Apple announced the iPhone Duo today — its first foldable iPhone. A 5.4-inch outer display, a 7.6-inch inner display when you open it, ships with iOS 27.x.
The marketing story is the hardware. The developer story is that a lot of assumptions baked into iPhone apps since 2007 just stopped being true. There is now more than one screen. The screen can change shape while your app is running. The safe area is no longer symmetric. And "portrait only" doesn't mean what you think it means anymore.
The good news: if you've been doing adaptive layout properly for iPad, most of this is a short afternoon. If your app hardcodes screen sizes and branches on orientation, you have some work to do.
Here's the practical version.
First: what happens if you do nothing?
