🧳 CoBook — Multiplayer Travel Booking

A Chrome extension + companion website that turns single-player travel booking sites (Airbnb, MakeMyTrip, Agoda, …) into live multiplayer sessions with automatic expense splitting.

See prd.md for the full product requirements document and project-documentation.md for system design notes.

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💡 The Idea

Group travel planning is painful — links get lost in group chats, dates collide, and one person ends up fronting ₹50,000+ on their credit card hoping friends pay them back.

CoBook solves this by:

1. Letting you start a session from any supported booking site via the extension.
2. Syncing the viewed property + an upvote/downvote board across all members in real-time.
3. Hijacking checkout to fractionalize the total cost across all session members and generate instant payment requests (UPI / Venmo / CashApp).

The product cannot be used solo — every session forces invites, creating a built-in viral loop (target K-Factor > 1.2).

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🧱 Tech Stack

Layer	Choice
Extension UI	React 18 + Vite + Tailwind CSS
Real-time backend	Supabase Realtime (Postgres + WebSocket)
Expense ledger	PostgreSQL NUMERIC(10,2) to avoid float errors
DOM parsing	JSON-based adapter schema (server-updateable, no Chrome re-review)
Hosting (web)	Vercel
Extension	Chrome MV3-compatible structure

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🗂️ Repo Layout

.
├── extension/                 # Chrome extension (the product itself)
│   ├── manifest.json
│   ├── popup.html / popup.jsx
│   └── src/
│       ├── content.jsx        # Injected on supported booking sites
│       ├── background.js      # MV3 service worker
│       ├── supabaseClient.js
│       ├── hooks/
│       │   ├── useSessionSync.js
│       │   └── usePaymentSync.js
│       ├── screens/           # Onboarding, Lobby, Payment, Success, …
│       └── utils/
│           ├── auth.js
│           └── scraper.js     # Adapter-driven DOM extraction
│
├── website/                   # Marketing / install / privacy site
│   ├── index.html
│   └── src/
│       ├── App.tsx
│       ├── components/
│       ├── pages/PrivacyPolicy.tsx
│       └── main.tsx
│
├── supabase_schema.sql        # Postgres schema
├── platform_adapters.sql      # Booking-site adapter definitions
├── prd.md                     # Product requirements doc
├── project-documentation.md   # Architecture deep-dive
└── CHANGES.md                 # Change log

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🚀 Running Locally

Extension

cd extension
npm install
npm run dev      # for the popup UI
# Then load the built `dist/` as an unpacked extension at chrome://extensions

Website

cd website
npm install
npm run dev      # Vite dev server (default :5173)

Backend

• Apply supabase_schema.sql to a fresh Supabase project.
• Optionally apply platform_adapters.sql and seed adapter rows.

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💰 Monetization (from PRD)

Stream	Mechanism
Affiliate routing	Final checkout URL passes through an affiliate network (1–5% on high-ticket bookings)
Convenience fee	Flat $2 / ₹50 micro-fee for auto payment routing

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📊 KPIs

• K-Factor must exceed 1.2
• Session-to-checkout rate
• Adapter failure rate (DOM scraper misses) — monitored via Sentry

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📚 Docs

• prd.md — full PRD (problem, audience, MVP, monetization, KPIs)
• project-documentation.md — architecture + design choices
• CHANGES.md — change log

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🤝 Contributing

This is currently a solo-founder project. Issues + PRs are welcome — please read prd.md first to stay aligned with the MVP scope (Airbnb + MakeMyTrip only, v1).

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📄 License

MIT — © 2026 Pranav Gawas