CoreSimulator runtime registry becomes inconsistent after upgrading to macOS 27 beta 2: simctl list runtimes reports an old runtime that cannot be deleted

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

1. 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)

1. 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

1. The runtime no longer appears anywhere in Xcode.

2. 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.

1. 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

1. The directory

/Library/Developer/CoreSimulator/Volumes/iOS_22F77

exists as an empty directory.

It appears to become active only when CoreSimulator queries the runtime.

1. 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.