Environment • macOS 27 beta 2 • Xcode 27 beta • Apple Silicon Mac Summary After upgrading to macOS 27 beta 2 and Xcode 27 beta, an old iOS 18.5 simulator runtime remains registered internally but cannot be removed. There appears to be an inconsistency between different CoreSimulator commands. Observed Behavior xcrun simctl runtime list only reports the current runtime: == Disk Images == -- iOS -- iOS 26.1 (23B86) - 0753590B-CF3F-4944-899E-4F70698DB87C (Ready) Total Disk Images: 1 (7.8G) However, xcrun simctl list runtimes -j still reports an additional runtime: identifier: com.apple.CoreSimulator.SimRuntime.iOS-18-5 SimulatorVersion: 18.5 Build: 22F77 bundlePath: /Library/Developer/CoreSimulator/Volumes/iOS_22F77/Library/Developer/CoreSimulator/Profiles/Runtimes/iOS 18.5.simruntime runtimeRoot: /Library/Developer/CoreSimulator/Volumes/iOS_22F77/Library/Developer/CoreSimulator/Profiles/Runtimes/iOS 18.5.simruntime/Contents/Resources/RuntimeRoot The runtime is reported as: "isAvailable": true The runtime no longer appears anywhere in Xcode. Attempting to remove it using the documented command fails: xcrun simctl runtime delete 22F77 Output: No runtime disk images or bundles found matching '22F77'. No matching images found to delete Using the runtime identifier also fails. The corresponding MobileAsset still exists: /System/Library/AssetsV2/com_apple_MobileAsset_iOSSimulatorRuntime/ It contains: c0d3fd05106683ba0b3680d4d1afec65f098d700.asset Its Info.plist contains: SimulatorVersion = 18.5 Build = 22F77 Another asset exists for the current runtime: SimulatorVersion = 26.1 Build = 23B86 The directory /Library/Developer/CoreSimulator/Volumes/iOS_22F77 exists as an empty directory. It appears to become active only when CoreSimulator queries the runtime. The runtime asset is no longer referenced by /System/Library/AssetsV2/com_apple_MobileAsset_iOSSimulatorRuntime/com_apple_MobileAsset_iOSSimulatorRuntime.xml Expected Result After upgrading Xcode/macOS: • old runtimes should either be removable through xcrun simctl runtime delete or • they should no longer remain registered if Xcode has already removed them. Actual Result Different CoreSimulator commands report different runtime states. simctl runtime list only reports iOS 26.1. simctl list runtimes -j still reports iOS 18.5 as available. The old runtime cannot be deleted using the official command. The MobileAsset remains on disk and occupies storage, but there appears to be no supported method to remove it. Notes This looks like CoreSimulator's runtime registry and the runtime deletion mechanism have become inconsistent after upgrading to macOS 27 beta 2 and Xcode 27 beta.