App styles are scoped to their own screens and hosted popups before activation, protecting Shell navigation. Existing published styles are checked against the actual host CSS registrations. Browsers must support CSS @scope; unsupported rules display a stylesheet-specific error. No SDK API update is required.

With the matching review runner, new submissions must avoid global imports, font registrations, root/host selectors and property registrations that differ from the host. Relative stylesheet assets remain supported. This protects selector boundaries; inherited CSS variables and arbitrary App JavaScript are not fully isolated.

Completed App review results can be acknowledged after an interrupted transfer without rebuilding the App. Failed or unconfirmed tests still block review and publication. Standard composition queries also validate their declared public identity against the disposable migrated database before approval.