langgraph
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CopilotKit
CopilotKit is an open-source company building the interface layer between humans and AI agents. Its SDK and the open AG-UI protocol let developers embed agents directly inside apps - rendering interactive UI, sharing state, and supporting human-in-the-loop workflows - instead of bolting on a text-only chatbot. Founded in 2023 by brothers Atai and Uli Barkai and headquartered in the Seattle area, the company raised a $27M Series A in May 2026 and counts Google, Microsoft, Amazon, Oracle, and a large share of the Fortune 500 among adopters of its protocol.
LangChain
LangChain is the agent engineering company. It builds the open-source frameworks (LangChain, LangGraph) and the commercial platform (LangSmith, LangGraph Platform) that developers use to design, deploy, evaluate and observe LLM-powered applications and autonomous agents in production.