Our app is a tool, which fits perfectly on one half of an iPhone Duo, and the user can put another app on the other half. We don't have enough content for an iPad or both halves of the Duo. It just doesn't make sense for us.
But since we're a tool, the user might want to use our app in conjunction with other apps, and seeing two apps side-by-side is a good usage.
We do support device rotation (landscape mode), but mainly for users with bad eyesight who need text to be extraordinarily big and don't want torn apart words. With normal to big font sizes, portrait mode is more useful, otherwise you have lots of unused space but still need to scroll.
But the user should be able to use our app in landscape mode, and we should then occupy the upper or lower half of a Duo screen, again leaving space for another app on the other half.
"Apps built against a pre-iOS 27 SDK get a compatibility mode" - that's exactly what we want, but we want this also when building with Xcode 27 (and 28...). Or asked the other way: Can we limit our app to being half-width on a Duo even when building against iOS 27.1 SDK?
Can we limit our app to being half-width on a Duo even when building against iOS 27.1 SDK?
No you cannot. The expectation going forward is that all apps, including iPhone-only ones, will be fully adaptive and adjust to any available scene size at runtime.
https://developer.apple.com/videos/play/wwdc2026/278/?time=99
