iPhone Duo AppsStart with the app you have
Preparing for iPhone Duo starts with checking how your app handles changing space. A document editor should keep the draft and current selection. A calendar should keep the event you're editing visible. Pick one task and follow it through compact and expanded layouts.
Apple's WWDC26 session Modernize your UIKit app explains the underlying work. It covers scene lifecycle, main-screen references, device-idiom checks and orientation assumptions. Layout should follow the space available to the current view or scene. These are useful checks for an existing iOS app today.
Check which tools are available
Use Apple's developer documentation and iOS updates as the starting points for API details. Record the Xcode, SDK, app and OS versions used in any test.
Apple's iPhone Duo announcement describes Duo support in Xcode Device Hub as upcoming. A screenshot of a generic resizable preview does not establish a Duo device test.
Turn the review into work you can check
Record each problem with steps, an observed result and the expected behavior. Keep camera, battery, folding transitions and other hardware-dependent questions for device testing.
Our readiness checklist gives you a review process. The audit service applies it to one user journey with up to five screens.