Lucas WintherandClaude Opus 5
8d2b2ca881
`Settings.digits` replaces `CurrencyDef.digits`. Every amount rounds to it, whatever its currency, and `digitsFor` is gone: the sixteen call sites read the setting, and the domain functions that took a currency table purely to look digits up take a `digits: number` instead. Schema 6. The owner asked for this with the cost in front of them, and the cost is real: a dataset mixing minor units cannot be described any more. Yen at 0 beside kroner at 2 has no correct global value — 2 gives ¥1234.56, an amount yen cannot represent; 0 rounds 49.95 DKK to 50 and drifts the carry from the bank. Nothing in the app warns. docs/specs/2026-09-02-global-decimals-design.md argues it in full, including what re-adding a per-currency override would take, and AGENTS.md §1 now says not to reintroduce one without revisiting the decision. The 5 -> 6 step takes the MAXIMUM of the per-currency digits, not the base currency's. A dataset holding a three-decimal currency already has three-decimal amounts in it, and adopting the base's 2 would truncate the next edit of one; the maximum can only keep more precision, never less. On every dataset this app has written all four currencies record 2, so nothing rounds differently than before. Changing the setting does not rewrite stored amounts. 49.95 stays 49.95 and shows as 50; totals recompute at the new precision. Rewriting each Money is a destructive whole-dataset write, which §1 owes a backup export first, and it is lossy one way. Display turned out to be the hole in the plan. src/ui/format.ts pinned minimumFractionDigits: 2 in a module-level Intl.NumberFormat, so it never read the dataset at all — equally broken under per-currency digits, where a JPY rendered "3,333.00", so a pre-existing gap rather than a regression. Shipping a Settings control that display ignores would look broken at 0 and be lossy at 3, hiding precision the dataset holds. So format.ts takes digits like roundMoney does, useMoneyFormat() binds them for the 64 call sites, and postRowCells takes the formatter as an argument because it is a plain helper, not a component. currencyDigits.test.ts is rewritten rather than deleted. Driving a dataset at ZERO decimals through rounding, both FX directions, both split modes, plan division, the fold and the month view still tells a real implementation from one assuming 2 — it just cannot prove per-currency flow, because there is none. It also asserts that raising the setting to 2 changes what the fold produces. Verified in Chrome, not only in tests: a v5 dataset with digits 2/0/3 written straight into IndexedDB migrates to a setting of 3, the table loses its Decimals column, and editing the control persists schema 6 with digits stripped from each currency and income left at 20000.55. The same month reads 600/206 at zero decimals and 600.000/205.561 at three, so the figures recompute rather than merely reformat. Not verified here: the .ods in a real spreadsheet. Co-Authored-By: Claude Opus 5 (1M context) <[email protected]>
Budget 2.0
A personal budgeting PWA. Envelope-style monthly budgets with rollover, split purchases, finance plans, multi-currency, and JSON/ODS export. All data lives in your browser — there is no server and no account.
Development
bun install
bun run dev # dev server with hot reload, on :3000
bun test # run the test suite
bun run build # production build into dist/
Self-hosting with Docker
docker build -t budget2 .
docker run --rm -p 3000:3000 budget2
To serve from a subpath, build and run with BUN_PUBLIC_BASE_PATH:
docker build -t budget2 --build-arg BUN_PUBLIC_BASE_PATH=/budget/ .
docker run --rm -p 3000:3000 -e BUN_PUBLIC_BASE_PATH=/budget/ budget2
GitHub Pages
Pushing to main builds and deploys to Pages automatically, using
/<repository-name>/ as the base path. Enable Pages with "GitHub Actions" as
the source in the repository settings.
Your data
Everything is stored in this browser's IndexedDB. Export regularly from Settings → Your data: the JSON export is both your backup and how you move your budget to another device.
Both destructive actions there — Import, and "Reset everything" — download a backup of your current data before replacing it, and abort if that download fails. Reset puts the app back to a brand-new install: the three starter posts, the DKK/USD/EUR currency table, this month at zero income, no purchases.
Known limitations
- Data is per-browser. There is no account and no sync. If you clear this browser's site data, or move to a different browser or device, your budget is gone unless you exported it first. The JSON export is not just a nice-to-have backup — it is the only way to move a budget between devices.
- Installing and offline use are unverified. The manifest ships the SVG plus 192×192 and 512×512 PNG icons, and the service worker demonstrably installs, activates and precaches every asset — but nobody has yet confirmed that Chrome offers its "Install app" prompt, or loaded the app with the network actually cut. It works as a regular tab regardless.
Documentation
docs/ARCHITECTURE.md— layers, data flow, and why the non-obvious choices are what they are.docs/PRODUCT.md— who this is for and what must never break.AGENTS.md— the rules for changing this codebase, and the test that catches each one when broken.CLAUDE.mdandGEMINI.mdpoint at it.docs/DECISIONS.md— an index of the choices that shaped the app, and what each was chosen over.docs/TODO.md— what is still queued.docs/specs/— one design document per piece of work, each recording the alternatives that were rejected.docs/plans/— task-by-task implementation plans.