Claude Code API Key and Base URL Setup

Claude Code is configured differently from regular OpenAI-compatible clients. The key points: do not add /v1 to the Base URL, and use ANTHROPIC_AUTH_TOKEN for the token.

What you need

• A valid API Key
• Claude Code installed
• Base URL: https://api.cheng-zi-ai.com
• Recommended model: claude-opus-4-8 or claude-sonnet-4-6

Temporary PowerShell setup

$env:ANTHROPIC_AUTH_TOKEN="sk-your-api-key"
Remove-Item Env:ANTHROPIC_API_KEY -ErrorAction SilentlyContinue
$env:ANTHROPIC_BASE_URL="https://api.cheng-zi-ai.com"
$env:ANTHROPIC_MODEL="claude-opus-4-8"
$env:ANTHROPIC_DEFAULT_HAIKU_MODEL="claude-haiku-4-5-20251001"
$env:ANTHROPIC_DEFAULT_SONNET_MODEL="claude-sonnet-4-6"
$env:ANTHROPIC_DEFAULT_OPUS_MODEL="claude-opus-4-8"
$env:CLAUDE_CODE_DISABLE_NONESSENTIAL_TRAFFIC="1"

Then run:

claude -p "Reply with exactly: OK" --model claude-opus-4-8

Persistent setup

You can write the settings to %USERPROFILE%\.claude\settings.json:

{
  "model": "claude-opus-4-8",
  "env": {
    "ANTHROPIC_BASE_URL": "https://api.cheng-zi-ai.com",
    "ANTHROPIC_AUTH_TOKEN": "sk-your-api-key",
    "ANTHROPIC_MODEL": "claude-opus-4-8",
    "ANTHROPIC_DEFAULT_HAIKU_MODEL": "claude-haiku-4-5-20251001",
    "ANTHROPIC_DEFAULT_SONNET_MODEL": "claude-sonnet-4-6",
    "ANTHROPIC_DEFAULT_OPUS_MODEL": "claude-opus-4-8",
    "CLAUDE_CODE_DISABLE_NONESSENTIAL_TRAFFIC": "1"
  }
}

Common mistakes

• Adding /v1 to the Claude Code Base URL.
• Keeping an old ANTHROPIC_API_KEY environment variable.
• Typing a model name manually instead of copying it from the console.
• Using a key that does not allow Claude-family models.

Usage advice

Claude Code is strong for large codebases, refactoring, and long-context tasks. Use lighter models for simple edits or short questions to reduce credit usage.