AnyRouter Transparent Proxy

A lightweight transparent HTTP proxy service based on FastAPI, specifically designed to resolve the 500 error issue with AnyRouter's Anthropic API in the Claude Code for VS Code plugin.

Demo Screenshots

Core Features
Project Structure
Quick Start
- Docker Deployment (Recommended)
- Local Setup
Configuration
Core Functionality
Usage Example
Architecture & Technology
Security
Contributing

Core Features

Fully Transparent - Supports all HTTP methods, seamlessly proxies requests
Streaming Response - Asynchronous architecture based on httpx.AsyncClient, perfect streaming support
Standards Compliant - Strictly follows RFC 7230 specification, correctly handles HTTP headers
Flexible Configuration - Supports environment variable configuration for target URL and System Prompt replacement
High Performance - Connection pool reuse, asynchronous processing, efficiently handles concurrent requests
Intelligent Processing - Automatically calculates Content-Length, avoiding protocol errors caused by request body modifications
Web Management Dashboard - Provides real-time monitoring, statistics analysis, and configuration management

Project Structure

AnyRouter-Transparent-Proxy/
├── backend/              # Backend service (FastAPI)
│   ├── app.py           # Core proxy logic
│   └── requirements.txt # Python dependencies
├── frontend/            # Frontend project (Vue 3 + TypeScript)
│   ├── src/            # Source code
│   ├── package.json    # Frontend dependencies
│   └── vite.config.ts  # Vite configuration
├── env/                 # Configuration files directory
│   ├── .env             # Environment variables config (copy from .env.example)
│   └── .env.headers.json # Custom request headers configuration
├── docs/                # Documentation
├── static/              # Frontend build artifacts (.gitignore)
├── Dockerfile           # Docker image build
├── docker-compose.yml   # Docker Compose configuration
├── .env.example         # Environment variable template
└── CLAUDE.md           # AI context index

Notes:

backend/ - Backend Python service, handles proxy logic and API processing
frontend/ - Frontend Vue project, provides Web management dashboard
static/ - Frontend build artifacts, automatically generated during Docker build, not committed to Git
env/ - Runtime configuration files directory

Quick Start

Docker Deployment (Recommended)

Using Docker Compose:

# Clone the project
git clone <repository-url>
cd AnyRouter-Transparent-Proxy

# Copy environment variable template (optional)
cp .env.example env/.env

# Edit env/.env file to modify configuration (optional)
# Default uses https://anyrouter.top

# Start the service
docker-compose up -d
# If you modified the source code after deployment, rebuild with --build --remove-orphans
docker-compose up -d --build --remove-orphans

# View logs
docker-compose logs -f

# Stop the service
docker-compose down

# Restart the service
docker-compose down && docker-compose up -d

Or using Docker commands:

# Build and run
docker build -t anthropic-proxy .
docker run -d --name anthropic-proxy -p 8088:8088 anthropic-proxy

# Custom target URL
docker run -d --name anthropic-proxy -p 8088:8088 \
  -e API_BASE_URL=https://anyrouter.top \
  anthropic-proxy

The service will start at http://localhost:8088, then configure this address in Claude Code.

~~Access the management dashboard at http://localhost:8088/admin.~~

The management dashboard can now be accessed directly from the homepage http://localhost:8088 with automatic redirection.

Local Setup

Requirements: Python 3.7+

# Install dependencies
pip install -r backend/requirements.txt

# Or install manually
pip install fastapi uvicorn httpx python-dotenv

# Copy environment variable template
cp env/.env.example env/.env

# Start the service (run from project root directory)
python -m backend.app

The service will start at http://localhost:8088.

Note: For local development, if you need to use the Web management dashboard, you need to build the frontend first:

cd frontend
npm install
npm run build
cd ..

The build artifacts will be output to the static/ directory (this directory is ignored in .gitignore).

~~Access the management dashboard at http://localhost:8088/admin.~~

The management dashboard can now be accessed directly from the homepage http://localhost:8088 with automatic redirection.

Configuration

Environment Variables

Create a env/.env file or set environment variables:

# API target address (default: https://anyrouter.top) or use reverse proxy address
API_BASE_URL=https://anyrouter.top

# System Prompt replacement (optional)
# Replaces the text content of the first element in the system array in the request body
SYSTEM_PROMPT_REPLACEMENT="You are Claude Code, Anthropic's official CLI for Claude."

# If you need to access through a proxy, please uncomment the two lines below and set the proxy address
# HTTP_PROXY=http://127.0.0.1:7890
# HTTPS_PROXY=http://127.0.0.1:7890

# Debug mode (default: false)
DEBUG_MODE=false

# Service port (default: 8088)
PORT=8088

# Enable Web management dashboard (default: true)
ENABLE_DASHBOARD=true

# Enable log persistence (default: true)
LOG_PERSISTENCE_ENABLED=true

# Log storage path (default: data/logs)
LOG_STORAGE_PATH=data/logs

# Log retention days (default: 7)
LOG_RETENTION_DAYS=7

# Daily log limit (default: 1000)
LOG_DAILY_LIMIT=1000

Custom Request Headers (Optional)

You can configure custom request headers through the env/.env.headers.json file, which will be injected into all proxied requests.

