AuthBridge

A Windows desktop application that acts as a local OpenAI-compatible proxy, routing requests to Claude, ChatGPT, and Gemini using your existing browser sessions.

Features

• OpenAI-Compatible API: Expose /v1/chat/completions endpoint on localhost:8000
• Multi-Provider Support: Claude, ChatGPT, Gemini, Perplexity
• Multi-Account: Add multiple accounts per provider with round-robin load balancing
• Secure Storage: Credentials encrypted with Windows DPAPI
• System Tray: Runs quietly in your system tray

Architecture

┌─────────────────────────────────────────────────────────────────────────┐
│                         AuthBridge Application                          │
├─────────────────────────────────────────────────────────────────────────┤
│  ┌──────────────────┐    ┌──────────────────┐    ┌──────────────────┐  │
│  │  System Tray UI  │◄──►│   Core Engine    │◄──►│  Credential Vault│  │
│  │  (WinForms)      │    │                  │    │  (DPAPI)         │  │
│  └──────────────────┘    └────────┬─────────┘    └──────────────────┘  │
│                                   │                                     │
│                                   ▼                                     │
│                    ┌──────────────────────────┐                         │
│                    │   Local Proxy Server     │                         │
│                    │   (Kestrel @ :8000)      │                         │
│                    └──────────────────────────┘                         │
└─────────────────────────────────────────────────────────────────────────┘

Building

# Restore packages
dotnet restore AuthBridge.sln

# Build
dotnet build AuthBridge.sln

# Run
dotnet run --project src/AuthBridge.UI.WinForms/AuthBridge.UI.WinForms.csproj

Usage

1. Launch AuthBridge (appears in system tray)
2. Right-click tray icon → "Accounts..."
3. Add an account:
   • Select provider (claude/chatgpt)
   • Enter display name
   • Click "Connect" and enter your session credentials
4. Start the server (right-click → "Start Server")
5. Configure your AI client to use http://localhost:8000/v1

Getting Session Credentials

For Claude:

1. Log into claude.ai in your browser
2. Open DevTools (F12) → Application → Cookies
3. Copy the sessionKey cookie value

For ChatGPT:

1. Log into chat.openai.com
2. Open DevTools (F12) → Network
3. Find any API request and copy the Authorization: Bearer <token> value

API Endpoints

Endpoint	Description
POST /v1/chat/completions	Chat completion (OpenAI format)
POST /v1/completions	Legacy completion
GET /v1/models	List available models
GET /health	Health check

Model Mapping

Request Model	Provider	Target Model
gpt-5.2	ChatGPT	gpt-5.2
gpt-4.1	ChatGPT	gpt-4.1
gpt-4o	ChatGPT	gpt-4o
gpt-4-turbo	ChatGPT	gpt-4-turbo
gpt-3.5-turbo	ChatGPT	gpt-3.5-turbo
o1	ChatGPT	o1
o1-mini	ChatGPT	o1-mini
o1-pro	ChatGPT	o1-pro
o3-mini	ChatGPT	o3-mini

Request Model	Provider	Target Model
claude-sonnet-4.5	Claude	claude-sonnet-4.5
claude-opus-4.1	Claude	claude-opus-4.1
claude-haiku-4.5	Claude	claude-haiku-4.5
claude-3-7-sonnet-20250219	Claude	claude-3-7-sonnet-20250219

Request Model	Provider	Target Model
gemini-3.0	Gemini	gemini-2.5-pro
gemini-3-pro	Gemini	gemini-2.5-pro
gemini-2.5-pro	Gemini	gemini-2.5-pro
gemini-2.0-flash	Gemini	gemini-2.0-flash
gemini-2.0-flash-lite	Gemini	gemini-2.0-flash-lite
gemini-2.0-pro-exp	Gemini	gemini-2.0-pro-exp
gemini-2.0-flash-thinking-exp	Gemini	gemini-2.0-flash-thinking-exp
gemini-1.5-pro	Gemini	gemini-1.5-pro
gemini-1.5-flash	Gemini	gemini-1.5-flash

Request Model	Provider	Target Model
pplx-7b-online	Perplexity	sonar
pplx-sonar	Perplexity	sonar
pplx-sonar-pro	Perplexity	sonar-pro
pplx-sonar-reasoning	Perplexity	sonar-reasoning
pplx-sonar-reasoning-pro	Perplexity	sonar-reasoning-pro
pplx-r1-1776	Perplexity	r1-1776

Configuration

Settings stored in %LOCALAPPDATA%\AuthBridge\settings.json:

{
  "ProxyPort": 8000,
  "AutoStart": false,
  "MinimizeToTray": true,
  "LoadBalanceStrategy": "RoundRobin",
  "RequestTimeoutSeconds": 120
}

Project Structure

AuthBridge/
├── src/
│   ├── AuthBridge.Core/        # Models, configuration, services
│   ├── AuthBridge.Security/    # DPAPI credential vault
│   ├── AuthBridge.Auth/        # OAuth callback server
│   ├── AuthBridge.Gateways/    # Provider implementations
│   ├── AuthBridge.Proxy/       # Kestrel HTTP server
│   └── AuthBridge.UI.WinForms/ # System tray application
└── docs/

Security Notes

• Credentials are encrypted using Windows DPAPI (tied to your user account)
• Proxy only binds to localhost (not accessible from network)
• Session tokens are stored securely, not logged

License

MIT

Disclaimer

AuthBridge is a local personal-use tool.
It does not circumvent provider restrictions and does not include any session tokens.
Users must ensure they comply with the Terms of Service of each provider.