Apple has confirmed the iPhone Duo will go on pre-order October 16, with shipments beginning October 23 — and developers are already live in the App Store pipeline. The device isn’t shipping yet, but apps built for it are already being accepted, reviewed, and tagged with a visible “iPhone Duo-optimized” badge in the store. That badge appears only if the app is compiled using Xcode 27.1, which Apple released ahead of launch and is now mandatory for Duo compatibility. Developers can submit today. No waiting. No gatekeeping beyond the toolchain requirement. And starting April 2027, every new app submitted to the App Store, regardless of device target. Must include at least one iPhone Duo screenshot. Not optional. Not deferred. Required. Apple is baking Duo readiness into the submission process before the phone ships. It’s not just marketing. It’s infrastructure. The company is also running in-person workshops for developers, sign-ups are open now. To walk teams through layout adaptation, dual-display interaction patterns, and how the Duo’s hardware split affects navigation, notifications, and multitasking. No specs, no pricing, no camera details leaked or announced here. Just this: the App Store is already building for the iPhone Duo. And it’s doing it in public, with deadlines, tooling, and enforcement baked in. Pre-orders open Thursday, October 16. Deliveries start Wednesday, October 23.