Extension Host (Vertex Swarm)

VS Code Extension Host runtime - handles OAuth, token management, and SSE streaming relay.

Architecture

Extension Host (Node.js/TypeScript)
├── token-manager.ts       # SecretStorage integration (OS keychain)
├── oauth-handler.ts       # Neon Auth OAuth 2.0 flow
├── sse-client/stream.ts   # EventSource → postMessage relay
└── extension.ts           # Main entry point + webview creation

Data Flow

1. Authentication:

   • Webview requests token → Extension opens browser OAuth flow
   • OAuth callback → token exchange → stored in SecretStorage
   • Token sent to Webview via postMessage

2. Streaming:

   • Webview sends start-stream message
   • Extension opens SSE connection to Backend /api/v1/chats/{chatId}/messages
   • Events parsed and relayed to Webview via postMessage
   • Webview updates Zustand store → React re-renders

3. Cancellation:

   • Webview sends cancel-stream message
   • Extension sends POST to Backend /api/v1/chats/{chatId}/cancel
   • Stream closes

Key Files

• token-manager.ts - Handles secure token storage using VS Code SecretStorage (OS keychain)
• oauth-handler.ts - Opens browser, listens for callback, exchanges code for JWT
• sse-client/stream.ts - Opens EventSource connection, parses events, relays via postMessage
• extension.ts - Webview panel creation, message routing, lifecycle management

Security Model

• Token Storage: OS keychain via SecretStorage (NOT in Webview)
• Relay Pattern: Extension Host holds token, never sends to Webview
• Webview: React UI only receives events/data, no sensitive credentials

Build

npm install
npm run build

Development

npm run dev

In VS Code, use the Run Vertex Swarm Extension debug configuration from .vscode/launch.json. It starts the extension host once and watches both the extension bundle and the frontend bundle in the background.