Set up project memory with CLAUDE.md - Claude Code Tutorial

Every time you start a Claude Code session, there is one file it reads first, automatically, every single time. That file is called CLAUDE.md, and it is Claude's permanent memory for your project. Think of it like the onboarding doc you wish every new teammate got on day one. The stuff that is not written anywhere, but someone really needs to know what belongs in it. Your build command, your style rules that your linter doesn't catch, the reasoning behind important decision in your codebase, how to run the test, basically anything a smart new developer would need to ask you about. What doesn't belong? Anything Claude can already read directly. Your npm scripts are written in package.json, your TypeScript config is in tsconfig.json. Do not copy that stuff in, you would just be wasting space. Keep it under 60 lines, short and dense bits, long and padded. For rules that absolutely cannot be broken, wrap them in critical tags. Those survive even when Claude has to compress older parts of…