Install the CLI globally. Requires Node.js 18+. After install, the claude command should be on your PATH. If it isn't, your shell's PATH likely doesn't include npm's global bin directory.

npm install -g @anthropic-ai/claude-code

claude --version

Run claude from any directory. On first launch it opens a browser to authenticate. You can use a claude.ai subscription (Pro/Teams) or an ANTHROPIC_API_KEY environment variable for direct API access. API key usage is billed separately from subscriptions.

claude

~/.claude/CLAUDE.md is your permanent memory. It loads before every conversation, in every project. Use it for personal preferences: language, style, commit conventions, things Claude should never do. Think of it as your system prompt that follows you everywhere.

~/.claude/CLAUDE.md

# Global Rules

## Style
- Always use TypeScript
- Prefer functional style over classes
- Keep responses concise

## Git
- Use conventional commits (feat:, fix:, docs:)
- Never commit .env or secrets

## Behavior
- Ask before running destructive commands
- Explain trade-offs when multiple approaches exist

A ./CLAUDE.md in your project root layers on top of your global rules. It's the right place for project-specific context: stack, conventions, architecture notes, and commands. Commit it — every teammate who opens Claude Code in this repo inherits the same context automatically.

./CLAUDE.md

# Project: my-app

## Stack
- Next.js 15, TypeScript, Tailwind
- Postgres via Drizzle ORM
- Tests: Vitest + React Testing Library

## Commands
- `npm run dev`   — dev server
- `npm run test`  — run all tests
- `npm run build` — production build

## Conventions
- Components in src/components/
- DB queries in src/db/
- No default exports

~/.claude/settings.json (global) and .claude/settings.json (project) control which tool calls Claude can make without asking. Project settings merge on top of global — they don't replace them. Use glob patterns to allow specific commands and deny dangerous ones.

{
  "permissions": {
    "allow": [
      "Bash(git *)",
      "Bash(npm run *)",
      "Bash(npx *)"
    ],
    "deny": [
      "Bash(rm -rf *)",
      "Bash(curl * | bash *)"
    ]
  }
}

Claude Code can show a live statusline in your terminal — model name, token count, cost, and active tool. It's off by default. Use the configurator below to build your statusline string, then drop it into your ~/.claude/settings.json.

 claude-sonnet-4-6 │ ↑1.2k ↓340 │ $0.023 │ ✦ Bash