I wanted to get my SwiftData previews working in my primary project, so I started modeling them after the SampleTrips project. After messing around with that & being unable to make it work, I brought the same (working) sample code into my main project, unfortunately that's not working... I've attached the preview error (note, there's nothing in the Diagnostic Reports). //Sample code that works in it's own project, but not my primary target. import SwiftUI import SwiftData struct TestSwiftDataStuffView: View { let trip: Trip var body: some View { VStack { Image(systemName: "globe") .imageScale(.large) .foregroundStyle(.tint) Text("Hello, \(trip.name)!") .padding() .foregroundColor(.red) } .padding() } } #Preview(traits: .sampleDataSecondary) { @Previewable @Query var trips: [Trip] TestSwiftDataStuffView(trip: trips.first!) } actor DataModelSecondary { struct TransactionAuthor { static let widget = "widget" } static let shared = DataModelSecondary() private init() {} nonisolated lazy var modelContainer: ModelContainer = { let modelContainer: ModelContainer let schema = Schema([ Trip.self ]) do { let modelConfiguration = ModelConfiguration(schema: schema, isStoredInMemoryOnly: false, cloudKitDatabase: .none) modelContainer = try ModelContainer(for: schema, configurations: [modelConfiguration]) } catch { fatalError("Failed to create the model container: \(error)") } return modelContainer }() } @Model class Trip { @Attribute(.preserveValueOnDeletion) var name: String init(name: String) { self.name = name } } extension Trip { static var previewTrips: [Trip] { [ Trip(name: "Revenant"), Trip(name: "Newcastle"), Trip(name: "Bianca") ] } } struct SampleDataSecondary: PreviewModifier { static func makeSharedContext() throws -> ModelContainer { let config = ModelConfiguration(isStoredInMemoryOnly: true) let container = try ModelContainer( for: Trip.self, configurations: config ) SampleDataSecondary.createSampleData(into: container.mainContext) return container } func body(content: Content, context: ModelContainer) -> some View { content.modelContainer(context) } static func createSampleData(into modelContext: ModelContext) { Task { @MainActor in let sampleDataTrips: [Trip] = Trip.previewTrips let sampleData: [any PersistentModel] = sampleDataTrips //+ sampleDataLA + sampleDataBLT sampleData.forEach { modelContext.insert($0) } try? modelContext.save() } } } @available(iOS 18.0, *) extension PreviewTrait where T == Preview.ViewTraits { @MainActor static var sampleDataSecondary: Self = .modifier(SampleDataSecondary()) } Xcode16Preview.txt