feat: add webchat pwa push subscription support

src/gateway/server.test.ts

@@ -554,6 +554,99 @@ describe('GatewayServer request body limits', () => {
   });
 });
 
+describe('GatewayServer WebChat push endpoints', () => {
+  const PUSH_PORT = 18894;
+  let pushServer: GatewayServer;
+
+  beforeAll(async () => {
+    if (!LISTEN_ALLOWED) {
+      return;
+    }
+    pushServer = new GatewayServer({
+      port: PUSH_PORT,
+      sessionManager: mockSessionManager as unknown as GatewayServerConfig['sessionManager'],
+      modelClient: mockModelClient,
+      systemPrompt: 'Test prompt',
+      toolRegistry: mockToolRegistry as unknown as GatewayServerConfig['toolRegistry'],
+      toolExecutor: mockToolExecutor as unknown as GatewayServerConfig['toolExecutor'],
+      auth: { token: 'push-secret' },
+      authHttp: true,
+      uiDir: resolve(import.meta.dirname, 'ui'),
+      webchatPush: {
+        enabled: true,
+        vapidPublicKey: 'BO_test_public_key',
+        maxSubscriptions: 2,
+      },
+    });
+    await pushServer.start();
+  });
+
+  afterAll(async () => {
+    if (!LISTEN_ALLOWED) {
+      return;
+    }
+    await pushServer.stop();
+  });
+
+  it('returns push public key metadata when authenticated', async () => {
+    if (!LISTEN_ALLOWED) {
+      return;
+    }
+
+    const res = await fetch(`http://127.0.0.1:${PUSH_PORT}/webchat/push/public-key`, {
+      headers: { Authorization: 'Bearer push-secret' },
+    });
+    expect(res.status).toBe(200);
+    const body = await res.json() as { enabled: boolean; vapidPublicKey: string | null };
+    expect(body.enabled).toBe(true);
+    expect(body.vapidPublicKey).toBe('BO_test_public_key');
+  });
+
+  it('stores and deletes webchat push subscriptions', async () => {
+    if (!LISTEN_ALLOWED) {
+      return;
+    }
+
+    const headers = { Authorization: 'Bearer push-secret', 'Content-Type': 'application/json' };
+    const payload = {
+      endpoint: 'https://example.invalid/sub/1',
+      keys: {
+        p256dh: 'p256dh-sample',
+        auth: 'auth-sample',
+      },
+      userAgent: 'vitest',
+    };
+
+    const putRes = await fetch(`http://127.0.0.1:${PUSH_PORT}/webchat/push/subscriptions`, {
+      method: 'POST',
+      headers,
+      body: JSON.stringify(payload),
+    });
+    expect(putRes.status).toBe(200);
+    const putBody = await putRes.json() as { stored: boolean; count: number };
+    expect(putBody.stored).toBe(true);
+    expect(putBody.count).toBe(1);
+
+    const listRes = await fetch(`http://127.0.0.1:${PUSH_PORT}/webchat/push/subscriptions`, {
+      headers: { Authorization: 'Bearer push-secret' },
+    });
+    expect(listRes.status).toBe(200);
+    const listBody = await listRes.json() as { count: number; maxSubscriptions: number };
+    expect(listBody.count).toBe(1);
+    expect(listBody.maxSubscriptions).toBe(2);
+
+    const delRes = await fetch(`http://127.0.0.1:${PUSH_PORT}/webchat/push/subscriptions`, {
+      method: 'DELETE',
+      headers,
+      body: JSON.stringify({ endpoint: payload.endpoint }),
+    });
+    expect(delRes.status).toBe(200);
+    const delBody = await delRes.json() as { removed: boolean; count: number };
+    expect(delBody.removed).toBe(true);
+    expect(delBody.count).toBe(0);
+  });
+});
+
 describe('GatewayServer WebSocket ingress rate limiting', () => {
   const RATE_PORT = 18895;
   let rateServer: GatewayServer;

src/gateway/server.ts

@@ -131,6 +131,23 @@ export interface GatewayServerConfig {
   feishuHandler?: Pick<FeishuAdapter, 'handleRequest'>;
   /** Optional Zalo adapter for inbound webhook events. */
   zaloHandler?: Pick<ZaloAdapter, 'handleRequest'>;
+  /** Optional WebChat PWA push-subscription settings. */
+  webchatPush?: {
+    enabled?: boolean;
+    vapidPublicKey?: string;
+    maxSubscriptions?: number;
+  };
+}
+
+interface WebchatPushSubscriptionRecord {
+  endpoint: string;
+  keys: {
+    p256dh: string;
+    auth: string;
+  };
+  userAgent?: string;
+  createdAt: number;
+  updatedAt: number;
 }
 
 export class GatewayServer {
@@ -158,6 +175,7 @@ export class GatewayServer {
     windowStartMs: number;
   }> = new Map();
   private connectionStateMap: Map<string, NodeConnectionState> = new Map();
+  private webchatPushSubscriptions: Map<string, WebchatPushSubscriptionRecord> = new Map();
   private config: GatewayServerConfig;
   private startTime: number = Date.now();
 
