What to Put in CLAUDE.md

Start with five conventions — expand as patterns emerge.

Include

Coding conventions and style rules
Architecture patterns and directory structure
Build and test commands
Preferred tools, SDKs, and frameworks
Common pitfalls specific to this project

Forbid

Never modify production configs directly
Never commit secrets or credentials
Never skip tests before committing
Never hardcode tenant IDs or client secrets
Never make breaking changes without plan mode

CLAUDE.md is living documentation

When Claude makes a mistake that a convention would have prevented, add that convention. Encode the lesson so it doesn't repeat. Treat your CLAUDE.md the same way you treat a runbook — every postmortem updates it.