Apple has opened the App Store submission pipeline for iPhone Duo–optimized apps — two weeks before pre-orders begin. Developers can now upload apps built with Xcode 27.1 Release Candidate 1, and those submissions will carry an “Optimized for iPhone Duo” badge on their App Store product pages. The badge appears automatically when the app is compiled using that version of Xcode, no extra certification or review step is required, per Apple’s Developer News Hub post published early Monday morning. But the clock is already ticking on compliance: all new submissions must include iPhone Duo–specific screenshots by April 2027. That’s not a soft deadline. Apple says it explicitly. Xcode 27.1 has supported Duo development since its beta phase, letting developers test across all screen poses and orientations via Device Hub. Apple is also holding in-person workshops this week to walk teams through layout adaptation, multitasking behaviour, and gesture handling unique to the Duo’s dual-display hinge. Pre-orders start Friday, October 16. First deliveries and retail availability follow on Thursday, October 23. Customers can begin configuring pre-orders as early as Saturday, October 12. Four days from now. This isn’t just about scaling UIs. The Duo’s hardware split means apps must handle window continuity, cross-display drag-and-drop, and state persistence across fold/unfold transitions. Apple hasn’t published public API docs for those features yet, but Xcode 27.1 RC1 ships with them enabled. No pricing, specs, or carrier details were included in the developer announcement. Those remain under Apple’s official launch event veil. Still unannounced, still expected before mid-October. What’s clear is the timeline: developers have less than eight days to get submissions ready before pre-orders go live. And they’ll need to ship updated screenshots within six months, or risk missing the badge entirely.