Pydantic AI Updates: April 29, 2026

1. Pydantic AI v1.88.0 Adds Output Validate/Process Hooks and Cross-Provider Service Tier Settings

Pydantic AI. Pydantic AI v1.88.0 ships output validate and process hooks via a new prepare_output_tools capability, giving authors a single place to inspect or rewrite tool outputs before they go back into the agent loop. The release also introduces a cross-provider service_tier model setting that maps to Anthropic Priority Tier, the Gemini API service tier, and Vertex Priority PayGo with a single configuration knob — useful for applications that target the same agent against multiple providers and want consistent latency/cost guarantees. There’s a new Anthropic “fast” speed mode for Claude Opus 4.6, OpenAI Responses phase support on assistant messages, and UI-adapter improvements (sanitize_messages, allowed_file_url_schemes). Bug fixes restore per-block cache_control for anthropic_cache_messages, fix error propagation when a CallToolsNode stream fails, and propagate Agent(retries=...) into user-provided toolsets. Source