v2.51.0 v2.52.0
pydantic/pydantic-aiSep 25, 2026 → Sep 30, 20264 days between releases
What's New
Bundles pydantic-ai-harness, introduces Workspaces, and fixes a web_fetch security vulnerability.
Breaking Changes
- pydantic-ai-harness version jumps from 0.36.0 to 0.52.0 (bundled).
- ModalSandbox's tools replaced by a Modal workspace.
- SubAgents no longer loads agent files by default.
- inherit_tools is deprecated.
- AnthropicModel default max_tokens raised from 4096 to 16384.
New Features
- Introduced ctx.workspace for tools to access files and commands.
- Added SpritesSandbox and E2BSandbox.
- Added SSHWorkspace and BubblewrapSandbox.
- Azure AI Voice Live support.
- OpenAI gpt-6.1-sol model support.
Improvements
- Run harness capabilities in any workspace.
- ModalSandboxBackend replaces ModalSandboxSession.
- Fixed moderate security vulnerability in web_fetch (GHSA-v36g-jcw9-x7cw).
Bug Fixes
- Keep the prompt as a DecisionModel's judged text after a retry.
Upgrade Notes
Update pydantic-ai-harness to 0.52.0 as it is now bundled. SubAgents no longer loads agent files by default, and inherit_tools is deprecated. AnthropicModel defaults increased to 16384 tokens.
The Two Releases
v2.51.0 (2026-09-25)
Sep 25, 2026· 26 days ago
Focuses on performance improvements, such as caching the agent graph and reducing overhead, while adding support for OpenAI GPT-Live and refining error handling for real-time sessions.
Full release notesv2.52.0 (2026-09-29)
Sep 30, 2026· 22 days ago
This release introduces the concept of 'Workspaces' for unified file and command execution, bundles `pydantic-ai-harness` into the main repository, and adds support for new sandbox environments and AI models.
Full release notes