Initial pre-inference capability probe (not a model inference failure):
Traceback (most recent call last):
  File "<string>", line 1, in <module>
AttributeError: module 'transformers.models.qwen3_5.modeling_qwen3_5' has no attribute 'is_fast_path_available'
2.10.0+cu128 12.8

Resolution: inspect the Transformers 5.17 decorated torch_chunk_gated_delta_rule / torch_recurrent_gated_delta_rule functions and their selected implementation closures. Both actual runs record all four optimized implementations.
