Cloudflare Agents SDK

Your knowledge of the Agents SDK may be outdated. Prefer retrieval over pre-training for any Agents SDK task.

Retrieval Sources

Cloudflare docs: https://developers.cloudflare.com/agents/

Capabilities

The Agents SDK provides:

• Persistent state — SQLite-backed, auto-synced to clients via setState
• Callable RPC — @callable() methods invoked over WebSocket
• Scheduling — One-time, recurring (scheduleEvery), and cron tasks
• Workflows — Durable multi-step background processing via AgentWorkflow
• Durable execution — runFiber() / stash() for work that survives DO eviction
• Queue — Built-in FIFO queue with retries via queue()
• Retries — this.retry() with exponential backoff and jitter
• MCP integration — Connect to MCP servers or build your own with McpAgent
• Email handling — Receive and reply to emails with secure routing
• Streaming chat — AIChatAgent with resumable streams, message persistence, tools
• Server-driven messages — saveMessages, waitUntilStable for proactive agent turns
• React hooks — useAgent, useAgentChat for client apps
• Observability — diagnostics_channel events for state, RPC, schedule, lifecycle
• Push notifications — Web Push + VAPID delivery from agents
• Webhooks — Receive and verify external webhooks
• Voice (experimental) — STT/TTS via @cloudflare/voice
• Browser tools (experimental) — CDP-powered browsing via agents/browser
• Think (experimental) — Higher-level chat agent via @cloudflare/think

FIRST: Verify Installation

npm ls agents  # Should show agents package

If not installed:

npm install agents

For chat agents:

npm install agents @cloudflare/ai-chat ai @ai-sdk/react

Wrangler Configuration

{  "compatibility_flags": ["nodejs_compat"],  "durable_objects": {    "bindings": [{ "name": "MyAgent", "class_name": "MyAgent" }]  },  "migrations": [{ "tag": "v1", "new_sqlite_classes": ["MyAgent"] }]}

Gotchas:

• Do NOT enable experimentalDecorators in tsconfig (breaks @callable)
• Never edit old migrations — always add new tags
• Each agent class needs its own DO binding + migration entry
• Add "ai": { "binding": "AI" } for Workers AI

Agent Class

import { Agent, routeAgentRequest, callable } from "agents";
type State = { count: number };
export class Counter extends Agent<Env, State> {  initialState = { count: 0 };
  validateStateChange(nextState: State, source: Connection | "server") {    if (nextState.count < 0) throw new Error("Count cannot be negative");  }
  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 })};

Routing

Requests route to /agents/{agent-name}/{instance-name}:

Client: useAgent({ agent: "Counter", name: "user-123" })

Custom routing: use getAgentByName(env.MyAgent, "instance-id") then agent.fetch(request).

Core APIs

React Client

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>  );}

References

Core

• references/state-scheduling.md [blocked] — State persistence, scheduling, SQL
• references/callable.md [blocked] — RPC methods, streaming, timeouts
• references/routing.md [blocked] — URL patterns, custom routing, getAgentByName
• references/configuration.md [blocked] — Wrangler config, bindings, Vite setup

Chat & Streaming

• references/streaming-chat.md [blocked] — AIChatAgent, resumable streams, tools
• references/client-sdk.md [blocked] — useAgent, useAgentChat, AgentClient
• references/server-driven-messages.md [blocked] — Trigger patterns, saveMessages
• references/human-in-the-loop.md [blocked] — Approval flows, needsApproval

Background Processing

• references/workflows.md [blocked] — Durable Workflows integration
• references/durable-execution.md [blocked] — runFiber, stash, surviving eviction
• references/queue-retries.md [blocked] — Built-in queue, retry with backoff

Integrations

• references/mcp.md [blocked] — MCP client and server, transports, securing
• references/email.md [blocked] — Email routing and handling
• references/webhooks-push.md [blocked] — Webhooks, push notifications
• references/observability.md [blocked] — Diagnostics-channel events

Experimental

• references/think.md [blocked] — @cloudflare/think higher-level chat agent
• references/voice.md [blocked] — @cloudflare/voice STT/TTS
• references/codemode.md [blocked] — Code Mode for tool orchestration
• references/browse-the-web.md [blocked] — CDP browser tools