CLAUDE.md: Your Project's Brain
CLAUDE.md is Claude Code's persistent memory. Every project that ships fast has a great CLAUDE.md. The difference between a junior using Claude Code and a senior using Claude Code is mostly the quality of their CLAUDE.md files.
Learning Objectives
After this lesson, you will be able to:
- Write a CLAUDE.md that captures your project's tech stack, conventions, and 'house rules' — so every Claude Code session starts already knowing the rules
- Use nested CLAUDE.md files in monorepos so each subproject loads its own context without bloating the top-level file
- Distinguish CLAUDE.md (always loaded) from .claude/rules/ (path-scoped) from settings.json (config) — and pick the right place for each rule
- Avoid the three CLAUDE.md anti-patterns that bloat context, encourage hallucination, or get ignored entirely
Prerequisites
Before You Start
#What CLAUDE.md Is
A markdown file at your project root (or any directory). When Claude Code starts a session, it auto-reads CLAUDE.md and includes its contents in the system prompt. Result: every conversation starts knowing the rules of YOUR project.