Updated 2026-10-13

Best AI frameworks for building agents

Libraries for developers building agents. If you want a product that runs the workflow for you, use the agents page instead.

Paid placement. Not part of the ranking.

A labeled placement sits above the ranking. Buying it does not move anyone up or down.

Ranked picks

Order is fit, quality, price and access, then freshness. Sponsorship is not an input.

01
LangGraphOpen source
Graphs for agents that branch, loop, and persist state. The default when the workflow is not a straight line.
Open-source library. You pay for the models. LangSmith hosting is separate.
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02
OpenAI Agents SDKOpen source
OpenAI's own SDK for handoffs, tools, and tracing, if you are already on their API.
The SDK is open source. You pay OpenAI for model usage.
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03
CrewAIOpen source
Role-based crews. Faster to sketch a multi-agent demo than wiring a raw graph.
Open-source framework. CrewAI's hosted product is a separate paid plan.
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04
MastraOpen source
TypeScript agents, workflows, and evals, for teams that already ship on the JS stack.
Open source. You pay the model provider.
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