Pydantic AI v2.64.0 (2026-10-30)
Pydantic AI v2.64.0 introduces new ModelFallback and retry capabilities, a BoxdSandbox workspace, artifact security scanning for Memory and Skills, and makes json-repair an optional dependency.
Why this signal matters
Pydantic AI version 2.64.0 brings significant updates across model resilience, execution environments, and agent safety. Key Highlights: - Model Resiliency: Introduces ModelFallback (constructible from agent specs, supporting sticky fallback routing), RetryModelRequest, and a first-event timeout model setting to enable fallback when streams stall. Transport errors giving up during retries now raise ModelHTTPError. - Tooling & Sandboxes: Adds BoxdSandbox for running Coder, Shell, FileSystem, and other harness capabilities within a boxd machine. Strict tool schemas for Coder are now disabled by default (opt-in via Coder(strict=True)). json-repair is shifted to an optional dependency needed only by Coder and RepairToolArguments. - Agent Security & Artifacts: Introduces ArtifactScanner for agent artifact security scanning across Memory and Skills. - Realtime & Speech: Adds output speech word timestamps for Azure AI Voice Live and ElevenLabs Agents, and fixes reconnection queuing and reference-counted session cleanup in realtime interfaces. - State and Protocol Handling: Stored response, item, conversation, and container IDs are now sent back only to the endpoint that created them via Model.accepts server state.
Actionable summary
Pydantic AI v2.64.0 adds ModelFallback capabilities with sticky routing, stream first-event timeouts, and per-attempt request preparation. Compatibility notes highlight turning off strict tool schemas for Coder by default, moving json-repair to an optional dependency, raising exhausted transport retries as ModelHTTPError, and restricting stored IDs to their creating endpoint via Model.accepts.
- Agent usefulness
- 77/100
- Confidence
- 96%
- Canonical data
- JSON + Markdown
What builders should check
- Opt into Coder(strict=True) if your application requires strict tool schemas when using Coder.
- Install json-repair explicitly if relying on Coder or RepairToolArguments in environments where optional dependencies are not installed by default.
- Review error handling for transport retries, anticipating ModelHTTPError to handle fallback logic.
- Verify endpoint configurations if relying on stored conversation or container IDs, as Model.accepts now limits returns strictly to the creating endpoint.