Configuration Steps:

Copy the template file to create configuration:

cp .env.headers.json.example env/.env.headers.json

Edit the env/.env.headers.json file and add the headers you need:
```
{
  "User-Agent": "claude-cli/2.0.8 (external, cli)"
}
```
Restart the service for the configuration to take effect

Notes:

Configuration file uses standard JSON format
Fields starting with __ will be ignored (can be used for comments)
If the file doesn't exist, defaults to empty configuration {}
Custom request headers will override headers with the same name in the original request

Note: Service restart required after configuration changes

Core Functionality

System Prompt Replacement

Dynamically replaces the text content of the first element in the system array in Anthropic API request bodies:

Customize Claude Code CLI behavior
Adjust Claude Agent SDK responses
Uniformly inject system-level prompts

Enable this feature by configuring the SYSTEM_PROMPT_REPLACEMENT variable.

Intelligent Request Header Handling

Automatic Filtering - Removes hop-by-hop headers (Connection, Keep-Alive, etc.)
Host Rewriting - Automatically rewrites to target server domain
Content-Length Auto-calculation - Automatically calculates based on actual content, avoiding length mismatches
Custom Injection - Supports overriding or adding arbitrary request headers
IP Tracking - Automatically maintains X-Forwarded-For chain

Usage Example

Change requests originally pointing to anyrouter.top or other APIs to point to the proxy service:

# Original request
curl https://anyrouter.top/v1/messages \
  -H "x-api-key: $ANTHROPIC_API_KEY" \
  -H "content-type: application/json" \
  -d '{"model": "claude-3-5-sonnet-20241022", "messages": [...]}'

# Through proxy
curl http://localhost:8088/v1/messages \
  -H "x-api-key: $ANTHROPIC_API_KEY" \
  -H "content-type: application/json" \
  -d '{"model": "claude-3-5-sonnet-20241022", "messages": [...]}'

Architecture & Technology

Request Processing Flow

Client Request
    ↓
proxy() catches route
    ↓
filter_request_headers() filters request headers
    ↓
process_request_body() processes request body (optional system prompt replacement)
    ↓
Rewrite Host header + Inject custom headers + Add X-Forwarded-For
    ↓
httpx.AsyncClient initiates upstream request via build_request() + send(stream=True)
    ↓
filter_response_headers() filters response headers
    ↓
StreamingResponse streams back to client with BackgroundTask for automatic connection cleanup

Key Technologies

Routing - @app.api_route("/{path:path}") catches all paths and HTTP methods
Lifecycle Management - Uses FastAPI lifespan events to manage HTTP client lifecycle
Connection Pool Reuse - Globally shared httpx.AsyncClient for connection reuse
Asynchronous Requests - 60-second timeout, supports long-running streaming responses
Streaming Transfer - build_request() + send(stream=True) + aiter_bytes() + BackgroundTask efficiently handles large payloads with automatic connection lifecycle management
Header Filtering - RFC 7230 compliant, bidirectional filtering of hop-by-hop headers

Technical Details

Request Header Filtering Rules (RFC 7230):

Removed headers: Connection, Keep-Alive, Proxy-Authenticate, Proxy-Authorization, TE, Trailers, Transfer-Encoding, Upgrade, Content-Length (automatically recalculated by httpx)

System Prompt Replacement Logic:

Check SYSTEM_PROMPT_REPLACEMENT configuration
Parse request body as JSON
Verify system field exists and is a non-empty array
Replace system[0].text content
Re-serialize to JSON

Falls back to original request body on failure, ensuring service stability.

HTTP Client Lifecycle:

Creates shared httpx.AsyncClient instance on startup
All requests reuse the same client during runtime, benefiting from connection pooling
Gracefully releases all connection resources on shutdown

Log Output Example

[Proxy] Original body (123 bytes): {...}
[System Replacement] Successfully parsed JSON body
[System Replacement] Original system[0].text: You are Claude Code...
[System Replacement] Replaced with: 你是一个有用的AI助手
[System Replacement] Successfully modified body (original size: 123 bytes, new size: 145 bytes)

Security

Redirect Attack Prevention - follow_redirects=False
Request Timeout - 60-second timeout prevents resource exhaustion
Error Handling - Returns 502 status code when upstream request fails
Automatic Fault Tolerance - Content-Length auto-calculation avoids protocol errors
Connection Management - Shared client pool ensures connections are properly closed
Logging - Detailed debugging information (recommend removing sensitive info in production)

Contributing

Issues and Pull Requests are welcome!

Note: This project is for learning and development testing purposes only. Please ensure compliance with the terms of service of related services.

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AnyRouter Transparent Proxy

Demo Screenshots

Table of Contents

Core Features

Project Structure

Quick Start

Docker Deployment (Recommended)

Local Setup

Configuration

Environment Variables

Custom Request Headers (Optional)

Core Functionality

System Prompt Replacement

Intelligent Request Header Handling

Usage Example

Architecture & Technology

Request Processing Flow

Key Technologies

Technical Details

Log Output Example

Security

Contributing

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README_en.md

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README_en.md

File metadata and controls

AnyRouter Transparent Proxy

Demo Screenshots

Table of Contents

Core Features

Project Structure

Quick Start

Docker Deployment (Recommended)

Local Setup

Configuration

Environment Variables

Custom Request Headers (Optional)

Core Functionality

System Prompt Replacement

Intelligent Request Header Handling

Usage Example

Architecture & Technology

Request Processing Flow

Key Technologies

Technical Details

Log Output Example

Security

Contributing