@@ -670,6 +688,160 @@ export class GatewayServer {
     };
   }
 
+  private getWebchatPushConfig(): { enabled: boolean; vapidPublicKey?: string; maxSubscriptions: number } {
+    const runtimeConfig = this.config.config?.server.webchat_push;
+    const override = this.config.webchatPush;
+    const enabled = override?.enabled ?? runtimeConfig?.enabled ?? false;
+    const vapidPublicKey = override?.vapidPublicKey ?? runtimeConfig?.vapid_public_key;
+    const maxSubscriptions = override?.maxSubscriptions ?? runtimeConfig?.max_subscriptions ?? 5000;
+    return { enabled, vapidPublicKey, maxSubscriptions };
+  }
+
+  private async handleWebchatPushRequest(req: IncomingMessage, res: ServerResponse): Promise<boolean> {
+    if (!req.url?.startsWith('/webchat/push')) {
+      return false;
+    }
+
+    const parsed = new URL(req.url, `http://${req.headers.host ?? 'localhost'}`);
+    const pathname = parsed.pathname;
+    const cfg = this.getWebchatPushConfig();
+
+    if (pathname === '/webchat/push/public-key' && req.method === 'GET') {
+      res.writeHead(200, { 'Content-Type': 'application/json' });
+      res.end(JSON.stringify({
+        enabled: cfg.enabled,
+        vapidPublicKey: cfg.vapidPublicKey ?? null,
+      }));
+      return true;
+    }
+
+    if (pathname === '/webchat/push/subscriptions' && req.method === 'GET') {
+      res.writeHead(200, { 'Content-Type': 'application/json' });
+      res.end(JSON.stringify({
+        enabled: cfg.enabled,
+        count: this.webchatPushSubscriptions.size,
+        maxSubscriptions: cfg.maxSubscriptions,
+      }));
+      return true;
+    }
+
+    if (pathname === '/webchat/push/subscriptions' && req.method === 'POST') {
+      if (!cfg.enabled) {
+        res.writeHead(409, { 'Content-Type': 'application/json' });
+        res.end(JSON.stringify({ error: 'WebChat push is disabled' }));
+        return true;
+      }
+
+      let rawBody: string;
+      try {
+        rawBody = await this.readRequestBody(req);
+      } catch (err) {
+        if (err instanceof RequestBodyTooLargeError) {
+          res.writeHead(413, { 'Content-Type': 'application/json' });
+          res.end(JSON.stringify({ error: 'Payload too large' }));
+          return true;
+        }
+        res.writeHead(400, { 'Content-Type': 'application/json' });
+        res.end(JSON.stringify({ error: 'Invalid request body' }));
+        return true;
+      }
+
+      let parsedBody: unknown;
+      try {
+        parsedBody = JSON.parse(rawBody);
+      } catch {
+        res.writeHead(400, { 'Content-Type': 'application/json' });
+        res.end(JSON.stringify({ error: 'Invalid JSON' }));
+        return true;
+      }
+
+      const body = parsedBody as {
+        endpoint?: unknown;
+        keys?: { p256dh?: unknown; auth?: unknown };
+        userAgent?: unknown;
+      };
+      const endpoint = typeof body.endpoint === 'string' ? body.endpoint.trim() : '';
+      const p256dh = typeof body.keys?.p256dh === 'string' ? body.keys.p256dh.trim() : '';
+      const auth = typeof body.keys?.auth === 'string' ? body.keys.auth.trim() : '';
+      const userAgent = typeof body.userAgent === 'string' ? body.userAgent.trim() : undefined;
+
+      if (!endpoint || !p256dh || !auth) {
+        res.writeHead(400, { 'Content-Type': 'application/json' });
+        res.end(JSON.stringify({ error: 'Missing subscription endpoint or keys' }));
+        return true;
+      }
+
+      if (!this.webchatPushSubscriptions.has(endpoint) && this.webchatPushSubscriptions.size >= cfg.maxSubscriptions) {
+        res.writeHead(429, { 'Content-Type': 'application/json' });
+        res.end(JSON.stringify({ error: `Subscription cap reached (${cfg.maxSubscriptions})` }));
+        return true;
+      }
+
+      const now = Date.now();
+      const previous = this.webchatPushSubscriptions.get(endpoint);
+      this.webchatPushSubscriptions.set(endpoint, {
+        endpoint,
+        keys: { p256dh, auth },
+        userAgent,
+        createdAt: previous?.createdAt ?? now,
+        updatedAt: now,
+      });
+
+      res.writeHead(200, { 'Content-Type': 'application/json' });
+      res.end(JSON.stringify({
+        stored: true,
+        count: this.webchatPushSubscriptions.size,
+      }));
+      return true;
+    }
+
+    if (pathname === '/webchat/push/subscriptions' && req.method === 'DELETE') {
+      let rawBody = '';
+      try {
+        rawBody = await this.readRequestBody(req);
+      } catch (err) {
+        if (err instanceof RequestBodyTooLargeError) {
+          res.writeHead(413, { 'Content-Type': 'application/json' });
+          res.end(JSON.stringify({ error: 'Payload too large' }));
+          return true;
+        }
+        res.writeHead(400, { 'Content-Type': 'application/json' });
+        res.end(JSON.stringify({ error: 'Invalid request body' }));
+        return true;
+      }
+
+      let endpoint = '';
+      if (rawBody.trim().length > 0) {
+        try {
+          const body = JSON.parse(rawBody) as { endpoint?: unknown };
+          endpoint = typeof body.endpoint === 'string' ? body.endpoint.trim() : '';
+        } catch {
+          res.writeHead(400, { 'Content-Type': 'application/json' });
+          res.end(JSON.stringify({ error: 'Invalid JSON' }));
+          return true;
+        }
+      } else {
+        endpoint = parsed.searchParams.get('endpoint')?.trim() ?? '';
+      }
+
+      if (!endpoint) {
+        res.writeHead(400, { 'Content-Type': 'application/json' });
+        res.end(JSON.stringify({ error: 'Missing subscription endpoint' }));
+        return true;
+      }
+
+      const removed = this.webchatPushSubscriptions.delete(endpoint);
+      res.writeHead(200, { 'Content-Type': 'application/json' });
+      res.end(JSON.stringify({
+        removed,
+        count: this.webchatPushSubscriptions.size,
+      }));
+      return true;
+    }
+
+    return false;
+  }
+
   /**
    * Handle incoming HTTP requests.
    * Optionally applies auth (when authHttp is enabled and a token is configured).
@@ -777,6 +949,11 @@ export class GatewayServer {
       }
     }
 
