Apple has opened the starting gate for iPhone Duo app development, but that means developers have a single month to finish the race.

On Friday, Apple released the first Xcode 27.1 beta, giving developers the tools they need to prepare for iPhone Duo. They now have roughly one month to test their apps across the foldable iPhone's many possible layouts. Xcode 27.1 includes Swift 6.4 and SDKs for iOS 27.1, iPadOS 27.1, and Apple's other operating systems. It also adds tools specifically intended to help developers see how their apps behave on iPhone Duo.

This means that devs can now preview content using a device's alternative display through a new Display group in Xcode's canvas. The beta also includes an iPhone Duo Simulator runtime, although there are some notable limitations at this time. For example, Apple notes that Stand By is not available, and running and debugging most app extensions also isn't currently supported.

Developers only gained access to these testing tools after Apple revealed iPhone Duo. The iPhone Duo goes up for pre-order on October 16 and becomes widely available on October 23.