Current contract
@openelement/element owns authoring; app and adapter-vite keep application and build behavior separate.
Explicit admission
Known packages can be configured as package islands and use available CEM metadata without importing retired package surfaces.
Current diagnostics
The 0.43 line ships Universal DSD/light/client-only classification, hydration-mismatch diagnostics and the tracked third-party WC SSR corpus. Admission still depends on explicit package-island configuration and observed metadata; it is not a blanket certification of every third-party component.