AG-UI¶

Supported middlewarePython example

AG-UI is the client-facing event protocol used between CopilotKit Runtime and agent backends. With ADK, use the ag-ui-adk package to expose an ADK agent as an AG-UI endpoint, then register that endpoint in CopilotKit Runtime.

Application clients should connect to CopilotKit Runtime. They should not call the Python AG-UI endpoint directly unless you are building and maintaining your own AG-UI client.

Install the ADK middleware¶

Use Python 3.10 through 3.14.

pip install google-adk ag-ui-adk fastapi "uvicorn[standard]"

Set your Google API key before starting the server:

export GOOGLE_API_KEY="your-api-key"

Create the ADK AG-UI endpoint:

app.py

from fastapi import FastAPI
from fastapi.middleware.cors import CORSMiddleware
from google.adk.agents import Agent
from google.adk.apps import App, ResumabilityConfig

from ag_ui_adk import ADKAgent, AGUIToolset, add_adk_fastapi_endpoint


root_agent = Agent(
    name="assistant",
    model="gemini-2.5-flash",
    instruction="You are a helpful ADK assistant.",
    tools=[AGUIToolset()],
)

adk_app = App(
    name="adk_ag_ui_app",
    root_agent=root_agent,
    resumability_config=ResumabilityConfig(is_resumable=True),
)

ag_ui_agent = ADKAgent.from_app(
    adk_app,
    user_id="local_user",
    session_timeout_seconds=3600,
    use_in_memory_services=True,
)

app = FastAPI()
app.add_middleware(
    CORSMiddleware,
    allow_origins=[
        "http://localhost:3000",
        "http://localhost:4200",
        "http://localhost:5173",
    ],
    allow_methods=["*"],
    allow_headers=["*"],
)
add_adk_fastapi_endpoint(app, ag_ui_agent, path="/ag-ui")

AGUIToolset() lets the ADK agent call tools supplied by CopilotKit clients. ADKAgent.from_app(...) keeps client tools and human-in-the-loop runs resumable.

Run the backend:

uvicorn app:app --reload --port 8000

The ADK agent now accepts AG-UI runs at http://localhost:8000/ag-ui.

Add CopilotKit Runtime¶

In the web app that hosts your frontend, register the ADK AG-UI endpoint with CopilotKit Runtime:

npm install @copilotkit/runtime @ag-ui/client hono

app/api/copilotkit/[[...slug]]/route.ts

import { HttpAgent } from "@ag-ui/client";
import {
  CopilotRuntime,
  InMemoryAgentRunner,
  createCopilotEndpoint,
} from "@copilotkit/runtime/v2";
import { handle } from "hono/vercel";

const runtime = new CopilotRuntime({
  agents: {
    default: new HttpAgent({
      url: process.env.ADK_AG_UI_URL ?? "http://localhost:8000/ag-ui",
    }),
  },
  runner: new InMemoryAgentRunner(),
});

const app = createCopilotEndpoint({
  runtime,
  basePath: "/api/copilotkit",
});

export const GET = handle(app);
export const POST = handle(app);
export const PATCH = handle(app);
export const DELETE = handle(app);

Your application clients now use /api/copilotkit. CopilotKit Runtime handles the AG-UI transport to the ADK backend.

Connect a client¶

After the runtime route is available, add a CopilotKit client:

Use A2UI when the agent should render structured UI, and use the patterns pages when the client needs tools, custom renderers, MCP Apps, or human-in-the-loop controls.