# Pydantic: what changed from 1 to 2

- Product: Pydantic (https://whatsnew.fyi/product/pydantic)
- Vendor: Pydantic
- Range: changelog entries numbered after v1.10.26 up to and including v2.13.5, stable releases only
- Entries below: 6 releases (newest first)
- Resolved: 1 is v1.10.26 and 2 is v2.13.5, the newest stable release of each major we track
- Carrying security changes: 0 · CVEs mentioned: 0 · Mentioning breaking changes: 1 · Removing or deprecating something: 0
- Page: https://whatsnew.fyi/product/pydantic/compare/1...2

What's New is an index, not a publisher: every entry below links to the vendor's own release notes, which are the authoritative source. Entries are labelled where they are hand-curated sample data, pre-releases, or drawn from a secondary source such as a developer blog.

Reuse: the summaries, labels and curation here are © What's New. Quote freely with attribution and a link back; wholesale republication of the corpus is not permitted — terms: https://whatsnew.fyi/terms. The vendors' own release notes remain their publishers'.

## What changed (13 changes, grouped by kind)

### Added

#### v2.13.0 (2026-04-13)

- Allow default factories of private attributes to take validated model data

### Changed

#### v2.13.0 (2026-04-13)

- Warn when serializing fixed length tuples with too few items
- Update jiter to v0.14.0 to fix a segmentation fault on musl Linux

### Fixed

#### v2.13.5 (2026-08-28)

- Allow reuse of validators when plugins are set
- Fix missing GC traversal on some pydantic-core struct fields
- Fix missing GC traversal in pydantic-core for GeneralFieldsSerializer
- Count validated model fields once in smart unions

#### v2.13.4 (2026-05-06)

- Preserve RootModel core metadata

#### v2.13.3 (2026-04-20)

- Handle AttributeError subclasses with from_attributes

#### v2.13.2 (2026-04-20)

- Fix ValidationInfo.field_name missing with model_validate_json()

#### v2.13.1 (2026-04-15)

- Fix ValidationInfo.data missing with model_validate_json()

#### v2.13.0 (2026-04-13)

- Change type of Any when synthesizing _build_sources for BaseSettings.__init__() signature in the mypy plugin
- Fix model equality when using runtime extra configuration

## Release notes

### v2.13.5

- Date: 2026-08-28
- Version: v2.13.5
- Original notes: https://github.com/pydantic/pydantic/releases/tag/v2.13.5
- Permalink: https://whatsnew.fyi/product/pydantic/releases/v2.13.5

- **fixed** — Allow reuse of validators when plugins are set
- **fixed** — Fix missing GC traversal on some pydantic-core struct fields
- **fixed** — Fix missing GC traversal in pydantic-core for GeneralFieldsSerializer
- **fixed** — Count validated model fields once in smart unions

##### v2.13.5 (2026-08-28)

###### What's Changed

###### Fixes

* Allow reuse of validators when plugins are set by @Viicos in [#13535](https://github.com/pydantic/pydantic/pull/13535)
* Fix missing GC traversal on some `pydantic-core` struct fields by @Viicos in [#13624](https://github.com/pydantic/pydantic/pull/13624)
* Fix missing GC traversal in `pydantic-core` for `GeneralFieldsSerializer` by @Viicos in [#13629](https://github.com/pydantic/pydantic/pull/13629)
* Count validated model fields once in smart unions by @tamird in [#13731](https://github.com/pydantic/pydantic/pull/13731)

### v2.13.4 — v2.13.4 2026-05-06

- Date: 2026-05-06
- Version: v2.13.4
- Original notes: https://github.com/pydantic/pydantic/releases/tag/v2.13.4
- Permalink: https://whatsnew.fyi/product/pydantic/releases/v2.13.4

- **fixed** — Preserve RootModel core metadata

##### v2.13.4 (2026-05-06)

###### What's Changed

###### Packaging

* Bump libc from 0.2.155 to 0.2.185 by @Viicos in [#13109](https://github.com/pydantic/pydantic/pull/13109)
* Adapt `pydantic-core` linker flags on macOS by @washingtoneg and @Viicos in [#13147](https://github.com/pydantic/pydantic/pull/13147)

###### Fixes

* Preserve `RootModel` core metadata by @Viicos in [#13129](https://github.com/pydantic/pydantic/pull/13129)

