[nicce]

I would say that legacy code is something that one does not simply change.

You cannot update any dependencies because then everything breaks. You cannot even easily add new features because it is difficult to even run the old dependencies your code is using.

With LLMs, creating legacy code is using some old APIs, old patterns to do something, that is not relevant anymore, but the LLM does not know about.

E.g. if you ask any LLM to use Tailwind CSS, they use V3 no matter what you try to do while the V4 is the latest. LLMs try to tell you that pure CSS configuration is wrong and you should use the .js config.