OpenMatthew

Disclaimer: This is an unofficial, community-made project. It is not affiliated with, endorsed by, or supported by Chiang Mai University or the Matthew AI team. Use it with your own CMU account at your own discretion. The authors take no responsibility for any account suspension or policy violations that may result from its use.

OpenCode plugin for CMU Matthew AI authentication — access GPT-5.2, GPT-4.1 and more using your Chiang Mai University credentials.

What is this?

This is an OpenCode plugin that enables authentication against Matthew AI, Chiang Mai University's generative AI platform. It allows you to use Matthew's AI models (GPT-5.2, GPT-5 Mini, GPT-4.1, GPT-4o, GPT-4o Mini) directly from OpenCode using your CMU account.

Inspired by opencode-antigravity-auth.

Prerequisites

• OpenCode installed
• A CMU Account (@cmu.ac.th)

No additional credentials or registration needed — the plugin uses Matthew's existing OAuth configuration.

Installation

Option A: Let an LLM do it

Paste this into any LLM agent (Claude Code, OpenCode, Cursor, etc.):

Install the opencode-matthew-auth plugin and add the Matthew AI model definitions to ~/.config/opencode/opencode.json by following: https://raw.githubusercontent.com/ChindanaiNaKub/OpenMatthew/main/README.md

Option B: Manual setup

1. Add the plugin to ~/.config/opencode/opencode.json:

   {
     "plugin": ["opencode-matthew-auth"]
   }

2. Login with your CMU account:

   opencode auth login

3. Add models — copy the full configuration below, or manually add to your opencode.json:

   {
     "provider": {
       "matthew": {
         "name": "CMU Matthew AI",
         "models": {
           "gpt-5.2": { "name": "GPT-5.2" },
           "gpt-5-mini": { "name": "GPT-5 Mini" },
           "gpt-4.1": { "name": "GPT-4.1" },
           "gpt-4o": { "name": "GPT-4o" },
           "gpt-4o-mini": { "name": "GPT-4o Mini" }
         }
       }
     }
   }

4. Use it:

   opencode run "Hello" --model=matthew/gpt-5.2

Step-by-Step Instructions

1. Edit the OpenCode configuration file at ~/.config/opencode/opencode.json

   Note: This path works on all platforms. On Windows, ~ resolves to your user home directory (e.g., C:\Users\YourName).

2. Add "opencode-matthew-auth" to the plugin array

3. Add the model definitions from the Available Models section under provider.matthew

4. Set provider to "matthew" and choose a model

Verification

opencode run "Hello" --model=matthew/gpt-5.2

Usage

1. Run opencode auth login → select "Login with CMU Account"
2. Browser opens matthew.cmu.ac.th → login with your CMU Account (+ MFA)
3. After login, press F12 → Console tab → paste this and press Enter:

   copy(localStorage.user)

4. Go back to OpenCode and press Ctrl+V to paste
5. Done! Select a model like matthew/gpt-5.2 and start coding

Pro tip: Bookmarklet (one-time setup)

Drag this link to your bookmarks bar to skip the console step next time:

javascript:void(navigator.clipboard.writeText(localStorage.user).then(()=>alert('Copied! Paste into OpenCode.')))

Create a bookmark, name it "Copy Matthew Token", and paste the above as the URL. After logging into Matthew, just click the bookmark → paste into OpenCode.

How it works

Authentication Flow

User → opencode auth login
  → Browser opens matthew.cmu.ac.th
  → User logs in with CMU Account (Microsoft SSO + MFA)
  → Token saved in browser localStorage
  → User copies token (console or bookmarklet)
  → Pastes into OpenCode → stored locally

Key Technical Details

• Auth provider: Microsoft Azure AD (tenant: cf81f1df-de59-4c29-91da-a2dfd04aa751)
• OAuth method: Authorization Code flow (code-based, no PKCE needed from client side)
• Token exchange: Handled by Matthew's backend at /api/oauth_callback
• API auth: Bearer token (Authorization: Bearer <token>)
• Chat API: SSE streaming via /api/thread_sse_response_stream

Matthew API Endpoints

| Endpoint | Method | Description | |----------|--------|-------------| | /api/oauth_callback | POST | Exchange auth code for access token | | /api/thread_sse_message | POST | Send a message to a thread | | /api/thread_sse_response_stream | GET (SSE) | Stream AI response | | /api/assistants | GET | List available AI assistants | | /api/apps | GET | List available apps |

Available Models

| Model | Description | |-------|-------------| | matthew/gpt-5.2 | GPT-5.2 — newest reasoning model for complex tasks | | matthew/gpt-5-mini | GPT-5 Mini — reasoning small model for everyday tasks | | matthew/gpt-4.1 | GPT-4.1 — smartest non-reasoning model | | matthew/gpt-4o | GPT-4o — high performance, supports images and tool calls | | matthew/gpt-4o-mini | GPT-4o Mini — lighter model, lower token usage |

Configuration

| Variable | Required | Description | |----------|----------|-------------| | MATTHEW_OAUTH_CLIENT_ID | No | Override the Azure AD client ID | | MATTHEW_API_BASE | No | Override the Matthew API base URL |

Development

npm install        # Install dependencies
npm run typecheck  # Type-check
npm run build      # Build to dist/

License

MIT