| name | cloudflare-agents |
| description | Comprehensive guide for the Cloudflare Agents SDK - build AI-powered autonomous agents on Workers + Durable Objects.
Use when: building AI agents, creating stateful agents with WebSockets, implementing chat agents with streaming, scheduling tasks with cron/delays, running asynchronous workflows, building RAG (Retrieval Augmented Generation) systems with Vectorize, creating MCP (Model Context Protocol) servers, implementing human-in-the-loop workflows, browsing the web with Browser Rendering, managing agent state with SQL, syncing state between agents and clients, calling agents from Workers, building multi-agent systems, or encountering Agent configuration errors.
Prevents 15+ documented issues: migrations not atomic, missing new_sqlite_classes, Agent class not exported, binding name mismatch, global uniqueness gotchas, WebSocket state handling, scheduled task callback errors, state size limits, workflow binding missing, browser binding required, vectorize index not found, MCP transport confusion, authentication bypassed, instance naming errors, and state sync failures.
Keywords: Cloudflare Agents, agents sdk, cloudflare agents sdk, Agent class, Durable Objects agents, stateful agents, WebSocket agents, this.setState, this.sql, this.schedule, schedule tasks, cron agents, run workflows, agent workflows, browse web, puppeteer agents, browser rendering, rag agents, vectorize agents, embeddings, mcp server, McpAgent, mcp tools, model context protocol, routeAgentRequest, getAgentByName, useAgent hook, AgentClient, agentFetch, useAgentChat, AIChatAgent, chat agents, streaming chat, human in the loop, hitl agents, multi-agent, agent orchestration, autonomous agents, long-running agents, AI SDK, Workers AI, "Agent class must extend", "new_sqlite_classes", "migrations required", "binding not found", "agent not exported", "callback does not exist", "state limit exceeded"
|
| license | MIT |
Cloudflare Agents SDK
Status: Production Ready ✅
Last Updated: 2025-10-21
Dependencies: cloudflare-worker-base (recommended)
Latest Versions: agents@latest, @modelcontextprotocol/sdk@latest
Production Tested: Cloudflare's own MCP servers (https://github.com/cloudflare/mcp-server-cloudflare)
What is Cloudflare Agents?
The Cloudflare Agents SDK enables building AI-powered autonomous agents that run on Cloudflare Workers + Durable Objects. Agents can:
- Communicate in real-time via WebSockets and Server-Sent Events
- Persist state with built-in SQLite database (up to 1GB per agent)
- Schedule tasks using delays, specific dates, or cron expressions
- Run workflows by triggering asynchronous Cloudflare Workflows
- Browse the web using Browser Rendering API + Puppeteer
- Implement RAG with Vectorize vector database + Workers AI embeddings
- Build MCP servers implementing the Model Context Protocol
- Support human-in-the-loop patterns for review and approval
- Scale to millions of independent agent instances globally
Each agent instance is a globally unique, stateful micro-server that can run for seconds, minutes, or hours.
Quick Start (10 Minutes)
1. Scaffold Project with Template
npm create cloudflare@latest my-agent -- \
--template=cloudflare/agents-starter \
--ts \
--git \
--deploy false
What this creates:
- Complete Agent project structure
- TypeScript configuration
- wrangler.jsonc with Durable Objects bindings
- Example chat agent implementation
- React client with useAgent hook
2. Or Add to Existing Worker
cd my-existing-worker
npm install agents
Then create an Agent class:
import { Agent, AgentNamespace } from "agents";
export class MyAgent extends Agent {
async onRequest(request: Request): Promise<Response> {
return new Response("Hello from Agent!");
}
}
export default MyAgent;
3. Configure Durable Objects Binding
Create or update wrangler.jsonc:
{
"$schema": "node_modules/wrangler/config-schema.json",
"name": "my-agent",
"main": "src/index.ts",
"compatibility_date": "2025-10-21",
"compatibility_flags": ["nodejs_compat"],
"durable_objects": {
"bindings": [
{
"name": "MyAgent",
"class_name": "MyAgent"
}
]
},
"migrations": [
{
"tag": "v1",
"new_sqlite_classes": ["MyAgent"]
}
]
}
CRITICAL Configuration Rules:
- ✅
name and class_name MUST be identical
- ✅
new_sqlite_classes MUST be in first migration (cannot add later)
- ✅ Agent class MUST be exported (or binding will fail)
- ✅ Migration tags CANNOT be reused (each migration needs unique tag)
4. Deploy
npx wrangler@latest deploy
Your agent is now running at: https://my-agent.<subdomain>.workers.dev
Configuration Deep Dive
Complete wrangler.jsonc Example
{
"$schema": "node_modules/wrangler/config-schema.json",
"name": "my-agent",
"main": "src/index.ts",
"account_id": "YOUR_ACCOUNT_ID",
"compatibility_date": "2025-10-21",
"compatibility_flags": ["nodejs_compat"],
"durable_objects": {
"bindings": [
{
"name": "MyAgent",
"class_name": "MyAgent"
}
]
},
"migrations": [
{
"tag": "v1",
"new_sqlite_classes": ["MyAgent"]
}
],
"ai": {
"binding": "AI"
},
"vectorize": {
"bindings": [
{
"binding": "VECTORIZE",
"index_name": "my-agent-vectors"
}
]
},
"browser": {
"binding": "BROWSER"
},
"workflows": [
{
"name": "MY_WORKFLOW",
"class_name": "MyWorkflow",
"script_name": "my-workflow-script"
}
],
"d1_databases": [
{
"binding": "DB",
"database_name": "my-agent-db",
"database_id": "your-database-id"
}
],
"r2_buckets": [
{
"binding": "BUCKET",
"bucket_name": "my-agent-files"
}
],
"vars": {
"ENVIRONMENT": "production"
},
"observability": {
"enabled": true
}
}
Migrations Best Practices
Atomic Deployments: Migrations are atomic operations - they cannot be gradually deployed.