**Full Changelog**: https://github.com/pydantic/pydantic/compare/v2.13.3...v2.13.4

### v2.13.3 — v2.13.3 2026-04-20

- Date: 2026-04-20
- Version: v2.13.3
- Original notes: https://github.com/pydantic/pydantic/releases/tag/v2.13.3
- Permalink: https://whatsnew.fyi/product/pydantic/releases/v2.13.3

- **fixed** — Handle AttributeError subclasses with from_attributes

##### v2.13.3 (2026-04-20)

###### What's Changed

###### Fixes

* Handle `AttributeError` subclasses with `from_attributes` by @Viicos in [#13096](https://github.com/pydantic/pydantic/pull/13096)

**Full Changelog**: https://github.com/pydantic/pydantic/compare/v2.13.2...v2.13.3

### v2.13.2 — v2.13.2 2026-04-17

- Date: 2026-04-20
- Version: v2.13.2
- Original notes: https://github.com/pydantic/pydantic/releases/tag/v2.13.2
- Permalink: https://whatsnew.fyi/product/pydantic/releases/v2.13.2

- **fixed** — Fix ValidationInfo.field_name missing with model_validate_json()

##### v2.13.2 (2026-04-17)

###### What's Changed

###### Fixes

* Fix `ValidationInfo.field_name` missing with `model_validate_json()` by @Viicos in [#13084](https://github.com/pydantic/pydantic/pull/13084)

**Full Changelog**: https://github.com/pydantic/pydantic/compare/v2.13.1...v2.13.2

### v2.13.1 — v2.13.1 2026-04-15

- Date: 2026-04-15
- Version: v2.13.1
- Original notes: https://github.com/pydantic/pydantic/releases/tag/v2.13.1
- Permalink: https://whatsnew.fyi/product/pydantic/releases/v2.13.1

- **fixed** — Fix ValidationInfo.data missing with model_validate_json()

##### v2.13.1 (2026-04-15)

###### What's Changed

###### Fixes

* Fix `ValidationInfo.data` missing with `model_validate_json()` by @davidhewitt in [#13079](https://github.com/pydantic/pydantic/pull/13079)

**Full Changelog**: https://github.com/pydantic/pydantic/compare/v2.13.0...v2.13.1

### v2.13.0 — v2.13.0 2026-04-13

- Date: 2026-04-13
- Version: v2.13.0
- Original notes: https://github.com/pydantic/pydantic/releases/tag/v2.13.0
- Permalink: https://whatsnew.fyi/product/pydantic/releases/v2.13.0

- **added** — Allow default factories of private attributes to take validated model data
- **changed** — Warn when serializing fixed length tuples with too few items
- **changed** — Update jiter to v0.14.0 to fix a segmentation fault on musl Linux
- **fixed** — Change type of Any when synthesizing _build_sources for BaseSettings.__init__() signature in the mypy plugin
- **fixed** — Fix model equality when using runtime extra configuration

##### v2.13.0 (2026-04-13)

The highlights of the v2.13 release are available in the [blog post](https://pydantic.dev/articles/pydantic-v2-13-release).
Several minor changes (considered non-breaking changes according to our [versioning policy](https://pydantic.dev/docs/validation/2.13/get-started/version-policy/#pydantic-v2)) are also included in this release. Make sure to look into them before upgrading.

This release contains the updated `pydantic.v1` namespace, matching version 1.10.26 which includes support for Python 3.14.

###### What's Changed

See the beta releases for all changes sinces 2.12.

###### Packaging

* Add zizmor for GitHub Actions workflow linting by @Viicos in [#13039](https://github.com/pydantic/pydantic/pull/13039)
* Update jiter to v0.14.0 to fix a segmentation fault on musl Linux by @Viicos in [#13064](https://github.com/pydantic/pydantic/pull/13064)

###### New Features

* Allow default factories of private attributes to take validated model data by @Viicos in [#13013](https://github.com/pydantic/pydantic/pull/13013)

###### Changes

* Warn when serializing fixed length tuples with too few items by @arvindsaripalli in [#13016](https://github.com/pydantic/pydantic/pull/13016)

###### Fixes

* Change type of `Any` when synthesizing `_build_sources` for  `BaseSettings.__init__()` signature in the mypy plugin by @Viicos in [#13049](https://github.com/pydantic/pydantic/pull/13049)
* Fix model equality when using runtime `extra` configuration by @Viicos in [#13062](https://github.com/pydantic/pydantic/pull/13062)

###### New Contributors

* @arvindsaripalli made their first contribution in [#13016](https://github.com/pydantic/pydantic/pull/13016)

**Full Changelog**: https://github.com/pydantic/pydantic/compare/v2.12.0...v2.13.0