remaining is untouched: carriedIn + allocation - charges, exactly as before, so
no figure the owner has reconciled against their bank can move when they add a
recurring cost. projected runs beside it on its own carry, subtracting
unconfirmed occurrences as well.
Two invariants pin it, both tested. With no recurring costs the tracks are
identical in every month — that is the behaviour-preservation guard for every
dataset that exists today. Once a month's occurrences are all confirmed they
reconverge there, because a confirmation is an ordinary purchase counted in
charges and skipped by expected.
An unconfirmed occurrence in a PAST month therefore holds projected below
remaining forever. That is the honest reading — an unreconciled commitment —
and the month view surfaces the count so it is not silent.
Also required to typecheck once PostMonthFigures gains these fields:
- src/store/migrations.test.ts: delete the two @ts-expect-error directives
that stood over the "NO figure changes" guard test since Task 2. That test
is now green — the point of this task.
- src/ui/meterSegments.test.ts: the figures() test helper builds a complete
PostMonthFigures literal; default expected to 0, projectedCarriedIn to
carriedIn, and projected to remaining, matching its existing partial.X ??
style.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Recurrence is two orthogonal fields, not a list of special cases: a kind
(everyNMonths / everyNDays / everyNWeeks) and an anchoring (calendar /
lastCharge). The phone bill that recharges early when its data cap is hit is
everyNDays(30) anchored to lastCharge — the domain never learns what a data cap
is, because confirming the occurrence early already records the date.
Purchase.source pairs occurrenceDate (identity: which slot this claims) with
Purchase.date (truth: when the money moved). They differ whenever a bill is
paid off schedule, and lastCharge measures from the latter.
RecurringCost.amount is a single mutable Money with no RuleVersion-style
series. Safe only because confirmed purchases hold what was actually paid;
under projection-only it would destroy history.
The 6 -> 7 step writes an empty array and reads nothing. Decimals took 6.
`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) <noreply@anthropic.com>
GBP joins the currencies the app comes with: £, two decimals, and a
committed fallback rate of 8.704735 DKK to the pound. build.ts now
fetches it too, so a build with a network bakes a live GBP rate and one
without still covers it — the coverage check derives from the seed table,
so it demanded GBP as soon as the table listed it.
The seed table alone would not have delivered this. Baked currencies and
rates seed a NEW dataset and nothing else, so an existing dataset would
have been left typing the code, name, symbol and decimals by hand. A
4 -> 5 migration adds sterling to a dataset that lacks it, with its rate.
Supplying a rate is the one thing the "rates never backstop a cleared
rate" rule permits here: it forbids re-supplying a number the owner
deleted, not introducing one for a currency they have never had. A GBP
the owner already defined, or a GBP rate they already hold, is left
exactly as it is — asserted, including the case where their definition is
"wrong" (zero decimals), because it is theirs.
This exposed a real latent bug. The 2 -> 3 step seeded the live
seed-currency table BY REFERENCE, so adding sterling there would have
retroactively changed what an old dataset received from a step it had
already been through — silently, and only for whoever had not migrated
yet. Every step now carries its own frozen copy, and a source-level guard
fails the build if a live default is imported again. Scoping that guard
took two goes: matching the whole file flagged the comment explaining the
rule, and then flagged the frozen local copy that is the fix.
Two test fixtures used GBP as their example of an UNSUPPORTED currency
and now use CHF, which no seed table lists.
Verified in a browser by writing a schemaVersion 4 dataset into IndexedDB
and reloading: the currency table gains "British pound / £ / 2" with
"manual · 2026-09-02", the post currency selector offers GBP, and the
income and post survive untouched. Note for the next person — a migration
applies in memory on load and is written back on the next mutation, so
reading IndexedDB straight after a reload still shows the OLD version.
That is recorded in docs/TODO.md, because it made this verification look
like a failure at first.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
"Fetch rates now" failed on the deployed site with nothing but a CORS
error. api.frankfurter.app now answers every request with a 301 to
api.frankfurter.dev/v1, and a redirect response must itself carry
Access-Control-Allow-Origin for a browser to follow it cross-origin. That
301 carries no CORS headers at all, so the request died before the
redirect could be taken.
Measured rather than guessed, with an Origin header set:
api.frankfurter.app -> 301, no access-control-* headers
api.frankfurter.dev -> 200, access-control-allow-origin: *
The response shape is unchanged, so parseFxResponse needed no edit.
Nothing was wrong at build time, which is why this went unnoticed: a
server-side fetch follows the 301 freely, so the baked rates were always
correct. Only the browser path was broken.
Two changes, because a new default alone fixes only some datasets:
- DEFAULT_FX_API_URL points at .dev/v1, with a test that fails if the
redirecting host ever comes back.
