Passing Data Across the Server-Client Boundary — Component References vs Server Actions

Component references and Server Actions are both serialized identically; the icon example fails only because of a naming collision with a built-in prop.

Ordinary functions and component types are not serializable data and cannot cross the RSC boundary as-is, whereas a "use server"-marked function is specially compiled by the framework into a callable reference that can be transmitted to the client and invoked there, triggering a server round-trip when called.

Client Components can invoke any Server Component function directly by import, so the serialization step is unnecessary in both cases.

The difference is purely a bundler configuration flag with no relationship to the function's directive.