TabSplits

A bill-splitting web app: scan a restaurant receipt (AI OCR), assign items to people, and settle up who owes whom — with shareable read-only receipt links.

Architecture

Migrated from Replit to GitHub + Vercel + Supabase (July 2026).

Layer	Technology
Frontend	React 18 + Vite, wouter, TanStack Query, Tailwind + shadcn/ui
API	Express (TypeScript), session auth via express-session + connect-pg-simple
Database	Supabase Postgres, accessed with Drizzle ORM (drizzle-orm/node-postgres over the Supabase transaction pooler)
File storage	Supabase Storage (private receipts bucket, signed upload/download URLs)
AI	OpenAI gpt-4o for receipt OCR and item categorization
Email	Resend (password reset)
Hosting	Vercel — static client from dist/public, the Express app as a serverless function

How it's wired

• shared/schema.ts — Drizzle table definitions + zod validation schemas (shared by client and server).
• server/app.ts — builds the Express app (sessions, logging, all routes) without listening; used by both entries below.
• server/index.ts — local entry: dev mode serves the client through Vite middleware with HMR; npm start serves the built client.
• api/index.mjs — Vercel serverless entry. At build time, build:vercel bundles server/app.ts into api/_app.mjs (generated, git-ignored) with esbuild.
• vercel.json — /api/* and /objects/* rewrite to the function; everything else falls back to the SPA's index.html.
• server/objectStorage.ts — receipt images. Clients request POST /api/uploads/request-url, PUT the file straight to the returned signed Supabase Storage URL, and store the /objects/uploads/<uuid> path; GET /objects/* redirects to a short-lived signed download URL.

Environment variables

See .env.example. All are server-side except VITE_POSTHOG_KEY.

Variable	Purpose
DATABASE_URL	Supabase Postgres transaction pooler URI (port 6543). URL-encode special characters in the password.
SUPABASE_URL	https://<project-ref>.supabase.co
SUPABASE_SERVICE_ROLE_KEY	Secret key; used server-side for Storage signed URLs
OPENAI_API_KEY	Receipt OCR + item categorization
RESEND_API_KEY / RESEND_FROM_EMAIL	Password-reset emails
SESSION_SECRET	Session cookie signing (openssl rand -hex 32)
VITE_POSTHOG_KEY	Optional client analytics

Secrets are never committed: .env is git-ignored; production values live in Vercel project env vars (vercel env).

Local setup

npm install
cp .env.example .env   # fill in values
npm run dev            # Express + Vite HMR on http://localhost:5000

Other scripts: npm run check (typecheck), npm run build + npm start (production server locally), npm run db:push (push schema changes to the database via drizzle-kit).

The database schema already exists in Supabase (migrated via pg_dump from the original Replit/Neon database). For a brand-new database, npm run db:push creates all tables; the session table is created automatically on first run.

Deployment

Pushes to main can be deployed with the Vercel CLI:

vercel deploy --prod

Production: https://tabsplits.vercel.app