When I use Claude to write code for my own projects, the code it generates is exactly the same code that I would have written had I done it by hand. If there is any deviation, I ask it to adjust but that is rare. At least 95% of the time, it's like it read my mind... Which is quite impressive when it outputs like 500+ lines from a single prompt and then it works straight away without any debugging necessary.

I don't even debug anymore on those projects. If Claude tries to add debugging logic in my code, I tell it not to and just provide additional information and it can usually find the solution faster that way.

This is when working on my own projects. When working on projects created by other people, it's a different story and I have to fight it constantly to stop it from implementing hacks and workarounds... It uses much more tokens to implement basic features. It's more work for both the AI agent and myself.

The project's existing code makes up most of the context so if the code is not great, you have to write long detailed prompts to set it on the right path. You have to make it clear that the existing code isn't good enough and your expectation is higher.

In this case, it usually gets better with more back-and-forth... At the beginning, it can't do anything because you keep pointing out a problem whenever it tries anything at all, but eventually, after a lot of criticism, it starts becoming more careful and adapting to your standards.

So yeah, even same person doing the prompting can lead to two very different experiences depending on who built the foundation.

So my conclusion is that the expertise comes from both the existing codebase and from the person doing the prompting... And TBH, I would say the codebase/foundation carries more weight than the person doing the prompting.

Pretty sure I could put an idiot on one of my codebases with Claude Code and they'd do a decent job.