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FA-59351 / Subscription proration billing / Open access

Daily plan-change proration: net rounding composition · case 01

The amount due differs by a cent from the printed charge minus the printed credit.

Verified by executionVariant 1 · 8 checks per implementationDownload source bundle ↓JSON ↗

ROOT CAUSE

The net is recomputed from the price difference with its own rounding instead of from the rounded line items.

VERIFIED REPAIR

Restore the contract rule at the net rounding composition step: use `net = charge - credit`.

Unsuccessful approach: The attempt still derives the net from the price difference and floors it, drifting further on downgrades.

Case contract

Input {old, new prices per period, start, end (exclusive), change} dates with start <= change < end. Remaining days = end - change; period days = end - start. Credit = old*remaining/period and charge = new*remaining/period, each rounded half-up. Net = charge - credit; a positive net is due now, a negative net becomes a credit balance. Return [credit, charge, amount_due, credit_balance].

Why this case matters

Mid-cycle plan changes must credit unused time on the old plan and charge the new plan for the same days.

1 / The failure

Exit 1
"""Failure Map reference implementation. Python standard library only."""
import json
import datetime
import calendar
N = 1
observations = []
def solve(x):
    s = datetime.date(*x['start'])
    e = datetime.date(*x['end'])
    c = datetime.date(*x['change'])
    total = (e - s).days
    remaining = (e - c).days
    def pr(p):
        return (p * remaining * 2 + total) // (2 * total)
    credit = pr(x['old'])
    charge = pr(x['new'])
    net = ((x['new'] - x['old']) * remaining * 2 + total) // (2 * total)
    return [credit, charge, max(0, net), max(0, -net)]
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
fixtures = [[('regression', {'old': 6384, 'new': 4900, 'start': [2023, 3, 23], 'end': [2023, 4, 23], 'change': [2023, 4, 13]}, [2059, 1581, 0, 478]), ('regression', {'old': 12063, 'new': 1999, 'start': [2024, 10, 16], 'end': [2024, 11, 14], 'change': [2024, 11, 2]}, [4992, 827, 0, 4165]), ('partial-repair probe', {'old': 999, 'new': 1999, 'start': [2023, 10, 16], 'end': [2023, 11, 13], 'change': [2023, 11, 8]}, [178, 357, 179, 0]), ('partial-repair probe', {'old': 38640, 'new': 36658, 'start': [2024, 12, 23], 'end': [2025, 1, 22], 'change': [2025, 1, 21]}, [1288, 1222, 0, 66]), ('normal control', {'old': 4900, 'new': 8489, 'start': [2024, 3, 22], 'end': [2024, 6, 20], 'change': [2024, 4, 18]}, [3430, 5942, 2512, 0]), ('normal control', {'old': 4900, 'new': 9900, 'start': [2024, 1, 10], 'end': [2024, 4, 9], 'change': [2024, 3, 7]}, [1797, 3630, 1833, 0]), ('normal control', {'old': 34933, 'new': 4900, 