FastAPI 0.156.1 has landed as a focused patch release. The only change in this version fixes a bug where Pydantic field metadata was being lost whenever request options were omitted. The fix was contributed by @tiangolo in PR #16549 and was merged almost immediately after the issue was identified, keeping the release cadence tight.
For most applications this is an invisible change, but for anyone leaning on Pydantic's richer field configuration — descriptions, examples, aliases, constraints, or custom JSON schema extras — it matters. Those annotations are what drive generated OpenAPI documentation and validation behaviour, and silently dropping them can produce schemas that look correct in code but are hollow in the docs.
- Preserve Pydantic field metadata when request options are omitted, covering descriptions, examples, aliases, constraints and other annotations attached to fields.
- The fix is a single change, PR #16549 by @tiangolo, so no other behaviour is affected.
- No new configuration, flags or migration steps are required to adopt it.
- Upgrade with
pip install --upgrade fastapior pinfastapi==0.156.1in your dependency file.
Because the release contains only this one fix, upgrading is low risk. If you previously worked around the metadata loss — for example by re-declaring fields in your path operation or hand-editing schema output — you can likely remove those workarounds and let FastAPI carry the annotations through again. Running your existing test suite and diffing the generated openapi.json after the bump is the quickest way to confirm the metadata now survives end to end.
Source: https://github.com/fastapi/fastapi/releases/tag/0.156.1