Browser Preview

You already know preview_serve and preview_stop. This skill fills the gap: what happens after preview_serve returns a URL — how the user actually sees it.

What is the Preview Panel

The frontend has a right-side panel with three tabs: Files, Preview, and Jobs. The Preview tab renders preview URLs inside an iframe. When you call preview_serve, the frontend automatically opens a Preview tab loading that URL.

Key facts:

• Each preview_serve call creates one Preview tab
• URL format: https://<host>/preview/{id}/
• Preview panel has a ⋮ menu (top-right) showing "RUNNING SERVICES" list
• Preview tab can be closed by the user without stopping the backend service
• Backend service stopping → Preview tab shows an error page

⚠️ CRITICAL: Never Tell Users to Access localhost

The user's browser CANNOT access localhost or 127.0.0.1. These addresses point to the server container, not the user's machine. The preview architecture uses a reverse proxy: