Agents SDK

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Your knowledge of the Agents SDK may be outdated.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/

| Topic | Docs URL | Use for |

|-------|----------|---------|

| Getting started | Quick start | First agent, project setup |

| Adding to existing project | Add to existing project | Install into existing Workers app |

| Configuration | Configuration | wrangler.jsonc, bindings, assets, deployment |

| Agent class | Agents API | Agent lifecycle, patterns, pitfalls |

| State | Store and sync state | setState, validateStateChange, persistence |

| Routing | Routing | URL patterns, routeAgentRequest |

| Callable methods | Callable methods | @callable, RPC, streaming, timeouts |

| Scheduling | Schedule tasks | schedule(), scheduleEvery(), cron |

| Workflows | Run workflows | AgentWorkflow, durable multi-step tasks |

| HTTP/WebSockets | WebSockets | Lifecycle hooks, hibernation |

| Chat agents | Chat agents | AIChatAgent, streaming, tools, persistence |

| Client SDK | Client SDK | useAgent, useAgentChat, React hooks |

| Client tools | Client tools | Client-side tools, autoContinueAfterToolResult |

| Server-driven messages | Trigger patterns | saveMessages, waitUntilStable, server-initiated turns |

| Resumable streaming | Resumable streaming | Stream recovery on disconnect |

| Email | Email | Email routing, secure reply resolver |

| MCP client | MCP client | Connecting to MCP servers |

| MCP server | MCP server | Building MCP servers with McpAgent |

| MCP transports | MCP transports | Streamable HTTP, SSE, RPC transport options |

| Securing MCP servers | Securing MCP | OAuth, proxy MCP, hardening |

| Human-in-the-loop | Human-in-the-loop | Approval flows, needsApproval, workflows |

| Durable execution | Durable execution | runFiber(), stash(), surviving DO eviction |

| Queue | Queue | Built-in FIFO queue, queue() |

| Retries | Retries | this.retry(), backoff/jitter |

| Observability | Observability | Diagnostics-channel events |

| Push notifications | Push notifications | Web Push + VAPID from agents |

| Webhooks | Webhooks | Receiving external webhooks |

| Cross-domain auth | Cross-domain auth | WebSocket auth, tokens, CORS |

| Readonly connections | Readonly | shouldConnectionBeReadonly |

| Voice | Voice | Experimental STT/TTS, withVoice |

| Browse the web | Browser tools | Experimental CDP browser automation |

| Think | Think | Experimental higher-level chat agent class |

| Migrations | AI SDK v5, AI SDK v6 | Upgrading @cloudflare/ai-chat |

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}:

| Class | URL |

|-------|-----|

| Counter | /agents/counter/user-123 |

| ChatRoom | /agents/chat-room/lobby |

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

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

Core APIs

| Task | API |

|------|-----|

| Read state | this.state.count |

| Write state | this.setState({ count: 1 }) |

| SQL query | this.sqlSELECT * 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) |

| Durable fiber | await this.runFiber("name", async (ctx) => { ... }) |

| Enqueue work | this.queue("handler", payload) |

| Retry with backoff | await this.retry(fn, { maxAttempts: 5 }) |

| Broadcast to clients | this.broadcast(message) |

| Get connections | this.getConnections(tag?) |

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

Chat & Streaming

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

Background Processing

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

Integrations

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

Experimental

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