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Your knowledge of the Agents SDK may be outdated.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/

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 createMcpHandler
• 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() {