{
"migrations": [
{
"tag": "v1",
"new_sqlite_classes": ["MyAgent"]
},
{
"tag": "v2",
"renamed_classes": [
{"from": "MyAgent", "to": "MyRenamedAgent"}
]
},
{
"tag": "v3",
"deleted_classes": ["OldAgent"]
},
{
"tag": "v4",
"transferred_classes": [
{
"from": "AgentInOldScript",
"from_script": "old-worker",
"to": "AgentInNewScript"
}
]
}
]
}
Migration Rules:
- ✅ Each migration needs a unique
tag
- ✅ Cannot enable SQLite on existing deployed class (must be in first migration)
- ✅ Migrations apply in order during deployment
- ✅ Cannot edit or remove previous migration tags
- ❌ Never deploy new migrations gradually (atomic only)
Environment-Specific Migrations
{
"migrations": [{"tag": "v1", "new_sqlite_classes": ["MyAgent"]}],
"env": {
"staging": {
"migrations": [
{"tag": "v1", "new_sqlite_classes": ["MyAgent"]},
{"tag": "v2-staging", "renamed_classes": [{"from": "MyAgent", "to": "StagingAgent"}]}
]
}
}
}
Agent Class API
The Agent class is the foundation of the Agents SDK. Extend it to create your agent.
Basic Agent Structure
import { Agent } from "agents";
interface Env {
OPENAI_API_KEY: string;
AI: Ai;
VECTORIZE: Vectorize;
DB: D1Database;
}
interface State {
counter: number;
messages: string[];
lastUpdated: Date | null;
}
export class MyAgent extends Agent<Env, State> {
initialState: State = {
counter: 0,
messages: [],
lastUpdated: null
};
async onStart() {
console.log('Agent started:', this.name, 'State:', this.state);
}
async onRequest(request: Request): Promise<Response> {
return Response.json({ message: "Hello from Agent", state: this.state });
}
async onConnect(connection: Connection, ctx: ConnectionContext) {
console.log('Client connected:', connection.id);
}
async onMessage(connection: Connection, message: WSMessage) {
if (typeof message === 'string') {
connection.send(`Echo: ${message}`);
}
}
async onError(connection: Connection, error: unknown): Promise<void> {
console.error('Connection error:', error);
}
async onClose(connection: Connection, code: number, reason: string, wasClean: boolean): Promise<void> {
console.log('Connection closed:', code, reason);
}
onStateUpdate(state: State, source: "server" | Connection) {
console.log('State updated:', state, 'Source:', source);
}
async customMethod(data: any) {
this.setState({
...this.state,
counter: this.state.counter + 1,
lastUpdated: new Date()
});
}
}
Accessing Agent Properties
Within any Agent method:
export class MyAgent extends Agent<Env, State> {
async someMethod() {
const apiKey = this.env.OPENAI_API_KEY;
const ai = this.env.AI;
const counter = this.state.counter;
this.setState({ ...this.state, counter: counter + 1 });
const results = await this.sql`SELECT * FROM users`;
const instanceName = this.name;
await this.schedule(60, "runLater", { data: "example" });
await this.customMethod({ foo: "bar" });
}
}
HTTP & Server-Sent Events
HTTP Request Handling
export class MyAgent extends Agent<Env> {
async onRequest(request: Request): Promise<Response> {
const url = new URL(request.url);
const method = request.method;
if (method === "POST" && url.pathname === "/increment") {
const counter = (this.state.counter || 0) + 1;
this.setState({ ...this.state, counter });
return Response.json({ counter });
}
if (method === "GET" && url.pathname === "/status") {
return Response.json({ state: this.state, name: this.name });
}
return new Response("Not Found", { status: 404 });
}
}
Server-Sent Events (SSE) Streaming
export class MyAgent extends Agent<Env> {
async onRequest(request: Request): Promise<Response> {
const stream = new ReadableStream({
async start(controller) {
const encoder = new TextEncoder();
controller.enqueue(encoder.encode('data: {"message": "Starting"}\n\n'));
await new Promise(resolve => setTimeout(resolve, 1000));
controller.enqueue(encoder.encode('data: {"message": "Processing"}\n\n'));
await new Promise(resolve => setTimeout(resolve, 1000));
controller.enqueue(encoder.encode('data: {"message": "Complete"}\n\n'));
controller.close();
}
});
return new Response(stream, {
headers: {
'Content-Type': 'text/event-stream',
'Cache-Control': 'no-cache',
'Connection': 'keep-alive'
}
});
}
}
SSE vs WebSockets:
| Feature | SSE | WebSockets |
|---|
| Direction | Server → Client only | Bi-directional |
| Protocol | HTTP | ws:// or wss:// |
| Reconnection | Automatic | Manual |
| Binary Data | Limited | Full support |
| Use Case | Streaming responses, notifications | Chat, real-time collaboration |
Recommendation: Use WebSockets for most agent applications (full duplex, better for long sessions).
