Since changing our app to the new UISceneDelegate architecture, we see the problem that viewWillTransition(to size: CGSize, with coordinator: UIViewControllerTransitionCoordinator)is not called on our ViewControllers anymore. Even when I remove everything which is not needed and just create a UIWindow and one UIViewController in scene(UIScene, willConnectTo: UISceneSession, options: UIScene.ConnectionOptions) it doesn't work. I created a new clean project where it works without problems and checked how the stack trace looks: 0x0000000102117320 in ViewController.viewWillTransition(to:with:) at ViewController.swift:20 0x000000010211766c in @objc ViewController.viewWillTransition(to:with:) () 0x0000000184673664 in +[UIViewController _performWithoutDeferringTransitionsAllowingAnimation:actions:] () 0x000000018486247c in -[UIViewController(AdaptiveSizing_Internal) _window:viewWillTransitionToSize:withTransitionCoordinator:] () 0x00000001846f5788 in __59-[UIWindow _rotateToBounds:withAnimator:transitionContext:]_block_invoke () 0x0000000184621064 in +[UIView(Animation) performWithoutAnimation:] () 0x0000000184ac2534 in -[UIWindow _rotateToBounds:withAnimator:transitionContext:] () 0x000000018494a6b8 in -[UIWindow _rotateWindowToOrientation:updateStatusBar:duration:skipCallbacks:] () 0x0000000184573ee4 in -[UIWindow _setRotatableClient:toOrientation:updateStatusBar:duration:force:isRotating:] () 0x0000000184b24b84 in -[UIWindow _setRotatableViewOrientation:updateStatusBar:duration:force:] () I created some symbolic breakpoints in the broken project and noticed that it is working until step 5, but apparently something is preventing [UIViewController(AdaptiveSizing_Internal) _window:viewWillTransitionToSize:withTransitionCoordinator:] from being called. Did anyone have a similar problem or an idea what could cause this problem?