Fix Guide: Tahoe Xcode Simulator Boot Loop Fix

Symptom: When attempting to launch a project in the Xcode Simulator on macOS Tahoe, the simulator stays stuck on the Apple logo or repeatedly crashes and restarts with a "CoreSimulator" error.

Why this happens

This loop is often caused by a corrupted CoreSimulator database or a mismatch between the simctl tool and the Tahoe kernel's new memory management policies. Specifically, the com.apple.CoreSimulator.CoreSimulatorService fails to properly initialize the virtual disk image for the simulator, leading to a timeout and a subsequent restart loop triggered by launchd.

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Fix 1: Wipe Simulator Runtimes and Cache

Clearing the cached state of the simulators forces macOS to rebuild the simulator device list and its associated metadata.

# Shutdown all running simulators
xcrun simctl shutdown all
# Erase all contents and settings from all simulators
xcrun simctl erase all
# Delete the CoreSimulator cache directory
rm -rf ~/Library/Developer/CoreSimulator/Devices

Fix 2: Reset the CoreSimulator Service

The background daemon responsible for simulators can become unresponsive or stuck in a zombie state.

# Kill the CoreSimulator service to force a restart
sudo killall -9 com.apple.CoreSimulator.CoreSimulatorService

Fix 3: Fix Simulator Disk Permissions

Sometimes the simulator disk images are flagged as "quarantined" by the com.apple.quarantine system on Tahoe.

# Remove quarantine attributes from the Xcode folder
sudo xattr -dr com.apple.quarantine /Applications/Xcode.app

Recommended Tool: CleanMyMac

Xcode is notorious for leaving behind gigabytes of "Derived Data" and old simulator runtimes that can cause conflicts. CleanMyMac’s "System Junk" scan includes a dedicated section for Xcode development junk, allowing you to safely clear out old caches that might be triggering boot loops.