- A 3 -> 4 migration drops settings.fxApiUrl when it holds exactly the
dead default, which is the case for anyone who edited that field. It is
DROPPED rather than rewritten, so the dataset follows whatever the
current default is and the next move of the service needs no second
migration for the same user; a URL the owner chose is left strictly
alone. No stored figure changes, so it cannot alter a number in the
budget.
Verified by clicking the button in a real browser: "Updated 2 rate(s)",
USD 6.456195 and EUR 7.474959 both stored with source "api" — and the USD
figure differs from the baked constant, so it is a genuine live fetch.
Two migration tests asserted the chain ends at 3; they now assert
SCHEMA_VERSION, since what they mean is "all the way through".
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Two requests. The second is small; the first changed the money layer.
TYPING THE CURRENCY. The purchase total field now reads "30$" as thirty
dollars, "€25,50" as EUR 25.50, "250 kr" as DKK, "1.234,56 usd" as USD
1234.56, and sets the currency selector from what was typed. Entry speed is a
stated product feature and a second control per amount works against it.
The field is type="text", not type="number": a number input silently discards
anything non-numeric, so "30$" would never reach the parser. It keeps its own
text so a half-typed "30." stays as typed and only commits when it parses.
Separator handling is where parseMoneyInput earns its 26 tests. With both "."
and "," present the LAST is the decimal point, which covers "1.234,56" and
"1,234.56" without knowing a locale. With one, it groups thousands if exactly
three digits follow and is a decimal point otherwise — so "1,500" is fifteen
hundred and "1,5" is one and a half. Spaces group thousands only in
three-digit groups, because "30 40" is two amounts typed by mistake and
committing it as 3040 would be worse than rejecting it. An unrecognised
currency returns null rather than falling back: reading "30 GBP" as 30 DKK
would book money at the wrong currency.
USER-DEFINED CURRENCIES. `Currency` was a closed union and decimal places were
a module constant, so "add a currency" was a code change. Both now live in the
dataset: `Dataset.currencies` is the authority on which codes are valid, what
they are called, their symbol, and how many decimals they round to. Settings
grows a table to add, edit and remove them.
That forced the money layer open. `roundMoney` takes a DIGIT COUNT, not a
currency code, and every one of its ~29 call sites resolves digits from the
dataset via `digitsFor`. Making digits a required number rather than an
optional one with a default of 2 is the whole safety argument: every site
became a compile error the type checker enumerated for me, where a default
would have left each one silently correct for DKK/USD/EUR and silently wrong
for the first zero-decimal currency the owner adds.
Because every existing currency uses two decimals, a broken version of this
refactor would still pass all 356 previous tests. src/domain/currencyDigits.test.ts
is the oracle that cannot lie: a JPY-style zero-decimal currency driven through
roundMoney, both FX directions, both split modes, finance-plan division, the
fold, and the month view, asserting no figure has a fractional yen in it.
Guards that come with it, all tested:
- Codes are identity — they key the FX table and every stored Money — so they
are normalised (" jpy " -> "JPY") and cannot be edited, only added/removed.
- A currency in use cannot be removed, and the refusal names what refers to
it. The same reasoning as posts being archived rather than deleted: stored
Money carries the code, and dangling references would make the import
validator refuse the owner's own exported file. Removing an unused one takes
its exchange rate with it, leaving no orphan row.
- The import validator now checks the currency table itself — codes, duplicate
codes, integer decimals 0-4 — and validates every Money against it. That
boundary check replaces the compile-time safety the closed union provided.
- parseFxResponse takes the accepted codes instead of a global constant, so a
rate service returning dozens cannot put unreachable rows in the table.
Migration v2 -> v3 seeds the currency table. Behaviour-preserving by
construction: every currency that existed had two decimal places and the
seeded table records two, so not one stored amount can round differently than
it did before. An existing `currencies` field is kept rather than overwritten,
since a hand-edited file could already carry currencies the owner added.
Verified in the browser, not just in tests: JPY added through the real Settings
form with 0 decimals, and the five inputs above typed into the real purchase
field, each setting the right currency.
Two obsolete test helpers went away. plans.test.ts and actions.test.ts used to
monkey-patch the CURRENCY_DIGITS constant to prove the table was consulted;
digits are an argument now, so those tests just ask for zero decimals.
types.test.ts no longer asserts "the supported currencies are exactly DKK,
USD, EUR" — that stopped being a property of the code.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Previously only an empty posts array was tested for the "no standingRule"
path; a post that IS present but lacks the field was exercised only by an
ad-hoc script, not a committed test. Asserts rules === [] (never a version
wrapping undefined, which would later crash resolveRule/ruleAt) and that a
sibling post's rule is unaffected.
A pure shape change: standingRule becomes one version effective from the fold
start, which is where it already applied from. Asserted behaviour-preserving —
every post in every month resolves to the same allocation before and after, so
no balance moves.
The dataset is one atomic record, so a write can never leave posts and
purchases inconsistent.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
