Push Notifications with Claude Code: Firebase FCM, Token Management, and Bulk Delivery

"Just send a push notification" sounds trivial. But real push notification systems need to handle multi-device token management, invalid token cleanup (stale tokens silently degrade your FCM delivery rate), silent vs visible notifications, and bulk delivery at scale. Claude Code generates the complete push notification infrastructure from CLAUDE.md rules. The CLAUDE.md Rules ## Push Notification Rules - One user can have multiple FCM tokens (multi-device: phone + tablet + web) - Remove invalid tokens immediately when FCM returns an error for them - Track lastUsedAt per token; delete tokens not used in 90+ days - Use sendEachForMulticast for per-token delivery status (not send — it stops on first error) - BullMQ queue for sends to 1000+ users (never block the HTTP response) - FCM batch API accepts max 500 tokens per request — chunk accordingly - iOS title limit: 178 characters - Use data payload (not notification payload) for in-app navigation control With these rules in CLAUDE.md, Clau