Uvicorn's `--ws auto` selected its `websockets_impl` protocol on 0.41.0, which is built on `websockets.legacy`. That module raises `AssertionError` in `_drain_helper` during keepalive pings and kills the websocket connection. Each crash runs the Socket.IO `disconnect` handler and drops the session from `SESSION_POOL`, so every subsequent server-to-browser call fails. The most visible symptom is the Pyodide code execution tool, which reaches the browser through `sio.call('events', ...)` and returns `{"stderr": "Client session disconnected."}` on every run.
Uvicorn 0.50.0 changed `--ws auto` to select the sans-io implementation whenever websockets is installed, and deprecated the legacy one. Bumping the pin therefore fixes this on every launch path at once, without adding a `--ws` flag to the startup scripts. Doing nothing is not stable either: websockets is unpinned apart from uvicorn's own `>=13.0` floor, and `websockets.legacy` is removed outright in websockets 17, which turns the current AssertionError into an ImportError on a fresh install.
Bumping to 0.51.0 rather than the minimum 0.50.0 also picks up the sans-io keepalive pings added in 0.44.0, so raw websocket endpoints keep the idle-timeout behaviour they have today behind a reverse proxy. Uvicorn 0.51.0 drops colorama from its `standard` extra and raises the httptools floor to 0.8.0, which the lockfile already satisfies.
Verified on the bumped pin: the backend boots, `/health` returns 200, `--ws auto` resolves to `WebSocketsSansIOProtocol`, a Socket.IO client completes a websocket handshake against the running app, and a bidirectional `sio.call` round trip succeeds. The unit test suite reports an identical 2273 passed / 7 failed on 0.41.0 and 0.51.0, with the 7 failures unrelated to uvicorn.
Fixes#27550
* chore: bump Python backend dependencies, drop unused peewee
Minor/patch + reviewed major bumps across requirements.txt,
requirements-min.txt, pyproject.toml and uv.lock; playwright image bumped in
docker-compose.playwright.yaml. peewee/peewee-migrate removed (zero imports).
Security-relevant: cryptography 46->48, authlib 1.6.10->1.7.2, PyJWT 2.11->2.13,
requests 2.33.1->2.34.2, RestrictedPython 8.1->8.2, pillow 12.1.1->12.2.0.
Reviewed majors: redis 7->8, pymilvus ->2.6.14, azure-search-documents 11->12,
chardet 5->7, unstructured 0.18->0.22, pycrdt 0.12->0.13.
Testing:
- Resolution: `uv lock` resolves the full bumped set with no conflicts; uv.lock
regenerated to match (peewee dropped, every pin including
azure-search-documents==12.0.0 resolves).
- Per-dependency contract tests (external tests repo, unit/deps/): 105 files,
2205 passed / 6 skipped, ruff-clean. One file per dependency pins the symbols,
signatures and behaviour the backend actually uses, so an API removal/rename in
a bumped version fails loudly instead of at runtime. Offline/deterministic.
- End-to-end embed->retrieve test driving transformers + sentence-transformers +
chromadb together through Open WebUI's real RAG path (cached model, in-memory
chroma, semantic retrieval asserted).
- Install/startup/health resolution gate added to the dep-bump workflow and the
integration suite (uv/pip resolve + uvicorn /health + Playwright dev visibility).
- Bugs surfaced while testing each got an isolated fix branch + regression test:
Mistral OCR aiohttp FilePayload (#25779), chroma has_collection (#25780),
aiocache per-user model-cache key (security), otel semconv deprecation,
pydub/audioop <3.13 note.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
* Bump python-multipart 0.0.22 -> 0.0.27 (CVE-2026-42561, CVE-2026-40347)
0.0.22 is affected by two DoS CVEs in the multipart parser that
Starlette/FastAPI run for every multipart/form-data request, so any
authenticated user hitting an upload endpoint can trigger them:
- CVE-2026-42561: unbounded part-header count/size -> CPU exhaustion (fixed 0.0.27)
- CVE-2026-40347: large multipart preamble/epilogue DoS (fixed 0.0.26)
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
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Co-authored-by: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Classic298