Xcode now hangs; SDKs are "status unavailable"

+1, this gave me a hard time when prewarming Xcode on our dedicated CI machines.

Same symptoms, xcrun simctl unresponsive, Xcode showing unavailable status, hanged in overall.

I can't really recall this happening ever before. 🤨

I have the same issue with Xcode 26.4 after installing macOS 26.4.

What help is (do it at your own risk, no guarantee):

1. Force quit Xcode
2. rm /Library/Developer/CoreSimulator/Images/images.plist
3. Wait 1-2 minutes
4. Launch Xcode

You will be able to download the Platform Support Components from Xcode again.

@diniska , does your remedy survive a reboot of the machine? When I tried my cleaning (I did the whole CoreSimulator directory, but now I see that I probably only needed to do the images.plist file), my simulators downloaded fine, but then they disappeared again after I rebooted my machine.

Hi All, I do have the same issue. Tried everything with the help of AI ... no success. Filed two complaints @ ... no answer. How could your QA not find this? My complete update plan for my apps is completely screwed now ... Please fix this asap!

Have been dealing with this too. Incredibly frustrating.

I also have this problem and I am going crazy, did a full macos restore (didn't wipe the HD yet) and it keeps doing that. Also noticed every 11 seconds a new SimRuntimeBundle is created in Macintosh HD > Library > Developer > CoreSimulator > Cryptex > Images > mnt folder very strange indeed.

As diniska wrote, this is what finally worked for me:

• Force quit Xcode
• rm /Library/Developer/CoreSimulator/Images/images.plist
• Wait 1-2 minutes
• Launch Xcode

You do need to reboot in recovery, turn off SIP, do the deletion, reboot in recovery, turn on SIP, and reboot. But it's been working ever since.

Here is a summary of my findings so far working with AI:

The Bug: macOS Tahoe 26.4 triggers a loop in the CoreSimulator subsystem where a new SimRuntimeBundle is created in /Library/Developer/CoreSimulator/Cryptex/Images/mnt/ every 11 seconds. This accumulates thousands of files and bloats the images.plist manifest.

Why Xcode Hangs: When Xcode launches, it starts CoreSimulatorService, which spawns a helper daemon called simdiskimaged via XPC. simdiskimaged is responsible for managing simulator disk images and runtimes. On startup, it tries to load and validate the entire contents of images.plist and the Cryptex directory. Because of the runaway loop, there are now 7,000+ files and a bloated manifest to parse. simdiskimaged exceeds its hardcoded 20MB jetsam memory limit and gets killed by the system (SIGKILL/-9). CoreSimulatorService sent a synchronous XPC message to simdiskimaged and is now waiting for a reply that will never come — it hangs forever on mach_msg2_trap. Everything downstream hangs: xcrun simctl, Xcode's SDK detection, simulator availability — all of it.

The Evidence: simdiskimaged was killed 1,165 times with exit reason JETSAM_REASON_MEMORY_PERPROCESSLIMIT

Its jetsam limit is 20MB active / 15MB inactive

The CoreSimulatorService stack trace shows a single thread blocked on SimDiskImageManager serviceVersionWithError: → xpc_connection_send_message_with_reply_sync → mach_msg2_trap

The service is programmatically submitted by CoreSimulatorService (no on-disk plist), so the memory limit can't be user-configured

Ok, here is my step by step (what I think is) a solution guide... (worked for me)

Fix: Xcode Hangs on macOS Tahoe 26.4 (SDKs "Status Unavailable")

The Problem

macOS Tahoe 26.4 introduces a bug where a CoreSimulator subprocess (simdiskimaged) repeatedly exceeds its 20MB memory limit and gets killed by the system. This causes CoreSimulatorService to hang indefinitely, which in turn causes Xcode to freeze, SDKs to show "status unavailable," and all simulators to become inaccessible.

The root cause is a runaway loop that creates new SimRuntimeBundle files every 11 seconds in /Library/Developer/CoreSimulator/Cryptex/Images/mnt/, bloating the state that simdiskimaged must load on startup beyond its jetsam memory limit.

The Fix

Step 1 — Grant Terminal Full Disk Access

The files that need to be deleted are protected by TCC (Transparency, Consent, and Control). Without this step, sudo rm will return "Operation not permitted."

1. Open System Settings → Privacy & Security → Full Disk Access
2. Click the + button
3. Add Terminal (located in /Applications/Utilities/)
4. Toggle it on
5. Quit and relaunch Terminal

Step 2 — Force Quit Xcode

Close Xcode completely. Force Quit if necessary.

Step 3 — Delete the Corrupted CoreSimulator State

Run the following commands in Terminal:

sudo rm /Library/Developer/CoreSimulator/Images/images.plist
sudo rm -rf /Library/Developer/CoreSimulator/Cryptex

Step 4 — Reboot

Restart your Mac.

Step 5 — Verify the Fix

Open Terminal and run:

xcrun simctl list devices

This should return a list of devices (marked "unavailable") without hanging. If it responds, the daemon is healthy again.

Step 6 — Clean Up Stale Runtime Data

Before re-downloading runtimes, clear any stale references that may cause duplicate errors:

xcrun simctl runtime delete all
sudo rm -rf /Library/Developer/CoreSimulator/Images/
sudo rm -rf ~/Library/Developer/CoreSimulator/Devices/

Step 7 — Re-Download Simulator Runtimes

1. Launch Xcode
2. Go to Xcode → Settings → Platforms
3. Download the simulator runtime(s) you need (e.g., iOS 26.4)

Xcode should now function normally.

Notes

• You do not need to reinstall Xcode or downgrade macOS.
• Consider filing a Feedback with Apple referencing the 20MB jetsam limit on simdiskimaged and the uncapped SimRuntimeBundle creation loop.
• This fix was developed by diagnosing the issue from the ground up: identifying the deadlocked XPC call in CoreSimulatorService, tracing it to the killed simdiskimaged daemon, and discovering the jetsam memory pressure caused by accumulated runtime state.
• You may want to remove full disk access from your terminal when you are done.