Reading agent state - Copilotkit

<video src="https://cdn.copilotkit.ai/docs/copilotkit/videos/coagents/shared-state.mp4" className="rounded-lg shadow-xl" loop playsInline controls autoPlay muted /> <Callout> This video shows the result of npx copilotkit@latest init with the implementation section applied to it. </Callout>

What is this?

You can easily use the realtime agent state not only in the chat UI, but also in the native application UX.

<Callout type="info"> CopilotKit consumes AG-UI protocol events streamed by AG2 over <code>/chat</code>. See the <a href="https://docs.ag2.ai/latest/docs/user-guide/ag-ui/" target="_blank">AG2 AG-UI integration docs</a>. </Callout>

When should I use this?

You can use this when you want to provide the user with feedback about your agent's state. As your agent's state updates, you can reflect these updates natively in your application.

Implementation

<Steps> <Step> ### Run and connect your agent Start your AG2 backend and connect your CopilotKit frontend to the AG-UI `/chat` endpoint. </Step> <Step> ### Define the Agent State

Create your AG2 backend with `ContextVariables` and emit `StateSnapshotEvent` whenever the state changes:

```python title="agent.py"
from typing import Annotated

from ag_ui.core import EventType, StateSnapshotEvent
from fastapi import FastAPI, Header
from fastapi.responses import StreamingResponse
from autogen import ConversableAgent, LLMConfig
from autogen.agentchat import ContextVariables
from autogen.ag_ui import AGUIStream, RunAgentInput

def read_state(context: ContextVariables) -> dict:
    return context.get("agent_state", {"language": "english"})

def write_state(context: ContextVariables, state: dict) -> StateSnapshotEvent:
    context["agent_state"] = state
    return StateSnapshotEvent(type=EventType.STATE_SNAPSHOT, snapshot=state)

agent = ConversableAgent(
    name="assistant",
    system_message=(
        "You are a helpful assistant for tracking language. "
        "Always respond in the current language."
    ),
    llm_config=LLMConfig({"model": "gpt-5.4-mini"}),
    human_input_mode="NEVER",
)

@agent.register_for_llm(description="Update the language in shared state.")
def set_language(
    context: ContextVariables,
    language: Annotated[str, "language such as english or spanish"],
) -> StateSnapshotEvent:
    return write_state(context, {"language": language.lower()})

agent.register_for_execution(name="set_language")(set_language)

stream = AGUIStream(agent)
app = FastAPI()

@app.post("/chat")
async def run_agent(
    message: RunAgentInput,
    accept: str | None = Header(None),
):
    return StreamingResponse(
        stream.dispatch(message, accept=accept),
        media_type=accept or "text/event-stream",
    )
```

</Step> <Step> ### Use the `useAgent` Hook With your agent connected and running all that is left is to call the [useAgent](/reference/v1/hooks/useAgent) hook, pass the agent's ID, and initialize missing UI-owned state after the connected agent is ready.

```tsx title="ui/app/page.tsx"
import { useEffect } from "react";
import { useAgent } from "@copilotkit/react-core/v2"; // [!code highlight]

// Define the agent state type, should match the actual state of your agent
type AgentState = {
  language: "english" | "spanish";
}

function YourMainContent() {
  // [!code highlight:4]
  const { agent, isReady } = useAgent({
    agentId: "my_agent", // MUST match the agent name in CopilotRuntime
  });
  const state = (agent.state ?? {}) as Partial<AgentState>;

  useEffect(() => {
    if (!isReady || state.language !== undefined) return;
    agent.setState({ ...(agent.state ?? {}), language: "english" });
  }, [agent, isReady, state.language]);

  // ...

  return (
    // style excluded for brevity
    <div>
      <h1>Your main content</h1>
      <p>Language: {agent.state.language}</p>
    </div>
  );
}
```

<Callout type="warn" title="Important">
  The `agentId` parameter must exactly match the agent name you defined in your CopilotRuntime configuration (e.g., `my_agent` from the quickstart).
</Callout>

<Callout type="info">
  The `agent.state` in `useAgent` is reactive and will automatically update when the agent's state changes.
</Callout>

</Step> <Step> ### Give it a try As the agent state updates, your `state` variable will automatically update with it. In this case, you'll see the language set to "english" after the connected agent is ready. </Step> </Steps>

Rendering agent state in your app

You can render the agent state in any React component under <CopilotKit>. Read agent.state and return ordinary JSX.

tsx

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

type AgentState = {
  language: "english" | "spanish";
};

function YourMainContent() {
  const { agent } = useAgent({
    agentId: "my_agent",
  });
  const state = (agent.state ?? {}) as Partial<AgentState>;

  if (!state.language) return null;
  return <div>Language: {state.language}</div>;
}

<Callout type="warn" title="Important"> The `name` parameter must exactly match the agent name you defined in your CopilotRuntime configuration (e.g., `my_agent` from the quickstart). </Callout> <Callout type="info"> The `agent.state` in `useAgent` is reactive and will automatically update when the agent's state changes. </Callout>

Intermediately Stream and Render Agent State

By default, AG2 state updates are visible to CopilotKit whenever your backend emits StateSnapshotEvent. For smoother long-running workflows, emit additional intermediate snapshots from your backend tools.