client/apps/pwa/todo.md

Web Push Backend TODO

The client can subscribe and decrypt version 1 push payloads, but reliable delivery requires backend support.

• Generate and securely store a VAPID key pair. Expose only the public key to the web build as VITE_WEB_PUSH_PUBLIC_KEY.
• Add authenticated MTP requests for registering, replacing, and deleting a browser PushSubscription per user and installation.
• Persist the endpoint, p256dh, auth, expiration time, stable installation ID, and last-seen time.
• Remove subscriptions when a push service returns HTTP 404 or 410 and rate-limit registrations per user.
• Send pushes when an encrypted live message cannot be delivered to an active browser client. Define duplicate suppression for clients that receive both MTP and Web Push.
• Keep the JSON payload within push-provider limits and use this version 1 shape:

{
  "version": 1,
  "senderId": 123,
  "sender": "Display name",
  "avatar": "https://optional.example/avatar",
  "message": { "content": "base64 encrypted message content" },
  "secret": {
    "chatId": "123:456",
    "secretId": "chat:123:456:main",
    "version": 1,
    "encryptedSecret": "base64 wrapped chat secret",
    "kemCiphertext": "base64 KEM ciphertext",
    "wrappingScheme": "mtp-chat-secret-kem-chacha20poly1305-hkdf-sha256-v1"
  }
}

• Ensure the wrapped secret is intended for the receiving user's MTP keyring. The server must never receive plaintext message content or plaintext chat secrets.
• Decide how edits, deletions, reactions, calls, read states, and per-chat notification cancellation map to push events.
• Add subscription rotation handling and unregister subscriptions when a user logs out or clears application data.
• Configure production HTTPS, SPA route fallback, application/manifest+json for manifest.json, and Cache-Control: no-cache for the service worker.