The substring-based detection in this PR (`_model_wants_tilelang` /
`_model_wants_causal_conv1d`) is brittle: it depends on what the user
typed for the model name, not on what the architecture actually needs.
Users typing custom model paths, future Qwen3.7 / non-Qwen GDN
architectures, and any model whose author renamed it would silently
fall back to the torch loop.
The correct signal is the one transformers itself uses to gate the
fast path. `transformers/models/qwen3_5_moe/modeling_qwen3_5_moe.py`
does at module import time:
if is_causal_conv1d_available():
from causal_conv1d import causal_conv1d_fn, causal_conv1d_update
if is_flash_linear_attention_available():
from fla.modules import FusedRMSNormGated
from fla.ops.gated_delta_rule import (
chunk_gated_delta_rule, fused_recurrent_gated_delta_rule,
)
Wrap both gates so the first call (always at modeling import, before
any forward pass) installs the matching kernel synchronously and
delegates to the original function. Any model whose architecture
queries those gates auto-triggers the install; models that never
query them (Llama, Gemma, dense Qwen, ...) never pay the cost.
Mechanics:
- Split `_ensure_flash_linear_attention` and `_ensure_tilelang_backend`
into `_unconditional` variants (no substring gate, retains python
/ torch / platform / skip-env guards) plus thin substring wrappers
used by the legacy fallback path.
- New `_install_fast_path_hooks(event_queue)` patches both gates on
`transformers.utils.import_utils` AND sweeps `sys.modules` so any
modeling file that already did `from ... import is_X` sees the
wrapper (the local binding survives a module-level reassignment).
- Wrappers clear the original's `lru_cache` before delegating, install
on False, re-check, and short-circuit on subsequent calls.
- Set `UNSLOTH_STUDIO_SKIP_FAST_PATH_HOOKS=1` to fall back to the
substring path.
Verified end-to-end against `transformers.models.qwen3_5_moe`:
PRE_STATE fla=False tilelang=False causal_conv1d=False
HOOK_INSTALLED
Hook fired for is_causal_conv1d_available; installing kernel...
Installing prebuilt causal-conv1d wheel...
Hook fired for is_flash_linear_attention_available; installing kernel...
Installing flash-linear-attention==0.5.0 (with fla-core==0.5.0) for the fast path...
Installed flash-linear-attention for the FLA fast path
Installing TileLang backend (apache-tvm-ffi==0.1.9, tilelang==0.1.8)...
Installed TileLang backend for FLA fast path
MODELING_IMPORT_OK
FAST_PATH_SYMBOLS {"chunk_gated_delta_rule": true,
"fused_recurrent_gated_delta_rule": true,
"FusedRMSNormGated": true,
"causal_conv1d_fn": true,
"causal_conv1d_update": true}
POST_STATE fla=True tilelang=True causal_conv1d=True
Adds 9 new tests covering: install-on-False, skip-on-True, idempotency,
install-failure handling, env-disable, lru_cache clear, sys.modules
rebind, missing-transformers fallback, substring fallback. Total
test count is now 36 (was 27).
6ce495a42d