Mine works by Deleting Xcode-beta.app , Reinstalling and follow the command line workaround (with "t" in "plist" in the second line) again I also had this problem and already downloaded metal toolchain in XCode. I followed 3 line command line workaround from release note and found many error from xcodebuild didn't point to xcode but CommandLineTool instead -> fix with this https://stackoverflow.com/questions/17980759/xcode-select-active-developer-directory-error something not exist when running sed ... -> add the missing "t" to the plis at the end of the line can't import component -> I tried xcodebuild -deleteComponent metalToolchain and importComponent again but it didn't work I guessed that the reason mine didn't work while other people's worked may come from something that happened when I download the MetalToolchain component in Xcode may obstruct the commandline workaroound. So, I tried deleting the Xcode-beta.app, deleting things in /tmp folder that the commandline download. ensure anything else created when running 3 lines workaround not successfully was removed expand Xcode_26_beta.xip (redownloaded this if you didn't keep this file) into Xcode-beta.app Rerun 3 lines of workaround in the command line After 3 commandlines run successfully, I recompile & run my xcodeproj that has .metal file and it just run smoothly with expected result as it used to be Thanks WWDC Metal Lab Engineer (Rich & Mayur) who helped pointing me to this thread and everyone here who raised and solved the issue before I came here

Just for the inspiration to solve the problem in your case. I managed to scope down to the root cause of my problem which come from one .usda file in my RealityKitContent Package. Inside that there's a quite ShaderGraphMaterial that has some internal part references back to another .usda file that I didn't copy to the new RC Pro project. Also has modules from older version of RC Pro. I guess the compiler fail to compile this and cause the error (for my case). As long as my RealityKitContent doesn't use this file it's going on well. (the moving Xcode to another folder, clear DerivedData folder, restart Xcode & Computer, etc. sometimes solve the problem but it reappears. Only this way effectively persists)

This happened to me, too. I tried so many ways. Last thing that solved the problem was moving newly downloaded Xcode which I expanded in Downloads folder to "Applications" Folder and it just worked (after the Xcode restarted).