I've been making a macos app with opus 4.8-5 and at first it was great, everything materialized in a week, but when I started tuning stuff and fixing performance problems I have spent a very frustrating month refactoring code where I had to constantly catch llm red-handed and explain and sometimes push obvious ways how to make things work properly (a general knowledge from a completely different stack). In the process CLAUDE.md and memory grew exponentially explaining what it should and what it should never do.