Claude Code Setup with a Custom API Gateway

Anthropic recommends the native installer. It installs the CLI without requiring Node.js and keeps Claude Code updated automatically.

curl -fsSL https://claude.ai/install.sh | bash
claude --version

irm https://claude.ai/install.ps1 | iex
claude --version

Homebrew is also supported: brew install --cask claude-code. The old global npm installation is no longer the recommended setup.

1. Open API Keys in the dashboard.
2. Create an sk-cs4-... key and select Basic or Pro.
3. Copy the key when it is shown. It is not displayed again.
4. Add a one-time usage pack from Plans if the account has no available balance.

The shortest setup is to export two variables in the same terminal where you start Claude Code.

export ANTHROPIC_BASE_URL="https://api.llmsrelay.com"
export ANTHROPIC_API_KEY="YOUR_SK_CS4_KEY"
export CLAUDE_CODE_ENABLE_GATEWAY_MODEL_DISCOVERY=1
unset ANTHROPIC_AUTH_TOKEN

claude

$env:ANTHROPIC_BASE_URL = "https://api.llmsrelay.com"
$env:ANTHROPIC_API_KEY = "YOUR_SK_CS4_KEY"
$env:CLAUDE_CODE_ENABLE_GATEWAY_MODEL_DISCOVERY = "1"
Remove-Item Env:ANTHROPIC_AUTH_TOKEN -ErrorAction SilentlyContinue

claude

Put the gateway variables in your user settings file so the terminal client and the official editor extension use the same configuration:

{
  "env": {
    "ANTHROPIC_BASE_URL": "https://api.llmsrelay.com",
    "ANTHROPIC_API_KEY": "YOUR_SK_CS4_KEY",
    "CLAUDE_CODE_ENABLE_GATEWAY_MODEL_DISCOVERY": "1"
  },
  "model": "claude-sonnet-4.6"
}

Check the model IDs available to your key, then use one source of truth for model selection. Model discovery adds the gateway catalog to Claude Code's model picker.

curl https://api.llmsrelay.com/v1/models \
  -H "x-api-key: $ANTHROPIC_API_KEY"

• Use the top-level "model" value in ~/.claude/settings.json for a persistent default.
• Use claude --model MODEL_ID for a one-off override.
• Use the Claude Code model picker when you want to switch interactively.

curl https://api.llmsrelay.com/healthz

claude -p "Reply with exactly: pong"

A pong response confirms that Claude Code loaded the gateway URL, authenticated the key, resolved the model, and completed a request.

In an interactive session, run /status and confirm that the displayed Anthropic base URL is https://api.llmsrelay.com and the active credential is ANTHROPIC_API_KEY.