I use Xcode 27.1 and the new iOS 27 and iOS 27.1 APIs to:
• Compare how apps compiled with earlier Xcode versions behave on iPhone Duo
• Improve toolbar behavior with ToolbarContent, visibility priorities, and overflow menus
• Keep important actions, including Add and Filter, visible when space is limited
• Use horizontal-only toolbar behavior to keep the Add button accessible
• Disable an unnecessary vertical toolbar for modal forms
• Visualize the fold, hinge, angle, and reserved regions with reusable helper views
• Use GeometryReader and reserved regions to detect when the device has a fold
• Build a fold-aware planner with the new arrangement view
• Split content into primary and secondary panes so the fold does not cut through scrolling content
• Support both iOS 26.5 and newer iOS 27.1 features with availability checks and compatibility helpers
This is the second part of my iPhone Duo series, so I recommend watching the previous iPad upgrade tutorial first. If you want to jump straight in, you can download the completed project from my GitHub repository. Start with the iPad Upgrade branch, and find the finished code for this video in the iPhone Duo Complete branch.
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