I'm experiencing a reproducible issue that completely blocks Xcode on an Apple Silicon Mac. Environment • MacBook Air (M4) • macOS 26.5.2 (25F84) • Xcode 26.6 (17F113) • Also reproduced with Xcode 26.5 (17F42) Issue Xcode terminates immediately before the main window appears. Instruments also terminates immediately. The command: xcodebuild -version works normally. However, any command that requires SDK initialization immediately terminates, for example: xcodebuild -showsdks The process is killed instantly. Crash reports consistently show: SIGKILL (Code Signature Invalid) Termination Reason: Namespace CODESIGNING, Code 2, Invalid Page The crash occurs during dyld page authentication: dyld4::fixupPageAuth64() What I have already tried • Reinstalled Xcode • Reinstalled macOS • Reinstalled Command Line Tools • Reinstalled Rosetta • Tested in Safe Mode • Tested with a newly created macOS user • Removed caches and DerivedData • Verified Xcode signatures The behavior is identical in every case. Interestingly, xcodebuild -version succeeds, but every SDK-related command is killed immediately, suggesting the failure occurs during SDK/framework initialization rather than Xcode startup itself. I have already submitted: Feedback Assistant: FB23586800 DTS Case: 20879405 Has anyone else seen the same issue on Apple Silicon (especially M4)? Any known workaround or confirmation that this may be a macOS 26.5.x / Xcode 26.5–26.6 regression would be greatly appreciated.