Multi-device push notifications

Design a multi-device push-notification system for a messaging app with 200M users, where a user has on average 3 active devices (phone, tablet, laptop) plus the web. When a message arrives, exactly one 'badge bump' should land per device, but if the user reads the message on any device the others should suppress or clear the notification. Pushes go through APNs/FCM (best-effort, can duplicate or drop). How do you deliver per-device pushes while deduplicating across devices and races?