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v2.10.0

pydantic/pydantic-aiv2.10.0Jul 15, 2026by dsfaccini

AI Summary

This release improves provider compatibility by making `message_history` provider-valid out of the box to repair tool-call/result pairing. It also adds support for OpenAI background mode and Anthropic's `stop_reason=pause_turn`, alongside several bug fixes and a security dependency update.

Key Highlights

  • `message_history` is now provider-valid out of the box
  • Support for OpenAI background mode and Anthropic `stop_reason=pause_turn`
  • Security update: Bump `transformers` floor to >=5.5.0 for CVE-2026-5241
  • Fix for `RenamedToolset` silently dropping tools on collision
  • Fix event-loop affinity in `run_stream_sync`

New Features

  • OpenAI background mode support
  • Anthropic `stop_reason=pause_turn` handling

Full Release Notes

<!-- Release notes generated using configuration in .github/release.yml at main -->

## What's Changed
### 🚀 Features
* Make `message_history` provider-valid out of the box (repair tool-call/result pairing) by @DouweM in https://github.com/pydantic/pydantic-ai/pull/6319
* Add support for OpenAI background mode and handle Anthropic `stop_reason=pause_turn` by @DouweM in https://github.com/pydantic/pydantic-ai/pull/6303
### 🐛 Bug Fixes
* Fix `has_values()` returning `True` for all-zero usage `details` by @sean-kim05 in https://github.com/pydantic/pydantic-ai/pull/6466
* Fix `RenamedToolset` silently dropping a tool on a name collision by @sean-kim05 in https://github.com/pydantic/pydantic-ai/pull/6462
* Preserve invalid UTF-8 `bytes` in instrumentation serialization by @alexmojaki in https://github.com/pydantic/pydantic-ai/pull/6483
* Fix event-loop affinity in `run_stream_sync` by @adtyavrdhn in https://github.com/pydantic/pydantic-ai/pull/6454
* Attach xAI `ToolCallPart` to the preceding reasoning message by @dsfaccini in https://github.com/pydantic/pydantic-ai/pull/5924
* Filter unconfigured Anthropic native tool calls by @hxaxd in https://github.com/pydantic/pydantic-ai/pull/6463
* Fix `DeferredToolResults` resume when an output tool call was settled in the same batch as deferred calls by @DouweM in https://github.com/pydantic/pydantic-ai/pull/6491
### 📦 Dependencies
* Bump `transformers` floor to >=5.5.0 for CVE-2026-5241 by @hramezani in https://github.com/pydantic/pydantic-ai/pull/6482

## New Contributors
* @sean-kim05 made their first contribution in https://github.com/pydantic/pydantic-ai/pull/6466
* @ShawnChen-Sirius made their first contribution in https://github.com/pydantic/pydantic-ai/pull/6467
* @deepakdevp made their first contribution in https://github.com/pydantic/pydantic-ai/pull/4718
* @hxaxd made their first contribution in https://github.com/pydantic/pydantic-ai/pull/6463

**Full Changelog**: https://github.com/pydantic/pydantic-ai/compare/v2.9.1...v2.10.0