oAI/Services/BackupService.swift

@@ -220,14 +220,23 @@ final class BackupService {
         }
 
         let localUpdatedAt = settings.favoriteModelsUpdatedAt
+        let localIds = settings.favoriteModelIds
         if remote.updatedAt > localUpdatedAt {
             settings.favoriteModelIds = Set(remote.ids)
             settings.favoriteModelsUpdatedAt = remote.updatedAt
             log.info("Applied \(remote.ids.count) favorite model(s) from iCloud (remote was newer)")
         } else if localUpdatedAt > remote.updatedAt {
             await pushFavorites()
+        } else if Set(remote.ids) != localIds {
+            // Tied timestamps (both empty is the common case: two machines that already had
+            // favorites before this sync feature existed, neither ever bumped the timestamp).
+            // Union rather than silently dropping one side's favorites.
+            settings.favoriteModelIds = localIds.union(remote.ids)
+            settings.favoriteModelsUpdatedAt = ISO8601DateFormatter().string(from: Date())
+            await pushFavorites()
+            log.info("Merged favorites from iCloud (tied timestamps) — union of \(localIds.count) local + \(remote.ids.count) remote")
         }
-        // Equal timestamps: already in sync, nothing to do.
+        // Equal timestamps and identical sets: already in sync, nothing to do.
     }
 
     // MARK: - Automatic Backup