The exact CLAUDE.md scope rules that actually work

I've tried a lot of CLAUDE.md scope rules. Some work, some get ignored. Here are the ones that hold in practice. Rules that work Specific file constraints: "Only modify files in src/api/. Do not touch src/web/ or any configuration files." Works because it's unambiguous. Claude knows exactly which files are in scope. The minimal footprint rule: "Minimal footprint. Only touch files directly required for the stated task.