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Add to existing project

This guide shows how to add agents to an existing Cloudflare Workers project. If you are starting fresh, refer to Building a chat agent instead.

Prerequisites

  • An existing Cloudflare Workers project with a Wrangler configuration file
  • Node.js 18 or newer

1. Install the package

Terminal window
npm i agents

For React applications, no additional packages are needed — React bindings are included.

For Hono applications:

Terminal window
npm i agents hono-agents

2. Create an Agent

Create a new file for your agent (for example, src/agents/counter.ts):

JavaScript
import { Agent } from "agents";


export class Counter extends Agent {
  initialState = { count: 0 };


  increment() {
    this.setState({ count: this.state.count + 1 });
    return this.state.count;
  }


  decrement() {
    this.setState({ count: this.state.count - 1 });
    return this.state.count;
  }
}

3. Update Wrangler configuration

Add the Durable Object binding and migration:

{
  "name": "my-existing-project",
  "main": "src/index.ts",
  "compatibility_date": "2025-01-01",
  "compatibility_flags": ["nodejs_compat"],


  "durable_objects": {
    "bindings": [
      {
        "name": "Counter",
        "class_name": "Counter",
      },
    ],
  },


  "migrations": [
    {
      "tag": "v1",
      "new_sqlite_classes": ["Counter"],
    },
  ],
}

Key points:

  • name in bindings becomes the property on env (for example, env.Counter)
  • class_name must exactly match your exported class name
  • new_sqlite_classes enables SQLite storage for state persistence
  • nodejs_compat flag is required for the agents package

4. Export the Agent class

Your agent class must be exported from your main entry point. Update your src/index.ts:

JavaScript
// Export the agent class (required for Durable Objects)
export { Counter } from "./agents/counter";


// Your existing exports...
export default {
  // ...
};

5. Wire up routing

Choose the approach that matches your project structure:

Plain Workers (fetch handler)

JavaScript
import { routeAgentRequest } from "agents";
export { Counter } from "./agents/counter";


export default {
  async fetch(request, env, ctx) {
    // Try agent routing first
    const agentResponse = await routeAgentRequest(request, env);
    if (agentResponse) return agentResponse;


    // Your existing routing logic
    const url = new URL(request.url);
    if (url.pathname === "/api/hello") {
      return Response.json({ message: "Hello!" });
    }


    return new Response("Not found", { status: 404 });
  },
};

Hono

JavaScript
import { Hono } from "hono";
import { agentsMiddleware } from "hono-agents";
export { Counter } from "./agents/counter";


const app = new Hono();


// Add agents middleware - handles WebSocket upgrades and agent HTTP requests
app.use("*", agentsMiddleware());


// Your existing routes continue to work
app.get("/api/hello", (c) => c.json({ message: "Hello!" }));


export default app;

With static assets

If you are serving static assets alongside agents, static assets are served first by default. Your Worker code only runs for paths that do not match a static asset:

JavaScript
import { routeAgentRequest } from "agents";
export { Counter } from "./agents/counter";


export default {
  async fetch(request, env, ctx) {
    // Static assets are served automatically before this runs
    // This only handles non-asset requests


    // Route to agents
    const agentResponse = await routeAgentRequest(request, env);
    if (agentResponse) return agentResponse;


    return new Response("Not found", { status: 404 });
  },
};

Configure assets in the Wrangler configuration file:

{
  "assets": {
    "directory": "./public",
  },
}

6. Add TypeScript types

You can generate types automatically from your Wrangler configuration file:

Terminal window
npx wrangler types env.d.ts

This creates an env.d.ts file with all your bindings typed. Alternatively, you can manually update your Env type to include the agent namespace:

TypeScript
import type { Counter } from "./agents/counter";


interface Env {
  // Your existing bindings
  MY_KV: KVNamespace;
  MY_DB: D1Database;


  // Add agent bindings
  Counter: DurableObjectNamespace<Counter>;
}

Refer to Configuration for more details on type generation.