WebSockets
Complete WebSocket Example
import { Agent, Connection, ConnectionContext, WSMessage } from "agents";
interface ChatState {
messages: Array<{ id: string; text: string; sender: string; timestamp: number }>;
participants: string[];
}
export class ChatAgent extends Agent<Env, ChatState> {
initialState: ChatState = {
messages: [],
participants: []
};
async onConnect(connection: Connection, ctx: ConnectionContext) {
const authHeader = ctx.request.headers.get('Authorization');
const userId = ctx.request.headers.get('X-User-ID') || 'anonymous';
this.setState({
...this.state,
participants: [...this.state.participants, userId]
});
connection.send(JSON.stringify({
type: 'welcome',
message: 'Connected to chat',
participants: this.state.participants
}));
}
async onMessage(connection: Connection, message: WSMessage) {
if (typeof message === 'string') {
try {
const data = JSON.parse(message);
if (data.type === 'chat') {
const newMessage = {
id: crypto.randomUUID(),
text: data.text,
sender: data.sender || 'anonymous',
timestamp: Date.now()
};
this.setState({
...this.state,
messages: [...this.state.messages, newMessage]
});
connection.send(JSON.stringify({
type: 'message_added',
message: newMessage
}));
}
} catch (e) {
connection.send(JSON.stringify({ type: 'error', message: 'Invalid message format' }));
}
}
}
async onError(connection: Connection, error: unknown): Promise<void> {
console.error('WebSocket error:', error);
}
async onClose(connection: Connection, code: number, reason: string, wasClean: boolean): Promise<void> {
console.log(`Connection ${connection.id} closed:`, code, reason, wasClean);
}
}
Connection Management
export class MyAgent extends Agent {
async onMessage(connection: Connection, message: WSMessage) {
const connId = connection.id;
const connState = connection.state;
connection.setState({ ...connection.state, lastActive: Date.now() });
connection.send("Message to this client");
connection.close(1000, "Goodbye");
}
}
State Management
Using setState()
interface UserState {
name: string;
email: string;
preferences: { theme: string; notifications: boolean };
loginCount: number;
lastLogin: Date | null;
}
export class UserAgent extends Agent<Env, UserState> {
initialState: UserState = {
name: "",
email: "",
preferences: { theme: "dark", notifications: true },
loginCount: 0,
lastLogin: null
};
async onRequest(request: Request): Promise<Response> {
if (request.method === "POST" && new URL(request.url).pathname === "/login") {
this.setState({
...this.state,
loginCount: this.state.loginCount + 1,
lastLogin: new Date()
});
return Response.json({ success: true, state: this.state });
}
return Response.json({ state: this.state });
}
onStateUpdate(state: UserState, source: "server" | Connection) {
console.log('State updated:', state);
console.log('Source:', source);
if (state.loginCount > 10) {
console.log('Frequent user!');
}
}
}
State Rules:
- ✅ State is JSON-serializable (objects, arrays, strings, numbers, booleans, null)
- ✅ State persists across agent restarts
- ✅ State is immediately consistent within the agent
- ✅ State automatically syncs to connected WebSocket clients
- ❌ State cannot contain functions or circular references
- ❌ Total state size limited by database size (1GB max per agent)
Using SQL Database
Each agent has a built-in SQLite database accessible via this.sql:
export class MyAgent extends Agent {
async onStart() {
await this.sql`
CREATE TABLE IF NOT EXISTS users (
id INTEGER PRIMARY KEY AUTOINCREMENT,
name TEXT NOT NULL,
email TEXT UNIQUE NOT NULL,
created_at DATETIME DEFAULT CURRENT_TIMESTAMP
)
`;
await this.sql`
CREATE INDEX IF NOT EXISTS idx_email ON users(email)
`;
}
async addUser(name: string, email: string) {
const result = await this.sql`
INSERT INTO users (name, email)
VALUES (${name}, ${email})
`;
return result;
}
async getUser(email: string) {
const users = await this.sql`
SELECT * FROM users WHERE email = ${email}
`;
return users[0] || null;
}
async getAllUsers() {
const users = await this.sql`
SELECT * FROM users ORDER BY created_at DESC
`;
return users;
}
async updateUser(id: number, name: string) {
await this.sql`
UPDATE users SET name = ${name} WHERE id = ${id}
`;
}
async deleteUser(id: number) {
await this.sql`
DELETE FROM users WHERE id = ${id}
`;
}
}
SQL Best Practices:
- ✅ Use tagged template literals (prevents SQL injection)
- ✅ Create indexes for frequently queried columns
- ✅ Use transactions for multiple related operations
- ✅ Query results are always arrays (even for single row)
- ❌ Don't construct SQL strings manually
- ❌ Be mindful of 1GB database size limit
Schedule Tasks
Agents can schedule tasks to run in the future using this.schedule().
Delay (Seconds)
export class MyAgent extends Agent {
async onRequest(request: Request): Promise<Response> {
const { id } = await this.schedule(60, "checkStatus", { requestId: "123" });
return Response.json({ scheduledTaskId: id });
}
async checkStatus(data: { requestId: string }) {
console.log('Checking status for request:', data.requestId);
}
}
Specific Date
export class MyAgent extends Agent {
async scheduleReminder(reminderDate: string) {
const date = new Date(reminderDate);
const { id } = await this.schedule(date, "sendReminder", {
message: "Time for your appointment!"