'start': [2024, 12, 28], 'end': [2025, 1, 28], 'change': [2025, 1, 22]}, [6761, 948, 0, 5813]), ('normal control', {'old': 4900, 'new': 9900, 'start': [2024, 6, 18], 'end': [2024, 7, 18], 'change': [2024, 6, 21]}, [4410, 8910, 4500, 0])], [('regression', {'old': 23223, 'new': 4900, 'start': [2025, 2, 5], 'end': [2025, 3, 8], 'change': [2025, 2, 9]}, [20226, 4268, 0, 15958]), ('regression', {'old': 999, 'new': 1999, 'start': [2024, 9, 16], 'end': [2024, 12, 15], 'change': [2024, 12, 10]}, [56, 111, 55, 0]), ('partial-repair probe', {'old': 4900, 'new': 14973, 'start': [2025, 4, 11], 'end': [2025, 5, 10], 'change': [2025, 4, 17]}, [3886, 11875, 7989, 0]), ('partial-repair probe', {'old': 4900, 'new': 9900, 'start': [2024, 11, 22], 'end': [2024, 12, 21], 'change': [2024, 12, 19]}, [338, 683, 345, 0]), ('normal control', {'old': 1999, 'new': 4900, 'start': [2023, 10, 12], 'end': [2024, 10, 11], 'change': [2024, 2, 28]}, [1238, 3034, 1796, 0]), ('normal control', {'old': 999, 'new': 9900, 'start': [2025, 5, 5], 'end': [2025, 6, 3], 'change': [2025, 5, 20]}, [482, 4779, 4297, 0]), ('normal control', {'old': 33928, 'new': 9900, 'start': [2025, 3, 24], 'end': [2025, 4, 24], 'change': [2025, 4, 16]}, [8756, 2555, 0, 6201]), ('normal control', {'old': 1999, 'new': 1999, 'start': [2024, 4, 24], 'end': [2024, 5, 25], 'change': [2024, 5, 23]}, [129, 129, 0, 0])], [('regression', {'old': 1999, 'new': 4900, 'start': [2023, 2, 4], 'end': [2024, 2, 5], 'change': [2023, 8, 2]}, [1021, 2504, 1483, 0]), ('regression', {'old': 999, 'new': 4900, 'start': [2025, 1, 22], 'end': [2025, 4, 22], 'change': [2025, 3, 8]}, [500, 2450, 1950, 0]), ('partial-repair probe', {'old': 27165, 'new': 30410, 'start': [2023, 10, 29], 'end': [2024, 1, 27], 'change': [2023, 12, 28]}, [9055, 10137, 1082, 0]), ('partial-repair probe', {'old': 1999, 'new': 9900, 'start': [2024, 7, 18], 'end': [2024, 8, 18], 'change': [2024, 8, 1]}, [1096, 5429, 4333, 0]), ('normal control', {'old': 1999, 'new': 1999, 'start': [2025, 5, 29], 'end': [2025, 6, 28], 'change': [2025, 6, 7]}, [1399, 1399, 0, 0]), ('normal control', {'old': 999, 'new': 4900, 'start': [2025, 5, 24], 'end': [2025, 6, 24], 'change': [2025, 5, 24]}, [999, 4900, 3901, 0]), ('normal control', {'old': 4900, 'new': 4900, 'start': [2024, 11, 23], 'end': [2025, 11, 24], 'change': [2025, 7, 22]}, [1673, 1673, 0, 0]), ('normal control', {'old': 1999, 'new': 1999, 'start': [2025, 3, 22], 'end': [2025, 6, 20], 'change': [2025, 5, 23]}, [622, 622, 0, 0])], [('regression', {'old': 999, 'new': 1999, 'start': [2023, 12, 29], 'end': [2024, 1, 26], 'change': [2024, 1, 17]}, [321, 643, 322, 0]), ('regression', {'old': 7276, 'new': 43371, 'start': [2024, 5, 21], 'end': [2024, 8, 19], 'change': [2024, 6, 13]}, [5417, 32287, 26870, 0]), ('partial-repair probe', {'old': 6384, 