●Change8

Migrating to Pydantic v2.12.1

Version v2.12.1 introduces 2 breaking changes. This guide details how to update your code.

Released: 10/13/2025

2
Breaking Changes
4
Migration Steps
6
Affected Symbols

⚠️ Check Your Code

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

ValidationInfoMultiHostUrlserialize_as_anyRootModelfield_validatormodel_serializer

Breaking Changes

●Issue #1

If you were relying on annotations being evaluated during the inspection of validators or serializers, this behavior has been corrected to prevent evaluation.

✓Solution

If your custom validation or serialization logic depended on side effects during annotation evaluation, you may need to move that logic to explicit runtime checks or initialization steps.

●Issue #2

The handling of `None` conversion when targeting Python 3.14 has been adjusted to explicitly convert `None` to `NoneType`.

✓Solution

This is primarily an internal fix for future Python compatibility; users should generally not need to change code unless they were relying on specific pre-3.14 behavior for `None` handling during validation.

Migration Steps

  1. 1
    Review your current Pydantic version. This guide applies when migrating from v2.12.0 or earlier to v2.12.1.
  2. 2
    Update your Pydantic dependency to version 2.12.1 or later using your package manager (e.g., pip install pydantic>=2.12.1).
  3. 3
    If you experienced issues related to validator/serializer inspection or `RootModel` serialization in v2.12.0, test your application thoroughly against v2.12.1.
  4. 4
    If you are using Python 3.14, be aware that `None` conversion behavior is now explicitly handled as `NoneType`.

Release Summary

This patch release addresses several regressions introduced in v2.12.0, specifically focusing on serialization fixes for RootModel and serialize_as_any, as well as Python 3.14 compatibility.

Need More Details?

View the full release notes and all changes for Pydantic v2.12.1.

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