I've been struggling to get a ValueTransformer to work while developing in Xcode 16 for iOS 18. Despite thinking I had everything set up correctly, I keep encountering the following error whenever I create a tag: let tag = Tag(name: name, color: color.toPlatformColor()) // Converts it to NSColor or UIColor modelContext.insert(tag) SwiftData/DataUtilities.swift:184: Fatal error: Unable to determine the primitive for Attribute - name: color, options: [transformable with Optional("ColorTransformer")], valueType: UIColor, defaultValue: UIExtendedSRGBColorSpace 0 0 1 1, hashModifier: nil Here’s what I’m dealing with: Tag Model: @Model public final class Tag: Identifiable { var name: String = "" @Attribute(.transformable(by: ColorTransformer.self)) var color: PlatformColor = PlatformColor.blue init(name: String, color: PlatformColor) { self.name = name self.color = color } } ColorTransformer: final class ColorTransformer: ValueTransformer { override func transformedValue(_ value: Any?) -> Any? { guard let color = value as? PlatformColor else { return nil } do { let data = try NSKeyedArchiver.archivedData( withRootObject: color, requiringSecureCoding: true) return data } catch { assertionFailure("Failed to transform `PlatformColor` to `Data`") return nil } } override func reverseTransformedValue(_ value: Any?) -> Any? { guard let data = value as? NSData else { return PlatformColor.black } do { let color = try NSKeyedUnarchiver.unarchivedObject( ofClass: PlatformColor.self, from: data as Data) return color } catch { assertionFailure("Failed to transform `Data` to `PlatformColor`") return nil } } override class func transformedValueClass() -> AnyClass { return PlatformColor.self } override class func allowsReverseTransformation() -> Bool { return true } public static func register() { ValueTransformer.setValueTransformer(ColorTransformer(), forName: .colorTransformer) } } extension NSValueTransformerName { static let colorTransformer = NSValueTransformerName(rawValue: "ColorTransformer") } Platform Alias: #if os(macOS) typealias PlatformColor = NSColor #else typealias PlatformColor = UIColor #endif The ValueTransformer is registered when the ModelContainer is created at app startup: var sharedModelContainer: ModelContainer = { ColorTransformer.register() // Other configurations... }() I've also tried not aliasing the colors to see if that changes anything, but I still encounter the same issue. Any guidance or suggestions would be greatly appreciated!