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FastAPI 0.143.0 makes OTel auto-setup opt-in, Pydantic 2.14 lands
By RepoJournal ยท Filed ยท About FastAPI & Pydantic ยท Composed from the cited sources ยท methodology
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Two breaking changes in one day: FastAPI stops wiring OpenTelemetry exporters for you unless you ask, and Pydantic 2.14 drops Python 3.9 support while promising less allocation per field validation.
0.143.0 fastapi/fastapi
Automatic OpenTelemetry exporter setup is now opt-in, so apps depending on FastAPI reading OTEL_* environment variables must set FASTAPI_OTEL_AUTO_CONFIGURE=true or pass FastAPI(telemetry={"auto_configure": True}). Code that configures its own providers and exporters needs no changes, and FastAPI Cloud still turns the automatic path on for you.
๐ฅ Require opt-in for automatic OpenTelemetry exporter setup fastapi/fastapi
The PR behind the release states the fix in one line: "to enable autoconfiguration of exporters, set the env var FASTAPI_OTEL_AUTO_CONFIGURE=true." The change ships with an explicit AI disclaimer from the author, noting it was made with Codex and manually reviewed.
v2.14.0 2026-10-08 pydantic/pydantic
Pydantic 2.14.0 drops Python 3.9 support and adds 3.15, and the release notes flag that several minor changes are non-breaking only under Pydantic's own versioning policy, so they are worth reading before you upgrade. The release date was corrected the same day after the initial post carried the wrong one.
Avoid Python tuple allocation during model fields validation pydantic/pydantic
Field validation no longer builds a Python tuple per model during validation, in a change that closes the linked allocation issue. Anyone validating high volumes of models stands to be affected; the PR body gives no benchmark figures, so treat the win as directional until you measure your own workload.
Fix `arguments-v3` schema with variadic keywords pydantic/pydantic
The long tail: the arguments-v3 schema now handles variadic keywords correctly, landing alongside the supporting fixture updates and release-note edits that kept the 2.14 train tidy.
Action items
- โ Set FASTAPI_OTEL_AUTO_CONFIGURE=true (or FastAPI(telemetry={"auto_configure": True})) if you rely on FastAPI to set u... fastapi/fastapi [immediate]
- โ Drop Python 3.9 from your CI and supported versions before upgrading to pydantic 2.14.0 pydantic/pydantic [plan]
