Open-source AI agent frameworks compared (2026)
Short answer: Our top pick is Pydantic AI 2.56.0, scored 7.7/10 in our hands-on test. Next: LangChain Deep Agents 0.7.23. 8 more recent releases are listed but not yet tested.
The latest releases of open-source AI agent frameworks: Pydantic AI, LangChain Deep Agents, CrewAI, Google ADK, Mastra, Agno and more. Only tools we've tested hands-on are ranked, using our fixed rubric. Every claim links to its source. Last updated 15 Oct 2026.
Ranked (tested)
Agent building Score: 7.7/10 Tested: yes (15 Oct 2026) Released 13 Oct 2026
Verdict: The cleanest typed-Python agent framework we've tried. In our offline test, tool calls and structured output worked on the first run with no API key, using the built-in TestModel. Live-model quality isn't tested yet.
Test notes: Hand-tested on 15 Oct 2026: installed pydantic-ai-slim==2.56.0 into a clean Python 3.13 venv, built an agent with one tool and a typed Pydantic output, and ran it with the built-in offline TestModel (no API key). The tool was called and a validated structured output came back in about 0.01 s. Downside: it prints a large observability/Logfire banner on run unless PYDANTIC_AI_NO_BANNER=1. Not yet run against a live LLM, so output quality is scored conservatively.
Pricing: Open source
Agent building Score: 7.2/10 Tested: yes (14 Oct 2026) Released 7 Oct 2026
Verdict: A small but useful release for anyone building skill-based subagent setups on LangGraph. In our hands-on smoke test it installed cleanly and ran out of the box, and the new skill pinning is in the code. Live-model quality isn't tested yet.
Test notes: Hand-tested on 14 Oct 2026: installed deepagents==0.7.23 from PyPI into a clean Python 3.13 venv, built an agent with create_deep_agent(), and ran it end to end against an offline stand-in model (no API key). It installed and ran cleanly, and pinned_skills is present in the skills/subagent middleware. Not yet run against a live LLM on our standard task, so output quality is scored conservatively.
Pricing: Open source
Recent releases, not yet tested
Not ranked. Verdicts come from public release notes only.
Agent building Score: provisional Tested: no Released 14 Oct 2026
Verdict: A useful debugging release for teams running crews in production: the new eval command targets the hardest question, where a run went wrong. Mostly fixes otherwise.
Test notes: Not tested: the verdict is based on the linked public release notes only.
Pricing: Open source
Agent building Score: provisional Tested: no Released 14 Oct 2026
Verdict: A strong pick for TypeScript teams that need agents to run code in sandboxes. The new Factory pieces matter most if you run many sandboxed sessions.
Test notes: Not tested: the verdict is based on the linked public release notes only.
Pricing: Open source
Agent building Score: provisional Tested: no Released 13 Oct 2026
Verdict: Worth a look if you're building multi-agent workflows for security operations. Its README positions it as a SecOps platform, not a general-purpose framework. We checked the repo and release notes but didn't install it (it needs uv, Node 22, and agent-browser).
Test notes: Not tested: it needs an account, a paid plan or a heavy local setup. The verdict is based on the linked public sources only.
Pricing: Open source
Agent building Score: provisional Tested: no Released 13 Oct 2026
Verdict: A solid release if you build on Google's stack: human-in-the-loop approvals and tool-output filtering are practical safety controls. The 40% speed-up is Google's own claim; we haven't measured it.
Test notes: Not tested: the verdict is based on the linked public release notes only.
Pricing: Open source
Agent building Score: provisional Tested: no Released 12 Oct 2026
Verdict: Interesting if you want to wrap the Claude and Codex agent SDKs in a durable, multi-replica service. Niche for simple single-process agents.
Test notes: Not tested: the verdict is based on the linked public release notes only.
Pricing: Open source
Agent building Score: provisional Tested: no Released 12 Oct 2026
Verdict: The low-level choice when you need explicit control over agent state, branching and persistence. More code than CrewAI's role-based crews, but more control.
Test notes: Not tested: the verdict is based on the linked public sources only.
Pricing: Open source
Agent building Score: provisional Tested: no Released 8 Oct 2026
Verdict: Most relevant for teams in the Microsoft/Azure stack that need policy controls such as Purview. Otherwise this is an incremental release.
Test notes: Not tested: the verdict is based on the linked public release notes only.
Pricing: Open source
Agent building Score: provisional Tested: no Released 2 Oct 2026
Verdict: A patch release with no new features. Listed for completeness; update when convenient.
Test notes: Not tested: the verdict is based on the linked public release notes only.
Pricing: Open source
FAQ
What is the best option on this list right now?
Our top pick is Pydantic AI 2.56.0, scored 7.7/10 in our hands-on test. Next: LangChain Deep Agents 0.7.23. 8 more recent releases are listed but not yet tested.
How does AgentPick rank these tools?
Only tools we've installed and run ourselves are ranked, scored on a fixed rubric: fit 25%, quality 25%, ease 15%, value 15%, reliability 10%, momentum 10%. Rankings can't be bought.
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Pydantic AI 2.56.0
LangChain Deep Agents 0.7.23
CrewAI 1.15.28
Mastra core 1.77.0
Flocks v2026.10.13
Google Agent Development Kit (Python) 2.12.0
Agno 3.1.3
LangGraph 1.2.15
Microsoft Agent Framework (Python) 1.21.0
OpenAI Agents SDK (Python) 0.23.1