Two defects between a loading model and a finished clip, both found by running it.

A repo id is not a directory. models.json holds what the model page registered —
"meituan-longcat/LongCat-Video" — and resolve_model_path handed it straight to
the service, which opens config.json, the VAE and the INT8 shards by path. Every
load died with "checkpoint directory does not exist" before reading a byte.
resolve_checkpoint() maps a repo id onto its newest snapshot in the hub cache,
by hand rather than through huggingface_hub so the server's 3.13 venv and the
service's 3.10 venv cannot disagree about where the weights are, and so a
checkpoint that was never fetched stays an error instead of becoming a silent
74 GB download.

And the offload added in v0.2.67 was only half of one. It held the text encoder
off the card until encode_prompt and then brought it over WITH the DiT still
resident: 13.6 GB of INT8 DiT plus ~11 GB of UMT5-XXL is 24.8 GB on a 24 GB
card. It OOM'd on the first prompt of the first generation. Model offload means
only the active component is on the card, so they take turns now — the DiT steps
off for the encode and comes back for the loop, in a finally, because a failed
prompt that stranded the DiT on the host would leave every later generation
running at PCIe speed with nothing to say why. Peak is max(), not sum.

The placement test passed on the broken version: it asserted the encoder arrived
and left, never that the DiT was not there too. It asserts co-residency now, and
fails on the old code.

Measured end to end on the 3090: 33 frames at 480x832, distilled stage, 16 steps
at 9.4 s/it, 13.6 GB resident, HTTP 200 with the mp4.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_0185zEBiy3KWB37xNGSrxL7w