Here's a fairly comprehensive list:

https://github.com/slavakurilyak/awesome-ai-agents

CrewAI is a popular VC-backed one, but two that I think are kind of interesting in the open source space are:

https://github.com/i-am-bee/beeai-framework

https://github.com/lastmile-ai/mcp-agent

... However I think the vast majority of "AI Agent" use-cases in practice right now are actually just workflows, and imo dify is great for those:

https://github.com/langgenius/dify

[edit] worth mentioning [langfuse](https://github.com/langfuse/langfuse), which is more like a platform that addresses the observability/evals/prompt management piece of the puzzle as opposed to a full-on "agent framework". In practice I have not yet run into a case where I needed something like what OpenAI just released, nor crewAI etc (despite it feeling like those cases may be coming)

Thanks. mcp-agent lacks tests so I'm skipping it for now: https://github.com/lastmile-ai/mcp-agent/tree/main/tests

I just realized BeeAI is IBM's project: https://www.ibm.com/think/news/beeai-open-source-multiagent

I also see there's https://ai.pydantic.dev/ but it lacks MCP support. Finally, the MCP site maintains a nice client list:

https://modelcontextprotocol.io/clients#feature-support-matr...