Split & Settle

Splitting a Goa trip means a spreadsheet, a calculator and twelve 'who paid for the cab?' messages. Splitwise needs everyone to sign up, rounds to the rupee, and stops at 'you owe ₹4,655' — the actual payment still happens somewhere else.

1. 01Money in integer paise with largest-remainder rounding, so every split adds up exactly; settle-up suggestions in at most n−1 payments, stable so recording one doesn't reshuffle the rest.
2. 02Guest sign-in with personal, single-use invite links — after debating the plan with a second AI reviewer, who caught that a shared link lets anyone claim a friend's name.
3. 03Trust built into the database: Postgres row-level security, server functions for joining and importing, a trigger that rejects shares that don't add up, and an audit log of every change.
4. 04Splitwise import from the official spreadsheet export rather than an API login — its terms require a commercial licence — rebuilt row by row and checked against Splitwise's own totals.

• Expo (React Native) app shipped first as an installable web app on Vercel, ready for the App Store later; Supabase with realtime sync and guest auth.
• Equal, exact, shares and percentage splits with live validation; edit, delete and restore with author/admin permissions; activity feed.
• Settle-up with UPI intent links (GPay, PhonePe, Paytm), a scannable QR on desktop, copy-UPI-ID fallback, and payment records anyone involved can undo.
• Personal and group invite links with QR and WhatsApp share, admin link reset and unlinking, plus an on-device demo group for visitors.

• Expo SDK 57
• React Native Web
• TypeScript
• Supabase (Postgres, RLS, Realtime, anonymous auth)
• Reanimated
• Vitest
• Playwright
• Vercel