* Bypass fast_generate for flash_attention_2 models (frozen KV / gibberish)
unsloth_base_fast_generate forces cache_implementation="static", which
pre-allocates the full prompt+max_new_tokens KV buffer. With SDPA the
not-yet-filled slots are masked out; flash_attention_2 does not receive such
a mask, so decoding attends over uninitialized cache memory and produces
incoherent output (observed: coherent prompt echo followed by gibberish
rollouts on Phi-4-mini-instruct during TRL GRPO training; the KV length
appears frozen at the pre-allocated size). Note that on transformers >=
4.56 UNSLOTH_DISABLE_STATIC_GENERATION=1 still selects the static cache, so
the env-var escape hatch does not help either.
Fall back to the wrapped model's original generate when the config reports
_attn_implementation == "flash_attention_2" - plain HF generate is correct
with FA2 (validated: prefill q=13/kv=13, cache grows 14, 15, ..., coherent
output; equivalent to UNSLOTH_DISABLE_FAST_GENERATION=1 but scoped to FA2).
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
* Fix FA2 vision generation fallback
* [pre-commit.ci] auto fixes from pre-commit.com hooks
for more information, see https://pre-commit.ci
* Detect FA2 in VLM llm configs
* Fix default FlashAttention config detection
* Honor language attention overrides
* [pre-commit.ci] auto fixes from pre-commit.com hooks
for more information, see https://pre-commit.ci
* Handle nested FA2 configs and cache cleanup
* Pin a dynamic cache on the FlashAttention fallback for PR #7429
* Cover the explicit cache kwarg and caller caches in the FA2 fallback for PR #7429
* Tighten the FlashAttention fallback comments for PR #7429
---------
Co-authored-by: Piotr Wąsiewicz <piotrwasiewicz72@mail.com>
Co-authored-by: Claude Fable 5 <noreply@anthropic.com>
Co-authored-by: Etherll <61019402+Etherll@users.noreply.github.com>
Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>
Co-authored-by: danielhanchen <danielhanchen@gmail.com>
