> copyright doesn't suddenly get declared as being of the model owner

That does not seem to be likely. The article you link indicates it is the prompter and provider of any other inputs (in the case discussed the photographer who took the photo the LLM modified) who might have claims.

> The US specifically has settled on it being (effectively?) public domain.

My understanding is that sufficient human input makes it copyright. This is not greatly different from German law.

In both cases something that is vibe coded in the strict sense of having only vague prompts will not be covered by copyright, something with real human input will.

That leads to a problem with "mostly" there. Does it mean mostly vibe coded, or mostly AI written? AI written under close guidance is covered by copyright so should be fine.

This does make it important to keep prompt history and record human edits of generated code as that is what will prove sufficient human input.

Also, its not just German law that matters to users. For many users law in their jurisdiction is what matters.