---
title: "useAgent"
description: "React hook for accessing AG-UI agent instances"
---

<Callout type="warning">
  `useAgent` is still supported, but we recommend migrating to [`useAgent`](/reference/v2/hooks/useAgent) from the v2 API (`@copilotkit/react-core/v2`).
</Callout>

## Overview

`useAgent` is a React hook that returns an [AG-UI AbstractAgent](https://docs.ag-ui.com/sdk/js/client/abstract-agent) instance. The hook subscribes to agent state changes and triggers re-renders when the agent's state, messages, or execution status changes.

**Throws error** if no agent is configured with the specified `agentId`.

## Signature

```tsx
function useAgent(options?: UseAgentOptions): { agent: AbstractAgent }
```

## Parameters

<PropertyReference name="options" type="UseAgentOptions">
  Configuration object for the hook.

  <PropertyReference name="agentId" type="string" default='"default"'>
    ID of the agent to retrieve. Must match an agent configured in `CopilotKitProvider`.
  </PropertyReference>

  <PropertyReference name="updates" type="UseAgentUpdate[]" default="[OnMessagesChanged, OnStateChanged, OnRunStatusChanged]">
    Controls which agent changes trigger component re-renders. Options:
    - `UseAgentUpdate.OnMessagesChanged` - Re-render when messages change
    - `UseAgentUpdate.OnStateChanged` - Re-render when state changes
    - `UseAgentUpdate.OnRunStatusChanged` - Re-render when execution status changes

    Pass an empty array `[]` to prevent automatic re-renders.
  </PropertyReference>
</PropertyReference>

## Return Value

<PropertyReference name="object" type="{ agent: AbstractAgent }">
  Object containing the agent instance.

  <PropertyReference name="agent" type="AbstractAgent">
    The AG-UI agent instance. See [AbstractAgent documentation](https://docs.ag-ui.com/sdk/js/client/abstract-agent) for full interface details.

    ### Core Properties

    <PropertyReference name="agentId" type="string | undefined">
      Unique identifier for the agent instance.
    </PropertyReference>

    <PropertyReference name="description" type="string">
      Human-readable description of the agent's purpose.
    </PropertyReference>

    <PropertyReference name="threadId" type="string">
      Unique identifier for the current conversation thread.
    </PropertyReference>

    <PropertyReference name="messages" type="Message[]">
      Array of conversation messages. Each message contains:
      - `id: string` - Unique message identifier
      - `role: "user" | "assistant" | "system"` - Message role
      - `content: string` - Message content
    </PropertyReference>

    <PropertyReference name="state" type="any">
      Shared state object synchronized between application and agent. Both can read and modify this state.
    </PropertyReference>

    <PropertyReference name="isRunning" type="boolean">
      Indicates whether the agent is currently executing.
    </PropertyReference>

    <PropertyReference name="debug" type="boolean">
      Enables debug logging for agent events and execution.
    </PropertyReference>

    ### Methods

    <PropertyReference name="runAgent" type="(options?: RunAgentOptions) => Promise<void>">
      Manually triggers agent execution.

      **Parameters:**
      - `options.forwardedProps?: any` - Data to pass to the agent execution context

      **Example:**
      ```tsx
      await agent.runAgent({
        forwardedProps: {
          command: { resume: "user response" }
        }
      });
      ```
    </PropertyReference>

    <PropertyReference name="setState" type="(newState: any) => void">
      Updates the shared state. Changes are immediately available to both application and agent.

      **Example:**
      ```tsx
      agent.setState({
        ...agent.state,
        theme: "dark"
      });
      ```
    </PropertyReference>

    <PropertyReference name="subscribe" type="(subscriber: AgentSubscriber) => { unsubscribe: () => void }">
      Subscribes to agent events. Returns cleanup function.

      **Subscriber Events:**
      - `onCustomEvent?: ({ event: { name: string, value: any } }) => void` - Custom events (e.g., LangGraph interrupts)
      - `onRunStartedEvent?: () => void` - Agent execution starts
      - `onRunFinalized?: () => void` - Agent execution completes
      - `onStateChanged?: (state: any) => void` - State changes
      - `onMessagesChanged?: (messages: Message[]) => void` - Messages added/modified

      **Example:**
      ```tsx
      const { unsubscribe } = agent.subscribe({
        onCustomEvent: ({ event }) => {
          console.log(event.name, event.value);
        }
      });

      // Cleanup
      unsubscribe();
      ```
    </PropertyReference>

    <PropertyReference name="addMessage" type="(message: Message) => void">
      Adds a single message to the conversation and notifies subscribers.

