You put it in a prompt when it needed a hook
In one sentence: You wrote "always run format after editing," "always run tests before committing," and "never touch these files" into CLAUDE.md, then expected me to do it every time. But to me a prompt is a suggestion, not a mechanism — I forget, I skip, I drift as the context grows. If it has to happen, don't leave it to my goodwill. Make it a hook.