# AG-UI protocol

AG-UI is an open, lightweight, event-based protocol that standardizes how AI agents connect to user-facing applications. Previously there was no shared convention for wiring an agent into an interface; AG-UI has agent backends emit events matching one of about 16 standard event types during execution and accept a few simple inputs, while a middleware layer adapts to any event transport such as SSE, WebSockets or webhooks. It grew out of CopilotKit's early partnership with LangChain and CrewAI, ships under the MIT license, and comes with a reference HTTP implementation and a default connector.

AG-UI is an open, lightweight, event-based protocol that standardizes how AI agents connect to user-facing applications. Previously there was no shared convention for wiring an agent into an interface; AG-UI has agent backends emit events matching one of about 16 standard event types during execution and accept a few simple inputs, while a middleware layer adapts to any event transport such as SSE, WebSockets or webhooks. It grew out of CopilotKit's early partnership with LangChain and CrewAI, ships under the MIT license, and comes with a reference HTTP implementation and a default connector.