@ToshiyukiTakeda Your assumption is reasonable based on Apple historical pattern. Apple hasn’t officially announced the App Store submission requirement for the iOS 27 SDK yet, but in recent years the deadline has typically been around late April. Although there’s no official confirmation yet, it’s worth planning the migration ahead of time. Starting early helps avoid a last minute rush and provides enough time for implementation, regression testing before the expected deadline.

@ToshiyukiTakeda It means building with the iOS 27 SDK, compiling your app using Xcode 27. Yes - it will continue to work. UIDesignRequiresCompatibility is ignored only for apps built with the iOS 27 SDK. Apps built with the iOS 26 SDK can still run on iOS 27 devices, and the compatibility mode will continue to apply.