Install the iPhone Duo Simulator

The simulator ships in Xcode 27.1 beta (27A9269) with the iOS 27.1 runtime (24A94401). The 27.2 beta does not include it — Apple points developers at 27.1 for iPhone Duo support.

1. Check your Mac meets the floor

   The beta requires macOS Tahoe 26.6 or later — the same floor as Xcode 27.0. Update first; the runtime won't pair otherwise.

2. Download Xcode 27.1 beta

   Get it from the Apple Developer downloads page (requires a free Apple Developer account). You'll receive a .xip archive.

3. Expand and install it side-by-side

   Don't overwrite your stable Xcode. Expand and move it to a versioned name:

   # expand the archive (takes a while)
   xip --expand ~/Downloads/Xcode_27.1_beta.xip
   
   # move it next to your stable Xcode
   mv Xcode-beta.app /Applications/Xcode-27.1-beta.app

4. Download the iOS 27.1 runtime

   The iPhone Duo device type needs its own runtime, fetched separately:

   # point your tools at the beta…
   export DEVELOPER_DIR=/Applications/Xcode-27.1-beta.app/Contents/Developer
   
   # …then pull the iOS 27.1 platform
   xcodebuild -downloadPlatform iOS

   Before trusting the install, confirm the build stamp: otool -l <app>/<binary> | grep -A4 LC_BUILD_VERSION should reference the 27.1 SDK.

5. Open the iPhone Duo device in Device Hub

   In the beta, open Device Hub and pick the iPhone Duo device (com.apple.CoreSimulator.SimDeviceType.iPhone-Duo, model iPhone19,4). Poses are buttons: open, closed, partially folded, portrait / landscape — fold it while your app runs and watch the layout respond.

6. Know the simulator's limits

   Per Apple's notes: first launch "can take several minutes". StandBy and most app extensions are unavailable in this runtime. For a quick layout sanity check without booting the sim, the beta's Previews canvas offers a Display group for the alternative display.

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