Writing agent state

This example demonstrates writing to shared state in the CopilotKit Feature Viewer.

What is this?#

You can easily write to your agent's state from your native application, allowing you to update the agent's working memory from your UI.

Important

This guide assumes you are embedding your Mastra agent inside of Copilot Runtime, like so.

const runtime = new CopilotRuntime({
  agents: MastraAgent.getLocalAgents({ mastra }),
});

This feature will not work if you are using a remote Mastra agent.

When should I use this?#

You can use this when you want to provide user input or control to your agent's working memory. As your application state changes, you can update the agent state to reflect these changes.

Implementation#

Run and connect your agent#

You'll need to run your agent and connect it to CopilotKit before proceeding. If you haven't done so already, you can follow the instructions in the Getting Started guide.

If you don't already have an agent, you can use the coagent starter as a starting point as this guide uses it as a starting point.

Define the Agent State#

Mastra has advanced working memory concepts to provide statefulness to your agents. CopilotKit leverages Mastra's working memory concept to allow you to implement shared state between your agent and your application.

Providing working memory to your agent is as simple as providing a Zod schema to your agent.

mastra/agents/language-agent.ts

import { openai } from "@ai-sdk/openai";
import { Agent } from "@mastra/core/agent";
import { LibSQLStore } from "@mastra/libsql";
import { z } from "zod";
import { Memory } from "@mastra/memory";

// 1. Define the agent state schema
export const AgentStateSchema = z.object({
  language: z.enum(["english", "spanish"]),
});

// 2. Infer the agent state type from the schema
export const AgentState = z.infer<typeof AgentStateSchema>;

// 3. Create the agent
export const languageAgent = new Agent({
  name: "Language Agent",
  model: openai("gpt-5.4"),
  instructions: "Always communicate in the preferred language of the user as defined in your working memory. Do not communicate in any other language.",
  memory: new Memory({
    storage: new LibSQLStore({ id: "mastra-storage", url: ":memory:" }),
    options: {
      workingMemory: {
        enabled: true,
        schema: AgentStateSchema,
      },
    },
  }),
});

Use the `useAgent` Hook#

With your agent connected and running all that is left is to call the useAgent hook, pass the agent's name, and use agent.setState to update the agent state.

ui/app/page.tsx

import { useAgent } from "@copilotkit/react-core/v2"; 
import { AgentState } from "@/mastra/agents/language-agent";

function YourMainContent() {
  const { agent } = useAgent({
    agentId: "your-mastra-agent-name",
    // optionally provide a type-safe initial state
    initialState: { language: "english" }
  });

  const toggleLanguage = () => {
    agent.setState({ language: agent.state?.language === "english" ? "spanish" : "english" }); 
  };

  return (
    // style excluded for brevity
    <div>
      <h1>Your main content</h1>
      <p>Language: {agent.state?.language}</p>
      <button onClick={toggleLanguage}>Toggle Language</button>
    </div>
  );
}

The agent.setState function in useAgent will update the working memory and trigger a rerender when the state changes.

Give it a try!#

You can now use the setState function to update the agent state and state to read it. Try toggling the language button and talking to your agent. You'll see the language change to match the agent's state.