The questions developers keep asking about building for iPhone Duo

Between developer forums, beta feedback, and our own inbox, a handful of questions about building for iPhone Duo keep coming up more than any others. Here is where things stand on each, current as of today.

"Do I have to rewrite my app before launch?"

No. Existing apps run on iPhone Duo without changes, though unmodified apps render in a fixed-size, letterboxed presentation rather than filling the available display. Whether that is good enough for your app at launch, or worth fixing first, is covered in our migration guide.

"Should I build a custom layout for tabletop mode?"

Apple's guidance says no — design for size classes instead of specific hinge angles or poses, and let ArrangementView and reserved regions handle the rest. We go into why in our piece on device poses.

"Can I use the hinge angle to drive my layout?"

Technically yes, but Apple's documentation explicitly recommends against it — onHingeChange and UIHingeInteraction are meant for interactive effects, not layout decisions. See our dedicated breakdown of what the API is actually for.

"Does my front-camera code need to change?"

Mostly no. The Virtual Front Camera API is designed to let existing front-camera code switch between the outer and inner physical cameras automatically. If you need finer control over mirroring or facing, AVCaptureDeviceDirectionCoordinator is available — details in our camera continuity piece.

"Can I open a second window on the outer display?"

No — according to what we have seen documented, windows opened through UIWindowSceneActivation only appear on the inner display. See our multiple windows explainer for what that means in practice.

"When can I upload iPhone Duo screenshots to App Store Connect?"

Not yet — Apple has said the feature is coming later this year. The required dimensions for both displays are already published, though, so you can prepare assets in advance. Full details in our App Store Connect checklist.

"Is there a real on-device AI API, or do I need my own backend?"

There is a real one: the Foundation Models framework gives native Swift access to on-device language models, including text generation, structured output, and tool-calling, without a network round-trip. See our walkthrough for what it supports today.

"What toolchain do I actually need installed?"

iOS 27.1 SDK, Xcode 27.1 beta, and macOS Tahoe 26.6 on your build machines — we cover why each of the three matters separately in our developer stack overview.

We will keep this page updated as more questions come up and as Apple confirms more details ahead of the October 23 launch.