'new': 4900, 'start': [2023, 3, 23], 'end': [2023, 4, 23], 'change': [2023, 4, 13]}, [2059, 1581, 0, 478]), ('partial-repair probe', {'old': 999, 'new': 9900, 'start': [2023, 10, 10], 'end': [2024, 10, 9], 'change': [2024, 4, 29]}, [446, 4421, 3975, 0]), ('normal control', {'old': 4900, 'new': 29832, 'start': [2023, 6, 23], 'end': [2023, 7, 21], 'change': [2023, 7, 16]}, [875, 5327, 4452, 0]), ('normal control', {'old': 4900, 'new': 9900, 'start': [2023, 11, 13], 'end': [2023, 12, 14], 'change': [2023, 11, 26]}, [2845, 5748, 2903, 0]), ('normal control', {'old': 4900, 'new': 4900, 'start': [2024, 5, 8], 'end': [2024, 6, 6], 'change': [2024, 6, 4]}, [338, 338, 0, 0]), ('normal control', {'old': 4900, 'new': 4900, 'start': [2024, 9, 16], 'end': [2024, 12, 15], 'change': [2024, 10, 23]}, [2886, 2886, 0, 0])], [('regression', {'old': 1999, 'new': 10802, 'start': [2025, 1, 26], 'end': [2025, 2, 24], 'change': [2025, 1, 31]}, [1654, 8940, 7286, 0]), ('regression', {'old': 4900, 'new': 46132, 'start': [2024, 4, 13], 'end': [2024, 5, 12], 'change': [2024, 4, 30]}, [2028, 19089, 17061, 0]), ('partial-repair probe', {'old': 23223, 'new': 4900, 'start': [2025, 2, 5], 'end': [2025, 3, 8], 'change': [2025, 2, 9]}, [20226, 4268, 0, 15958]), ('partial-repair probe', {'old': 17701, 'new': 4900, 'start': [2024, 7, 1], 'end': [2024, 8, 1], 'change': [2024, 7, 6]}, [14846, 4110, 0, 10736]), ('normal control', {'old': 4900, 'new': 9900, 'start': [2023, 8, 19], 'end': [2023, 9, 18], 'change': [2023, 9, 4]}, [2287, 4620, 2333, 0]), ('normal control', {'old': 1999, 'new': 9900, 'start': [2024, 9, 13], 'end': [2024, 12, 12], 'change': [2024, 11, 10]}, [711, 3520, 2809, 0]), ('normal control', {'old': 4900, 'new': 1999, 'start': [2023, 7, 16], 'end': [2023, 10, 14], 'change': [2023, 9, 2]}, [2287, 933, 0, 1354]), ('normal control', {'old': 41031, 'new': 1999, 'start': [2023, 6, 12], 'end': [2023, 7, 13], 'change': [2023, 7, 6]}, [9265, 451, 0, 8814])]]
for i, (label, args, expected) in enumerate(fixtures[N-1]):
    check("%s %d" % (label, i), solve(args), expected)
print(json.dumps({"observations": observations, "passed": all(x["passed"] for x in observations)}, ensure_ascii=False))
raise SystemExit(0 if all(x["passed"] for x in observations) else 1)
Boundary fixtureActualExpectedOutcome
regression 0[2059, 1581, 0, 479][2059, 1581, 0, 478]Failed
regression 1[4992, 827, 0, 4164][4992, 827, 0, 4165]Failed
partial-repair probe 2[178, 357, 179, 0][178, 357, 179, 0]Passed
partial-repair probe 3[1288, 1222, 0, 66][1288, 1222, 0, 66]Passed
normal control 4[3430, 5942, 2512, 0][3430, 5942, 2512, 0]Passed
normal control 5[1797, 3630, 1833, 0][1797, 3630, 1833, 0]Passed
normal control 6[6761, 948, 0, 5813][6761, 948, 0, 5813]Passed
normal control 7[4410, 8910, 4500, 0][4410, 8910, 4500, 0]Passed

