For anyone who finds themself in this situation and is confused about how to remove the group identifier from the old account, the trick is to switch to App Groups from the filter on the right on the "Identifiers" page of "Certificates, Identifiers & Profiles". By default, it only shows App IDs. This link should go their directly: https://developer.apple.com/account/resources/identifiers/list/applicationGroup

@DTS Engineer I tried that workaround, and am still seeing the issue. I have tried restarting my computer as well. Interestingly, from the command line it now finds the metal toolchain, but it's still not working within Xcode, when using my build rules. Command line (this used to complain about not being able to find metal toolchain, now it seems ok) From Xcode, still getting the same error

Seems to be working with Xcode 26 beta 2, without any of the workarounds.

@DTS Engineer I am encountering the issue as well. It appears to have been introduced in iOS 26.1, and is still present in iOS 26.2 beta 2. I filed an issue in Feedback Assistant: FB21061796. I included the sample project @rezo0L created, since it illustrates the issue. It's a nice animation and not the easiest thing to recreate, so it would be great if this could be fixed ASAP, thanks!