Thanks. Couldn't succeed after many tries of downloading and install (errors about permissions to read or execute...). I succeeded following the "protocol" described here: https://medium.com/@sergey-pekar/how-to-fix-annoying-xcode-26-not-building-swiftui-previews-error-cannot-execute-tool-metal-due-49564e20357c What I don"t understand is that on my M1Max MBP, Metal was already OK without any setting, and I could compile my project once XCode 26 was downloaded and installed

I also have the same problem on a MacStudio M1Max (and not on a MBP M1Max) after upgrading to Xcode 26.1.1: no MetalToolchain accessible from this application. Running on Tahoe 26.1 Running today xcodebuild -downloadComponent metalToolchain gives: `Beginning asset download... Downloaded asset to: /System/Library/AssetsV2/com_apple_MobileAsset_MetalToolchain/68d8db6212b48d387d071ff7b905df796658e713.asset/AssetData/Restore/022-20369-066.dmg Done downloading: Metal Toolchain 17B54.` Then when I run "xcrun metal --version", I got an error message: error: error: cannot execute tool 'metal' due to missing Metal Toolchain; use: xcodebuild -downloadComponent MetalToolchain Last when I run: "xcodebuild -showComponent metalToolchain", I got: 2025-12-12 18:34:14.045 xcodebuild[27394:1591467] IDEDownloadableMetalToolchainCoordinator: Failed to remount the Metal Toolchain: The file “com.apple.MobileAsset.MetalToolchain-v17.2.54.0.BttmuJ” couldn’t be opened because you don’t have permission to view it. 2025-12-12 18:34:14.339 xcodebuild[27394:1591469] IDEDownloadableMetalToolchainCoordinator: Failed to remount the Metal Toolchain: The file “com.apple.MobileAsset.MetalToolchain-v17.2.54.0.BttmuJ” couldn’t be opened because you don’t have permission to view it. 2025-12-12 18:34:14.341 xcodebuild[27394:1591468] IDEDownloadableMetalToolchainCoordinator: Failed to remount the Metal Toolchain: The file “com.apple.MobileAsset.MetalToolchain-v17.2.54.0.BttmuJ” couldn’t be opened because you don’t have permission to view it. Asset Path: /System/Library/AssetsV2/com_apple_MobileAsset_MetalToolchain/68d8db6212b48d387d071ff7b905df796658e713.asset/AssetData Build Version: 17B54 Status: installed Toolchain Search Path: /private/var/run/com.apple.security.cryptexd/mnt/com.apple.MobileAsset.MetalToolchain-v17.2.54.0.BttmuJ

Problem seems to be solved. After hours of looking after the project files, I tried to upload my application to the Appstore directly: • My first and numerous tries were made like this in Organizer: Distribute App -> Custom -> App Store Connect all these tries had the problem • I managed today another way: Distribute App -> TestFlight & App Store This route succeeded at first try and my build is now available in App Store Connect… A bug in Xcode 15?

Corrected. I had forgotten to update the - (BOOL)panel:(id)sender shouldEnableURL:(NSURL *)url method to manage UT types instead of UTI strings

UPDATE: In fact, to the contrary of what I wrote, I can't even read files setting myPanel.allowOtherFileTypes to TRUE

Thanks for your reply. So, there is no way, in a sandboxed app, to perform an extension check? It's a pity as it denies to the app the right to prevent a user typo. In this case, no other compatible application will be able to open the file directly, unless the user corrects itself the extension in the Finder… What I don't understand it that this code works in one of my classes… So why are the Sandbox rules considered as violated in a class, and not in another class using the same code?