Because you are human, and can thus create copyrighted works, and can assign that copyright when you do work for hire. Monkeys and AIs can't create copyrighted works, so there is nothing to assign when doing it for hire

The other line of argument avoids that issue by arguing that you personally created the code with the help of a tool (like a compiler or camera), not just commissioned it

Sure, but that's not what GP stated at all, unless possibly if they're anthropomorphizing to the point that they refer to Claude as "someone".

GP's (or rather GGGP's) statement was "I did not write that code but I paid money". So they claim no authorship. Anthropic is a company, they can't be the author either. So the only one left as author in that reasoning is Claude.

I don't think that necessarily anthropomorphizes it. We speak of monkeys as authors without calling them human. And really the legally important fact is that there was no human author. You can also treat it like CCTV footage which is generally not under copyright because there is no human author (even though most would hesitate to call the camera the author either)

As a human, it is possible for you to create copyrightable works and transfer the copyright to Microsoft in exchange for money. It is not possible for Claude Code to do those things because Claude Code is not a human.

Yes, but Claude code is hardly a "someone", so that's not what the comment I replied to was arguing at all.

They retain ownership over that code because you signed a contract saying explicitly that. Did you sign the same thing with Anthropic? Did your company?

Anthropic isn't a party to such contract either because they (most likely, in the reasonable reading of relevant laws) hold no copyright over the output of their LLM.