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. Open System Settings → Privacy & Security → Full Disk Access Click the + butt
Topic:
Developer Tools & Services
SubTopic:
Xcode