+    // WebChat PWA push-subscription endpoints (auth-protected)
+    if (await this.handleWebchatPushRequest(req, res)) {
+      return;
+    }
+
     const uiDir = this.config.uiDir;
 
     if (uiDir) {

src/gateway/static.ts

@@ -9,6 +9,7 @@ const CONTENT_TYPES: Record<string, string> = {
   '.js': 'application/javascript',
   '.mjs': 'application/javascript',
   '.json': 'application/json',
+  '.webmanifest': 'application/manifest+json',
   '.svg': 'image/svg+xml',
   '.png': 'image/png',
   '.ico': 'image/x-icon',

src/gateway/ui/app.js

@@ -4,6 +4,7 @@
  * Hash-based routing with page lifecycle management.
  */
 import { getClient } from './lib/ws-client.js';
+import { registerPwaServiceWorker } from './lib/pwa.js';
 
 const routes = new Map();
 let currentPage = null;
@@ -55,6 +56,7 @@ async function render() {
 export function initRouter() {
   contentEl = document.getElementById('content');
   window.addEventListener('hashchange', render);
+  void registerPwaServiceWorker().catch(() => undefined);
   render();
 }
 

src/gateway/ui/flynn-icon.svg

@@ -0,0 +1,11 @@
+<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 256 256" role="img" aria-label="Flynn icon">
+  <defs>
+    <linearGradient id="g" x1="0" x2="1" y1="0" y2="1">
+      <stop offset="0%" stop-color="#25c2a0"/>
+      <stop offset="100%" stop-color="#1877f2"/>
+    </linearGradient>
+  </defs>
+  <rect width="256" height="256" rx="48" fill="#0b0f14"/>
+  <path d="M58 72h140v28H90v28h90v28H90v52H58z" fill="url(#g)"/>
+  <circle cx="188" cy="188" r="16" fill="#25c2a0"/>
+</svg>

