Openhost Frontend Preview

OpenHost frontend live preview (/proxy/<port>/)

Run a Vite dev server (HMR) for the Sculptor web UI and reach it from any logged-in browser — including a phone — through the OpenHost nginx front, entirely behind OpenHost's owner SSO. Nothing is exposed publicly.

When this applies — OpenHost only

Use this ONLY inside the openhost-deployed Sculptor. Quick checks:

• test -f /app/openhost-nginx.conf (the nginx front config), and
• PID 1 is nginx: ps -p 1 -o args= -> nginx ... (backend is on loopback :5051).

If those are NOT true (local dev, Electron, a plain backend on :5050), this skill does not apply — use normal pnpm run dev / just frontend there instead.

How it works (read first)

• nginx owns :5050 (the only port OpenHost proxies) and routes /proxy/<port>/* -> 127.0.0.1:<port>; everything else -> the backend on :5051.
• A preview is just a Vite dev server on a loopback port in the 51000-59999 band, served with base=/proxy/<port>/, dialing HMR back over wss://...:443/proxy/<port>/. Its /api + /ws calls are same-origin absolute, so they hit the ONE shared backend — there is no per-preview backend.
• So this previews frontend changes. Full-stack per-workspace instances (each with its own backend) are not supported on one origin: every backend would set the same session cookie on the same origin, and they collide.

What surrounds a preview (already wired — don't rebuild it)

• Switchboard + down-page: /proxy/ (no port) serves a self-contained page (openhost-preview-fallback.html, repo root) that scans the band from the browser and links to live previews. nginx serves the SAME page when a /proxy/<port>/ target is dead, with a way back and an auto-reload poll that returns to the preview once its server is back.
• Identity meta: each preview's index.html carries <meta name="sculptor-preview" content="<branch>@<sha>[*]"> (* = dirty tree), injected per request by previewIdentity in sculptor/frontend/vite.base.config.ts under SCULPTOR_OPENHOST_PROXY. A tree with no .git reports the frontend dir it serves from instead — e.g. /app/sculptor/frontend for a preview of the deploy image, which ships no git history. The switchboard and the switcher extension show this label.
• Preview-switcher pill: the openhost-preview-switcher extension (sculptor/frontend/extensions/, auto-installed at boot by openhost-run.sh) renders a bottom-left pill in the deployed app listing live previews in 51000-51099, and an amber badge with a way back when ON a preview. Switching preserves the #/ route.
• HMR keepalive: the dev server sends a no-op custom HMR event to every client every 25s (previewHmrKeepalive in sculptor/frontend/vite.base.config.ts, also SCULPTOR_OPENHOST_PROXY-gated). Without it the idle HMR websocket gets killed by the edge and Vite hard-reloads the page about once a minute (and on every return from the background). If "random reloads" ever reappear, check the keepalive before suspecting app code.

Run a preview

Use a port in the 51000-51099 band. The preview-switcher pill in the deployed app only auto-discovers that range (and the /proxy/ switchboard page, openhost-preview-fallback.html, quick-scans it on load), so a preview there shows up without a full-band scan. A higher port (51100-59999) still works, but it will not appear in the pill — you'd reach it only via the switchboard's full-band scan or a direct /proxy/<port>/ URL, so don't reach for a random high port. The zero-friction way to get a valid one is to let the script pick: run launch-preview.sh with no argument and it auto-selects a free 51000-51099 port (printed to the log).

Launch it DETACHED — do NOT use a tracked background task; this Sculptor will not release your turn to the user while one is alive:

cd <frontend-dir>
setsid bash launch-preview.sh 51042 >/tmp/vite-51042.log 2>&1 </dev/null &

(or setsid bash launch-preview.sh >/tmp/vite-preview.log 2>&1 </dev/null & with no port to auto-pick a free 510xx one — then read the chosen port and the ready in line from the log.)

<frontend-dir> is either:

• /app/sculptor/frontend — preview the deployed UI as-is (its node_modules and .venv are already there, so it starts fast), or
• your workspace's sculptor/frontend — preview YOUR edits with HMR. A fresh worktree has no node_modules, so run pnpm install there once first (slow), then launch.

launch-preview.sh [port] sets SCULPTOR_FRONTEND_PORT + SCULPTOR_OPENHOST_PROXY and runs pnpm run dev — the /proxy/<port>/ base AND the OpenHost wss/HMR override are both derived from those env vars in vite.base.config.ts, so do NOT pass --base yourself (pnpm forwards a stray -- that Vite reads as end-of-options and silently drops the flag). First start pre-bundles deps (~tens of seconds) — watch /tmp/vite-<port>.log for ready in. Then open, on any logged-in browser:

https://sculptor.<your-zone>/proxy/51042/

Edits to the frontend source hot-reload live.

Stop a preview

Do NOT pkill -f vite... — the pattern matches your own shell command and kills the call. Stop by port -> pid -> process group:

PID=$(ss -tlnpH | grep ':51042' | grep -oE 'pid=[0-9]+' | head -1 | cut -d= -f2)
PGID=$(ps -o pgid= -p "$PID" | tr -d ' ')
kill -9 -"$PGID"

Gotchas

• Detached, not background. Launch via setsid ... & from a normal foreground command so your turn releases. A run_in_background task or persistent Monitor blocks the user from talking to you until it ends.
• One browser per workspace page. Sculptor syncs tab state via localStorage, so the same workspace open in two browsers can desync — preview on a different page/tab than the one you're chatting in.
• Same-origin trust. Previews share the app's origin, so preview JS runs with your session's privileges — only run frontend code you trust.