One package, two vendors, two API shapes

A multiplatform UI build usually has two suppliers for the same UI toolkit: the platform vendor's artifact, which only exists for the platform target, and the multiplatform vendor's port, which covers every target. They publish the same package name — that is deliberate, and it is what lets shared code import one symbol and get whichever copy the target resolves.

They do not release together. The platform vendor's line runs ahead, so at any moment a symbol may have a different shape in each:

// adapted — the platform vendor's newer line moved this off the scope
interface MenuBoxScope { @Composable fun Menu(…) }          // multiplatform port: a member
@Composable fun MenuBoxScope.Menu(…)                        // platform vendor: a top-level extension