> ## Documentation Index
> Fetch the complete documentation index at: https://docs.ag-ui.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Google ADK JavaScript quickstart

> Run a native Google ADK JavaScript agent behind an AG-UI endpoint.

`@ag-ui/adk-js` adapts a server-side Google ADK JavaScript `Runner` to an AG-UI
`AbstractAgent`. Use it when the agent and web runtime run in Node.js. The
existing `@ag-ui/adk` package remains the HTTP client for the Python ADK
middleware.

## Prerequisites

* Node.js 20.19 or newer
* `@ag-ui/client` and `@ag-ui/core` 1.x (use a CopilotKit release that
  resolves the 1.x line)
* A Gemini API key from [Google AI Studio](https://aistudio.google.com/apikey)

## Add ADK JavaScript to an application

Install the server dependencies:

```bash theme={null}
npm install @ag-ui/adk-js @google/adk @copilotkit/runtime hono
```

`@ag-ui/adk-js` requires `@google/adk` 2.x.

Set your Gemini key in the environment the server reads:

```dotenv theme={null}
GOOGLE_GENAI_API_KEY=your-api-key
GOOGLE_GENAI_USE_VERTEXAI=0
```

Create `app/api/copilotkit/route.ts`:

```typescript theme={null}
import { ADKJSAgent } from "@ag-ui/adk-js"
import {
  CopilotRuntime,
  InMemoryAgentRunner,
  createCopilotEndpointSingleRoute,
} from "@copilotkit/runtime/v2"
import { Agent, InMemorySessionService } from "@google/adk"
import { handle } from "hono/vercel"

export const runtime = "nodejs"

const rootAgent = new Agent({
  name: "assistant",
  model: "gemini-2.5-flash",
  instruction: "Be concise and use frontend tools when appropriate.",
})

const copilotRuntime = new CopilotRuntime({
  agents: {
    assistant: new ADKJSAgent({
      appName: "assistant_app",
      sessionService: new InMemorySessionService(),
      agent: rootAgent,
      userId: "user-123", // resolve from server-side auth
    }),
  },
  runner: new InMemoryAgentRunner(),
})

const endpoint = createCopilotEndpointSingleRoute({
  runtime: copilotRuntime,
  basePath: "/api/copilotkit",
})

export const POST = handle(endpoint)
```

The frontend can now select the `assistant` agent through any AG-UI client. A
CopilotKit React application uses `runtimeUrl="/api/copilotkit"` and
`agent="assistant"` on its `CopilotKit` provider.

## Runs and concurrency

Different threads run concurrently on one shared agent instance; a second run
on the same user and thread is refused with `THREAD_BUSY`. ADK closes every
toolset after each run, so give roots that share a closable toolset (or keep
per-run state) per-run instances with a factory
(`agent: () => new Workflow(...)`), or pass `runner:` to bring a fully
configured Runner. Failures after the client disconnected go to `logger`
(default `console`).

## Supported integration behavior

* Streaming assistant messages and lifecycle events
* Backend and frontend tool calls
* AG-UI state snapshots and RFC 6902 state deltas
* ADK input, confirmation, and credential requests as resumable interrupts.
  A tool that raises its own confirmation at runtime must also answer `true`
  from `checkRequireConfirmation` (or declare `requireConfirmation` on a
  `FunctionTool`), because ADK 2.x binds an approval to the tool it names.
* Restored message history with stable message IDs
* Provider/model token usage when ADK reports it
* A bare ADK `Workflow` as the `Runner` root (its workflow nodes are reported
  as sub-agents and their frontend tools are discovered)
* The AG-UI subagent protocol for ADK multi-agent trees (see below)

The integration is server-only. Never import `@ag-ui/adk-js` or `@google/adk`
from a browser component. See the
[live Dojo examples](https://dojo.ag-ui.com/adk-js/feature/agentic_chat?openCopilot=true)
for tools, shared state, generative UI, and interrupts.

## Sub-agents

`subagents: "steps"` emits `STEP_STARTED` / `STEP_FINISHED` (`agent:<name>`) and
`CUSTOM` `MultiAgentHandoff` events around ADK sub-agent work — safe for every
client and what the Dojo multi-agent page reads. `subagents: "attributed"` adds
the AG-UI subagent protocol (`SUBAGENT_STARTED/FINISHED/ERROR`, `subagentRunId`
on events, messages, and interrupts, continuation of a suspended sub-agent under
the same id on resume); the consuming client needs `@ag-ui/client` 1.x,
because older clients reject those event types before any application code
runs. The default is `off`.