Nest is a private household finance dashboard, self-hosted on a Mac Mini and reachable only over Tailscale. It gives a couple one honest picture of their money and the route to debt-free, then a house deposit.

After a first build that leaned on uploading PDFs and AI-extracting them, the data layer was rebuilt from scratch in June 2026. The lesson was simple: for accuracy-critical money, a disciplined manual review beats any automated extractor. So the app has no upload and no import of any kind, by design.

Architecture

Layer	Technology
Frontend	Next.js 16 App Router, React 19, TypeScript strict, Tailwind CSS v4
Data	better-sqlite3 (one local file), Drizzle ORM, integer pence throughout
Engine	Pure, unit-tested avalanche / snowball / hybrid payoff engine (17 tests)
Charts	Recharts
Hosting	launchd service on a Mac Mini, nightly SQLite backup, password gate, Tailscale-private

Pages

Page	What
Overview	The road to zero: debt-free date, cards-cleared date, total owed, interest burn, the one move to make
Debts	The full register with provenance and a plan-vs-actual debt-over-time chart
Money	Real cashflow, with internal transfers separated from spend
Mark & Kelly	The inter-person ledger: who owes whom, logged and settled
Review	The monthly manual update, the only way data gets in

How the data stays accurate

• One declared source per account; dedupe enforced by a database constraint; transaction flow type set at ingest so internal transfers never leak into spend.
• Every debt figure carries a confidence and an as-of date; anything over a month old is flagged amber so the numbers never silently drift.
• Cards and loans are one entity with their terms attached, no double-counting.
• A frozen plan baseline lets the dashboard show actual vs plan, not just a moving projection.