Templates for Writing Effective CLAUDE.md Files in Real Projects

CLAUDE.md is a markdown file that Claude Code loads automatically into every session, serving as the agent's only reliable persistent memory across sessions. Because the file costs context on every load, the templates recommend keeping it under about 120 lines and including only content that changes agent behavior. The first section lists exact commands for install, build, test, lint, and run, including both full-suite and single-file test commands so agents don't skip checks or guess package managers. Further sections cover code conventions, explicit boundaries such as never editing generated files or committing to main, and a working agreement and definition of done. A Python microservice variant adds architecture rules like thin handlers, a services layer, a clients layer for external calls, and environment-based configuration.