Holix Studio Frontend Backend

When to use (always in Studio)

Apply this skill whenever you start, fix, or demo a web frontend (or FE+API) in Holix Studio:

• User asks to run the app, open the UI, “подними фронт”, “запусти preview”, “открой в браузере”
• Project has Vite / Next / Nuxt / CRA / static SPA ± API
• You are about to say the app is ready

This skill is platform / required: do not ignore it for Studio web work.

Non‑negotiable rules

1. Listen on 0.0.0.0 (never only 127.0.0.1) for any process that Studio Preview must reach
   (Vite/Nuxt host: '0.0.0.0', uvicorn --host 0.0.0.0, nginx published port, etc.).
2. Always form real preview links in chat after the app listens:
   • Call MCP open_preview_url(port=…) (and for FE+BE, for every public port users need).
   • Paste into the chat reply: frame_url / public origin from the tool result (Markdown link).
   • Never tell the user to open localhost / bare host:port as the main URL.
3. Prefer docker-compose + nginx for “run the app” demos:
   • One published port on the host (nginx).
   • Frontend and backend only on the compose network (expose, not host-publish unless needed).
   • Nginx routes UI + API on the same origin (/ → FE, /api/ → BE) so the browser does not need a separate API host when possible.
4. Do not use Desktop / noVNC for web apps — only Studio → Browser via open_preview_url.
5. Do not claim “preview is ready” without a successful tool result that includes the public URL.

Preferred architecture (FE + BE)

Browser → Studio preview (public HTTPS) → host:PORT → nginx container
                                              ├─ /        → frontend:3000
                                              └─ /api/    → backend:8000

Single public port → one open_preview_url → one link in chat.

docker-compose.yml (template — adapt ports/paths)

Write under the project (e.g. docker-compose.yml or deploy/docker-compose.studio.yml):

services:
  frontend:
    build: ./frontend   # or image + command for node
    # CRITICAL: app inside container must listen 0.0.0.0
    environment:
      - HOST=0.0.0.0
      - PORT=3000
      # Prefer same-origin /api via nginx — no absolute localhost API
      - VITE_API_URL=/api
      - NEXT_PUBLIC_API_URL=/api
    expose:
      - "3000"
    # no ports: on host — only nginx publishes

  backend:
    build: ./backend
    environment:
      - HOST=0.0.0.0
      - PORT=8000
    expose:
      - "8000"

  nginx:
    image: nginx:alpine
    depends_on:
      - frontend
      - backend
    ports:
      # Published port = Studio preview port (pick free project port)
      - "8080:80"
    volumes:
      - ./deploy/nginx.studio.conf:/etc/nginx/conf.d/default.conf:ro

nginx.studio.conf (template)

server {
    listen 80;
    server_name _;
    client_max_body_size 50m;

    # Frontend (Vite/Next/Nuxt/static)
    location / {
        proxy_pass http://frontend:3000;
        proxy_http_version 1.1;
        proxy_set_header Host $host;
        proxy_set_header X-Real-IP $remote_addr;
        proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
        proxy_set_header X-Forwarded-Proto $scheme;
        proxy_set_header Upgrade $http_upgrade;
        proxy_set_header Connection "upgrade";
    }

    # Backend API (adjust prefix to match the app)
    location /api/ {
        proxy_pass http://backend:8000/;   # trailing slash strips /api prefix if BE has no /api
        # use proxy_pass http://backend:8000;  # if BE routes already start with /api
        proxy_http_version 1.1;
        proxy_set_header Host $host;
        proxy_set_header X-Real-IP $remote_addr;
        proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
        proxy_set_header X-Forwarded-Proto $scheme;
    }

    # Optional OpenAPI / health
    location /docs {
        proxy_pass http://backend:8000/docs;
        proxy_set_header Host $host;
    }
    location /health {
        proxy_pass http://backend:8000/health;
        proxy_set_header Host $host;
    }
}

Frontend API base when nginx fronts both

Only if the user must call a separate public BE port (no nginx): set API base from MCP backend public origin (not localhost) — see “Split ports” below.

