Frontend and agent developers who need a standard way to stream agent state into user interfaces.

An open, event-based protocol standardizing how AI agent backends communicate with front-end applications, covering streaming text, tool calls, state updates, and generative UI.

Implemented as SDKs across languages and adopted as a transport layer between agent frameworks and web or mobile clients.

Use when building a chat or agent UI that must work across multiple agent frameworks without custom glue code per integration.

It replaces bespoke, framework-specific streaming integrations with one shared contract between agents and UIs.

Adopted by frameworks including LangGraph, CrewAI, Mastra, and AG2, and built by the CopilotKit team.

Open source, MIT licensed, no credentials required; governed as an open protocol with multiple framework integrations.