Pydantic AI vs Claude Agent SDK
The Claude Agent SDK gives you the agent loop behind Claude Code: a Python package that drives the bundled claude CLI, with Anthropic’s built-in tools, permissions and sub-agents already wired up. Pydantic AI gives you the loop itself: a typed Agent on any model, and Coder as a complete coding agent built from capabilities you can swap, extend or leave out.
Pydantic AI is one part of a stack: the Harness SDK for capabilities and complete agents, Pydantic Evals, Pydantic Graph, Pydantic Logfire for observability, and Pydantic itself for validation. The tables below cover the whole of it.
Already built on the Claude Agent SDK? The migrating-claude-agent-sdk-to-pydantic-ai skill ports an existing application to Pydantic AI one working path at a time, preserving behavior rather than translating API names.
| Claude Agent SDK | Pydantic AI and Harness SDK | |
|---|---|---|
| Language | Python SDK wrapping the TypeScript claude CLI | Python |
| License | MIT | MIT |
| Model providers | Claude (Anthropic, Bedrock, Vertex, Foundry) | Many |
| Extensibility | Hooks, allowed_tools | Capabilities and toolsets; 50+ with the Harness SDK |
| Harnesses | Claude Code’s; hooks extend it, you cannot recompose it | Built-in Coder and Researcher, or compose your own |
| Observability | OpenTelemetry from the CLI | OpenTelemetry, including Pydantic Logfire |
| Durable execution | No | Seven integrations |
| Interfaces | CLI | CLI, web chat, AG-UI, Vercel AI, ACP (experimental) |
| Realtime voice | No | Realtime |
| Evals | No | Pydantic Evals |
| Image generation | No | Image Generation |
| Claude Agent SDK | Pydantic AI and Harness SDK | |
|---|---|---|
| Multi-agent | Yes | Subagents, delegation, or pydantic-graph |
| Planning | Yes | Planning |
| Skills | Yes | Skills |
| Memory | Yes | Memory |
| Compaction | Yes | Compaction |
| Guardrails | Yes | Guardrails |
| Code sandboxes | Yes | Execution environments |
| Browser use | No | Web & research |
Can I build my own coding agent harness? Yes. Give your agent the
Coder() capability, or assemble your own from the
same Agent; the harness repository has a
complete coding agent
built from the pieces Coder puts together.
Can I run my agents in CI? Yes. GitHub Agentic Workflows runs Pydantic AI agents
from a Markdown workflow file in GitHub Actions, or run a Python script directly with uv run;
nothing requires an Action.