Push notifications — background message delivery

[lmanchu]

Problem

When the app is in background or closed, users miss incoming messages because Nostr relay WebSocket connections are dropped by iOS.

Solution

Run a lightweight Sigil Push Service (open source, self-hostable):

Architecture

┌─────────────────┐     ┌──────────────────────┐     ┌─────────┐
│ Nostr Relay      │────▶│ Sigil Push Service    │────▶│  APNs   │
│ (relay.damus.io) │     │ (sigil-push)          │     │  / FCM  │
│                  │     │                        │     │         │
│ kind:4 / kind:17 │     │ • Listens for DMs      │     │ Push to │
│ events for npub  │     │ • Matches device tokens │     │ device  │
└─────────────────┘     │ • Sends push via APNs   │     └─────────┘
                         └──────────────────────┘
                           Open source, self-hostable

Components

1. sigil-push server (Rust or Node.js)

   • Connects to configured relays
   • Subscribes to NIP-04/NIP-17 events for registered npubs
   • On new event → send push notification via APNs (iOS) / FCM (Android)
   • REST API: POST /register { npub, device_token, platform }
   • REST API: DELETE /unregister { device_token }

2. iOS client changes

   • Register for remote notifications on launch
   • Send device token + npub to sigil-push service
   • Handle incoming push → show notification with sender name + preview (or "Encrypted message" if can't decrypt)

3. Default instance

   • Sigil project runs a default push service (e.g., push.sigil.chat)
   • Users can point to their own self-hosted instance in settings

Privacy

• Push service sees which npubs receive messages but NOT message content (NIP-04/NIP-17 encrypted)
• Self-hosting eliminates this metadata exposure
• Device tokens are stored server-side, deleted on unregister

Implementation Order

1. iOS: register for push notifications, obtain device token
2. Server: relay listener + APNs integration
3. iOS: send device token to server on connect
4. iOS: handle push notification display
5. Settings: custom push server URL

Prior Art

• Signal runs their own push service (closed source)
• SimpleX has optional push relay
• ntfy.sh — open source push notification service (different protocol)