src/gateway/ui/index.html

@@ -3,7 +3,10 @@
 <head>
   <meta charset="UTF-8">
   <meta name="viewport" content="width=device-width, initial-scale=1.0">
+  <meta name="theme-color" content="#101216">
   <title>Flynn</title>
+  <link rel="manifest" href="manifest.webmanifest">
+  <link rel="icon" type="image/svg+xml" href="flynn-icon.svg">
   <link rel="stylesheet" href="style.css">
   <script src="https://cdn.jsdelivr.net/npm/marked/marked.min.js"></script>
   <link rel="stylesheet" href="https://cdnjs.cloudflare.com/ajax/libs/highlight.js/11.9.0/styles/github-dark.min.css">

src/gateway/ui/lib/pwa.js

@@ -0,0 +1,158 @@
+function readGatewayToken() {
+  const params = new URLSearchParams(window.location.search);
+  const token = params.get('token');
+  return token && token.trim() ? token.trim() : null;
+}
+
+function withToken(path) {
+  const token = readGatewayToken();
+  if (!token) {
+    return path;
+  }
+  const separator = path.includes('?') ? '&' : '?';
+  return `${path}${separator}token=${encodeURIComponent(token)}`;
+}
+
+async function requestJson(path, options) {
+  const response = await fetch(withToken(path), {
+    ...(options ?? {}),
+    headers: {
+      'Content-Type': 'application/json',
+      ...(options?.headers ?? {}),
+    },
+  });
+
+  let body = null;
+  try {
+    body = await response.json();
+  } catch {
+    body = null;
+  }
+
+  if (!response.ok) {
+    const message = typeof body?.error === 'string'
+      ? body.error
+      : `Request failed (${response.status})`;
+    throw new Error(message);
+  }
+
+  return body;
+}
+
+function urlBase64ToUint8Array(base64String) {
+  const padding = '='.repeat((4 - (base64String.length % 4)) % 4);
+  const base64 = (base64String + padding).replace(/-/g, '+').replace(/_/g, '/');
+  const rawData = window.atob(base64);
+  const outputArray = new Uint8Array(rawData.length);
+
+  for (let i = 0; i < rawData.length; ++i) {
+    outputArray[i] = rawData.charCodeAt(i);
+  }
+
+  return outputArray;
+}
+
+export function isPushSupported() {
+  return 'serviceWorker' in navigator && 'PushManager' in window && 'Notification' in window;
+}
+
+export async function registerPwaServiceWorker() {
+  if (!('serviceWorker' in navigator)) {
+    return null;
+  }
+  return navigator.serviceWorker.register(withToken('/sw.js'));
+}
+
+export async function getPushStatus() {
+  const supported = isPushSupported();
+  if (!supported) {
+    return {
+      supported: false,
+      permission: 'unsupported',
+      subscribed: false,
+      enabled: false,
+      configured: false,
+      message: 'Push is not supported by this browser.',
+    };
+  }
+
+  const registration = await navigator.serviceWorker.ready;
+  const subscription = await registration.pushManager.getSubscription();
+  const publicKeyPayload = await requestJson('/webchat/push/public-key', { method: 'GET' });
+  const configured = Boolean(publicKeyPayload?.vapidPublicKey);
+
+  return {
+    supported: true,
+    permission: Notification.permission,
+    subscribed: Boolean(subscription),
+    enabled: Boolean(publicKeyPayload?.enabled),
+    configured,
+    message: null,
+  };
+}
+
+export async function enablePushNotifications() {
+  if (!isPushSupported()) {
+    throw new Error('Push notifications are not supported by this browser.');
+  }
+
+  const publicKeyPayload = await requestJson('/webchat/push/public-key', { method: 'GET' });
+  if (!publicKeyPayload?.enabled) {
+    throw new Error('WebChat push is disabled on the gateway.');
+  }
+  if (!publicKeyPayload?.vapidPublicKey) {
+    throw new Error('Gateway is missing server.webchat_push.vapid_public_key.');
+  }
+
+  const permission = await Notification.requestPermission();
+  if (permission !== 'granted') {
+    throw new Error('Notification permission was not granted.');
+  }
+
+  const registration = await navigator.serviceWorker.ready;
+  let subscription = await registration.pushManager.getSubscription();
+
+  if (!subscription) {
+    subscription = await registration.pushManager.subscribe({
+      userVisibleOnly: true,
+      applicationServerKey: urlBase64ToUint8Array(publicKeyPayload.vapidPublicKey),
+    });
+  }
+
+  const json = subscription.toJSON();
+  await requestJson('/webchat/push/subscriptions', {
+    method: 'POST',
+    body: JSON.stringify({
+      endpoint: subscription.endpoint,
+      keys: json.keys ?? {},
+      userAgent: navigator.userAgent,
+    }),
+  });
+
+  return getPushStatus();
+}
+
+export async function disablePushNotifications() {
+  if (!('serviceWorker' in navigator)) {
+    return {
+      supported: false,
+      permission: 'unsupported',
+      subscribed: false,
+      enabled: false,
+      configured: false,
+      message: 'Push is not supported by this browser.',
+    };
+  }
+
+  const registration = await navigator.serviceWorker.ready;
+  const subscription = await registration.pushManager.getSubscription();
+  if (subscription) {
+    await requestJson('/webchat/push/subscriptions', {
+      method: 'DELETE',
+      body: JSON.stringify({ endpoint: subscription.endpoint }),
+    });
+    await subscription.unsubscribe();
+  }
+
+  return getPushStatus();
+}

