Reported from the first live run: the idea works (opening reads as t2v,
character details preserved) but the output is full of noise artifacts, as if
under-denoised, with the last steps seemingly skipped. That was a real bug, not
the concept.
comfy's CONST scaling is x = sigma*noise + (1-sigma)*latent_image, and it
treats latent_image as a CLEAN image. Pass 2 was handed the PARTIALLY DENOISED
latent as latent_image, so at a 0.725 cut it entered at
0.725*fresh_noise + 0.275*picture — pass 1's content attenuated to a quarter
and buried under a full dose of new noise, with only the tail steps left to
recover. Exactly the reported symptom.
I cited segmented detailing's stage-2 tail as the precedent for this re-entry,
but that recipe feeds a FINISHED latent, where re-noising is correct. The
precedent does not transfer mid-trajectory. My error.
Fix — the two modes are now actually different things:
- CONTINUE (restart sigma 0, the default): pass 2 resumes from exactly the
state pass 1 handed over. Passing that state as BOTH noise and latent_image
collapses the CONST expression to an identity (s*x + (1-s)*x == x), so no
noise is added at all. Cost still one full schedule.
- REWIND (restart sigma > 0): pass 1 now runs the WHOLE schedule to a finished
clip first, the shift is applied to that, and pass 2 re-noises it upward and
denoises down. That is the img2img recipe, and it is valid precisely because
the input is finished. Costs a full schedule plus the tail.
Also fixed pass 2's progress offset, which restarted at pass 1's, so the bar
appeared to stall short of the end.
Two new tests reproduce the CONST arithmetic directly and assert the identity
holds in continue mode and does not in rewind mode. Their comfy stubs are now
snapshot/restored — the first version leaked into other modules and shifted the
suite off baseline (3 unrelated tests changed result). Back to baseline: 22
pre-existing failures, 272 passing.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
