Claude Code users often overlook the critical .claude folder, treating it as a black box. This guide reveals its true purpose as the project's AI command center, holding instructions, custom commands, and permission rules. Understanding its anatomy unlocks precise control over Claude's behavior.

The folder contains two key directories: a project-level folder committed to Git for team-wide consistency and a personal ~/.claude/ folder for machine-specific settings. The most vital file is CLAUDE.md, acting as the system prompt. Writing effectively here is crucial: focus on build commands, architectural decisions, and non-obvious gotchas, keeping it under 200 lines.

Avoid generic documentation or long theoretical explanations.