useAgent

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

Pass an empty array `[]` to prevent automatic re-renders.

### 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>

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>
  );
}

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

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

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

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

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;
}

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>
  );
}

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>;
}