The watch is a read-only consumer of the phone's snapshot: WatchConnectivity carries a trimmed CalendarrSnapshot to the watch, which writes it into its own App Group container through the same SnapshotStore. One format, one reader. Also specifies the iOS background refresh the watch depends on, which fixes a pre-existing staleness in the home-screen widgets as a side effect. Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>