The floating chat overlay bubble explorer-app renders over the shell. Baselined from
Shell.ChatOverlay.Enabled; a host that owns its own AI surface for some audience (a learner
portal, say) narrows it here instead of hiding the bubble with route-scoped CSS.
The shell's chrome as one resolved set: which header affordances render and how the app switcher and record-opening behave. Instance Config supplies the platform-wide answer (
Shell.SearchBar.Enabledand friends); a host's BaseShellChromePolicy may narrow it.