uikit – UISplitViewController structure distinction between iOS 17 and iOS 18

I’ve a easy UISplitViewController structure of at all times seen major and secondary columns.

    func scene(_ scene: UIScene, willConnectTo session: UISceneSession, choices connectionOptions: UIScene.ConnectionOptions) {
        guard let windowScene = (scene as? UIWindowScene) else { return }

        // Create a UISplitViewController
        let splitViewController = UISplitViewController(type: .doubleColumn)
        splitViewController.preferredDisplayMode = .oneBesideSecondary
        splitViewController.presentsWithGesture = false

        // Arrange major and secondary view controllers
        let primaryVC = UIViewController()
        primaryVC.view.backgroundColor = .systemBlue
        let secondaryVC = UIViewController()
        secondaryVC.view.backgroundColor = .systemGreen

        // Assign them to the break up view controller
        splitViewController.setViewController(primaryVC, for: .major)
        splitViewController.setViewController(secondaryVC, for: .secondary)

        // Set most popular width and min/max column width
        splitViewController.preferredPrimaryColumnWidth = 80
        splitViewController.minimumPrimaryColumnWidth = 80
        splitViewController.maximumPrimaryColumnWidth = 80

        // Initialize the window
        window = UIWindow(windowScene: windowScene)
        window?.rootViewController = splitViewController
        window?.makeKeyAndVisible()
    }

It labored succesfully like that for my app for a while. Nonetheless, I’ve seen some layouting points on iOS18 and began to dig a bit deeper. It seems that one thing modified in UISplitViewController’s construction between releases.

I am operating the follwing debuger command:

po splitViewController?.view.subviews.first?.subviews

On iPadOS 18:

; layer = >
; layer = >
>

On iPadOS 17.5:

; layer = >
; layer = >
; layer = >

In each circumstances we’ve 2 tab containers and a divider. Nonetheless, on iOS 18 it seems that the divider is positioned not by facet however moderately above the container view.

When attaching a view to the view.leadingAnchor or view.safeAreaLayoutGuide.leadingAnchor of secondary view controller

on iPadOS 18 it goes behind the divider:

on iPadOS 17 it goes subsequent to the divider:

Now, my query is, assuming that is not an Apple bug – is there technique to get this 0.5px dimension of the divider in any elegant method? It would not appear to be mirrored by protected space values or something comparable.