Use Anthropic clients (like Claude Code) with Gemini or OpenAI backends. 🤝

A proxy server that lets you use Anthropic clients with Gemini or OpenAI models via LiteLLM. 🌉

• LiteLLM Proxy Server and API Key
• uv installed.

1. Clone this repository:

   git clone https://github.com/1rgs/claude-code-openai.git
   cd claude-code-openai

2. Install uv (if you haven't already):

   curl -LsSf https://astral.sh/uv/install.sh | sh

   (uv will handle dependencies based on pyproject.toml when you run the server)

3. Configure Environment Variables: Copy the example environment file:

   cp .env.example .env

   Edit .env and fill in your API keys and model configurations:

   • OPENAI_API_KEY: Your LiteLLM API key (Required).
   • OPENAI_API_BASE: Your LiteLLM server URL (Required).
   • PREFERRED_PROVIDER: Set to openai (default). This determines the primary backend for mapping haiku/sonnet.
   • BIG_MODEL (Optional): The model to map sonnet requests to. Defaults to anthropic/claude-sonnet-4-20250514.
   • SMALL_MODEL (Optional): The model to map haiku requests to. Defaults to anthropic/claude-3-5-haiku-latest.

4. Run the server:

   uv run uvicorn server:app --host 0.0.0.0 --port 8082 --reload

   (--reload is optional, for development)

1. Install Claude Code (if you haven't already):

   npm install -g @anthropic-ai/claude-code

2. Connect to your proxy:

   ANTHROPIC_BASE_URL=http://localhost:8082 claude

3. That's it! Your Claude Code client will now use the configured backend models (defaulting to OpenAI) through the proxy. 🎯

This setup allows you to chain proxies: Claude Code → This Proxy → LiteLLM Proxy → Multiple LLM Providers 🔄

The proxy automatically maps Claude models to every model available based on the configured model:

The proxy automatically adds the appropriate prefix to model names:

• OpenAI models get the openai/ prefix
• Gemini models get the gemini/ prefix
• The BIG_MODEL and SMALL_MODEL will get the appropriate prefix based on whether they're in the OpenAI or Gemini model lists

For example:

• gpt-4o becomes openai/gpt-4o
• gemini-2.5-pro-preview-03-25 becomes gemini/gemini-2.5-pro-preview-03-25
• When BIG_MODEL is set to a Gemini model, Claude Sonnet will map to gemini/[model-name]

This proxy leverages LiteLLM to provide seamless translation between different LLM providers while maintaining Anthropic API compatibility.

The proxy is built on top of LiteLLM, a unified interface for calling 100+ LLM APIs. This provides several key benefits:

• Universal Provider Support: Connect to OpenAI, Google (Gemini), Anthropic, Azure, AWS Bedrock, and many other providers
• Automatic Format Translation: LiteLLM handles the conversion between different API formats automatically
• Consistent Response Structure: All providers return responses in a standardized format
• Built-in Error Handling: Robust error handling and retry logic across providers

The proxy works by:

1. Receiving requests in Anthropic's API format 📥
2. Model mapping - translates Claude model names (haiku/sonnet) to target provider models 🗺️
3. LiteLLM processing - uses LiteLLM's unified interface to call the target provider 🔄
4. Response formatting - converts LiteLLM's standardized response back to Anthropic format 🔄
5. Returning the formatted response to the client ✅

• Streaming Support: Full support for streaming responses via LiteLLM's streaming capabilities
• Provider Fallbacks: Can fallback between providers (e.g., Google → OpenAI) if needed
• Model Prefix Handling: Automatically adds provider prefixes (openai/, gemini/) for LiteLLM routing
• Flexible Configuration: Environment-based configuration for easy provider switching
• Chain-able: Can proxy to other LiteLLM instances for complex routing scenarios

The proxy maintains full compatibility with all Claude clients while providing access to the entire LiteLLM ecosystem. 🌟

Contributions are welcome! Please feel free to submit a Pull Request. 🎁