The foundation layer
CLAUDE.md is the most used and most abused feature in Claude Code. It is the first thing most developers configure and the last thing they clean up. Over weeks and months, it accumulates instructions like sediment — each one added after a bad experience, none ever removed, until the file is a geological record of every mistake Claude has ever made in your project.
This module teaches you to use CLAUDE.md properly. Not as a dumping ground for everything Claude should know, but as a lean, focused foundation that carries only the context every session needs.
The principle is simple: if you would not put it in a new hire's first-day onboarding document, it does not belong in CLAUDE.md. Build commands, yes. Project architecture, yes. A 30-step PR review checklist, no — that is a skill. Detailed API design conventions for one specific module, no — that is a rule.
