A chunk that samples to completion and returns NaN/Inf currently sails through
everything: the scene blend spreads it into the already-finished scenes, the VAE
decodes it, and the first thing that objects is ffmpeg's AAC encoder — "Input
contains (near) NaN/+-Inf", naming nothing that produced it, after the whole
montage has been paid for. The video half never objects at all: NaN through
astype(np.uint8) is undefined but silent, so it degrades with a warning.
_sample_chunk now checks the returned latent and raises with the run-phase label
("scene 2/3 · pass 1 of 2"), which stream, how many values and what dtype, plus
the causes worth testing in order — mismatched LoRA, a mis-inferred checkpoint
layout, a dtype the model cannot hold. It raises rather than warns because a
non-finite latent is unrecoverable and blending it forward destroys the scenes
that were still good. One isfinite() per chunk against a multi-second sample is
not a cost worth weighing; a latent the helper cannot read is ignored, never
fatal.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
