$ cat fastapi/week/2026-10-12.log
the week in review · Oct 12 – Oct 18, 2026
FastAPI 0.143.3 and 0.143.4 fix stream float serialization
By RepoJournal · composed from the cited sources · human-reviewed weekly · methodology
Two patch releases in three days, the second adding httpx2 to optional dependencies, while Pydantic lands pydantic-core GC and unpickling fixes.
🐛 Fix non-finite float serialization in JSONL and SSE streams fastapi/fastapi
Non-finite floats previously broke JSONL and SSE stream output; the fix shipped in 0.143.3, so anything streaming floats to clients should be upgraded rather than patched locally.
Fix various issues about GC tracking in `pydantic-core` pydantic/pydantic
The hooks on ValidatorCallable, AssignmentValidatorCallable and ValidatorIterator stop traversing InternalValidator.validator, which is an Arc clone of a subtree the SchemaValidator already owns, so objects are no longer visited twice during GC.
Fix unpickling of generic classes defined in separate module pydantic/pydantic
Generic classes defined in a separate module now unpickle correctly. The change notes that one previously resolving import path no longer resolves, so check any cached or stored pickles from before the fix.
🐛 Fix blocking frontend fallback file checks (#16503) fastapi/fastapi
Frontend fallback file checks were blocking the event loop on every request; the fix landed this week and matters if your app mounts a SPA behind FastAPI's static file handling.
Fix JSON Schema cache key mismatch with nested `json_schema_mode_override` pydantic/pydantic
Nested json_schema_mode_override settings could produce colliding JSON Schema cache keys, which meant a schema generated under one mode could be served for another. Fixes a mismatch tracked as issue 13971.
⬆️ Add httpx2 to optional dependencies fastapi/fastapi
httpx2 joined the optional dependencies in 0.143.4. No action needed for existing TestClient users, but new installs pulling the extras will pick it up.
Honor `ser_json_inf_nan` in Python serialization with `mode=json` pydantic/pydantic
ser_json_inf_nan was ignored when serializing in Python with mode=json; this makes the setting apply there too, matching the behavior already seen on the JSON-schema and streaming side.
Revise Pydantic Logfire description in README (#13990) pydantic/pydantic
Alongside: the Pydantic README got two passes on its Logfire description and a docs conversion table update, plus infrastructure work in the release script, CI hardening, and a pre-commit hook that caught 30 no-break spaces and one word joiner in the repo.
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