Qwen-Image: diffusers registers a no-op identity lambda for
QwenImageTransformer2DModel; from_single_file silently accepted any
key naming and loaded with mismatches. QWEN_SPEC sets converter=None
to short-circuit the no-op.
Custom transformer classes (Lens, Step1X-Edit, VIBE Sana, f-lite):
runtime-registered onto diffusers, never in SINGLE_FILE_LOADABLE_CLASSES.
Specs land in each arch's existing pipelines/<arch>/__init__.py.
NextStep skipped: loader returns None up front.
CalamitousFelicitousness
Vladimir Mandic