Build AI agents on Cloudflare Workers using the Agents SDK. Load when creating stateful agents, durable workflows, real-time WebSocket apps, scheduled tasks, MCP servers, or chat applications. Covers Agent class, state management, callable RPC, Workflows integration, and React hooks.
STOP. Your knowledge of the Agents SDK may be outdated. Prefer retrieval over pre-training for any Agents SDK task.
Fetch current docs from https://github.com/cloudflare/agents/tree/main/docs before implementing.
| Topic | Doc | Use for |
|---|---|---|
| Getting started | docs/getting-started.md | First agent, project setup |
| State | docs/state.md | setState, validateStateChange, persistence |
| Routing | docs/routing.md | URL patterns, routeAgentRequest, basePath |
| Callable methods | docs/callable-methods.md | @callable, RPC, streaming, timeouts |
| Scheduling |
docs/scheduling.md |
schedule(), scheduleEvery(), cron |
| Workflows | docs/workflows.md | AgentWorkflow, durable multi-step tasks |
| HTTP/WebSockets | docs/http-websockets.md | Lifecycle hooks, hibernation |
docs/email.md | Email routing, secure reply resolver |
| MCP client | docs/mcp-client.md | Connecting to MCP servers |
| MCP server | docs/mcp-servers.md | Building MCP servers with McpAgent |
| Client SDK | docs/client-sdk.md | useAgent, useAgentChat, React hooks |
| Human-in-the-loop | docs/human-in-the-loop.md | Approval flows, pausing workflows |
| Resumable streaming | docs/resumable-streaming.md | Stream recovery on disconnect |
Cloudflare docs: https://developers.cloudflare.com/agents/
The Agents SDK provides:
@callable() methods invoked over WebSocketscheduleEvery), and cron tasksAgentWorkflowMcpAgentAIChatAgent with resumable streamsuseAgent, useAgentChat for client appsnpm ls agents # Should show agents package
If not installed:
npm install agents
{
"durable_objects": {
"bindings": [{ "name": "MyAgent", "class_name": "MyAgent" }],
},
"migrations": [{ "tag": "v1", "new_sqlite_classes": ["MyAgent"] }],
}
import { Agent, routeAgentRequest, callable } from "agents"
type State = { count: number }
export class Counter extends Agent<Env, State> {
initialState = { count: 0 }
// Validation hook - runs before state persists (sync, throwing rejects the update)
validateStateChange(nextState: State, source: Connection | "server") {
if (nextState.count < 0) throw new Error("Count cannot be negative")
}
// Notification hook - runs after state persists (async, non-blocking)
onStateUpdate(state: State, source: Connection | "server") {
console.log("State updated:", state)
}
@callable()
increment() {
this.setState({ count: this.state.count + 1 })
return this.state.count
}
}
export default {
fetch: (req, env) => routeAgentRequest(req, env) ?? new Response("Not found", { status: 404 }),
}
Requests route to /agents/{agent-name}/{instance-name}:
| Class | URL |
|---|---|
Counter | /agents/counter/user-123 |
ChatRoom | /agents/chat-room/lobby |
Client: useAgent({ agent: "Counter", name: "user-123" })
| Task | API |
|---|---|
| Read state | this.state.count |
| Write state | this.setState({ count: 1 }) |
| SQL query | this.sql`SELECT * FROM users WHERE id = ${id}` |
| Schedule (delay) | await this.schedule(60, "task", payload) |
| Schedule (cron) | await this.schedule("0 * * * *", "task", payload) |
| Schedule (interval) | await this.scheduleEvery(30, "poll") |
| RPC method | @callable() myMethod() { ... } |
| Streaming RPC | @callable({ streaming: true }) stream(res) { ... } |
| Start workflow | await this.runWorkflow("ProcessingWorkflow", params) |
import { useAgent } from "agents/react"
function App() {
const [state, setLocalState] = useState({ count: 0 })
const agent = useAgent({
agent: "Counter",
name: "my-instance",
onStateUpdate: (newState) => setLocalState(newState),
onIdentity: (name, agentType) => console.log(`Connected to ${name}`),
})
return <button onClick={() => agent.setState({ count: state.count + 1 })}>Count: {state.count}</button>
}