●Change8

Migrating to FastAPI 0.126.0

Version 0.126.0 introduces 1 breaking change. This guide details how to update your code.

Released: 12/20/2025

1
Breaking Changes
3
Migration Steps
4
Affected Symbols

⚠️ Check Your Code

If you use any of these symbols, you need to read this guide:

pydanticpydantic.v1pydantic-settingspydantic-extra-types

Breaking Changes

●Issue #1

Dropped support for Pydantic v1. Users must upgrade to Pydantic v2.7.0 or higher. Temporary support for Pydantic v2's 'pydantic.v1' bridge is maintained.

Migration Steps

  1. 1
    Upgrade Pydantic to version >= 2.7.0.
  2. 2
    If using 'standard' dependencies, ensure pydantic-settings >= 2.0.0 and pydantic-extra-types >= 2.0.0 are installed.
  3. 3
    Update any code relying on Pydantic v1 internals to use Pydantic v2 or the 'pydantic.v1' compatibility layer.

Release Summary

This release drops support for Pydantic v1, establishing Pydantic v2.7.0 as the new minimum requirement while adding performance testing via CodSpeed.

Need More Details?

View the full release notes and all changes for FastAPI 0.126.0.

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