AG-UI Event Streaming

AG-UI transports execution events to a web client. It does not provide a browser application or host the Go server on GitHub Pages.

Mount a Handler

http.Handle("/agent", agui.NewHandler(cfg))

The handler accepts GET for capabilities and POST for a run. Wrap it with host authentication, authorization, body-size limits, and request budgets. SSE needs an http.Flusher; middleware must preserve that capability.

Request and Response

{
  "threadId": "conversation-123",
  "runId": "run-456",
  "messages": [
    {"id": "user-1", "role": "user", "content": "Hello"}
  ]
}

Use the exported RunAgentInput contract for additional fields. The current handler runs the final user message; do not assume an arbitrary client-supplied transcript replaces persisted server history. Configure a store when the thread must continue across requests.

The response is SSE covering run lifecycle, text/thinking, tools, state, and custom events. Read terminal run/error events, not only text deltas. A successful HTTP connection does not prove that the agent run succeeded.

Snapshots and Reconnection

When saved thread state is available, the handler can send a messages snapshot. Client state input can be emitted as a state snapshot. Distinguish these application-state snapshots from durable server checkpoints.

The underlying event bus can drop buffered events. For robust reconnects, reconcile against persisted history and treat streamed text as transient until committed. Handle failed-attempt reset semantics rather than appending duplicate partial responses.

Resume and Client Tools

Resume input is currently translated into steering messages. It is not equivalent to directly calling Agent.Resume after a host-validated approval. Client-provided tool/state fields do not automatically register executable server tools or map every call configuration option. Implement those boundaries explicitly in the host if your workflow needs them.

A2UI Binding

A2UI surface updates can be carried as AG-UI custom events. The client needs a catalog-aware renderer and data binding implementation; receiving the event does not render a component automatically.

See AG-UI and event semantics.