こういう悲しい感じのworkaroundを使ってた https://github.com/TokamakUI/Tokamak#example-codestruct CounterApp: App { var body: some Scene { WindowGroup("Counter Demo") { Counter(count: 5, limit: 15) } } } // @main attribute is not supported in SwiftPM apps. // See https://bugs.swift.org/browse/SR-12683 for more details. CounterApp.main()