P1 #1: ``_release_llama_for()`` now verifies ``llama.unload_model``
did not return False AND that ``is_loaded`` / ``is_active`` /
``loading_model_identifier`` are all cleared after the call. The
previous version only treated raised exceptions as failure, so a
subprocess refusing to terminate or an in-flight GGUF download
let the next workload allocate on top.
P1 #2: ``DiffusionBackend._release_other_gpu_owners_for_diffusion``
now raises RuntimeError when ``exp._shutdown_subprocess`` fails on
a settled checkpoint. Direct backend callers used to log at debug
level and proceed toward diffusion allocation while the export
checkpoint still owned VRAM.
P1 #3 + P1 #7: ``/images/load`` no longer drops chat + idle export
before the cheap backend validation runs. ``DiffusionBackend.load_model``
already calls the strict ``_release_other_gpu_owners_for_diffusion``
and ``_release_chat_backend_for_diffusion`` helpers AFTER family
inference and GGUF filename checks pass, so the GPU is still
freed before allocation and a malformed payload no longer
silently unloads the user's chat / chat-export pair.
P1 #4: ``_release_chat_backend_for_diffusion`` now also rejects a
post-unload state where ``loading_model_identifier`` is still set,
matching the route-level ``_release_llama_for`` strictness. A GGUF
download mid-flight before the diffusion handoff used to slip
through and end up double-owning VRAM after diffusion allocated.
P1 #5: ``_release_diffusion_for`` no longer swallows a post-unload
``status()`` failure as ``after = {}``. Training / chat / export
handoffs need proof that the diffusion pipeline released VRAM;
the helper now raises HTTP 503 when the verification status call
itself raises, so the caller retries.
P1 #6: ``DiffusionBackend._release_other_gpu_owners_for_diffusion``
raises RuntimeError when ``get_export_backend()`` itself raises.
Direct backend callers used to silently ``return`` here and
proceed to GPU allocation without being able to verify export
ownership.
P1 #8: ``/training/start`` releases settled export BEFORE chat,
matching the chat-load helpers. If idle export shutdown fails the
user's chat model is preserved instead of being dropped for a
training run that never starts.
P2 #9: GGUF load-error scrubber also collapses ``local_gguf_path``,
the resolved HF cache path passed to
``transformer_cls.from_single_file()``. Without this an exception
like ``OSError: cannot load /home/alice/.cache/huggingface/.../flux.gguf``
would leak the operator's filesystem layout through ``last_error``
and ``/images/status``.
All 85 diffusion-relevant backend tests pass locally.
da27143520