IOS application developers have six months to get their applications ready for iOS 13, the company said on Tuesday. The phone giant warned that developers must build all new apps and updates with the iOS 13 SDK and support the iPhone XS Max’s all-screen design starting in April 2020.

They also must migrate to Xcode 11, for which the golden master (GM) seed version is now available. This contains SDKs for iOS 13, iPadOS, watchOS 6, tvOS 12, and macOS Catalina. “Build your apps using Xcode 11 GM seed, test them on iOS devices running the latest GM seeds, and submit them for review,” the company commanded.

Developers have a range of options to keep their apps updated with Apple’s shiny new features. One of the most obvious is dark mode, which Xcode 11 supports in its Interface Builder. This is a non-negotiable for Apple, which said: “If you need more time to make your apps look fantastic in Dark Mode or if Dark Mode is not suited for your app, you’ll need to opt out.”

Xcode 11’s GM seed may give developers some problems. Using the application with named colours may create lookup failures that don’t return any values for apps running on iOS 11 or earlier. The company has pledged to fix this in a future Xcode update.

The only way for early-bird developers to solve this problem right now is to limit the iOS versions that their apps can run on. “To avoid this issue, raise the minimum deployment target to iOS 12 or later to submit to the App Store now, or rebuild with the next Xcode GM candidate seed when it’s available,” the company said.

Bugs aside, XCode 11 does yield some interesting information: it appears to confirm Apple’s long-rumoured augmented reality headset. Developer Steve Troughton-Smith discovered an interesting readme file in the iOS 13 SDK:

StarBoard frameworks on iOS 13 now. StarBoard is Apple’s system shell for stereo augmented reality apps (headset). Guess secrecy is out? pic.twitter.com/XTnlqQgpHh

— Steve Troughton-Smith (@stroughtonsmith) September 10, 2019

Documented features that developers can opt to support in iOS 13 include the updated version of ARKit, Apple’s augmented reality toolbox. Version 3 lets developers integrate human movement into their AR apps, enabling their artificial models to move in front of and behind live people in the frame.

Developers can take advantage of updates to the Siri AI-powered assistant, which enable users to ask follow-up questions. On the AI side, there’s a new Create ML tool, which lets developers build machine learning models without delving into the intricacies of coding neural networks.