Memory & CLAUDE.md

Every Claude Code session starts with an empty context window. Two systems carry knowledge across sessions: CLAUDE.md files that you write to give Claude persistent instructions, and auto memory that Claude writes for itself as it learns from your corrections. Both load at the start of every conversation.

This is the first chapter because it is the single highest-leverage thing you can do with Claude Code. A well-tended CLAUDE.md improves output quality across every other feature in this book — skills, commands, hooks, subagents — because they all run with CLAUDE.md in context.

The Items in this chapter cover, in order: the mindset of treating CLAUDE.md as living shared knowledge; the mental model that separates it from enforcement; how to write entries Claude will actually follow; how to keep it from bloating; where to put it for the scope it applies to; how to scale past a single file with .claude/rules/; and how auto memory fits in alongside.