The money arithmetic every invariant rests on now lives in one kernel,
ledger-core/src/kernel.rs: signing a line, totals, net, per-account
movements, reversal, normal balances, trial-balance columns, closing
lines, and the rounding plug for member splits. It is generic over a
checked `Amount` trait. The engine runs it on Decimal (validate,
movements, reverse_entry, account_balance, close_period_to, allocate,
trial_balance): there is one copy of the arithmetic, and it is the one
under proof.
Three layers, docs/verification.md maps every law to its proofs:
- Kani (src/proofs.rs): 17 harnesses prove the kernel at i64 for every
input up to 4 lines over 3 accounts. An entry is accepted exactly
when it is two or more positive, in-range lines whose debits equal
credits; accepted entries net to zero; grouping by account loses
nothing; a reversal mirrors and cancels its original; trial-balance
columns balance iff the books net to zero; closing lines zero their
accounts and a close balances however the net is split; the plug
makes parts sum to the whole. No panics, no overflow. kani::cover!
shows the proofs are not vacuous.
- Lean 4 (verify/lean): 24 headline theorems for books of any size. The
ledger is a state machine (add account, draft, post, reverse, open,
close), and in every reachable state the books net to zero, the trial
balance balances (as of any date), and the accounting equation holds.
Posting only appends ("posted is forever"), closed periods are
frozen, a close zeroes revenue and expenses and credits exactly the net
income, and period statements add up. Audit.lean shows standard axioms
only, no sorry.
- Bridge (tests/kernel_bridge.rs): the Decimal and i64 kernels agree.
What the proofs found (each one missed by every test, fuzzer, and
mutant):
- The engine accepted negative line amounts; only MCP refused them. Now
NegativeAmountLine: direction is the side's job.
- Summing lines near Decimal::MAX panicked. Lines are now capped at one
quadrillion and ten decimal places (AmountOutOfRange), which keeps
every realistic sum exact, and the kernel's sums are checked.
- FX conversion (foreign_amount * fx_rate) could panic the same way; it
is now a checked multiply.
- Kani itself: 0.68 mis-models symbolic-length copy_from_slice
(model-checking/kani#4904) and reported a reversal that doesn't net to
zero. The counterexample, replayed natively, passes, and a 15-line
standalone crate reproduces the bug. Harnesses avoid bulk copies, and
a should_panic canary will flag the upstream fix.
`just prove` runs it all (Kani memory- and time-capped, fails on an
unsatisfiable cover or a non-standard Lean axiom). AGENTS.md now makes
formal coverage part of every core change.
Also, docs: GnuCash is *an* oracle, never *the* oracle (Stephen). The
spec is accounting principles, proved. Golden files are recomputed from
principles. External implementations (GnuCash, the old Sheet, QBO/Xero)
are cross-checks whose disagreements get adjudicated, never obeyed.
docs/oracle.md gains "Who is right"; AGENTS, README, architecture,
roadmap, parity, and STATUS are reworded to match.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01GWVo7x3UHw5kwCUaWxiejX
egui/wgpu app for owners and their accountant: Overview, Cash, Profit,
Transactions (with rendered receipts and journal history), Reports
(statements with interval columns, comparisons, drill-down), Accounts,
Documents, Company, Journal; Ctrl+K palette; back/forward; light/dark.
Follows the journal live (~30 ms from write to screen). --demo opens a
deterministic demo company, also used for screenshot tests.
Engine: ledger-store Snapshot (read-only, incremental, tolerant of a
half-written tail); ledger-core analysis (intervals, balance series,
P&L by interval, cash flows); ledger-config extracted from ledger-mcp
with the full company profile and cash_accounts.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01MtYEaR6M6Ybdhm6X98BWNu
Records three more dashboard references Stephen shared: the QuickBooks
Online dashboard cards, KPI tiles with period-over-period change, and a
cash-flow dashboard (runway, forecast, A/P and A/R aging, burn).
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01MtYEaR6M6Ybdhm6X98BWNu
Every report a CPA expects, laid out the way US small-business books
read (QuickBooks as the reference):
- Exports: books.export gains general_ledger (by account, running
balances, splits), general_journal (the entry-ordered listing, which
the CPA package used to mislabel "general ledger"; alias journal),
members_equity, and trial_balance as of a date, in xlsx/csv/json, and
PDF for all five statements (P&L, balance sheet, cash flow, trial
balance, members' equity). books.trial_balance takes as_of.
- CPA package: every statement as PDF and XLSX, plus the general ledger
and general journal, all for the fiscal year to date.
- Layout (ledger-import::report): multi-column statements (Total;
Debit/Credit; one column per member plus Total), "$" on subtotals and
totals, a rule above every sum (none over an empty section), a double
rule under statement totals, zero as 0.00, negatives in parentheses
with the closing paren hanging so decimal points align.
- Terms: "Net income (loss)"; for a multi-member LLC, "Members' equity",
member contributions and distributions named in the cash flow, and the
balance sheet splitting retained earnings (the Retained Earnings
account plus earnings not yet closed from earlier years) from the
fiscal year's net income (loss); the cash flow's "Adjustments to
reconcile net income (loss) to net cash from operating activities" and
"Net increase (decrease) in cash".
- PDF: Inter replaces the typst-assets serif fonts (bundled, SIL OFL 1.1,
license in fonts/; from the official v4.1 release), centered title
block, column-header row, full-width rules, footer "Accrual basis ·
Prepared <date> · Journal seq N" with page numbers. Amounts on total
rows stay regular weight so bold figures can't leave the decimal
column. typst-assets dependency removed.
- XLSX: centered title block, header row, Excel accounting formats with
"$" attached on sums, general ledger and general journal workbooks.
- Config: wanderbooks.toml [[company.members]] (name, share "50%" or
"0.5", capital_account; shares must total 100%) and [books]
accounting_basis (accrual | cash).
- Core: RETAINED_EARNINGS_CODE names the "3999" that period close uses.
- Fix: "today" is local time, not UTC; in US evenings UTC is tomorrow,
so reports defaulting to "through today" included the next day and
footers carried the wrong date.
Tests: layout (currency and rule placement, retained earnings vs. this
year's net income for a member LLC, footer text); exact template data;
deterministic PDFs; config parsing (members, shares, basis); stdio:
trial balance as of, February general ledger (beginning 1,004.00, splits,
ending 1,003.50), members' equity (contributions 1,000.00, net income
3.50, ending 1,003.50), members' equity PDF, the CPA package's ten files.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01MtYEaR6M6Ybdhm6X98BWNu
swaitsandClaude Opus 5.5