A few things to note:
a) Use the "Projects" feature in Claude web. The context makes a significant amount of difference in the output. Curate what it has in the context; prune out old versions of files and replace them. This is annoying UX, yes, but it'll give you results.
b) Use the project prompt to customize the response. E.g. I usually tell it not to give me redundant code that I already have. (Claude can otherwise be overly helpful and go on long riffs spitting out related code, quickly burning through your usage credits).
c) If the initial result doesn't work, give it feedback and tell it what's broken (build messages, descriptions of behavior, etc).
d) It's not perfect. Don't give up if you don't get perfection.