorch loop for the GatedDeltaNet layers. In a
60-step run on unsloth/Qwen3.5-2B on B200, this fallback costs ~2.35x
vs the full fast path.
On top of that, FLA dispatches its hottest GDN kernels through a
TileLang backend when tilelang is importable. Adding tilelang plus a
pinned apache-tvm-ffi gives another ~26% on the same workload (4.73
s/step to 3.50 s/step) and is what users have been getting indirectly
when they install mamba-ssm (mamba-ssm transitively pulls tilelang and
pins apache-tvm-ffi<=0.1.9, which is the last working version on
sm_100; 0.1.10 and 0.1.11 crash Triton with misaligned address).
Changes:
* _ensure_flash_linear_attention: pure-Python PyPI install gated on
the same model match set as _ensure_causal_conv1d_fast_path.
* _ensure_tilelang_backend: installs apache-tvm-ffi==0.1.9 and
tilelang==0.1.8 in one pip resolve so the tvm-ffi pin wins over
tilelang's >=0.1.2 constraint. Gated on the Qwen3.5 family only;
SSM models (Nemotron-H, Falcon-H1, Granite-H, LFM2) do not use
FLA's GDN dispatch.
* UNSLOTH_STUDIO_SKIP_TILELANG_INSTALL=1 escape hatch matching the
flash-attn pattern.
* Orchestration block reordered: causal-conv1d -> fla -> mamba-ssm
-> tilelang -> flash-attn (long context).
* 7 new tests covering the new helpers, including SSM-model skip,
skip-env, full Qwen3 family name variants, and graceful pip
install failure.
Combined Qwen3.5-2B-Vision step time on B200 in our bench goes from
5.0 s/step (current Studio: causal-conv1d only) to 3.5 s/step
(causal-conv1d + fla + tilelang), a 1.43x speedup with no notebook
or user code changes required.
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