Installation & First-Time Setup
Install Claude Code, authenticate with your Anthropic account, and configure your environment for maximum productivity.
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
| Flag | Purpose |
|------|---------|
| --no-update | Pin the version (useful for CI) |
| --print | Non-interactive mode, output to stdout |
| --dangerously-skip-permissions | Auto-approve tools (use only in trusted automation) |
| --model claude-opus-4-5 | Override the default model |
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.