Mandatory agent workflow

A. Default: compose + nginx (propose this first)

1. Inspect project (package.json, existing Dockerfile/compose, ports).

2. Propose (and implement if user agrees / task implies run):

   • docker-compose with frontend, backend (if any), nginx
   • nginx joins FE+BE as above
   • host bind 0.0.0.0 inside services; one published host port on nginx

3. Start stack from workspace:

   • Studio Docker tools / docker compose up -d --build in the project dir
   • Or background process if user forbids Docker — still 0.0.0.0 + preview

4. Wait until nginx port accepts HTTP (health / log / check_background_process / docker ps).

5. open_preview_url(port=NGINX_HOST_PORT) (e.g. 8080).

6. In the same assistant message after tools succeed, include Markdown links, e.g.:

   **Приложение:** [открыть preview](<frame_url or public origin from tool>)
   Порт: 8080 · nginx → frontend + `/api` → backend
   

7. If FE-only (no BE), still use nginx (or the FE process on 0.0.0.0) and still call open_preview_url + link in chat.

B. Dev servers without Docker (fallback)

Only if Docker is unavailable or user forbids it:

1. Start processes with host 0.0.0.0:
   • Vite: server: { host: '0.0.0.0', port, strictPort: true, allowedHosts: true }
   • Nuxt: devServer: { host: '0.0.0.0', port }
   • uvicorn: --host 0.0.0.0 --port …
2. Prefer a small local nginx (compose one-service nginx + upstream host network) still if possible.
3. open_preview_url for each user-facing port; put all links in chat.
4. If FE and BE are separate public ports (no shared nginx origin):
   • open_preview_url for FE and BE
   • Set FE env to backend public origin from resolve_preview_origin_tool / preview_origins
   • CORS on BE must allow frontend public origin

C. Split ports (no nginx) — API base

Same as before, but secondary to nginx:

1. resolve_preview_origin_tool(port=BACKEND) or preview_origins
2. FE env = backend origin (H2 or path proxy) — never http://localhost:PORT for the browser
3. Restart FE after env change; re-open previews; link both URLs in chat

Vite / Nuxt HMR (secondary)

HMR WebSocket may fail behind Studio preview. SPA can still work without hot reload.

• Keep listen port consistent with open_preview_url
• Prefer allowedHosts: true, host 0.0.0.0
• If HMR spam: hmr: false or clientPort: 443 for wss edge — see stack docs
• Do not confuse HMR errors with broken REST API

Do NOT

• Start web servers only on 127.0.0.1 when Studio preview is required
• Advertise localhost as the user URL
• Invent H2 hostnames — only MCP open_preview_url / preview_origins
• Open web apps via Desktop/noVNC
• Install random host nginx/yadisk/rclone for “preview” when Studio Browser + compose is available
• Say “я открыл preview” without a tool result containing the URL
• Skip proposing docker-compose + nginx for FE+BE run tasks

Checklist before “done”

• Services listen on 0.0.0.0 (or via nginx published port)
• docker-compose + nginx proposed (and used when possible) for FE+BE
• Nginx routes / → FE and /api/ (or project prefix) → BE
• FE uses same-origin /api or backend public origin (not laptop localhost)
• open_preview_url called for the public port(s)
• Chat message includes clickable preview link(s) from tool output
• User told: Studio Browser / the link — not localhost

Related tools (Studio)

• MCP holix_studio: open_preview_url, list_preview_targets, preview_origins, resolve_preview_origin_tool
• Docker panel / compose tools for workspace stacks
• start_background_process / terminal only as fallback when compose is impossible

Telegram + Studio (same Holix profile)

Processes started from Telegram for a user profile must appear in Studio for that same profile (Processes panel + Browser targets):

• Holix persists a shared index: HOLIX_HOME/profiles/<profile>/data/background_processes.json
• Always use start_background_process (not detached raw nohup outside Holix)
• Bind 0.0.0.0 and call open_preview_url so Studio Browser can attach
• Workspace cwd must stay under the profile workspace so Studio can list the app

Slash

/holix-studio-frontend-backend — re-apply this workflow (ports, compose+nginx, preview links).