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Push notifications

Send browser push notifications from your agent — even when the user has closed the tab. By combining the agent's persistent state (for storing push subscriptions), scheduling (for timed delivery), and the Web Push API ↗, you can reach users who are completely offline.

How it works

Browser                              Agent (Durable Object)
───────                              ──────────────────────
1. Register service worker
2. Subscribe to push (VAPID key)
3. Send subscription to agent ──────► Store in this.state
4. Create reminder ─────────────────► this.schedule(delay, "sendReminder", payload)


   ... user closes tab ...


5.                                    Alarm fires → sendReminder()
                                      web-push sends encrypted payload
                                              │
6. Service worker receives push ◄─────────────┘
7. showNotification()

The agent stores push subscriptions durably in its state and uses this.schedule() to fire notifications at the right time. When the alarm triggers, the agent calls the push service endpoint using the web-push ↗ library. The browser's service worker receives the push event and displays a native notification.

Prerequisites

Generate VAPID keys

Web Push requires a VAPID (Voluntary Application Server Identification) key pair. Generate one:

Terminal window
npx web-push generate-vapid-keys

Store the keys in a .env file for local development:

VAPID_PUBLIC_KEY=BGxK...
VAPID_PRIVATE_KEY=abc1...
VAPID_SUBJECT=mailto:you@example.com

For production, use wrangler secret put:

Terminal window
wrangler secret put VAPID_PUBLIC_KEY
wrangler secret put VAPID_PRIVATE_KEY
wrangler secret put VAPID_SUBJECT

Create the agent

The agent has three responsibilities: store push subscriptions, schedule reminders, and send notifications when alarms fire.

JavaScript
import { Agent, callable, routeAgentRequest } from "agents";
import webpush from "web-push";


export class ReminderAgent extends Agent {
  initialState = {
    subscriptions: [],
    reminders: [],
  };


  @callable()
  getVapidPublicKey() {
    return this.env.VAPID_PUBLIC_KEY;
  }


  @callable()
  async subscribe(subscription) {
    const exists = this.state.subscriptions.some(
      (s) => s.endpoint === subscription.endpoint,
    );
    if (!exists) {
      this.setState({
        ...this.state,
        subscriptions: [...this.state.subscriptions, subscription],
      });
    }
    return { ok: true };
  }


  @callable()
  async unsubscribe(endpoint) {
    this.setState({
      ...this.state,
      subscriptions: this.state.subscriptions.filter(
        (s) => s.endpoint !== endpoint,
      ),
    });
    return { ok: true };
  }


  @callable()
  async createReminder(message, delaySeconds) {
    const id = crypto.randomUUID();
    const scheduledAt = Date.now() + delaySeconds * 1000;
    const reminder = { id, message, scheduledAt, sent: false };


    this.setState({
      ...this.state,
      reminders: [...this.state.reminders, reminder],
    });


    await this.schedule(delaySeconds, "sendReminder", { id, message });
    return reminder;
  }


  async sendReminder(payload) {
    webpush.setVapidDetails(
      this.env.VAPID_SUBJECT,
      this.env.VAPID_PUBLIC_KEY,
      this.env.VAPID_PRIVATE_KEY,
    );


    const deadEndpoints = [];


    await Promise.all(
      this.state.subscriptions.map(async (sub) => {
        try {
          await webpush.sendNotification(
            sub,
            JSON.stringify({
              title: "Reminder",
              body: payload.message,
              tag: `reminder-${payload.id}`,
            }),
          );
        } catch (err) {
          const statusCode =
            err instanceof webpush.WebPushError ? err.statusCode : 0;
          if (statusCode === 404 || statusCode === 410) {
            deadEndpoints.push(sub.endpoint);
          }
        }
      }),
    );


    if (deadEndpoints.length > 0) {
      this.setState({
        ...this.state,
        subscriptions: this.state.subscriptions.filter(
          (s) => !deadEndpoints.includes(s.endpoint),
        ),
      });
    }


    this.setState({
      ...this.state,
      reminders: this.state.reminders.map((r) =>
        r.id === payload.id ? { ...r, sent: true } : r,
      ),
    });


    this.broadcast(
      JSON.stringify({
        type: "reminder_sent",
        id: payload.id,
        timestamp: Date.now(),
      }),
    );
  }
}


export default {
  async fetch(request, env) {
    return (
      (await routeAgentRequest(request, env)) ??
      new Response("Not found", { status: 404 })
    );
  },
};

The sendReminder callback handles three things: delivering the push notification via the web-push library, cleaning up dead subscriptions (the push service returns 404 or 410 when a subscription is no longer valid), and broadcasting to any connected clients so the UI updates in real time.

