Tidepool Duo

Build a web app called Tidepool Duo: a fork of Tidepool for couples who share some money, not all of it.

What it does

Forked from Tidepool. Adds a shared space for two people: split categories, who-owes-who that settles itself, and a monthly summary you'll both want to read.

Stack

Use Next.js, Supabase, Tailwind. The original was built with Claude Code in 1 weekend, for about $11 in AI usage.

How it fits together

• A server-rendered web app with a small API layer
• A database for user data, with row level security on every table
• Sign-in so each person only sees their own data

Build it in this order

1. Set up the project, the database and sign-in, and deploy an empty page
2. Build the main screen with realistic sample data
3. Connect it to real data and add the one action the app exists for
4. Add the empty states and error messages a new user will hit
5. Write tests for anything that touches money, dates or other people's data

Tools to connect

• Supabase MCP: new tables for shared spaces

A prompt that worked: Extend a fork without breaking upstream

This is a fork of Tidepool. Add shared spaces for two users without changing any existing table or component. Put everything new under features/shared/. Keep the upstream parsers untouched so I can still merge their updates. List every file you changed outside features/shared/ and why.

Watch out for

• Don't build settings, teams or billing before the main screen works
• Keep the first screen useful with sample data, so the app makes sense before anyone has set it up

Done when

• A new user can sign in and get value in under two minutes
• Everything works on a phone
• Tests pass for the core logic

Before writing code, ask me up to five questions about who this finance web app is for and what the first version must do. Then work in small steps: after each one, tell me how to try it and wait for my feedback.