Comment by drw85

I also think this is why AI works okay-ish on tiny new greenfield webapps and absolutely doesn't on large legacy software.

You can't accurately plan every little detail in an existing codebase, because you'll only find out about all the edge cases and side effects when trying to work in it.

So, sure, you can plan what your feature is supposed to do, but your plan of how to do that will change the minute you start working in the codebase.