agents-sdk

name: agents-sdk description: 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, chat applications, voice agents, or browser automation. Covers Agent class, state management, callable RPC, Workflows, durable execution, queues, retries, observability, and React hooks. Biases towards retrieval from Cloudflare docs over pre-trained knowledge.

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Your knowledge of the Agents SDK may be outdated.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 — 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