});
return id;
}
async sendReminder(data: { message: string }) {
console.log('Sending reminder:', data.message);
}
}
Cron Expressions
export class MyAgent extends Agent {
async setupRecurringTasks() {
await this.schedule("*/10 * * * *", "checkUpdates", {});
await this.schedule("0 8 * * *", "dailyReport", {});
await this.schedule("0 9 * * 1", "weeklyReport", {});
await this.schedule("0 * * * *", "hourlyCheck", {});
}
async checkUpdates(data: any) {
console.log('Checking for updates...');
}
async dailyReport(data: any) {
console.log('Generating daily report...');
}
async weeklyReport(data: any) {
console.log('Generating weekly report...');
}
async hourlyCheck(data: any) {
console.log('Running hourly check...');
}
}
Managing Scheduled Tasks
export class MyAgent extends Agent {
async manageSchedules() {
const allTasks = this.getSchedules();
console.log('Total tasks:', allTasks.length);
const taskId = "some-task-id";
const task = await this.getSchedule(taskId);
if (task) {
console.log('Task:', task.callback, 'at', new Date(task.time));
console.log('Payload:', task.payload);
console.log('Type:', task.type);
const cancelled = await this.cancelSchedule(taskId);
console.log('Cancelled:', cancelled);
}
const upcomingTasks = this.getSchedules({
timeRange: {
start: new Date(),
end: new Date(Date.now() + 24 * 60 * 60 * 1000)
}
});
console.log('Upcoming tasks:', upcomingTasks.length);
const cronTasks = this.getSchedules({ type: "cron" });
const delayedTasks = this.getSchedules({ type: "delayed" });
}
}
Scheduling Constraints:
- Each task maps to a SQL database row (max 2 MB per task)
- Total tasks limited by:
(task_size * count) + other_state < 1GB
- Cron tasks continue running until explicitly cancelled
- Callback method MUST exist on Agent class (throws error if missing)
CRITICAL ERROR: If callback method doesn't exist:
await this.schedule(60, "nonExistentMethod", {});
await this.schedule(60, "existingMethod", {});
async existingMethod(data: any) {
}
Run Workflows
Agents can trigger asynchronous Cloudflare Workflows.
Workflow Binding Configuration
wrangler.jsonc:
{
"workflows": [
{
"name": "MY_WORKFLOW",
"class_name": "MyWorkflow"
}
]
}
If Workflow is in a different script:
{
"workflows": [
{
"name": "EMAIL_WORKFLOW",
"class_name": "EmailWorkflow",
"script_name": "email-workflows"
}
]
}
Triggering a Workflow
import { Agent } from "agents";
import { WorkflowEntrypoint, WorkflowEvent, WorkflowStep } from "cloudflare:workers";
interface Env {
MY_WORKFLOW: Workflow;
MyAgent: AgentNamespace<MyAgent>;
}
export class MyAgent extends Agent<Env> {
async onRequest(request: Request): Promise<Response> {
const userId = new URL(request.url).searchParams.get('userId');
const instance = await this.env.MY_WORKFLOW.create({
id: `user-${userId}`,
params: { userId, action: "process" }
});
await this.schedule(300, "runWorkflow", { userId });
return Response.json({ workflowId: instance.id });
}
async runWorkflow(data: { userId: string }) {
const instance = await this.env.MY_WORKFLOW.create({
id: `delayed-${data.userId}`,
params: data
});
await this.schedule("*/5 * * * *", "checkWorkflowStatus", { id: instance.id });
}
async checkWorkflowStatus(data: { id: string }) {
console.log('Checking workflow:', data.id);
}
}
export class MyWorkflow extends WorkflowEntrypoint<Env> {
async run(event: WorkflowEvent<{ userId: string }>, step: WorkflowStep) {
const result = await step.do('process-data', async () => {
return { processed: true };
});
return result;
}
}
Agents vs Workflows
| Feature | Agents | Workflows |
|---|
| Purpose | Interactive, user-facing | Background processing |
| Duration | Seconds to hours | Minutes to hours |
| State | SQLite database | Step-based checkpoints |
| Interaction | WebSockets, HTTP | No direct interaction |
| Retry | Manual | Automatic per step |
| Use Case | Chat, real-time UI | ETL, batch processing |
Best Practice: Use Agents to coordinate multiple Workflows. Agents can trigger, monitor, and respond to Workflow results while maintaining user interaction.
Browse the Web
Agents can browse the web using Browser Rendering.
Browser Rendering Binding
wrangler.jsonc:
{
"browser": {
"binding": "BROWSER"
}
}
Installation
npm install @cloudflare/puppeteer
Web Scraping Example
import { Agent } from "agents";
import puppeteer from "@cloudflare/puppeteer";
interface Env {
BROWSER: Fetcher;
OPENAI_API_KEY: string;
}
export class BrowserAgent extends Agent<Env> {
async browse(urls: string[]) {
const responses = [];
for (const url of urls) {
const browser = await puppeteer.launch(this.env.BROWSER);
const page = await browser.newPage();
await page.goto(url);
await page.waitForSelector("body");
const bodyContent = await page.$eval("body", el => el.innerHTML);
const data = await this.extractData(bodyContent);
responses.push({ url, data });
await browser.close();
}
return responses;
}
async extractData(html: string): Promise<any> {
const response = await fetch('https://api.openai.com/v1/chat/completions', {
method: 'POST',
headers: {
'Authorization': `Bearer ${this.env.OPENAI_API_KEY}`,
'Content-Type': 'application/json'
},
body: JSON.stringify({
model: 'gpt-4o-mini',
messages: [{
role: 'user',
content: `Extract product info from HTML: ${html.slice(0, 4000)}`
}],
response_format: { type: "json_object" }
})
});
const result = await response.json();
return JSON.parse(result.choices[0].message.content);
}
async onRequest(request: Request): Promise<Response> {
const url = new URL(request.url).searchParams.get('url');
if (!url) {
return new Response("Missing url parameter", { status: 400 });
}
const results = await this.browse([url]);
return Response.json(results);
}
}
Screenshot Capture
export class ScreenshotAgent extends Agent<Env> {
async captureScreenshot(url: string): Promise<Buffer> {
const browser = await puppeteer.launch(this.env.BROWSER);
const page = await browser.newPage();
await page.goto(url);
const screenshot = await page.screenshot({ fullPage: true });
await browser.close();
return screenshot;
}
}
Retrieval Augmented Generation (RAG)
Implement RAG using Vectorize + Workers AI embeddings.
