## Why
#750 made a shared account count only your share of every transaction —
on the
dashboard and on the cashflow screen. Budgets were left out and shipped
as a
known gap: `budget_transactions.amount` is a snapshot written when a
transaction
is assigned, so a 50% joint account still spent **100%** of every
expense against
its budget. The same category could read €400 on the dashboard and €800
in
Budgets.
This closes that gap.
## What
A €100 expense on an account you own 50% of now counts €50 towards your
budgets.
Because every budget reader funnels through
`BudgetPeriod::spentAmount()` — a sum
of those snapshots — weighing the snapshot covers the budget cards, the
detail
page, the spending chart, carry-over, the limit alert emails and the MCP
tools in
one move.
- **Assignment writes the owner's share.** Both paths (the
per-transaction
listener and the historical backfill) go through one `recordSnapshot()`.
- **Changing an account's share rewrites its history.** A single SQL
`UPDATE`
re-weighs every budget row of that account, in every period, past ones
included.
- **A migration re-weighs the rows written before this**, so existing
shared
accounts are correct on deploy instead of on the next edit.
## How
The share is computed at the same two choke points #750 established:
- **PHP** — `Transaction::ownerShareOf()` (extracted from
`ConvertsTransactionCurrency`, which was doing the same null dance
inline)
feeds `BudgetTransactionService::recordSnapshot()`.
- **SQL** — `BudgetTransactionService::reweighAccountSnapshots()` reuses
`Transaction::OWNED_AMOUNT_SQL`, so the rounding matches what PHP would
have
written. A test pins both to the same answer on an uneven share.
The re-weigh hangs off `Account::booted()` rather than
`AccountController`, so a
seeder, an artisan command or a future MCP write tool cannot silently
skip it.
It also clears the period's `close_to_limit_notified` /
`over_limit_notified`
flags, the same way a refund that drops a budget back under its limit
does —
otherwise a budget that fell out of "over limit" would stay claimed and
never
alert on the next real crossing.
The owning account is eager loaded **withTrashed** everywhere the
snapshot is
written, because `OWNED_AMOUNT_SQL` joins `accounts` without the
soft-delete
scope; without it a transaction whose account was deleted would snapshot
at 100%
in PHP and at the real share in SQL.
## Deliberate boundaries
- **Transaction rows still show the real bank amount** — #750's rule.
The budget
detail page is the one screen where a weighted total sits directly above
its
own itemised list, so it now says so in a line under the chart. The
alert email
had the same mismatch inside one message and now quotes your share.
- **`carried_over_amount` is not re-derived.** It is a second snapshot
taken when
a period closes. `remainingAmount()` deliberately ignores it and the UI
only
types the field; it surfaces solely through MCP. Left alone rather than
adding
a second re-derivation path.
- The migration's `down()` restores the full transaction amount, which
is what
those rows held — it cannot know a share an account no longer has.
## Testing
`tests/Feature/SharedAccountOwnershipTest.php` gains the budget cases:
assignment,
the historical backfill, the re-weigh through the settings screen,
PHP/SQL
rounding parity on 33% of 3333, and the alert flags being cleared.
`tests/Feature/WeighBudgetTransactionsMigrationTest.php` covers the
backfill,
including that it is idempotent and that it keeps refunds negative (the
fix from
`2026_02_24_193117`). Fixing that test needed the `BudgetTransaction`
factory,
which had been pointing at a `BudgetPeriodAllocation` model that no
longer exists.
Manual QA on real local data — budget "Miami Flight", account "Daily"
set to 50%:
| | Before | At 50% | Back at 100% |
|---|---|---|---|
| Miami Flight spent | €3,229.40 | **€1,955.79** | €3,229.40 |
| Yearly Padel spent | €1,514.91 | €785.49 | €1,514.91 |
€1,955.79 is €3,229.40 − €1,273.61, exactly half of the €2,547.24 that
account
had in the budget. The round trip lands back on the original figure to
the cent,
so the re-weigh is idempotent on real data too.
## Demo
<!-- PLACEHOLDER: drag the QA video here -->
https://github.com/user-attachments/assets/1fa5b98a-2a11-4cad-b927-496b434d3295
