You can use this in the windowcontroller.swift override func windowDidLoad() { super.windowDidLoad() window.delegate = self window.toggleFullScreen(self) But I am having an issue on shutdown or reboot if the user selects "relaunch open apps" the app launches in full screen but then a black screen covers the app. Switching to the finder and back to the app resolves the blackout but I'd like a way to resolve this issue.

I'm having the same issue with a mac app that we have in the app store. Would be nice to be able to use the new TestFlight feature for testing since it's an in app purchase app.

Very sorry, I did not see this reply until today: import Foundation extension Locale { var voiceLanguage: String { (languageCode ?? "") + "-" + (regionCode ?? "") } }

Looks like this is working as of Ventura!