Pydantic AI Updates: September 1, 2026

1. Pydantic AI v2.37.0 Adds glm-5.3-flash Support and Hardens Durable Operations

Pydantic AI released v2.37.0, which adds support for the glm-5.3-flash model and reworks the Z.AI test suite onto recorded cassettes, alongside accepting and mapping Z.AI’s non-standard finish_reason values. The release routes Vertex versus Gemini API branches in GoogleModel by client transport rather than provider name, and emits an AG-UI TEXT_MESSAGE_START event for assistant messages so tool-call streaming behaves correctly. Several fixes target durable execution, including context-managing models rebuilt inside durable operations, rejecting per-run capabilities= on DBOS to match Temporal behavior, and journaling Prefect tool discovery in tasks. It also preserves all conditions in pruned span queries and skips inactive capability hooks in agent tracebacks. Source