Three round-32 reviewer findings, plus documentation cleanup for
the local-path Tauri/FE plumbing gap.
Concurrency: direct DiffusionBackend.load_model callers now publish
the helper/advisor pending marker symmetrically (round 32 P1 #3).
_raise_if_helper_advisor_busy_for_diffusion gains an optional
publish_pending flag; load_model passes True so the destructive
unload window is gated by a "diffusion-backend" tag published
under _HELPER_ADVISOR_START_LOCK. The route layer's "diffusion"
tag and the backend's "diffusion-backend" tag refcount
independently (sum > 0 still blocks helper starts), so neither
side's clear can erase the other's still-active marker. The
existing _release_chat_backend_for_diffusion(check_helper_advisor=
True) path stays snapshot-only (publish_pending defaults False) so
test / direct callers of that helper do not leak a counter.
Validation: export save_directory now rejects ALL ASCII control
characters (round 32 P1, save_directory tab finding). The earlier
CR / LF only guard missed TAB / VT / FF / DEL, which a caller
could smuggle past the export worker's logged subprocess argv.
Documentation: DiffusionLoadRequest.repo_id and base_repo updated
to reflect that local-path support is gated on a Tauri /
frontend load-diffusion-model directory lease producer that has
not shipped yet (round 32 P1 #1 from multiple reviewers). The
backend lease boundary is correct; what is missing is the FE /
native side that mints the matching grant. Until that lands,
local paths through the Images route always 400 with "Native
path grant is required", which the docstring now spells out.
Skipped (consistent with prior rounds):
* Hub-pin findings (R32 P1 #4-#6): live B200 install with
huggingface_hub==0.36.2 + transformers==4.57.6 + diffusers==
0.37.1 verifiably imports Flux2KleinPipeline. Empirical
justification documented in R30 / R30 follow-up commit msgs.
* Tauri / native enum surgery (R32 P1 #1, 6 votes): real
architectural work but out of scope for this PR's Python
surface. Documented now; FE / Rust ticket to follow.
98 targeted backend tests pass (test_diffusion_routes,
test_diffusion_backend, test_inference_model_validation,
test_models_get_model_config_case_resolution, test_data_recipe_seed,
test_training_raw_support, test_export_log_cursor).
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