Installation & First-Time Setup

Installing Claude Code

Claude Code is a Node.js CLI distributed via npm. Install it globally so it's available in any directory:

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

Verify the installation:

claude --version

Authentication

Claude Code uses OAuth against your Anthropic account. On first launch, it opens a browser window for you to sign in. Your session token is stored locally — you won't need to re-authenticate every session.

If you're on a headless server or CI environment, use an API key instead:

export ANTHROPIC_API_KEY=sk-ant-...
claude

Creating Your Global CLAUDE.md

Claude Code reads a CLAUDE.md file in your project directory as persistent instructions. Create a global one at ~/.claude/CLAUDE.md that applies everywhere:

# My Global Preferences
- TypeScript strict mode always
- Prefer functional patterns
- Always run tests before marking done
- Never commit without explaining why

Project-level CLAUDE.md files override the global one.

Shell Configuration

Add these aliases to your ~/.zshrc or ~/.bashrc for a smoother experience:

alias cc="claude"
alias ccp="claude --print"  # Print-only mode (no interactive)

Key Startup Flags

First Session Tips

Start by asking Claude to explain the codebase structure before asking for edits. This gives Claude the context it needs to make accurate changes. The /status command shows what files Claude has read, what tools are enabled, and the current session cost.