Why does Xcode 27.2 have two iOS 27.2 simulator SDKs?

Thanks for the post, have you previously installed Xcode 27.1? Those in the picture looks like 2 different builds so my guess is one is overriding the older build.

When the installation is over you can check those with xcrun simctl runtime list -v and copy the output here as will show the full platform name platform and UUID.

You can also look at the list when running an app into a simulator.

As a suggestion, you can always remove any simulator you do not want.

Albert  WWDR

@DTS Engineer Hi, Albert, thanks for replying. I went directly from Xcode 27 to 27.2; I never downloaded 27.1. There is no option to delete just one of the two iOS 27.2 SDKs, because, as my screenshot shows, they are listed together in a single entry; I would have to ask to delete both of them together. I'm certainly willing to do that if doing so will cause just one SDK to be downloaded. But will it?

Here is the output of the runtime list command:

== Disk Images ==
-- iOS --
iOS 27.2 (24B8117) - 3A72BB85-5BCA-4BC4-B2EC-812377CD1D40
    State: Ready
    Image Kind: Patchable Cryptex Disk Image
    Signature State: Unknown
    Deletable: YES
    Mounting Mode: Cryptex
    Mount Policy: Automatic
    Mount Path: /private/var/run/com.apple.security.cryptexd/mnt/com.apple.iPhoneOS.SimulatorRuntime-v24.2.8117.0.mDg5wD
    Image Path: /System/Library/AssetsV2/com_apple_MobileAsset_iOSSimulatorRuntime/7a0695c167683c7fbc650e5913eca65d628b525d.asset/AssetData
    Size: 7.7G
    Bundle Path: /private/var/run/com.apple.security.cryptexd/mnt/com.apple.iPhoneOS.SimulatorRuntime-v24.2.8117.0.mDg5wD/Library/Developer/CoreSimulator/Profiles/Runtimes/iOS 27.2.simruntime
    Supported Architectures: arm64
    Parent Mount Path: /System/Library/AssetsV2/com_apple_MobileAsset_iOSSimulatorRuntime/7a0695c167683c7fbc650e5913eca65d628b525d.asset/AssetData

iOS 27.2 (24B91016s) - AF412CA1-CAC3-467C-A91D-AF2E40C04DCB
    State: Ready
    Image Kind: Patchable Cryptex Disk Image
    Signature State: Unknown
    Deletable: YES
    Mounting Mode: Cryptex
    Mount Policy: Automatic
    Mount Path: /private/var/run/com.apple.security.cryptexd/mnt/com.apple.iPhoneOS.SimulatorRuntime-v24.2.91016.19.TViktM
    Image Path: /System/Library/AssetsV2/com_apple_MobileAsset_iOSSimulatorRuntime/246a2ca14728178a0982606799e2019b401aeace.asset/AssetData
    Size: 7.8G
    Bundle Path: /private/var/run/com.apple.security.cryptexd/mnt/com.apple.iPhoneOS.SimulatorRuntime-v24.2.91016.19.TViktM/Library/Developer/CoreSimulator/Profiles/Runtimes/iOS 27.2.simruntime
    Supported Architectures: arm64
    Parent Mount Path: /System/Library/AssetsV2/com_apple_MobileAsset_iOSSimulatorRuntime/246a2ca14728178a0982606799e2019b401aeace.asset/AssetData

Total Disk Images: 2 (15.5G)

@DTS Engineer OK, so I asked Xcode to delete the iOS 27.2 SDKs, and it did. But my only option at this point is to download both simulator SDKs again (16.64GB). Which brings me back to my original question: what's going on here? Why does iOS 27.2 need to have two 8GB simulator files?

One is for iPhone Duo Device (24B91016s), the other for the rest.

The iPhone Duo is running a different version of iOS, because some Duo changes to UIKit and to other UI frameworks have not been merged yet into UIKit main branch, or something like that.