A proxy server that transforms Anthropic API requests to OpenAI format and sends it to openrouter.ai. This enables you to use Anthropic's API format while connecting to OpenAI-compatible endpoints.

With this command, you can start the proxy server with your OpenRouter API key on port 3000:

OPENROUTER_API_KEY=your-api-key npx anthropic-proxy

Environment variables:

• OPENROUTER_API_KEY: Your OpenRouter API key (required when using OpenRouter)
• ANTHROPIC_PROXY_BASE_URL: Custom base URL for the transformed OpenAI-format message (default: openrouter.ai)
• PORT: The port the proxy server should listen on (default: 3000)
• REASONING_MODEL: The reasoning model to use (default: google/gemini-2.0-flash-exp:free)
• COMPLETION_MODEL: The completion model to use (default: google/gemini-2.0-flash-exp:free)
• DEBUG: Set to 1 to enable debug logging

Note: When ANTHROPIC_PROXY_BASE_URL is set to a custom URL, the OPENROUTER_API_KEY is not required.

To use the proxy server as a backend for Claude Code, you have to set the ANTHROPIC_BASE_URL to the URL of the proxy server:

ANTHROPIC_BASE_URL=http://0.0.0.0:3000 claude

This proxy can be deployed to Cloudflare Workers or Cloudflare Pages.

1. Install Wrangler CLI:

   npm install -g wrangler

2. Login to your Cloudflare account:

   wrangler login

3. Deploy the worker:

   npm run deploy:worker

4. Set your secrets in the Cloudflare dashboard or using Wrangler:

   wrangler secret put OPENROUTER_API_KEY

• OPENROUTER_API_KEY: Your OpenRouter API key (required when using OpenRouter)
• ANTHROPIC_PROXY_BASE_URL: Custom base URL for the transformed OpenAI-format message (default: openrouter.ai)
• REASONING_MODEL: The reasoning model to use (default: google/gemini-2.0-flash-exp:free)
• COMPLETION_MODEL: The completion model to use (default: google/gemini-2.0-flash-exp:free)
• DEBUG: Set to 1 to enable debug logging

You can also deploy this as a Cloudflare Pages application:

1. Create a new Pages project in your Cloudflare dashboard
2. Connect your GitHub repository
3. Set the build settings:
   • Build command: npm run build (if you add a build script)
   • Build output directory: public
4. Add environment variables in the Pages project settings

Licensed under MIT license. Copyright (c) 2025 Max Nowack

Contributions are welcome. Please open issues and/or file Pull Requests.