SHA-256 / 0904942f0a84815a3b0727b64d76f33474db8c68d0c0986d8c3e11c4bb6e7bc3

2 / The unsuccessful fix

Exit 1
"""Failure Map reference implementation. Python standard library only."""
import json
import datetime
import calendar
N = 1
observations = []
def solve(x):
    s = datetime.date(*x['start'])
    e = datetime.date(*x['end'])
    c = datetime.date(*x['change'])
    total = (e - s).days
    remaining = (e - c).days
    def pr(p):
        return (p * remaining * 2 + total) // (2 * total)
    credit = pr(x['old'])
    charge = pr(x['new'])
    net = (x['new'] - x['old']) * remaining // total
    return [credit, charge, max(0, net), max(0, -net)]
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
fixtures = [[('regression', {'old': 6384, 'new': 4900, 'start': [2023, 3, 23], 'end': [2023, 4, 23], 'change': [2023, 4, 13]}, [2059, 1581, 0, 478]), ('regression', {'old': 12063, 'new': 1999, 'start': [2024, 10, 16], 'end': [2024, 11, 14], 'change': [2024, 11, 2]}, [4992, 827, 0, 4165]), ('partial-repair probe', {'old': 999, 'new': 1999, 'start': [2023, 10, 16], 'end': [2023, 11, 13], 'change': [2023, 11, 8]}, [178, 357, 179, 0]), ('partial-repair probe', {'old': 38640, 'new': 36658, 'start': [2024, 12, 23], 'end': [2025, 1, 22], 'change': [2025, 1, 21]}, [1288, 1222, 0, 66]), ('normal control', {'old': 4900, 'new': 8489, 'start': [2024, 3, 22], 'end': [2024, 6, 20], 'change': [2024, 4, 18]}, [3430, 5942, 2512, 0]), ('normal control', {'old': 4900, 'new': 9900, 'start': [2024, 1, 10], 'end': [2024, 4, 9], 'change': [2024, 3, 7]}, [1797, 3630, 1833, 0]), ('normal control', {'old': 34933, 'new': 4900, 'start': [2024, 12, 28], 'end': [2025, 1, 28], 'change': [2025, 1, 22]}, [6761, 948, 0, 5813]), ('normal control', {'old': 4900, 'new': 9900, 'start': [2024, 6, 18], 'end': [2024, 7, 18], 'change': [2024, 6, 21]}, [4410, 8910, 4500, 0])], [('regression', {'old': 23223, 'new': 4900, 'start': [2025, 2, 5], 'end': [2025, 3, 8], 'change': [2025, 2, 9]}, [20226, 4268, 0, 15958]), ('regression', {'old': 999, 'new': 1999, 'start': [2024, 9, 16], 'end': [2024, 12, 15], 'change': [2024, 12, 10]}, [56, 111, 55, 0]), ('partial-repair probe', {'old': 4900, 'new': 14973, 'start': [2025, 4, 11], 'end': [2025, 5, 10], 'change': [2025, 4, 17]}, [3886, 11875, 7989, 0]), ('partial-repair probe', {'old': 4900, 'new': 9900, 'start': [2024, 11, 22], 'end': [2024, 12, 21], 'change': [2024, 12, 19]}, [338, 683, 345, 0]), ('normal control', {'old': 1999, 'new': 4900, 'start': [2023, 10, 12], 'end': [2024, 10, 11], 'change': [2024, 2, 28]}, [1238, 3034, 1796, 0]), ('normal control', {'old': 999, 'new': 9900, 'start': [2025, 5, 5], 'end': [2025, 6, 3], 'change': [2025, 5, 20]}, [482, 4779, 4297, 0]), ('normal control', {'old': 33928, 'new': 9900, 'start': [2025, 3, 24], 'end': [2025, 4, 24], 'change': [2025, 4, 16]}, [8756, 2555, 0, 6201]), ('normal control', {'old': 1999, 'new': 1999, 'start': [2024, 4, 24], 'end': [2024, 5, 25], 'change': [2024, 5, 23]}, [129, 129, 0, 0])], [('regression', {'old': 1999, 'new': 4900, 'start': [2023, 2, 4], 'end': [2024, 2, 5], 'change': [2023, 8, 2]}, [1021, 2504, 1483, 0]), ('regression', {'old': 999, 'new': 4900, 'start': [2025, 1, 22], 'end': [2025, 4, 22], 'change': [2025, 3, 8]}, [500, 2450, 1950, 0]), ('partial-repair probe', {'old': 27165, 'new': 30410, 'start': [2023, 10, 29], 'end': [2024, 1, 27], 'change': [2023, 12, 28]}, [9055, 10137, 1082, 0]), ('partial-repair probe', {'old': 1999, 'new': 9900, 'start': [2024, 7, 18], 'end': [2024, 8, 18], 'change': [2024, 8, 1]}, [1096, 5429, 4333, 0]), ('normal control', {'old': 1999, 'new': 1999, 'start': [2025, 