Pydantic AI v2.20.0 adds Claude Opus 5 and OpenAI reasoning context support

Full analysis

Pydantic AI, an agent-building framework built on the Pydantic data-validation library, released v2.20.0 on July 28 2026. The headline features are support for Anthropic's Claude Opus 5 model and OpenAI Responses API reasoning.context (defaulting to all_turns) for the GPT-5.4/5.5/5.6 model families — meaning agents can now maintain full reasoning chains across turns rather than discarding them.

The release also fixes several agent-reliability issues: MCP (Model Context Protocol, a standard for agent tool connectivity) errors are now recoverable rather than fatal, tool-search history is preserved when switching between providers, and Anthropic 'thinking tokens' (extended reasoning token usage) are now correctly captured in usage metrics. These fixes collectively improve multi-provider orchestration and observability for production agent deployments.