One thing I keep discovering about the agentic era of programming is that all of the old lessons and bits of wisdom about programming are still valid. They're just 10 to 100x more important now that you can generate 10,000 lines in an hour.
e.g. Break your code up into loosely coupled modules, don't have leaky abstractions, don't have huge God files, have good black box end-to-end testing, do the design work before the implementation, do lots of automated testing, have good documentation, etc.
Here is another one that was always true, end users only care about the observable behavior of your program. Does it solve the problem in a performant way? Is it reliable?
And another one, it was common when you inherited a large code base that was mature and written before you to not have any clue how most of it worked.
We have to accept that the art of nudging the text around is just not part of producing code for money anymore.