November 2026 Summaries

Firebase Cloud Messaging Android Config v2 (ACv2) is designed to improve the predictability and timeliness of Android push notifications, addressing delays caused by battery controls, Doze mode, app standby, and the legacy single-callback delivery model. Unlike ACv1, which relied on broad broadcasts, ambiguous high or normal priorities, and an onMessageReceived callback that provided no delivery feedback, ACv2 distinguishes explicitly between BackgroundSync for batched, non-urgent data updates and RemoteNotification for urgent, user-visible alerts. Google Play services and the FCM SDK can render RemoteNotification payloads directly, while apps that need to customize content can use mutable_content and return a NotificationResponse through the new onNotificationReceived callback; a server-provided fallback notification is posted if processing fails or exceeds the 20-second timeout. Background synchronization uses a separate onBackgroundSyncReceived callback and supports collapse keys to retain only the latest queued update for offline devices, while onDeletedMessages enables full resynchronization after messages are dropped. The updated AndroidConfigV2 server API retains options such as TTL and collapse keys, infers delivery treatment from message type, and is backward compatible with older clients, allowing backend and app migrations to occur independently. ACv2 also introduces safeguards, including a limit on suppressing background notifications, to balance app customization with reliable user delivery.