Another interesting tidbit. I remoted into a jenkins agent node, completely reinstalled Xcode 26 beta 4. The first build with this agent succeeded from jenkins, and the actool --version reported correctly. The next build after that failed, and actool --version reported the ibtool incorrect information, so it's like the command line tools are corrupting themselves somehow.

Confirmed, still happening with beta 5. I filed a new feedback against beta 5: FB19447083