src/gateway/ui/manifest.webmanifest

@@ -0,0 +1,17 @@
+{
+  "name": "Flynn WebChat",
+  "short_name": "Flynn",
+  "start_url": "/#/chat",
+  "display": "standalone",
+  "background_color": "#101216",
+  "theme_color": "#101216",
+  "description": "Flynn WebChat companion UI",
+  "icons": [
+    {
+      "src": "/flynn-icon.svg",
+      "sizes": "any",
+      "type": "image/svg+xml",
+      "purpose": "any"
+    }
+  ]
+}

src/gateway/ui/pages/settings.js

@@ -4,6 +4,12 @@
  * Read-only config view (redacted), editable hook patterns,
  * tool list, and channel overview.
  */
+import {
+  isPushSupported,
+  getPushStatus,
+  enablePushNotifications,
+  disablePushNotifications,
+} from '../lib/pwa.js';
 
 function escapeHtml(text) {
   const div = document.createElement('div');
@@ -14,6 +20,75 @@ function escapeHtml(text) {
 let _client = null;
 let _el = null;
 
+function describePushStatus(status) {
+  if (!status.supported) {
+    return status.message || 'Push notifications are not supported in this browser.';
+  }
+  if (!status.enabled) {
+    return 'Gateway push is disabled (`server.webchat_push.enabled: false`).';
+  }
+  if (!status.configured) {
+    return 'Gateway push key is missing (`server.webchat_push.vapid_public_key`).';
+  }
+  if (status.permission === 'denied') {
+    return 'Browser notifications are blocked. Allow notifications in browser settings.';
+  }
+  if (status.subscribed) {
+    return 'Push notifications are enabled for this browser.';
+  }
+  return 'Push is configured. Click Enable to subscribe this browser.';
+}
+
+async function renderPushStatus() {
+  const statusEl = _el.querySelector('#push-status');
+  const enableBtn = _el.querySelector('#push-enable');
+  const disableBtn = _el.querySelector('#push-disable');
+  if (!statusEl || !enableBtn || !disableBtn) {
+    return;
+  }
+
+  try {
+    const status = await getPushStatus();
+    statusEl.textContent = describePushStatus(status);
+    statusEl.className = status.subscribed ? 'text-sm text-success' : 'text-sm text-muted';
+    enableBtn.disabled = !status.supported || !status.enabled || !status.configured || status.subscribed;
+    disableBtn.disabled = !status.supported || !status.subscribed;
+  } catch (err) {
+    statusEl.textContent = `Push status error: ${err.message}`;
+    statusEl.className = 'text-sm text-error';
+    enableBtn.disabled = true;
+    disableBtn.disabled = true;
+  }
+}
+
+async function onEnablePush() {
+  const statusEl = _el.querySelector('#push-status');
+  if (!statusEl) {return;}
+  statusEl.textContent = 'Enabling push notifications...';
+  statusEl.className = 'text-sm text-muted';
+  try {
+    await enablePushNotifications();
+    await renderPushStatus();
+  } catch (err) {
+    statusEl.textContent = `Enable failed: ${err.message}`;
+    statusEl.className = 'text-sm text-error';
+  }
+}
+
+async function onDisablePush() {
+  const statusEl = _el.querySelector('#push-status');
+  if (!statusEl) {return;}
+  statusEl.textContent = 'Disabling push notifications...';
+  statusEl.className = 'text-sm text-muted';
+  try {
+    await disablePushNotifications();
+    await renderPushStatus();
+  } catch (err) {
+    statusEl.textContent = `Disable failed: ${err.message}`;
+    statusEl.className = 'text-sm text-error';
+  }
+}
+
 async function loadSettings() {
   if (!_client || !_el) {return;}
 