7. Connect from the frontend

React

JavaScript
import { useState } from "react";
import { useAgent } from "agents/react";


function CounterWidget() {
  const [count, setCount] = useState(0);


  const agent = useAgent({
    agent: "Counter",
    onStateUpdate: (state) => setCount(state.count),
  });


  return (
    <>
      {count}
      <button onClick={() => agent.stub.increment()}>+</button>
      <button onClick={() => agent.stub.decrement()}>-</button>
    </>
  );
}

Vanilla JavaScript

JavaScript
import { AgentClient } from "agents/client";


const agent = new AgentClient({
  agent: "Counter",
  name: "user-123", // Optional: unique instance name
  onStateUpdate: (state) => {
    document.getElementById("count").textContent = state.count;
  },
});


// Call methods
document.getElementById("increment").onclick = () => agent.call("increment");

Adding multiple agents

Add more agents by extending the configuration:

JavaScript
// src/agents/chat.ts
export class Chat extends Agent {
  // ...
}


// src/agents/scheduler.ts
export class Scheduler extends Agent {
  // ...
}

Update the Wrangler configuration file:

{
  "durable_objects": {
    "bindings": [
      { "name": "Counter", "class_name": "Counter" },
      { "name": "Chat", "class_name": "Chat" },
      { "name": "Scheduler", "class_name": "Scheduler" },
    ],
  },
  "migrations": [
    {
      "tag": "v1",
      "new_sqlite_classes": ["Counter", "Chat", "Scheduler"],
    },
  ],
}

Export all agents from your entry point:

JavaScript
export { Counter } from "./agents/counter";
export { Chat } from "./agents/chat";
export { Scheduler } from "./agents/scheduler";

Common integration patterns

Agents behind authentication

Check auth before routing to agents:

JavaScript
export default {
  async fetch(request, env) {
    // Check auth for agent routes
    if (request.url.includes("/agents/")) {
      const authResult = await checkAuth(request, env);
      if (!authResult.valid) {
        return new Response("Unauthorized", { status: 401 });
      }
    }


    const agentResponse = await routeAgentRequest(request, env);
    if (agentResponse) return agentResponse;


    // ... rest of routing
  },
};

Custom agent path prefix

By default, agents are routed at /agents/{agent-name}/{instance-name}. You can customize this:

JavaScript
import { routeAgentRequest } from "agents";


const agentResponse = await routeAgentRequest(request, env, {
  prefix: "/api/agents", // Now routes at /api/agents/{agent-name}/{instance-name}
});

Refer to Routing for more options including CORS, custom instance naming, and location hints.

Accessing agents from server code

You can interact with agents directly from your Worker code:

JavaScript
import { getAgentByName } from "agents";


export default {
  async fetch(request, env) {
    if (request.url.endsWith("/api/increment")) {
      // Get a specific agent instance
      const counter = await getAgentByName(env.Counter, "shared-counter");
      const newCount = await counter.increment();
      return Response.json({ count: newCount });
    }
    // ...
  },
};

Troubleshooting

Agent not found, or 404 errors

  1. Check the export - Agent class must be exported from your main entry point.
  2. Check the binding - class_name in the Wrangler configuration file must exactly match the exported class name.
  3. Check the route - Default route is /agents/{agent-name}/{instance-name}.

No such Durable Object class error

Add the migration to the Wrangler configuration file:

{
  "migrations": [
    {
      "tag": "v1",
      "new_sqlite_classes": ["YourAgentClass"],
    },
  ],
}

WebSocket connection fails

Ensure your routing passes the response unchanged:

JavaScript
// Correct - return the response directly
const agentResponse = await routeAgentRequest(request, env);
if (agentResponse) return agentResponse;


// Wrong - this breaks WebSocket connections
if (agentResponse) return new Response(agentResponse.body);

State not persisting

Check that:

  1. You are using this.setState(), not mutating this.state directly.
  2. The agent class is in new_sqlite_classes in migrations.
  3. You are connecting to the same agent instance name.

Next steps

State management Manage and synchronize agent state.
Schedule tasks Background tasks and cron jobs.
Agent class internals Full lifecycle and methods reference.
Agents API Complete API reference for the Agents SDK.