Set up the service worker

The service worker runs in the browser and receives push events even when no tabs are open. Place this file at public/sw.js so it is served from the root of your domain:

JavaScript
self.addEventListener("push", (event) => {
  if (!event.data) return;


  const data = event.data.json();


  event.waitUntil(
    self.registration.showNotification(data.title || "Notification", {
      body: data.body || "",
      icon: data.icon || "/favicon.ico",
      tag: data.tag,
      data: data.data,
    }),
  );
});


self.addEventListener("notificationclick", (event) => {
  event.notification.close();


  event.waitUntil(
    self.clients.matchAll({ type: "window" }).then((windowClients) => {
      for (const client of windowClients) {
        if (
          client.url.includes(self.location.origin) &&
          "focus" in client
        ) {
          return client.focus();
        }
      }
      return self.clients.openWindow("/");
    }),
  );
});

The push event handler parses the JSON payload and displays a native notification. The notificationclick handler focuses an existing tab or opens a new one when the user taps the notification.

Build the client

The client needs to: register the service worker, request notification permission, subscribe to push using the VAPID public key, and send the subscription to the agent.

Register the service worker

JavaScript
useEffect(() => {
  if (!("serviceWorker" in navigator) || !("PushManager" in window)) {
    return;
  }
  navigator.serviceWorker.register("/sw.js");
}, []);

Subscribe to push

Fetch the VAPID public key from the agent, then subscribe through the Push API:

JavaScript
function base64urlToUint8Array(base64url) {
  const padded = base64url + "=".repeat((4 - (base64url.length % 4)) % 4);
  const binary = atob(padded.replace(/-/g, "+").replace(/_/g, "/"));
  const bytes = new Uint8Array(binary.length);
  for (let i = 0; i < binary.length; i++) bytes[i] = binary.charCodeAt(i);
  return bytes;
}


async function subscribeToPush(agent) {
  const permission = await Notification.requestPermission();
  if (permission !== "granted") return;


  const vapidPublicKey = await agent.call("getVapidPublicKey");
  const reg = await navigator.serviceWorker.ready;
  const subscription = await reg.pushManager.subscribe({
    userVisibleOnly: true,
    applicationServerKey: base64urlToUint8Array(vapidPublicKey).buffer,
  });


  const subJson = subscription.toJSON();
  await agent.call("subscribe", [
    {
      endpoint: subJson.endpoint,
      expirationTime: subJson.expirationTime ?? null,
      keys: subJson.keys,
    },
  ]);
}

Create reminders

With the subscription stored, creating a reminder is a single RPC call. The agent handles scheduling and delivery:

JavaScript
await agent.call("createReminder", ["Check the oven", 300]);

The agent schedules an alarm for 300 seconds (5 minutes). When it fires, the push notification arrives — even if the user closed the tab minutes ago.

Configuration

wrangler.jsonc

JSONC
{
  "name": "push-notifications",
  "compatibility_date": "2026-01-28",
  "compatibility_flags": ["nodejs_compat"],
  "main": "src/server.ts",
  "durable_objects": {
    "bindings": [
      { "name": "ReminderAgent", "class_name": "ReminderAgent" },
    ],
  },
  "migrations": [{ "tag": "v1", "new_sqlite_classes": ["ReminderAgent"] }],
  "assets": {
    "not_found_handling": "single-page-application",
  },
}

The nodejs_compat compatibility flag is required for the web-push library.

Dependencies

Terminal window
npm install agents web-push

Production considerations

Subscription expiry

Push subscriptions can expire or be revoked by the user. Always handle 404 and 410 responses from the push service by removing the dead subscription from state, as shown in the sendReminder example above.

Per-user vs shared agents

For most applications, use one agent per user (using the user ID as the agent name). This isolates each user's subscriptions and reminders. For broadcast-style notifications (same message to many users), a shared agent can store all subscriptions, but be aware of the state size as the subscription list grows.

Combining push with WebSocket broadcast

Use this.broadcast() for clients that are currently connected (instant, no push service roundtrip) and Web Push for clients that are offline. The sendReminder example above does both — connected clients get a real-time WebSocket message, and offline clients get a push notification.

Multiple devices

A single user may subscribe from multiple browsers or devices. The agent stores each subscription separately, and sendReminder iterates over all of them. Each device receives its own push notification.

Retry on failure

If the push service returns a 5xx error (temporary failure), you can retry using this.schedule() with a short delay:

JavaScript
try {
  await webpush.sendNotification(sub, payload);
} catch (err) {
  const statusCode = err instanceof webpush.WebPushError ? err.statusCode : 0;
  if (statusCode >= 500) {
    await this.schedule(60, "retrySendNotification", {
      endpoint: sub.endpoint,
      payload,
    });
  }
}

Next steps

Schedule tasks Learn about scheduling and keepAlive for long-running operations.
Store and sync state Manage agent state for storing subscriptions.
Callable methods Expose agent methods as RPC endpoints.