Vectorize Binding
wrangler.jsonc:
{
"ai": {
"binding": "AI"
},
"vectorize": {
"bindings": [
{
"binding": "VECTORIZE",
"index_name": "my-agent-vectors"
}
]
}
}
Create Index
npx wrangler vectorize create my-agent-vectors \
--dimensions=768 \
--metric=cosine
Complete RAG Implementation
import { Agent } from "agents";
import { generateText } from "ai";
import { openai } from "@ai-sdk/openai";
interface Env {
AI: Ai;
VECTORIZE: Vectorize;
OPENAI_API_KEY: string;
}
export class RAGAgent extends Agent<Env> {
async ingestDocuments(documents: Array<{ id: string; text: string; metadata: any }>) {
const vectors = [];
for (const doc of documents) {
const { data } = await this.env.AI.run('@cf/baai/bge-base-en-v1.5', {
text: [doc.text]
});
vectors.push({
id: doc.id,
values: data[0],
metadata: { ...doc.metadata, text: doc.text }
});
}
await this.env.VECTORIZE.upsert(vectors);
return { ingested: vectors.length };
}
async queryKnowledge(userQuery: string, topK: number = 5) {
const { data } = await this.env.AI.run('@cf/baai/bge-base-en-v1.5', {
text: [userQuery]
});
const results = await this.env.VECTORIZE.query(data[0], { topK });
const context = results.matches.map(match => match.metadata.text).join('\n\n');
return context;
}
async chat(userMessage: string) {
const context = await this.queryKnowledge(userMessage);
const { text } = await generateText({
model: openai('gpt-4o-mini'),
messages: [
{
role: 'system',
content: `You are a helpful assistant. Use the following context to answer questions:\n\n${context}`
},
{
role: 'user',
content: userMessage
}
]
});
return { response: text, context };
}
async onRequest(request: Request): Promise<Response> {
const { message } = await request.json();
const result = await this.chat(message);
return Response.json(result);
}
}
Metadata Filtering
await this.env.VECTORIZE.createMetadataIndex("category");
await this.env.VECTORIZE.createMetadataIndex("language");
const results = await this.env.VECTORIZE.query(queryVector, {
topK: 10,
filter: {
category: { $eq: "documentation" },
language: { $eq: "en" }
}
});
See: cloudflare-vectorize skill for complete Vectorize guide.
Using AI Models
AI SDK (Vercel)
npm install ai @ai-sdk/openai @ai-sdk/anthropic
import { Agent } from "agents";
import { generateText, streamText } from "ai";
import { openai } from "@ai-sdk/openai";
import { anthropic } from "@ai-sdk/anthropic";
export class AIAgent extends Agent {
async generateResponse(prompt: string) {
const { text } = await generateText({
model: openai('gpt-4o-mini'),
prompt
});
return text;
}
async streamResponse(prompt: string): Promise<Response> {
const result = streamText({
model: anthropic('claude-sonnet-4-5'),
prompt
});
return result.toTextStreamResponse();
}
async extractData(text: string) {
const { object } = await generateObject({
model: openai('gpt-4o-mini'),
schema: z.object({
name: z.string(),
email: z.string().email(),
age: z.number().optional()
}),
prompt: `Extract user info from: ${text}`
});
return object;
}
}
Workers AI
interface Env {
AI: Ai;
}
export class WorkersAIAgent extends Agent<Env> {
async generateText(prompt: string) {
const response = await this.env.AI.run('@cf/meta/llama-3-8b-instruct', {
messages: [{ role: 'user', content: prompt }]
});
return response;
}
async generateImage(prompt: string) {
const response = await this.env.AI.run('@cf/black-forest-labs/flux-1-schnell', {
prompt
});
return response;
}
}
See: cloudflare-workers-ai skill for complete Workers AI guide.
Calling Agents
Using routeAgentRequest
Automatically route requests to agents based on URL pattern /agents/:agent/:name:
import { Agent, AgentNamespace, routeAgentRequest } from 'agents';
interface Env {
MyAgent: AgentNamespace<MyAgent>;
}
export default {
async fetch(request: Request, env: Env): Promise<Response> {
const response = await routeAgentRequest(request, env);
if (response) {
return response;
}
return new Response("Not Found", { status: 404 });
}
} satisfies ExportedHandler<Env>;
export class MyAgent extends Agent<Env> {
async onRequest(request: Request): Promise<Response> {
return Response.json({ agent: this.name });
}
}
URL Pattern: /agents/my-agent/user-123
my-agent = class name in kebab-case
user-123 = agent instance name
Using getAgentByName
For custom routing or calling agents from Workers:
import { Agent, AgentNamespace, getAgentByName } from 'agents';
interface Env {
MyAgent: AgentNamespace<MyAgent>;
}
export default {
async fetch(request: Request, env: Env): Promise<Response> {
const userId = new URL(request.url).searchParams.get('userId') || 'anonymous';
const agent = getAgentByName<Env, MyAgent>(env.MyAgent, `user-${userId}`);
return (await agent).fetch(request);
}
} satisfies ExportedHandler<Env>;
export class MyAgent extends Agent<Env> {
}
Calling Agent Methods Directly
export default {
async fetch(request: Request, env: Env): Promise<Response> {
const agent = getAgentByName<Env, MyAgent>(env.MyAgent, 'user-123');
const result = await (await agent).customMethod({ data: "example" });
return Response.json({ result });
}
}
export class MyAgent extends Agent<Env> {
async customMethod(params: { data: string }): Promise<any> {
return { processed: params.data };
}
}
Multi-Agent Communication
interface Env {
AgentA: AgentNamespace<AgentA>;
AgentB: AgentNamespace<AgentB>;
}
export class AgentA extends Agent<Env> {
async processData(data: any) {
const agentB = getAgentByName<Env, AgentB>(this.env.AgentB, 'processor-1');
const result = await (await agentB).analyze(data);
return result;
}
}
export class AgentB extends Agent<Env> {
async analyze(data: any) {
return { analyzed: true, data };
}
}
Authentication Patterns
export default {
async fetch(request: Request, env: Env): Promise<Response> {
const authHeader = request.headers.get('Authorization');
if (!authHeader) {
return new Response("Unauthorized", { status: 401 });
}
const userId = await verifyToken(authHeader);
if (!userId) {
return new Response("Forbidden", { status: 403 });
}
const agent = getAgentByName<Env, MyAgent>(env.MyAgent, `user-${userId}`);
return (await agent).fetch(request);
}
}
CRITICAL: Always authenticate in Worker, NOT in Agent. Agents should assume the caller is authorized.
