Top 10 Open-Source AI Agent Frameworks of May 2025

AI agent frameworks have exploded in popularity as developers shift from simply calling LLMs to building autonomous systems that can reason, plan, use tools, and even collaborate with other agents. The past year has seen remarkable innovation in this space, with new frameworks emerging to address different aspects of agent development.
Whether you're building a RAG-based assistant, a multi-agent research system, or enterprise AI workflows, finding the right framework is crucial. This guide compares the top open-source AI agent frameworks of 2025, analyzing their architectures, capabilities, and optimal use cases.