This is not a bug. After extensive line-by-line and case-by-case testing, I realized I misunderstood how initializing default values in SwiftData works. You can read more about the issue here: https://fatbobman.com/en/posts/relationships-in-swiftdata-changes-and-considerations/#the-misconception-of-setting-default-values-for-relationships

Can confirm, this crash still occurs in Xcode 15.4 whether I use an enum with Comparable or its rawValue. var descriptor: FetchDescriptor<FoodItem> { // SwiftData cannot currently sort by custom Enum type, even if it conforms to Comparable and Int let sortDescriptor = SortDescriptor(\MyItem.rarity, order: .forward) let descriptor = FetchDescriptor(sortBy: [sortDescriptor]) return descriptor } ... @Query(descriptor) var items: [MyItem]