Client APIs
AgentClient (Browser)
import { AgentClient } from "agents/client";
const client = new AgentClient({
agent: "chat-agent",
name: "room-123",
host: window.location.host
});
client.onopen = () => {
console.log("Connected");
client.send(JSON.stringify({ type: "join", user: "alice" }));
};
client.onmessage = (event) => {
const data = JSON.parse(event.data);
console.log("Received:", data);
};
client.onclose = () => {
console.log("Disconnected");
};
agentFetch (HTTP Requests)
import { agentFetch } from "agents/client";
async function getData() {
const response = await agentFetch(
{ agent: "my-agent", name: "user-123" },
{
method: "GET",
headers: { "Authorization": `Bearer ${token}` }
}
);
const data = await response.json();
return data;
}
useAgent Hook (React)
import { useAgent } from "agents/react";
import { useState } from "react";
function ChatUI() {
const [messages, setMessages] = useState([]);
const connection = useAgent({
agent: "chat-agent",
name: "room-123",
onMessage: (event) => {
const data = JSON.parse(event.data);
if (data.type === 'message') {
setMessages(prev => [...prev, data.message]);
}
},
onOpen: () => console.log("Connected"),
onClose: () => console.log("Disconnected")
});
const sendMessage = (text: string) => {
connection.send(JSON.stringify({ type: 'chat', text }));
};
return (
<div>
{messages.map((msg, i) => <div key={i}>{msg.text}</div>)}
<button onClick={() => sendMessage("Hello")}>Send</button>
</div>
);
}
State Synchronization
import { useAgent } from "agents/react";
import { useState } from "react";
function Counter() {
const [count, setCount] = useState(0);
const agent = useAgent({
agent: "counter-agent",
name: "my-counter",
onStateUpdate: (newState) => {
setCount(newState.counter);
}
});
const increment = () => {
agent.setState({ counter: count + 1 });
};
return (
<div>
<p>Count: {count}</p>
<button onClick={increment}>Increment</button>
</div>
);
}
useAgentChat Hook
import { useAgentChat } from "agents/ai-react";
function ChatInterface() {
const { messages, input, handleInputChange, handleSubmit, isLoading } = useAgentChat({
agent: "ai-chat-agent",
name: "chat-session-123"
});
return (
<div>
<div>
{messages.map((msg, i) => (
<div key={i}>
<strong>{msg.role}:</strong> {msg.content}
</div>
))}
</div>
<form onSubmit={handleSubmit}>
<input
value={input}
onChange={handleInputChange}
placeholder="Type a message..."
disabled={isLoading}
/>
<button type="submit" disabled={isLoading}>
{isLoading ? "Thinking..." : "Send"}
</button>
</form>
</div>
);
}
Model Context Protocol (MCP)
Build MCP servers using the Agents SDK.
MCP Server Setup
npm install @modelcontextprotocol/sdk agents
Basic MCP Server
import { McpAgent } from "agents/mcp";
import { McpServer } from "@modelcontextprotocol/sdk/server/mcp.js";
import { z } from "zod";
export class MyMCP extends McpAgent {
server = new McpServer({ name: "Demo", version: "1.0.0" });
async init() {
this.server.tool(
"add",
"Add two numbers together",
{
a: z.number().describe("First number"),
b: z.number().describe("Second number")
},
async ({ a, b }) => ({
content: [{ type: "text", text: String(a + b) }]
})
);
}
}
Stateful MCP Server
type State = { counter: number };
export class StatefulMCP extends McpAgent<Env, State> {
server = new McpServer({ name: "Counter", version: "1.0.0" });
initialState: State = { counter: 0 };
async init() {
this.server.resource(
"counter",
"mcp://resource/counter",
(uri) => ({
contents: [{ uri: uri.href, text: String(this.state.counter) }]
})
);
this.server.tool(
"increment",
"Increment the counter",
{ amount: z.number() },
async ({ amount }) => {
this.setState({
...this.state,
counter: this.state.counter + amount
});
return {
content: [{
type: "text",
text: `Counter is now ${this.state.counter}`
}]
};
}
);
}
}
MCP Transport Configuration
import { Hono } from 'hono';
const app = new Hono();
app.mount('/mcp', MyMCP.serve('/mcp').fetch, { replaceRequest: false });
app.mount('/sse', MyMCP.serveSSE('/sse').fetch, { replaceRequest: false });
export default app;
Transport Comparison:
- /mcp: Streamable HTTP (modern, recommended)
- /sse: Server-Sent Events (legacy, deprecated)
MCP with OAuth
import { OAuthProvider } from '@cloudflare/workers-oauth-provider';
export default new OAuthProvider({
apiHandlers: {
'/sse': MyMCP.serveSSE('/sse'),
'/mcp': MyMCP.serve('/mcp')
},
clientId: 'your-client-id',
clientSecret: 'your-client-secret',
});
Testing MCP Server
npx @modelcontextprotocol/inspector@latest
Cloudflare's MCP Servers: See reference for production examples.