5, 29], 'end': [2025, 6, 28], 'change': [2025, 6, 7]}, [1399, 1399, 0, 0]), ('normal control', {'old': 999, 'new': 4900, 'start': [2025, 5, 24], 'end': [2025, 6, 24], 'change': [2025, 5, 24]}, [999, 4900, 3901, 0]), ('normal control', {'old': 4900, 'new': 4900, 'start': [2024, 11, 23], 'end': [2025, 11, 24], 'change': [2025, 7, 22]}, [1673, 1673, 0, 0]), ('normal control', {'old': 1999, 'new': 1999, 'start': [2025, 3, 22], 'end': [2025, 6, 20], 'change': [2025, 5, 23]}, [622, 622, 0, 0])], [('regression', {'old': 999, 'new': 1999, 'start': [2023, 12, 29], 'end': [2024, 1, 26], 'change': [2024, 1, 17]}, [321, 643, 322, 0]), ('regression', {'old': 7276, 'new': 43371, 'start': [2024, 5, 21], 'end': [2024, 8, 19], 'change': [2024, 6, 13]}, [5417, 32287, 26870, 0]), ('partial-repair probe', {'old': 6384, 'new': 4900, 'start': [2023, 3, 23], 'end': [2023, 4, 23], 'change': [2023, 4, 13]}, [2059, 1581, 0, 478]), ('partial-repair probe', {'old': 999, 'new': 9900, 'start': [2023, 10, 10], 'end': [2024, 10, 9], 'change': [2024, 4, 29]}, [446, 4421, 3975, 0]), ('normal control', {'old': 4900, 'new': 29832, 'start': [2023, 6, 23], 'end': [2023, 7, 21], 'change': [2023, 7, 16]}, [875, 5327, 4452, 0]), ('normal control', {'old': 4900, 'new': 9900, 'start': [2023, 11, 13], 'end': [2023, 12, 14], 'change': [2023, 11, 26]}, [2845, 5748, 2903, 0]), ('normal control', {'old': 4900, 'new': 4900, 'start': [2024, 5, 8], 'end': [2024, 6, 6], 'change': [2024, 6, 4]}, [338, 338, 0, 0]), ('normal control', {'old': 4900, 'new': 4900, 'start': [2024, 9, 16], 'end': [2024, 12, 15], 'change': [2024, 10, 23]}, [2886, 2886, 0, 0])], [('regression', {'old': 1999, 'new': 10802, 'start': [2025, 1, 26], 'end': [2025, 2, 24], 'change': [2025, 1, 31]}, [1654, 8940, 7286, 0]), ('regression', {'old': 4900, 'new': 46132, 'start': [2024, 4, 13], 'end': [2024, 5, 12], 'change': [2024, 4, 30]}, [2028, 19089, 17061, 0]), ('partial-repair probe', {'old': 23223, 'new': 4900, 'start': [2025, 2, 5], 'end': [2025, 3, 8], 'change': [2025, 2, 9]}, [20226, 4268, 0, 15958]), ('partial-repair probe', {'old': 17701, 'new': 4900, 'start': [2024, 7, 1], 'end': [2024, 8, 1], 'change': [2024, 7, 6]}, [14846, 4110, 0, 10736]), ('normal control', {'old': 4900, 'new': 9900, 'start': [2023, 8, 19], 'end': [2023, 9, 18], 'change': [2023, 9, 4]}, [2287, 4620, 2333, 0]), ('normal control', {'old': 1999, 'new': 9900, 'start': [2024, 9, 13], 'end': [2024, 12, 12], 'change': [2024, 11, 10]}, [711, 3520, 2809, 0]), ('normal control', {'old': 4900, 'new': 1999, 'start': [2023, 7, 16], 'end': [2023, 10, 14], 'change': [2023, 9, 2]}, [2287, 933, 0, 1354]), ('normal control', {'old': 41031, 'new': 1999, 'start': [2023, 6, 12], 'end': [2023, 7, 13], 'change': [2023, 7, 6]}, [9265, 451, 0, 8814])]]
for i, (label, args, expected) in enumerate(fixtures[N-1]):
    check("%s %d" % (label, i), solve(args), expected)
print(json.dumps({"observations": observations, "passed": all(x["passed"] for x in observations)}, ensure_ascii=False))
raise SystemExit(0 if all(x["passed"] for x in observations) else 1)
Boundary fixtureActualExpectedOutcome
regression 0[2059, 1581, 0, 479][2059, 1581, 0, 478]Failed
regression 1[4992, 827, 0, 4165][4992, 827, 0, 4165]Passed
partial-repair probe 2[178, 357, 178, 0][178, 357, 179, 0]Failed
partial-repair probe 3[1288, 1222, 0, 67][1288, 1222, 0, 66]Failed
normal control 4[3430, 5942, 2512, 0][3430, 5942, 2512, 0]Passed
normal control 5[1797, 3630, 1833, 0][1797, 3630, 1833, 0]Passed
normal control 6[6761, 948, 0, 5813][6761, 948, 0, 5813]Passed
normal control 7[4410, 8910, 4500, 0][4410, 8910, 4500, 0]Passed

