preview

name	preview
description	Expose a dev server running in this session at a public preview URL. Use when the user asks to run, preview, or share the project's web app/dev server.

brigade preview

This session runs inside brigade. Any HTTP server you start here can be reached from the user's browser at a deterministic preview URL — no port forwarding needed.

How to expose a dev server

1. Start the server on any free port. If this session runs in Docker, bind to 0.0.0.0, not localhost (the proxy connects over the container network):

   • vite: vite --host 0.0.0.0; also allow the preview host via server.allowedHosts: true (or list the host) in vite config;
   • next: next dev -H 0.0.0.0;
   • python: python3 -m http.server 8000 --bind 0.0.0.0.

2. Build the preview URL: take $BRIGADE_PREVIEW_URL_TEMPLATE and replace {port} with the actual port. The template is already the full, correct URL for this deployment (subdomain or single-host cookie form) — just substitute the port, do not assemble it yourself. Examples:

   • http://abc-{port}.localhost:10000 → http://abc-3000.localhost:10000
   • https://preview.example.com/?id=abc-{port} → https://preview.example.com/?id=abc-3000

3. Register the port so the link shows up in the brigade UI. This calls the brigade.v1.AgentBridgeService/RegisterPreview ConnectRPC method — plain POST with a JSON body, no client library needed:

   curl -sf -X POST "$BRIGADE_API_URL/brigade.v1.AgentBridgeService/RegisterPreview" \
     -H "Authorization: Bearer $BRIGADE_PREVIEW_TOKEN" \
     -H "Content-Type: application/json" \
     -d "{\"sessionId\": \"$BRIGADE_SESSION_ID\", \"port\": 3000, \"name\": \"vite\"}"
   

   The response contains the final URL: {"url": "..."}.

4. Tell the user the preview URL.

Notes:

• The URL works as soon as the server is listening; registration only adds the link to the UI.
• Re-register after restarting brigade if the link disappeared from the UI.