deploy-fullstack-vercel · git:20260511.854e970 · 2026-05-11 · sha256 6e7abf2e708817b3
deploy-fullstack-vercel git:20260511.854e970B
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---
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:
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
Before deploying, check for a Vercel API credential:
1. Run `credential_store list` and look for a `vercel/api_token` entry.
2. If found with `injection_templates`, the credential can be used automatically via `network_mode: "proxied"` with `credential_ids`.
3. If no credential exists, use `credential_store prompt` to ask the user for their Vercel API token. Direct them to https://vercel.com/account/tokens to create one.
4. Fall back to the Vercel CLI only if no usable credential exists. Install with `bun install -g vercel` (not npm — npm is not available in the sandbox).
## 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\\.js|assets/).*)",
"destination": "/index.html"
}
]
}
```
Then deploy using the Vercel API credential (preferred) or CLI.
## Deploying a Custom Full-Stack Project
### 1. Build the Frontend
```bash
cd <project>/frontend
bun install
bunx vite build
```
This produces static files in `frontend/dist/`.
### 2. Create the Vercel Deploy Directory
```
<project>/vercel-deploy/
├── api/
│ ├── index.py ← FastAPI app wrapper (entry point)
│ ├── database.py ← DB config (use /tmp for SQLite)
│ ├── models.py
│ ├── schemas.py
│ ├── seed_data.py ← Must seed ALL required data (users, etc.)
│ ├── routers/
│ │ ├── __init__.py
│ │ └── *.py
│ └── requirements.txt ← Python deps (fastapi, sqlalchemy, pydantic)
├── index.html ← From frontend/dist/
├── assets/ ← From frontend/dist/assets/
└── vercel.json
```
**Key steps:**
```bash
mkdir -p <project>/vercel-deploy/api
# Copy frontend build output to deploy root
cp -r <project>/frontend/dist/* <project>/vercel-deploy/
# Copy backend files into api/
cp <project>/backend/models.py <project>/vercel-deploy/api/
cp <project>/backend/database.py <project>/vercel-deploy/api/
cp <project>/backend/schemas.py <project>/vercel-deploy/api/
cp <project>/backend/seed_data.py <project>/vercel-deploy/api/
cp -r <project>/backend/routers <project>/vercel-deploy/api/
cp <project>/backend/requirements.txt <project>/vercel-deploy/api/
```
### 3. Create api/index.py (Serverless Entry Point)
```python
import sys, os
sys.path.insert(0, os.path.dirname(__file__))
from fastapi import FastAPI
from fastapi.middleware.cors import CORSMiddleware
from database import engine, Base, SessionLocal
from seed_data import seed_exercises, seed_default_user # all seed functions
from routers import users, exercises, workouts, schedule, progress
# Create tables and seed on EVERY cold start
Base.metadata.create_all(bind=engine)
db = SessionLocal()
try:
seed_exercises(db)
seed_default_user(db) # IMPORTANT: seed all required data
finally:
db.close()
app = FastAPI(title="MyApp")
app.add_middleware(
CORSMiddleware,
allow_origins=["*"],
allow_credentials=True,
allow_methods=["*"],
allow_headers=["*"],
)
app.include_router(users.router)
# ... other routers
@app.get("/api/health")
def health_check():
return {"status": "ok"}
```
### 4. Update database.py for Vercel
**Critical:** Vercel serverless functions can only write to `/tmp`. Update the SQLite path:
```python
SQLALCHEMY_DATABASE_URL = "sqlite:////tmp/app.db"
```
### 5. Seed ALL Required Data
**This is the #1 gotcha.** Since `/tmp` is ephemeral, every cold start gets a fresh database. If your frontend assumes certain data exists (like user ID 1), you MUST seed it:
```python
def seed_default_user(db: Session):
count = db.query(UserProfile).count()
if count > 0:
return
user = UserProfile(name="Demo User", ...)
db.add(user)
db.commit()
```
### 6. Create vercel.json
```json
{
"rewrites": [
{ "source": "/api/(.*)", "destination": "/api/index.py" },
{ "source": "/((?!assets/).*)", "destination": "/index.html" }
]
}
```
This routes:
- `/api/*` → Python serverless function
- Everything else → React SPA (index.html)
### 7. Deploy
```bash
cd <project>/vercel-deploy
vercel --yes --prod
```
### 8. Verify
```bash
curl -s <deployed-url>/api/health
# Should return: {"status":"ok"}
```
## Gotchas & Limitations
| Issue | Solution |
| --------------------------- | ------------------------------------------------------------------------ |
| SQLite resets on cold start | Seed ALL required data in index.py startup |
| No persistent storage | Acceptable for demos. For production, use Vercel Postgres or Supabase |
| No auth | Fine for demos/portfolios. Add auth layer for real apps |
| `requirements.txt` location | Must be inside `api/` folder (next to index.py) |
| Module imports in routers | Use `sys.path.insert(0, os.path.dirname(__file__))` in index.py |
| CORS | Set `allow_origins=["*"]` for demo deployments |
| `--name` flag deprecated | Don't use `--name` with Vercel CLI, just deploy from the directory |
| Vellum bridge APIs | Use the vellum-shim.js to provide localStorage-backed data + no-op stubs |
| npm not available | Use `bun install -g vercel` to install Vercel CLI in sandbox |
## Vercel CLI Quick Reference
```bash
bun install -g vercel # Install
vercel login # Authenticate (opens browser — last resort)
vercel --yes --prod # Deploy to production (skip prompts)
vercel logs --project <name> # Check function logs
```