iOS 26 Degenerate Layout Crash caused by UIStackView

If you have a complex Auto Layout setup like I do, you may encounter a ‘Degenerate Layout’ crash when you upgrade your app to the iOS 26 SDK. The error will look like this:

Thread 1: "Degenerate layout! Layout feedback loop detected in subtree of <UIStackView: 0x103a7c430; frame = (0 0; 402 874); wants auto layout; tAMIC = NO; >. More info may be available in the log for com.apple.UIKit.LayoutLoop"

The root cause was that I set isLayoutMarginsRelativeArrangement to true on one of my UIStackViews. A change in UIKit’s layout system caused it to enter an infinite loop when there was an ambiguous layout.

        buttonStackView.layoutMargins = UIEdgeInsets(top: 30.0,
                                                     left: EntryCell.layoutMargins.left,
                                                     bottom: 10.0,
                                                     right:  EntryCell.layoutMargins.right)
        buttonStackView.isLayoutMarginsRelativeArrangement = true

The fix is simple: avoid using UIStackView.isLayoutMarginsRelativeArrangement and replace it with a container view, with a little help from this layout gist: (UIView+Pin.swift).

        let buttonContainer = UIView()
        buttonContainer.addSubview(buttonStackView)
        let insets = UIEdgeInsets(top: 30.0, left: EntryCell.layoutMargins.left, bottom: 10.0, right: EntryCell.layoutMargins.right)
        buttonStackView.pinToEdges(of: buttonContainer, insets: insets)

Posted 2025-06-28

programming