Deploy Fullstack Vercel

What the source does

• FilesystemNone observedNo reads or writes in the source
• NetworkNone observedNo outbound calls in the source
• ShellNone observedNo commands run in the source
• DependenciesPinnedNothing floats
• SecretsNone foundNo keys in source

Five audit layers

Gates applied: no behavioural pass.

assistant/CLAUDE.md

assistant/src/approvals/CLAUDE.md

assistant/src/notifications/CLAUDE.md

assistant/src/runtime/CLAUDE.md

gateway/CLAUDE.md

Audit 0.4.1 · source sha 19bc86343b63 · 14 Oct 2026Report an issue or request a re-scan

• Publishervellum-ai GitHub organizationOwner of the repository this skill is read from
• Source foldervellum-ai/vellum-assistant/skills/deploy-fullstack-vercelThe exact folder we audited
• LicenceMITAs the repository states it
• Commit pinned for this verdict19bc86343b63A new audit runs when the source changes
• Repository statusNot archivedLast push 1 day ago
• Sandboxed runNot runSkills are read, not executed; layer L4 is skipped

Its description: Build and deploy a full-stack app (React frontend + Python/FastAPI backend) or a Vellum app to Vercel as a serverless demo with seeded data

---
name: deploy-fullstack-vercel
description: Build and deploy a full-stack app (React frontend + Python/FastAPI backend) or a Vellum app to Vercel as a serverless demo with seeded data
compatibility: "Designed for Vellum personal assistants"
metadata:
  emoji: "🚀"
  vellum:
    category: "development"
    display-name: "Deploy Fullstack to Vercel"
---

# Deploy Fullstack to Vercel

Deploy a full-stack app with a React/Vite frontend and Python/FastAPI backend to Vercel as a serverless demo, OR deploy a Vellum-built app from the library. No auth required - meant for demos, portfolio pieces, and quick showcases.

## When to Use

- User says "deploy this to Vercel", "host this", "publish this"
- User has a project with a frontend + backend they want live
- User wants to deploy a Vellum app that uses backend features (data store, custom routes)
- User wants a quick demo deployment (no persistent database needed)

## Authentication

### Vellum App Publishing

For publishing Vellum apps from the library, use the built-in `publish_page` tool. This is the preferred path — it uses the stored Vercel API token (`vercel/api_token`) via the brokered publish flow without exposing the token to shell commands.

**The stored Vercel API token is reserved for brokered `publish_page` and `unpublish_page` actions only.** Do not pass it to `bash`, `curl`, Vercel CLI commands, or proxy credential injection. Do not use `network_mode: "proxied"` with `credential_ids` for Vercel deployments.

### Custom Full-Stack Deployments

For custom projects that need Vercel deployment (not Vellum app publishing):

1. Install the Vercel CLI with `bun install -g vercel` (not npm — npm is not available in the sandbox).
2. Use `vercel login` to authenticate interactively (opens browser for the user).
3. If the user does not want to use CLI auth, stop and ask them for an approved deployment path. Do not extract, inject, or shell with the stored API token.

## Deploying a Vellum App

When the user asks to deploy a Vellum app from their library (from `/workspace/data/apps/<app-name>/`):

### 1. Detect Vellum Bridge Usage

Check the compiled app for Vellum bridge API usage:

```bash
grep -l "window\.vellum\.\|vellum\.fetch\|vellum\.data\|vellum\.sendAction" /workspace/data/apps/<app-name>/dist/*.js /workspace/data/apps/<app-name>/dist/*.html 2>/dev/null
```

If found, the app depends on the Vellum bridge and needs a shim to work standalone.

### 2. Create Vellum Bridge Shim

The app uses `window.vellum.*` APIs that are normally injected by the Vellum viewer. For standalone deployment, create a `vellum-shim.js` file in the app's `dist/` directory that provides browser-native replacements.

**Before writing the shim, read the app's compiled JavaScript** (`dist/main.js` or equivalent) to understand exactly which `window.vellum.*` APIs the app calls and what data shapes it expects. The shim must match the app's actual usage — don't guess at signatures.

**Common APIs to shim (implement only what the app actually uses):**

| Bridge API                    | Standalone replacement                                | Notes                                                                                                                    |
| ----------------------------- | ----------------------------------------------------- | ------------------------------------------------------------------------------------------------------------------------ |
| `vellum.data.query()`         | localStorage-backed store                             | Read the app code to determine the record shape — some apps expect `{id, data: {...}}` wrappers, others use flat records |
| `vellum.data.create(...)`     | localStorage insert with `crypto.randomUUID()`        | Match the argument signature the app passes (some pass a payload, others pass `{id, ...fields}`)                         |
| `vellum.data.update(...)`     | localStorage update                                   | Match the argument signature (typically `(id, payload)`)                                                                 |
| `vellum.data.delete(...)`     | localStorage delete                                   | Typically `(id)`                                                                                                         |
| `vellum.fetch(path, opts)`    | `console.warn` + return empty success Response        | Custom routes aren't available standalone                                                                                |
| `vellum.sendAction(id, data)` | No-op with `console.warn`                             | Surface actions aren't available standalone                                                                              |
| `vellum.openLink(url)`        | `window.open(url, '_blank')`                          |                                                                                                                          |
| `vellum.widgets.toast(msg)`   | Create a temporary styled `<div>` that auto-dismisses |                                                                                                                          |
| `vellum.route`                | `null`                                                | Deep-link routes aren't available standalone                                                                             |

**Structure:** Wrap everything in an IIFE that guards against the real bridge: `(function() { if (window.vellum) return; ... })();`

### 3. Inject the Shim into index.html

Add a `<script src="vellum-shim.js"></script>` tag in `dist/index.html` BEFORE any `<script type="module">` tags:

```bash
sed -i 's|<script type="module"|<script src="vellum-shim.js"></script>\n<script type="module"|' dist/index.html
```

### 4. Deploy the App

```bash
cd /workspace/data/apps/<app-name>/dist
```

Create a `vercel.json` in the dist directory:

```json
{
  "rewrites": [
    {
      "source": "/((?!main\\.js|main\\.css|vellum-shim\\.j

Excerpt, first 6,001 characters of SKILL.md, verbatim from the audited commit. It is text from someone else’s repository, quoted so you can judge it before your agent reads it.

git clone https://github.com/vellum-ai/vellum-assistant
git -C vellum-assistant checkout 19bc86343b63

Works in

1. 2026-10-14
   ✓SAFE B 89 / 100

   first audit · source 19bc86343b63

Questions about Deploy Fullstack Vercel

• github.com/vellum-ai/vellum-assistant/tree/main/skills/deploy-fu — the audited source at commit 19bc86343b63 and every finding aboveObserved · 14 Oct 2026

Spotted something wrong? Report a correction · Methodology