SHA-256 / 23644e052b0ac8b4397892746df368d27e03a0dcedd99db1a972100b4c0f1ede

3 / The verified repair

Exit 0
"""Failure Map reference implementation. Python standard library only."""
import json
import datetime
import calendar
N = 1
observations = []
def solve(x):
    s = datetime.date(*x['start'])
    e = datetime.date(*x['end'])
    c = datetime.date(*x['change'])
    total = (e - s).days
    remaining = (e - c).days
    def pr(p):
        return (p * remaining * 2 + total) // (2 * total)
    credit = pr(x['old'])
    charge = pr(x['new'])
    net = charge - credit
    return [credit, charge, max(0, net), max(0, -net)]
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
fixtures = [[('regression', {'old': 6384, 'new': 4900, 'start': [2023, 3, 23], 'end': [2023, 4, 23], 'change': [2023, 4, 13]}, [2059, 1581, 0, 478]), ('regression', {'old': 12063, 'new': 1999, 'start': [2024, 10, 16], 'end': [2024, 11, 14], 'change': [2024, 11, 2]}, [4992, 827, 0, 4165]), ('partial-repair probe', {'old': 999, 'new': 1999, 'start': [2023, 10, 16], 'end': [2023, 11, 13], 'change': [2023, 11, 8]}, [178, 357, 179, 0]), ('partial-repair probe', {'old': 38640, 'new': 36658, 'start': [2024, 12, 23], 'end': [2025, 1, 22], 'change': [2025, 1, 21]}, [1288, 1222, 0, 66]), ('normal control', {'old': 4900, 'new': 8489, 'start': [2024, 3, 22], 'end': [2024, 6, 20], 'change': [2024, 4, 18]}, [3430, 5942, 2512, 0]), ('normal control', {'old': 4900, 'new': 9900, 'start': [2024, 1, 10], 'end': [2024, 4, 9], 'change': [2024, 3, 7]}, [1797, 3630, 1833, 0]), ('normal control', {'old': 34933, 'new': 4900, 'start': [2024, 12, 28], 'end': [2025, 1, 28], 'change': [2025, 1, 22]}, [6761, 948, 0, 5813]), ('normal control', {'old': 4900, 'new': 9900, 'start': [2024, 6, 18], 'end': [2024, 7, 18], 'change': [2024, 6, 21]}, [4410, 8910, 4500, 0])], [('regression', {'old': 23223, 'new': 4900, 'start': [2025, 2, 5], 'end': [2025, 3, 8], 'change': [2025, 2, 9]}, [20226, 4268, 0, 15958]), ('regression', {'old': 999, 'new': 1999, 'start': [2024, 9, 16], 'end': [2024, 12, 15], 'change': [2024, 12, 10]}, [56, 111, 55, 0]), ('partial-repair probe', {'old': 4900, 'new': 14973, 'start': [2025, 4, 11], 'end': [2025, 5, 10], 'change': [2025, 4, 17]}, [3886, 11875, 7989, 0]), ('partial-repair probe', {'old': 4900, 'new': 9900, 'start': [2024, 11, 22], 'end': [2024, 12, 21], 'change': [2024, 12, 19]}, [338, 683, 345, 0]), ('normal control', {'old': 1999, 'new': 4900, 'start': [2023, 10, 12], 'end': [2024, 10, 11], 'change': [2024, 2, 28]}, [1238, 3034, 1796, 0]), ('normal control', {'old': 999, 'new': 9900, 'start': [2025, 5, 5], 'end': [2025, 6, 3], 'change': [2025, 5, 