What appears to have fixed it for me was copying the relevant lines from ~/.ssh/known_hosts into /etc/ssh/ssh_known_hosts Update: verified that this fixed it for some colleagues as well. Ensure that the file has ownership root:wheel and permissions 644, and pay attention to the file name (ssh_known_hosts, not known_hosts).

Thank you! That clarifies the situation. We (primarly) aren't interested in running Xcode on our VMs, just testing. I was just involving Xcode to see if it had changed how devices were provisioned on the Developer portal. So for our use case, just upgrading the VM from macOS 15 to macOS 26 appears to work as expected, as the UDID is preserved, and our existing provisioning profiles work.