The method I wanted was NSTextStorage edited(_:range:changeInLength:)

If anyone else with the same problem ever stumbles upon this post, my workaround is just to work with the WindowGroup in the Scene so I can use previews and get error warnings, and then comment it out when i want to actually build and run the app @main struct MyApp: App { @State var document: TextDocument = TextDocument() var body: some Scene { WindowGroup { NavigationStack { ContentView(document: $document) } } DocumentGroup(newDocument: TextDocument()) { file in ContentView(document: file.$document) } } }