I'm still getting started with SwiftData and having trouble understanding how to persist a model with a relationship in a container. I've tried to distill the example below to be pretty simple. Here are some example model definitions. I would like to be able to define a n Item. That Item can have SubItems related to it in a one-to-many fashion. Each SubItem is required to be attached to a parent Item. final class Item { var name: String var subitems: [Item]? init( name: String, subitems: [SubItem]? = nil ) { self.name = name } } @Model final class SubItem { var name: String init(name: String) { self.name = name } } In my app I am then defining a preview container with some pre-saved data already. Item( name: "item1", subitems: [ SubItem(name: "subItemA"), SubItem(name: "subItemB") ] ), Item( name: "item2", subitems: [ SubItem(name: "subItemC"), SubItem(name: "subItemD") ] ) ] @MainActor let PreviewContainer: ModelContainer = { do { let schema = Schema([ Item.self, SubItem.self, ]) let container = try ModelContainer( for: schema, configurations: ModelConfiguration(isStoredInMemoryOnly: true) ) for item in PreviewItems { container.mainContext.insert(item) for subItem in item.subitems! { container.mainContext.insert(subItem) } } return container } catch { fatalError("Failed to create container") } }() My app is then defined as follows... struct SwiftDataTestApp: App { var body: some Scene { WindowGroup { ContentView() } .modelContainer(PreviewContainer) } } struct ContentView: View { @Environment(\.modelContext) private var modelContext @Query private var items: [Item] var body: some View { HStack { VStack { Text(items[0].name) Text(String(items[0].subitems!.count)) // Text(items[0].subitems![0].name) // Text(items[0].subitems![1].name) } Spacer() VStack { Text(items[1].name) Text(String(items[1].subitems!.count)) // Text(items[0].subitems![0].name) // Text(items[0].subitems![1].name) } } .padding(100) } } #Preview { ContentView() .modelContainer(PreviewContainer) } The preview loads without an issue, but if I uncomment the lines that access the SubItems it crashes. In the preview I can also see that each Item has 0 SubItems related to it. For some reason, the model container is not actually storing the `SubItem even though they are defined in PreviewItems. Some things I've tried Explicitly adding the relationship Adding a Item property in SubItem to link back to it's parent In the PreviewContainer definition, manually insert the SubItems as well as the parent Items Any help is appreciated, thanks