Pydantic AI
Typed Python agent loop with a snap-on Coder harness
AI Agents / Coding Agents · OSS/MIT · 19.7k
What's Good
This is a different product from Pydantic-the-validator already on the Python stack. Core is a typed agent loop: structured output, typed deps, typed tools, model as a string swap (OpenAI, Anthropic, Gemini, Bedrock, Groq, Ollama, and more). Pydantic AI Harness snaps on Coder—workspace-rooted files, allowlisted shell, repo orientation, planning, sub-agents, context management—as a regular combined capability you can use whole or take apart (FileSystem, Shell, RepoContext, Planning). Same agent runs as CLI (clai), web chat, realtime voice, or a durable Temporal/DBOS/Prefect job. MIT.
The Catch
ACP (Agent Client Protocol, for editors like Zed) is experimental: it lives under pydantic_ai_harness.experimental.acp, may change or be removed in any release without a deprecation period, and importing it emits HarnessExperimentalWarning. Coder is a capability you assemble, not a turnkey SWE agent like OpenHands. Logfire is the convenient observability path; OpenTelemetry works with any backend. Do not confuse this gem with Pydantic validation.
Verdict
The typed Python agent SDK. Not the validator. ACP is still experimental.
Embed
[](https://stackgems.com/gems/pydantic-ai)