20]}, [482, 4779, 4297, 0]), ('normal control', {'old': 33928, 'new': 9900, 'start': [2025, 3, 24], 'end': [2025, 4, 24], 'change': [2025, 4, 16]}, [8756, 2555, 0, 6201]), ('normal control', {'old': 1999, 'new': 1999, 'start': [2024, 4, 24], 'end': [2024, 5, 25], 'change': [2024, 5, 23]}, [129, 129, 0, 0])], [('regression', {'old': 1999, 'new': 4900, 'start': [2023, 2, 4], 'end': [2024, 2, 5], 'change': [2023, 8, 2]}, [1021, 2504, 1483, 0]), ('regression', {'old': 999, 'new': 4900, 'start': [2025, 1, 22], 'end': [2025, 4, 22], 'change': [2025, 3, 8]}, [500, 2450, 1950, 0]), ('partial-repair probe', {'old': 27165, 'new': 30410, 'start': [2023, 10, 29], 'end': [2024, 1, 27], 'change': [2023, 12, 28]}, [9055, 10137, 1082, 0]), ('partial-repair probe', {'old': 1999, 'new': 9900, 'start': [2024, 7, 18], 'end': [2024, 8, 18], 'change': [2024, 8, 1]}, [1096, 5429, 4333, 0]), ('normal control', {'old': 1999, 'new': 1999, 'start': [2025, 5, 29], 'end': [2025, 6, 28], 'change': [2025, 6, 7]}, [1399, 1399, 0, 0]), ('normal control', {'old': 999, 'new': 4900, 'start': [2025, 5, 24], 'end': [2025, 6, 24], 'change': [2025, 5, 24]}, [999, 4900, 3901, 0]), ('normal control', {'old': 4900, 'new': 4900, 'start': [2024, 11, 23], 'end': [2025, 11, 24], 'change': [2025, 7, 22]}, [1673, 1673, 0, 0]), ('normal control', {'old': 1999, 'new': 1999, 'start': [2025, 3, 22], 'end': [2025, 6, 20], 'change': [2025, 5, 23]}, [622, 622, 0, 0])], [('regression', {'old': 999, 'new': 1999, 'start': [2023, 12, 29], 'end': [2024, 1, 26], 'change': [2024, 1, 17]}, [321, 643, 322, 0]), ('regression', {'old': 7276, 'new': 43371, 'start': [2024, 5, 21], 'end': [2024, 8, 19], 'change': [2024, 6, 13]}, [5417, 32287, 26870, 0]), ('partial-repair probe', {'old': 6384, 'new': 4900, 'start': [2023, 3, 23], 'end': [2023, 4, 23], 'change': [2023, 4, 13]}, [2059, 1581, 0, 478]), ('partial-repair probe', {'old': 999, 'new': 9900, 'start': [2023, 10, 10], 'end': [2024, 10, 9], 'change': [2024, 4, 29]}, [446, 4421, 3975, 0]), ('normal control', {'old': 4900, 'new': 29832, 'start': [2023, 6, 23], 'end': [2023, 7, 21], 'change': [2023, 7, 16]}, [875, 5327, 4452, 0]), ('normal control', {'old': 4900, 'new': 9900, 'start': [2023, 11, 13], 'end': [2023, 12, 14], 'change': [2023, 11, 26]}, [2845, 5748, 2903, 0]), ('normal control', {'old': 4900, 'new': 4900, 'start': [2024, 5, 8], 'end': [2024, 6, 6], 'change': [2024, 6, 4]}, [338, 338, 0, 0]), ('normal control', {'old': 4900, 'new': 4900, 'start': [2024, 9, 16], 'end': [2024, 12, 15], 'change': [2024, 10, 23]}, [2886, 2886, 0, 0])], [('regression', {'old': 1999, 'new': 10802, 'start': [2025, 1, 26], 'end': [2025, 2, 24], 