Max-testing pass, ranks 4-6 and step 9 for ledger-core.
Fuzzing (rank 4): fuzz_op_sequence now drives balanced pairs, foreign
lines, periods, closes, and amounts from raw decimal bits, and asserts
the books stay valid (TB balances, posted entries validate, no draft in
a closed period); new fuzz_core_serde (every persisted core type
round-trips) and fuzz_store_open (a corrupt journal is an error, never a
panic); hangs count (-timeout=10). 54M executions; one crash:
- fuzz_journal_line: a number too big for an integer parsed as a float,
and its canonical form (which the hash chain covers) re-canonicalized
differently. The journal never holds floats (R-2), so the reader now
refuses them (JournalLine::parse, used by every journal reader);
regression a_journal_line_with_a_float_is_refused. Checked first: the
real books' journal has none. Rerun: 13.2M executions, clean.
Seeds in fuzz/seeds/ (synthetic, minimal); the grown corpora stay out of
git. `just fuzz <target> <seconds>`.
Miri (rank 4): the core's unit, bridge, and invariant tests under Miri
(our code has no unsafe; rust_decimal and chrono do): no undefined
behavior. `just miri`. A pinned nightly (nightly-2026-10-01, with miri)
is now in mise.toml.
Benchmarks (rank 6): criterion (new dev-dependency: the playbook's Rust
benchmark tool; none existed) in benches/books.rs; baselines in
docs/testing.md. The store's per-command rehearsal clone costs ~1 ms at
10k entries. No budget yet, so nothing gates on them. `just bench`.
CI: .github/workflows/check.yml runs `just check` on every push;
scheduled.yml runs proofs, the GnuCash oracle, fuzzing, and mutation
weekly. Tools come from mise.toml.
docs/testing.md: every layer, its oracle rank, command, runtime, and
gate; benchmark baselines; the ASSUMED invariants for Stephen to reject;
the gap list with triggers. docs/oracle.md's fuzzing paragraph had
claimed persistent corpora that didn't exist; corrected.
Also: ledger-import now inherits the workspace lints (nightly cargo
warned).
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01GWVo7x3UHw5kwCUaWxiejX
Max-testing pass, steps 2-4.
Spec-blind tests (rank 1-2): four agents, each given only the specs and
the public interface (doc comments and signatures, every body removed,
never src/ or the existing tests), wrote tests/spec_reports.rs (62),
spec_ledger.rs (72), spec_arap.rs (42), spec_assets_payroll.rs (50):
hand-computed examples per scenario and a proptest law per invariant
(conservation, partition, invariance, scaling, reversal cancels,
"a refusal leaves the books unchanged" over random invalid commands).
They found:
1. A refused payroll run changed the books: an all-zero run passed
validation, then failed at post after creating seven payroll
accounts and using up an entry id. validate_payroll_lines now
refuses a run with no gross pay.
2. A refused add_account used up an account id (empty code, duplicate,
unknown parent). The id is now taken only when the account is added.
3. Stale prose: close_period_to and members_equity still described the
old last-member rounding.
4. Open (left #[ignore]d pending Stephen): depreciation_schedule's doc
says "through the month containing" the date; the code prorates that
month by days.
GnuCash oracle (rank 3, an oracle never the spec): `just oracle` builds
GnuCash 5.10 in a container pinned by base digest and package versions
(oracle/gnucash/) and runs tests/oracle_gnucash.rs: 200 seeded random
books built through wanderbooks (entries, foreign lines, reversals,
monthly closes), every account's balance at month ends and random dates
and each month's P&L, compared exactly: 15,800 comparisons. First run:
4,724 differences, all from foreign lines; without them, zero.
Adjudicated from principles (rules.md B-3): wanderbooks booked
foreign * rate unrounded ($108.34567); a ledger in one money holds no
fractions of its smallest unit, and its cash must match a bank. Stephen
decided: book in the base currency's minor unit, half away from zero.
add_line_fx now rounds; minor units per ISO 4217 list one (2026-09-17,
SIX), generated into Currency::minor_units and recorded in
docs/spec/sources/iso-4217.md. Replay now takes the journaled base
amount (replay_add_line_fx), so lines booked before replay exactly as
booked (contract: books_written_under_older_rules_still_open). Now:
zero differences, foreign lines included.
Tests: 449, from 223.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01GWVo7x3UHw5kwCUaWxiejX
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
swaitsandClaude Opus 5.5