Pydantic AI 2.38.0 highlights: (1) new typed `CustomEvent`/`CapabilityEvent` — application code and capabilities can now emit custom events into the Agent's run event stream and subscribe with `@on_event`, filling in a general-purpose observability and extension layer; (2) `RunContext` gains `context_window_used` and `ModelProfile` gains `context_window`, so agent code can read how much of the model's context window remains, for the first time; (3) new model support for `gemini-3.8-flash`, Claude Fable 5.1, and Claude Mythos 5.1, plus a new `VLLMProvider`. No breaking changes in this release.
Pydantic AI 2.36.0 highlights: (1) new `@durable_operation` decorator turns any custom capability method into a replay-safe durable unit under Temporal/Prefect/DBOS and other engines; (2) a public backend API (`BaseDurabilityCapability`, `CallableOperationBackend`, `RegisteredOperationBackend`) lets third-party durable engines integrate with zero private imports — verified against three out-of-tree engines; (3) one compatibility tightening: MCP tools can no longer opt out of durable execution via tool metadata (previously allowed on DBOS), plus a Prefect dynamic-tool cache-key fix.
These seven tools are not one product category: LangGraph, MAF, and Mastra emphasize durable workflows; CrewAI and AG2 emphasize multi-agent collaboration; Pydantic AI emphasizes typed Python agents; DSPy optimizes AI programs against data and metrics. Choose the control model first.
Pydantic AI models an agent as Agent[Deps, Output]: dependencies, tool inputs, and final outputs are typed, and model results must pass Pydantic validation.
Sorted by GitHub Stars, a survey of 15 mainstream AI Agent frameworks in 2026 — their positioning, key features, and ideal use cases. Not a ranking — it's a map.