Patterns & Concepts
Chat Agents (AIChatAgent)
import { AIChatAgent } from "agents/ai-chat-agent";
import { streamText } from "ai";
import { openai } from "@ai-sdk/openai";
export class MyChatAgent extends AIChatAgent<Env> {
async onChatMessage(onFinish) {
const result = streamText({
model: openai('gpt-4o-mini'),
messages: this.messages,
onFinish
});
return result.toTextStreamResponse();
}
async onStateUpdate(state, source) {
console.log('Chat state updated:', this.messages.length, 'messages');
}
}
Human-in-the-Loop (HITL)
export class ApprovalAgent extends Agent {
async processRequest(data: any) {
const processed = await this.autoProcess(data);
if (processed.confidence < 0.8) {
this.setState({
...this.state,
pendingReview: {
data: processed,
requestedAt: Date.now(),
status: 'pending'
}
});
await this.notifyHuman(processed);
return { status: 'pending_review', id: processed.id };
}
return this.complete(processed);
}
async approveReview(id: string, approved: boolean) {
const pending = this.state.pendingReview;
if (approved) {
await this.complete(pending.data);
} else {
await this.reject(pending.data);
}
this.setState({
...this.state,
pendingReview: null
});
}
}
Tools Concept
Tools enable agents to interact with external services:
export class ToolAgent extends Agent {
async searchFlights(from: string, to: string, date: string) {
const response = await fetch(`https://api.flights.com/search`, {
method: 'POST',
body: JSON.stringify({ from, to, date })
});
return response.json();
}
async bookFlight(flightId: string, passengers: any[]) {
const response = await fetch(`https://api.flights.com/book`, {
method: 'POST',
body: JSON.stringify({ flightId, passengers })
});
return response.json();
}
async sendEmail(to: string, subject: string, body: string) {
return { sent: true };
}
async bookTrip(params: any) {
const flights = await this.searchFlights(params.from, params.to, params.date);
const booking = await this.bookFlight(flights[0].id, params.passengers);
await this.sendEmail(params.email, "Booking Confirmed", `Booking ID: ${booking.id}`);
return booking;
}
}
Multi-Agent Orchestration
interface Env {
ResearchAgent: AgentNamespace<ResearchAgent>;
WriterAgent: AgentNamespace<WriterAgent>;
EditorAgent: AgentNamespace<EditorAgent>;
}
export class OrchestratorAgent extends Agent<Env> {
async createArticle(topic: string) {
const researcher = getAgentByName<Env, ResearchAgent>(
this.env.ResearchAgent,
`research-${topic}`
);
const research = await (await researcher).research(topic);
const writer = getAgentByName<Env, WriterAgent>(
this.env.WriterAgent,
`writer-${topic}`
);
const draft = await (await writer).write(research);
const editor = getAgentByName<Env, EditorAgent>(
this.env.EditorAgent,
`editor-${topic}`
);
const final = await (await editor).edit(draft);
return final;
}
}
Critical Rules
Always Do ✅
- Export Agent class - Must be exported for binding to work
- Include new_sqlite_classes in v1 migration - Cannot add SQLite later
- Match binding name to class name - Prevents "binding not found" errors
- Authenticate in Worker, not Agent - Security best practice
- Use tagged template literals for SQL - Prevents SQL injection
- Handle WebSocket disconnections - State persists, connections don't
- Verify scheduled task callback exists - Throws error if method missing
- Use global unique instance names - Same name = same agent globally
- Check state size limits - Max 1GB total per agent
- Monitor task payload size - Max 2MB per scheduled task
- Use workflow bindings correctly - Must be configured in wrangler.jsonc
- Create Vectorize indexes before inserting - Required for metadata filtering
- Close browser instances - Prevent resource leaks
- Use setState() for persistence - Don't just modify this.state
- Test migrations locally first - Migrations are atomic, can't rollback
Never Do ❌
- Don't add SQLite to existing deployed class - Must be in first migration
- Don't gradually deploy migrations - Atomic only
- Don't skip authentication in Worker - Always auth before agent access
- Don't construct SQL strings manually - Use tagged templates
- Don't exceed 1GB state per agent - Hard limit
- Don't schedule tasks with non-existent callbacks - Runtime error
- Don't assume same name = different agent - Global uniqueness
- Don't use SSE for MCP - Deprecated, use /mcp transport
- Don't forget browser binding - Required for web browsing
- Don't modify this.state directly - Use setState() instead
Known Issues Prevention
This skill prevents 15+ documented issues:
Issue 1: Migrations Not Atomic
Error: "Cannot gradually deploy migration"
Source: https://developers.cloudflare.com/durable-objects/reference/durable-objects-migrations/
Why: Migrations apply to all instances simultaneously
Prevention: Deploy migrations independently of code changes, use npx wrangler versions deploy
Issue 2: Missing new_sqlite_classes
Error: "Cannot enable SQLite on existing class"
Source: https://developers.cloudflare.com/agents/api-reference/configuration/
Why: SQLite must be enabled in first migration
Prevention: Include new_sqlite_classes in tag "v1" migration
Issue 3: Agent Class Not Exported
Error: "Binding not found" or "Cannot access undefined"
Source: https://developers.cloudflare.com/agents/api-reference/agents-api/
Why: Durable Objects require exported class
Prevention: export class MyAgent extends Agent (with export keyword)
Issue 4: Binding Name Mismatch
