On what you are maintaining, and how you approach it. The code I maintain, if I need to add new functionality to a function, and I can describe it to claude easily enough then I'll tell claude code what file, what function add a marker where I want the code and explain what I want. I don't let it just edit on it's own I have it show me what it wants to do, and if it looks good I'll have them do it.
Just telling claude hey add this functionality to my code base, and hoping it gets it right, which from what I am understanding seems a lot of people are doing, is a good way to get bad results.