      **Example:**
      ```tsx
      agent.addMessage({
        id: crypto.randomUUID(),
        role: "user",
        content: "Hello"
      });
      ```
    </PropertyReference>

    <PropertyReference name="addMessages" type="(messages: Message[]) => void">
      Adds multiple messages to the conversation and notifies subscribers once.
    </PropertyReference>

    <PropertyReference name="setMessages" type="(messages: Message[]) => void">
      Replaces the entire message history with a new array of messages.
    </PropertyReference>

    <PropertyReference name="connectAgent" type="(options?: RunAgentParameters) => Promise<RunAgentResult>">
      Connects to a streaming agent endpoint. Similar to `runAgent` but uses the `connect()` method for persistent connections.
    </PropertyReference>

    <PropertyReference name="detachActiveRun" type="() => Promise<void>">
      Detaches from the currently active agent run without aborting it. The run continues in the background but stops updating the local agent state.
    </PropertyReference>

    <PropertyReference name="abortRun" type="() => void">
      Aborts the currently running agent execution. Implementation varies by agent type.
    </PropertyReference>

    <PropertyReference name="clone" type="() => AbstractAgent">
      Creates a deep copy of the agent with cloned messages, state, and configuration.
    </PropertyReference>

    <PropertyReference name="use" type="(...middlewares: Middleware[]) => this">
      Adds middleware to the agent's execution pipeline. Middlewares can intercept and transform agent runs.
    </PropertyReference>

  </PropertyReference>
</PropertyReference>

## Usage

### Basic Usage

```tsx
import { useAgent } from "@copilotkit/react-core/v2";

function AgentStatus() {
  const { agent } = useAgent();

  return (
    <div>
      <div>Agent: {agent.agentId}</div>
      <div>Messages: {agent.messages.length}</div>
      <div>Running: {agent.isRunning ? "Yes" : "No"}</div>
    </div>
  );
}
```

### Accessing State

```tsx
function StateDisplay() {
  const { agent } = useAgent();

  return <pre>{JSON.stringify(agent.state, null, 2)}</pre>;
}
```

### Updating State

```tsx
function StateController() {
  const { agent } = useAgent();

  return (
    <button onClick={() => agent.setState({ ...agent.state, count: 1 })}>
      Increment
    </button>
  );
}
```

### Event Subscription

```tsx
import { useEffect } from "react";
import { useAgent } from "@copilotkit/react-core/v2";
import type { AgentSubscriber } from "@ag-ui/client";

function EventListener() {
  const { agent } = useAgent();

  useEffect(() => {
    const { unsubscribe } = agent.subscribe({
      onRunStartedEvent: () => console.log("Started"),
      onRunFinalized: () => console.log("Finished"),
    });

    return unsubscribe;
  }, []);

  return null;
}
```

### Multiple Agents

```tsx
function MultiAgentView() {
  const { agent: primary } = useAgent({ agentId: "primary" });
  const { agent: support } = useAgent({ agentId: "support" });

  return (
    <div>
      <div>Primary: {primary.messages.length}</div>
      <div>Support: {support.messages.length}</div>
    </div>
  );
}
```

### Optimizing Re-renders

Control when your component re-renders using the `updates` parameter:

```tsx
import { useAgent, UseAgentUpdate } from "@copilotkit/react-core/v2";

// Only re-render when messages change
function MessageCount() {
  const { agent } = useAgent({
    updates: [UseAgentUpdate.OnMessagesChanged]
  });

  return <div>Messages: {agent.messages.length}</div>;
}

// Manually manage subscriptions (no automatic re-renders)
function ManualSubscription() {
  const { agent } = useAgent({ updates: [] });

  useEffect(() => {
    const { unsubscribe } = agent.subscribe({
      onMessagesChanged: () => {
        // Handle changes manually
      }
    });
    return unsubscribe;
  }, [agent]);

  return <div>Manual mode</div>;
}
```

## Behavior

- **Automatic Re-renders**: Component re-renders when agent state, messages, or execution status changes (configurable via `updates` parameter)
- **Error Handling**: Throws error if no agent exists with specified `agentId`
- **State Synchronization**: State updates via `setState()` are immediately available to both app and agent
- **Event Subscriptions**: Subscribe/unsubscribe pattern for lifecycle and custom events

## Related

- [AG-UI AbstractAgent](https://docs.ag-ui.com/sdk/js/client/abstract-agent) - Full agent interface documentation
