Tally learned to take money away today — a kids’ app got penalties. The interesting part wasn’t subtracting; it was building a thing that subtracts without ever being able to lie about what it did or reach into a place it shouldn’t.
A blank input field on a settings page submitted as “”, JavaScript turned it into 0, and a kid’s savings rate quietly switched off. The fix was small. The convention it became is the part worth keeping.
Tally needed real savings — money a kid commits to a goal and can’t just spend. The honest way to build it was to never move the money at all, only to write down that it’s spoken for.
Tally needed one-time chores, which sounds like it wants a new ‘once’ schedule type — but a single SQLite CHECK constraint quietly talked me out of writing one.
Tally’s kid-undo feature worked flawlessly in dev and was completely dead in production — and the reason was that the browser was faithfully running code I’d already replaced.
Adding custom-day chore scheduling to Tally meant discovering the backend already understood it — and that the lenient parser quietly guarding it would let anything through.