Two quantization orders existed and met at exactly one comparison.
SavingsLedger quantizes every realized candidate to integer øre and sums the
ints; run.py's goal baselines summed Project.total_cost FLOATS across items and
projects and quantized the total once. _goal_limit_if_reached compared the
former against a threshold derived from the latter — so whether a portfolio pass
stops early was decided by two differently-computed sides.
Measured divergence: three 60000.005 NOK lines are 18000003 øre quantized first
but 18000001 summed first (the float sum drifts to 180000.01499999998).
Decision: quantize per cost line, then sum integers. Each CostItem IS a money
amount — S4.0 made per-line quantity/unit_cost the validator's ground truth — and
integer addition is associative, keeping totals order-independent under the D-D
wave model, which the float fold is not.
ledger.to_ore is now the framework's one NOK->øre conversion; run.py imports it
rather than keeping a private copy (the S4.0 REPLIES precedent).
Measuring the mutations found two further gaps, both now closed: the per-project
baseline is a SECOND call site whose mutation survived the whole suite, and
realize bypassing to_ore with a raw float*100 was caught by nothing.
Load-bearing MEASURED (tests/test_money_quantization_loadbearing.py), five
mutations all red: detach the portfolio baseline · detach the per-project
baseline · reintroduce a private copy in run.py · change the rounding mode · let
realize bypass to_ore. 615 -> 621 tests.
Honesty boundary: sum_claimed_saving_nok (run.py:_aggregate) is deliberately
untouched — a float NOK reporting field that is never quantized and never
compared against the ledger, hence outside the ordering defect.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01WiY53sm8JFqk7NN75g5wRS
Kjell Tore Guttormsen
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