'change': [2025, 1, 31]}, [1654, 8940, 7286, 0]), ('regression', {'old': 4900, 'new': 46132, 'start': [2024, 4, 13], 'end': [2024, 5, 12], 'change': [2024, 4, 30]}, [2028, 19089, 17061, 0]), ('partial-repair probe', {'old': 23223, 'new': 4900, 'start': [2025, 2, 5], 'end': [2025, 3, 8], 'change': [2025, 2, 9]}, [20226, 4268, 0, 15958]), ('partial-repair probe', {'old': 17701, 'new': 4900, 'start': [2024, 7, 1], 'end': [2024, 8, 1], 'change': [2024, 7, 6]}, [14846, 4110, 0, 10736]), ('normal control', {'old': 4900, 'new': 9900, 'start': [2023, 8, 19], 'end': [2023, 9, 18], 'change': [2023, 9, 4]}, [2287, 4620, 2333, 0]), ('normal control', {'old': 1999, 'new': 9900, 'start': [2024, 9, 13], 'end': [2024, 12, 12], 'change': [2024, 11, 10]}, [711, 3520, 2809, 0]), ('normal control', {'old': 4900, 'new': 1999, 'start': [2023, 7, 16], 'end': [2023, 10, 14], 'change': [2023, 9, 2]}, [2287, 933, 0, 1354]), ('normal control', {'old': 41031, 'new': 1999, 'start': [2023, 6, 12], 'end': [2023, 7, 13], 'change': [2023, 7, 6]}, [9265, 451, 0, 8814])]]
for i, (label, args, expected) in enumerate(fixtures[N-1]):
    check("%s %d" % (label, i), solve(args), expected)
print(json.dumps({"observations": observations, "passed": all(x["passed"] for x in observations)}, ensure_ascii=False))
raise SystemExit(0 if all(x["passed"] for x in observations) else 1)
Boundary fixtureActualExpectedOutcome
regression 0[2059, 1581, 0, 478][2059, 1581, 0, 478]Passed
regression 1[4992, 827, 0, 4165][4992, 827, 0, 4165]Passed
partial-repair probe 2[178, 357, 179, 0][178, 357, 179, 0]Passed
partial-repair probe 3[1288, 1222, 0, 66][1288, 1222, 0, 66]Passed
normal control 4[3430, 5942, 2512, 0][3430, 5942, 2512, 0]Passed
normal control 5[1797, 3630, 1833, 0][1797, 3630, 1833, 0]Passed
normal control 6[6761, 948, 0, 5813][6761, 948, 0, 5813]Passed
normal control 7[4410, 8910, 4500, 0][4410, 8910, 4500, 0]Passed

SHA-256 / bea707d9976e4216adeac9f9d04c9e6931361e5f3fb9c7dc93ccd32ffde9f1ea

Verification & scope

A deterministic teaching model of a stipulated billing rule. It makes no claim to reproduce any billing provider's exact behaviour and is not billing software. This reproducer isolates one failure mechanism. Results cover the supplied fixtures. Variants within a family share a test contract and should remain grouped when constructing evaluation splits. Related mechanisms with a shared evaluation_group must also remain together; these controlled models are not independent production incidents.

Observations recorded using Python 3.12.14 at 2026-09-29T14:46:35.484851+00:00.

Case digest / 4f1aa86b39d5fb729c7bf6ac535c98873160cda49ac076bdc3c438c0fd3bd47e