Claude Code Install & Usage

Claude Code is a powerful AI coding assistant for the terminal. This guide covers install and configuration.

System requirements

Node.js ≥ 18.0
macOS, Linux, or Windows (WSL)

Quick start

1. Install Node.js

Tip: Skip if you already have Node.js 18+.

Ubuntu / Debian

# Install Node.js LTS
curl -fsSL https://deb.nodesource.com/setup_lts.x | sudo bash -
sudo apt-get install -y nodejs

# Verify
node --version

macOS

# Xcode Command Line Tools
sudo xcode-select --install

# Homebrew (if needed)
/bin/bash -c "$(curl -fsSL https://raw.githubusercontent.com/Homebrew/install/HEAD/install.sh)"

# Install Node.js
brew install node

# Verify
node --version

2. Install Claude Code


# Official install macOS/Linux
curl -fsSL https://claude.ai/install.sh | bash
# Official install Windows
irm https://claude.ai/install.ps1 | iex
# Official install Homebrew
brew install --cask claude-code
# Official install Winget
winget install Anthropic.ClaudeCode

## After install, Claude may ask you to configure PATH
echo 'export PATH="$HOME/.local/bin:$PATH"' >> ~/.bashrc && source ~/.bashrc

3. Get a token

Setting	Description	How to get
ANTHROPIC_AUTH_TOKEN	API auth token	Console → API Tokens → Add token (starts with `sk-`)
ANTHROPIC_BASE_URL	API base URL	Same as the main site URL

Recommended token settings:

Name: anything

Quota: unlimited

Group: Claude Code exclusive, promo Claude Code, or Official-relay Claude 1+. Do not use default or reverse-engineered groups (no tool calling).

Other options: defaults

4. settings.json

# Full settings.json example
  {
    "env": {
         "ANTHROPIC_BASE_URL": "https://4zapi.com",  
    # Your API token
    "ANTHROPIC_AUTH_TOKEN": "sk-*********",  
    # Primary interactive model
    "ANTHROPIC_MODEL": "claude-opus-4-6",
    # Explore subagent / light background tasks
    "ANTHROPIC_DEFAULT_HAIKU_MODEL": "claude-opus-4-6", 
    # opusplan execution stage
    "ANTHROPIC_DEFAULT_SONNET_MODEL": "claude-opus-4-6",
    # opusplan planning stage
    "ANTHROPIC_DEFAULT_OPUS_MODEL": "claude-opus-4-6",
    # 300s timeout
    "API_TIMEOUT_MS": "300000",  
    # Claude Code experimental beta flags
    "CLAUDE_CODE_DISABLE_EXPERIMENTAL_BETAS": "1"
    }
  }

Linux / Unix / macOS / Windows WSL settings.json:

cd your-project-folder

# Step 1
cat > ~/.claude/settings.json << 'EOF'

# Step 2 — replace token/models, remove comments, then continue
  {
    "env": {
    "ANTHROPIC_BASE_URL": "https://4zapi.com",  
    "ANTHROPIC_AUTH_TOKEN": "sk-*********",  
    "ANTHROPIC_MODEL": "claude-opus-4-6",
    "ANTHROPIC_DEFAULT_HAIKU_MODEL": "claude-opus-4-6", 
    "ANTHROPIC_DEFAULT_SONNET_MODEL": "claude-opus-4-6",
    "ANTHROPIC_DEFAULT_OPUS_MODEL": "claude-opus-4-6",
    "API_TIMEOUT_MS": "300000",  
    "CLAUDE_CODE_DISABLE_EXPERIMENTAL_BETAS": "1"
    }
  }
  
  # Step 3
  EOF
  
  # Step 4 — verify
  cat ~/.claude/settings.json
  
  # Step 5 — start
  claude

First-run setup

Theme → pick one + Enter
Safety → accept + Enter
Terminal → keep defaults + Enter
Trust directory → trust current dir + Enter

You can start coding with your AI partner.

FAQ

Q: "Invalid API Key · Please run /login"?

A: Env vars were not detected. Check:

ANTHROPIC_AUTH_TOKEN and ANTHROPIC_BASE_URL are set
Token starts with sk-
If using persistent config, restart the terminal

Q: Why does it show "offline"?

A: Claude Code probes Google for online status. "offline" does not block usage; it only means Google is unreachable.

Q: Why does web Fetch fail?

A: Claude Code calls Claude for a safety check before fetching pages. You need:

Stable international internet
A global proxy when required

Q: Requests always show "fetch failed"?

A: Likely network. Try a proxy tool.

Q: How to handle API errors?

A: Relay instability is possible:

Exit Claude Code (Ctrl+C)
Rerun claude
Retry later if it persists

Q: Web login errors?

A: Clear this site's cookies and sign in again.

Notes

This site relays official Claude Code traffic
Only Claude Code API traffic is supported
Keep your API token private