The error is due to the macro for @Observable converting prop0 to be a computed property. One alternative is this: @Observable final class Model { var prop0: Int { didSet { guard oldValue != self.prop0 else { return } UserDefaults.standard.set(self.prop0, forKey: "prop0") } } private init() { prop0 = UserDefaults.standard.integer(forKey: "prop0") } }

In the Settings app, in the Battery view, on the Power Adapter tab, is 3 minutes the setting for "Turn display off after"? For me, if I only use my external keyboard, my external monitor will go to sleep after duration set in my settings. I only need to touch my external TrackPad to keep my Mac Book Pro and monitor awake. While you wait for the fix from Apple, you could try to increase the duration in order to make the attempted sleeping less frequent.