Five fixes from a review pass over the diffusion work.
delete-finetuned rmtree'd a model the Images or Video engine was holding: every
guard on that route is chat-only, and Images loads any local path, so deleting a
local diffusion model under the storage root pulled the weights (and the
companion VAE / text encoders sd.cpp re-reads each generation) out from under a
live pipeline. The cached-model route already refuses this; the trained/exported
one now does too, matching by path rather than repo id, and failing open on a
chat-only install so it cannot block ordinary deletes.
A staged download finishing while its page was hidden loaded the model and
evicted whatever the user was actually using: both diffusion pages stay mounted
behind the router and a load takes the GPU unconditionally. The pick is now held
until its page is on screen again, which is also what chat does.
A scoped download could report success having fetched nothing. With Hugging Face
metadata unavailable no manifest is written, so verification is a no-op, and
snapshot_download returns an existing snapshot folder without downloading when
its own repo_info call fails. A repo already on disk from a full snapshot job
(which ignores *.gguf) therefore completed with no weights and auto-loaded
against them. The requested file list needs no network, so it is checked against
the disk directly.
The XET to HTTP retry reclaimed the job slot without the scoped file list, and
that claim overwrites the stored record, so a later identical scoped start
compared an empty list against the real one and 409'd instead of adopting the
running download.
The DiT accelerator gate probed torch.mps.is_available(), which only exists from
torch 2.5 while the supported floor is 2.4. All three probes shared one
try/except, so on torch 2.4 the AttributeError read as 'no block' and a CPU-only
host still evicted the resident pipeline, downloaded the encoders and died in
the child. Each accelerator is probed on its own now, through
torch.backends.mps.
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