The 9 open-source agent frameworks in the directory, compared on protocol support and evidence — not on GitHub star counts or marketing claims.
LangChain and LangGraph are separate listings under the same company and share a license family, but protocol support is tracked independently for each — LangGraph's A2A support, for example, is specific to its Agent Server and doesn't extend to core LangChain. Check each row's own source link rather than assuming shared support across related projects from one vendor. All 9 frameworks here are open source, which is close to a defining trait of this category rather than a differentiator within it — see enterprise agent platforms or identity solutions for categories where that flag varies more.