@@ -52,6 +127,16 @@ async function loadSettings() {
   _el.innerHTML = `
     <h1 class="page-title">Settings</h1>
 
+    <h2 class="section-title">WebChat Push Notifications</h2>
+    <div class="settings-section">
+      ${isPushSupported() ? '' : '<div class="text-sm text-muted">This browser does not support PushManager APIs.</div>'}
+      <div style="display: flex; gap: 8px; margin-bottom: 8px;">
+        <button id="push-enable" class="btn btn-primary" type="button">Enable Push</button>
+        <button id="push-disable" class="btn btn-secondary" type="button">Disable Push</button>
+      </div>
+      <div id="push-status" class="text-sm text-muted"></div>
+    </div>
+
     <h2 class="section-title">Hook Patterns</h2>
     <div class="settings-section">
       <div class="hook-editor">
@@ -133,6 +218,9 @@ async function loadSettings() {
 
   // Bind save hooks
   _el.querySelector('#hooks-save').addEventListener('click', saveHooks);
+  _el.querySelector('#push-enable').addEventListener('click', onEnablePush);
+  _el.querySelector('#push-disable').addEventListener('click', onDisablePush);
+  await renderPushStatus();
 }
 
 async function saveHooks() {

src/gateway/ui/sw.js

@@ -0,0 +1,92 @@
+const CACHE_NAME = 'flynn-webchat-v1';
+const token = new URL(self.location.href).searchParams.get('token');
+const withToken = (path) => {
+  if (!token) {
+    return path;
+  }
+  const sep = path.includes('?') ? '&' : '?';
+  return `${path}${sep}token=${encodeURIComponent(token)}`;
+};
+const OFFLINE_ASSETS = ['/', '/index.html', '/style.css', '/app.js', '/manifest.webmanifest'].map(withToken);
+
+self.addEventListener('install', (event) => {
+  event.waitUntil(
+    caches.open(CACHE_NAME)
+      .then((cache) => cache.addAll(OFFLINE_ASSETS))
+      .catch(() => undefined),
+  );
+  self.skipWaiting();
+});
+
+self.addEventListener('activate', (event) => {
+  event.waitUntil(
+    caches.keys().then((keys) => Promise.all(
+      keys
+        .filter((key) => key !== CACHE_NAME)
+        .map((key) => caches.delete(key)),
+    )),
+  );
+  self.clients.claim();
+});
+
+self.addEventListener('fetch', (event) => {
+  if (event.request.method !== 'GET') {
+    return;
+  }
+
+  event.respondWith((async () => {
+    const cached = await caches.match(event.request, { ignoreSearch: true });
+    if (cached) {
+      return cached;
+    }
+
+    try {
+      return await fetch(event.request);
+    } catch {
+      const fallback = await caches.match('/index.html', { ignoreSearch: true });
+      return fallback || new Response('Offline', { status: 503 });
+    }
+  })());
+});
+
+self.addEventListener('push', (event) => {
+  let payload = {
+    title: 'Flynn',
+    body: 'You have a new update.',
+  };
+
+  try {
+    const parsed = event.data?.json();
+    if (parsed && typeof parsed === 'object') {
+      payload = {
+        ...payload,
+        ...parsed,
+      };
+    }
+  } catch {
+    const text = event.data?.text();
+    if (text) {
+      payload.body = text;
+    }
+  }
+
+  event.waitUntil(self.registration.showNotification(payload.title, {
+    body: payload.body,
+    tag: payload.tag || 'flynn-webchat',
+    renotify: false,
+    data: payload.data || {},
+  }));
+});
+
+self.addEventListener('notificationclick', (event) => {
+  event.notification.close();
+
+  event.waitUntil((async () => {
+    const clients = await self.clients.matchAll({ type: 'window', includeUncontrolled: true });
+    if (clients.length > 0) {
+      await clients[0].focus();
+      return;
+    }
+    await self.clients.openWindow('/#/chat');
+  })());
+});