anthropic-bridge

A proxy server that exposes an Anthropic Messages API-compatible endpoint while routing requests to various LLM providers through OpenRouter.

Features

• Anthropic Messages API compatible (/v1/messages)
• Streaming SSE responses
• Tool/function calling support
• Multi-round conversations
• Support for multiple providers: Gemini, OpenAI, Grok, DeepSeek, Qwen, MiniMax
• Extended thinking/reasoning support for compatible models
• Reasoning cache for Gemini models across tool call rounds

Installation

pip install anthropic-bridge

For development:

git clone https://github.com/michaelgendy/anthropic-bridge.git
cd anthropic-bridge
pip install -e ".[test,dev]"

Usage

Set your OpenRouter API key and start the server:

export OPENROUTER_API_KEY=your_key
anthropic-bridge --port 8080 --host 127.0.0.1

Then point your Anthropic SDK client to http://localhost:8080:

from anthropic import Anthropic

client = Anthropic(
    api_key="not-used",
    base_url="http://localhost:8080"
)

response = client.messages.create(
    model="google/gemini-2.5-pro-preview",  # Any OpenRouter model
    max_tokens=1024,
    messages=[{"role": "user", "content": "Hello!"}]
)

API Endpoints

Endpoint	Method	Description
/	GET	Health check
/health	GET	Health check
/v1/messages	POST	Anthropic Messages API
/v1/messages/count_tokens	POST	Token counting (approximate)

Configuration

Environment Variable	Required	Description
OPENROUTER_API_KEY	Yes	Your OpenRouter API key

CLI Flag	Default	Description
--port	8080	Port to run on
--host	127.0.0.1	Host to bind to

Supported Models

Any model available on OpenRouter can be used. Provider-specific optimizations exist for:

• Google Gemini (google/*) - Reasoning detail caching
• OpenAI (openai/*) - Extended thinking support
• xAI Grok (x-ai/*) - XML tool call parsing
• DeepSeek (deepseek/*)
• Qwen (qwen/*)
• MiniMax (minimax/*)

License

MIT