iPhone Duo Adaptation Checklist

Click items to check them off — progress is saved in your browser. Built from Apple's guidance and the Xcode 27.1 simulator's actual behavior.

Layout fundamentals

• No hard-coded widths — every screen uses flexible layouts and size classesOuter display is only 466 pt wide; fixed 390+ pt layouts will clip.
• Tested in both size-class combos: compact × regular (outer) and regular × regular (inner)The inner display gets the iPad idiom — verify you get the layout you expect, not the iPad one by accident.
• TabView / NavigationSplitView (or UIKit equivalents) adapt automaticallyStandard components handle the transition; custom containers need manual work.
• State survives trait-collection transitions mid-sessionFold/unfold resizes the live window — don't cache the launch-time size class.

Poses, hinge & displays

• App tested in every Device Hub pose: open, closed, partially folded, portrait, landscapePoses are buttons in the simulator — run through all of them, not just open/closed.
• Hinge area handled — no critical controls or text under the foldVerify on the inner display with content spanning the center.
• Outer ↔ inner display handoff is smooth (app moves between displays)Check for flashes, reloads, or lost scroll position on transition.
• Split View and dual-display configurations testedYour app can share the device with another app on the other display.
• Orientation changes work on both displays independentlyInner display landscape is 951 × 669 pt — a distinct layout case.

Build & test setup

• Building against the iOS 27.1 SDK (not just iOS 27)Only the 27.1 SDK unlocks the full screen space; iOS 27 gives better resizing but not everything.
• Simulator device type is iPhone Duo (iPhone19,4) on the iOS 27.1 runtimeMinimum runtime is 27.1 — a 27.0 runtime won't pair.
• Aware of simulator limits: no StandBy, most app extensions unavailableDon't file bugs against sim-only gaps; verify on device after Oct 23.
• Previews canvas Display group checked for the alternative displayQuick layout sanity check without booting the simulator.