Error: "Binding 'X' not found"
Source: https://developers.cloudflare.com/agents/api-reference/configuration/
Why: Binding name must match class name exactly
Prevention: Ensure name and class_name are identical in wrangler.jsonc
Issue 5: Global Uniqueness Not Understood
Error: Unexpected behavior with agent instances
Source: https://developers.cloudflare.com/agents/api-reference/agents-api/
Why: Same name always returns same agent instance globally
Prevention: Use unique identifiers (userId, sessionId) for instance names
Issue 6: WebSocket State Not Persisted
Error: Connection state lost after disconnect
Source: https://developers.cloudflare.com/agents/api-reference/websockets/
Why: WebSocket connections don't persist, but agent state does
Prevention: Store important data in agent state via setState(), not connection state
Issue 7: Scheduled Task Callback Doesn't Exist
Error: "Method X does not exist on Agent"
Source: https://developers.cloudflare.com/agents/api-reference/schedule-tasks/
Why: this.schedule() calls method that isn't defined
Prevention: Ensure callback method exists before scheduling
Issue 8: State Size Limit Exceeded
Error: "Maximum database size exceeded"
Source: https://developers.cloudflare.com/agents/api-reference/store-and-sync-state/
Why: Agent state + scheduled tasks exceed 1GB
Prevention: Monitor state size, use external storage (D1, R2) for large data
Issue 9: Scheduled Task Too Large
Error: "Task payload exceeds 2MB"
Source: https://developers.cloudflare.com/agents/api-reference/schedule-tasks/
Why: Each task maps to database row with 2MB limit
Prevention: Keep task payloads minimal, store large data in agent state/SQL
Issue 10: Workflow Binding Missing
Error: "Cannot read property 'create' of undefined"
Source: https://developers.cloudflare.com/agents/api-reference/run-workflows/
Why: Workflow binding not configured in wrangler.jsonc
Prevention: Add workflow binding before using this.env.WORKFLOW
Issue 11: Browser Binding Required
Error: "BROWSER binding undefined"
Source: https://developers.cloudflare.com/agents/api-reference/browse-the-web/
Why: Browser Rendering requires explicit binding
Prevention: Add "browser": { "binding": "BROWSER" } to wrangler.jsonc
Issue 12: Vectorize Index Not Found
Error: "Index does not exist"
Source: https://developers.cloudflare.com/agents/api-reference/rag/
Why: Vectorize index must be created before use
Prevention: Run wrangler vectorize create before deploying agent
Issue 13: MCP Transport Confusion
Error: "SSE transport deprecated"
Source: https://developers.cloudflare.com/agents/model-context-protocol/transport/
Why: SSE transport is legacy, streamable HTTP is recommended
Prevention: Use /mcp endpoint with MyMCP.serve('/mcp'), not /sse
Issue 14: Authentication Bypass
Error: Security vulnerability
Source: https://developers.cloudflare.com/agents/api-reference/calling-agents/
Why: Authentication done in Agent instead of Worker
Prevention: Always authenticate in Worker before calling getAgentByName()
Issue 15: Instance Naming Errors
Error: Cross-user data leakage
Source: https://developers.cloudflare.com/agents/api-reference/calling-agents/
Why: Poor instance naming allows access to wrong agent
Prevention: Use namespaced names like user-${userId}, validate ownership
Dependencies
Required
- cloudflare-worker-base - Foundation (Hono, Vite, Workers setup)
Optional (by feature)
- cloudflare-workers-ai - For Workers AI model calls
- cloudflare-vectorize - For RAG with Vectorize
- cloudflare-d1 - For additional persistent storage beyond agent state
- cloudflare-r2 - For file storage
- cloudflare-queues - For message queues
NPM Packages
agents - Agents SDK (required)
@modelcontextprotocol/sdk - For building MCP servers
@cloudflare/puppeteer - For web browsing
ai - AI SDK for model calls
@ai-sdk/openai - OpenAI models
@ai-sdk/anthropic - Anthropic models
Official Documentation
Bundled Resources
Templates (templates/)
wrangler-agents-config.jsonc - Complete configuration example
basic-agent.ts - Minimal HTTP agent
websocket-agent.ts - WebSocket handlers
state-sync-agent.ts - State management patterns
scheduled-agent.ts - Task scheduling
workflow-agent.ts - Workflow integration
browser-agent.ts - Web browsing
rag-agent.ts - RAG implementation
chat-agent-streaming.ts - Streaming chat
calling-agents-worker.ts - Agent routing
react-useagent-client.tsx - React client
mcp-server-basic.ts - MCP server
hitl-agent.ts - Human-in-the-loop
References (references/)
agent-class-api.md - Complete Agent class reference
client-api-reference.md - Browser client APIs
state-management-guide.md - State and SQL deep dive
websockets-sse.md - WebSocket vs SSE comparison
scheduling-api.md - Task scheduling details
workflows-integration.md - Workflows guide
browser-rendering.md - Web browsing patterns
rag-patterns.md - RAG best practices
mcp-server-guide.md - MCP server development
mcp-tools-reference.md - MCP tools API
hitl-patterns.md - Human-in-the-loop workflows
best-practices.md - Production patterns
Examples (examples/)
chat-bot-complete.md - Full chat agent
multi-agent-workflow.md - Agent orchestration
scheduled-reports.md - Recurring tasks
browser-scraper-agent.md - Web scraping
rag-knowledge-base.md - RAG system
mcp-remote-server.md - Production MCP server
Last Verified: 2025-10-21
Package Versions: agents@latest
Compliance: Cloudflare Agents SDK official documentation