In the Console, when presenting my view in a horizontally compact environment, I see: UINavigationController for collapsing UISplitViewController about to push view controller <UINavigationController: 0x107933c00> This message repeats infinitely, until the Xcode debugger eventually says: QUARANTINED DUE TO HIGH LOGGING VOLUME Of note is that this only occurs in the beta, does not occur when using the iOS 18.x SDK, and only occurs in a compact environment. EDIT: This occurs only when setting the secondary column of a doubleColumn UISplitViewController: splitVC.setViewController(secondary, for: .secondary) EDIT 2 and WORKAROUND: If this action is deferred until after viewDidAppear, it self-resolves: public override func viewDidAppear(_ animated: Bool) { super.viewDidAppear(animated) if let deferredSecondaryViewController { splitVC.showDetailViewController(deferredSecondaryViewController, sender: nil) } }