FA-61326 / Bond day-count conventions / Open access

Coupon period lookup for a settlement date: settlements before the first coupon are rejected as not issued · case 01

Trades in the first coupon period are refused.

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

ROOT CAUSE

The not-issued guard compares against the first coupon date instead of the issue date.

VERIFIED REPAIR

Reject only settlements strictly before the issue date.

Unsuccessful approach: Rejecting settlement on the issue date itself blocks primary settlement.

Case contract

Inputs issue date, ascending coupon schedule (last = maturity) and settlement. Settlement before issue returns "not issued"; on or after maturity returns "matured". Otherwise return [period start, next coupon] where a settlement on a coupon date belongs to the following period and the first period starts at issue.

Why this case matters

Bond accrual and pricing systems depend on exact day-count arithmetic; a single-day error changes settlement cash.

1 / The failure

Exit 1

"""Failure Map reference implementation. Python standard library only."""
import json
import datetime
import bisect
N = 1
observations = []
def solve(issue, schedule, settle):
    I = datetime.date(*issue)
    dates = [datetime.date(*d) for d in schedule]
    S = datetime.date(*settle)
    if S < dates[0]:
        return 'not issued'
    if S >= dates[-1]:
        return 'matured'
    i = bisect.bisect_right(dates, S)
    prev = dates[i - 1] if i > 0 else I
    nxt = dates[i]
    return [[prev.year, prev.month, prev.day], [nxt.year, nxt.month, nxt.day]]
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
fixtures = [[['regression pre-issue guard 1', [[2024, 4, 9], [[2024, 6, 16], [2025, 6, 16]], [2024, 5, 16]], [[2024, 4, 9], [2024, 6, 16]]], ['regression pre-issue guard 2', [[2026, 4, 22], [[2027, 3, 22], [2027, 9, 22]], [2026, 7, 12]], [[2026, 4, 22], [2027, 3, 22]]], ['partial repair probe 1', [[2020, 2, 21], [[2020, 3, 30], [2020, 6, 30], [2020, 9, 30]], [2020, 2, 21]], [[2020, 2, 21], [2020, 3, 30]]], ['partial repair probe 2', [[2019, 4, 25], [[2019, 12, 11], [2020, 3, 11], [2020, 6, 11], [2020, 9, 11], [2020, 12, 11]], [2019, 4, 25]], [[2019, 4, 25], [2019, 12, 11]]], ['normal control 1', [[2023, 5, 23], [[2023, 9, 30], [2024, 3, 30], [2024, 9, 30], [2025, 3, 30]], [2023, 5, 19]], 'not issued'], ['normal control 2', [[2037, 8, 30], [[2037, 11, 30], [2038, 2, 28], [2038, 5, 30], [2038, 8, 30], [2038, 11, 30]], [2038, 7, 31]], [[2038, 5, 30], [2038, 8, 30]]], ['normal control 3', [[2006, 5, 24], [[2006, 7, 31], [2006, 10, 31], [2007, 1, 31]], [2006, 8, 31]], [[2006, 7, 31], [2006, 10, 31]]], ['normal control 4', [[2033, 10, 20], [[2034, 1, 12], [2034, 7, 12], [2035, 1, 12]], [2035, 1, 12]], 'matured']], [['regression pre-issue guard 1', [[2038, 7, 13], [[2039, 6, 30], [2040, 6, 30], [2041, 6, 30], [2042, 6, 30], [2043, 6, 30]], [2038, 8, 30]], [[2038, 7, 13], [2039, 6, 30]]], ['regression pre-issue guard 2', [[2019, 9, 14], [[2020, 9, 29], [2021, 3, 29], [2021, 9, 29], [2022, 3, 29], [2022, 9, 29]], [2020, 3, 16]], [[2019, 9, 14], [2020, 9, 29]]], ['partial repair probe 1', [[2008, 7, 7], [[2008, 9, 15], [2008, 12, 15]], [2008, 7, 7]], [[2008, 7, 7], [2008, 9, 15]]], ['partial repair probe 2', [[2022, 1, 3], [[2022, 7, 31], [2023, 1, 31], [2023, 7, 31], [2024, 1, 31], [2024, 7, 31]], [2022, 1, 3]], [[2022, 1, 3], [2022, 7, 31]]], ['normal control 1', [[2004, 8, 30], [[2005, 5, 30], [2005, 11, 30], [2006, 5, 30]], [2005, 5, 30]], [[2005, 5, 30], [2005, 11, 30]]], ['normal control 2', [[2021, 4, 1], [[2021, 6, 30], [2022, 6, 30]], [2021, 9, 29]], [[2021, 6, 30], [2022, 6, 30]]], ['normal control 3', [[2035, 6, 6], [[2036, 6, 2], [2036, 12, 2]], [2036, 7, 30]], [[2036, 6, 2], [2036, 12, 2]]], ['normal control 4', [[2039, 11, 18], [[2040, 3, 28], [2040, 6, 28], [2040, 9, 28], [2040, 12, 28], [2041, 3, 28]], [2040, 4, 5]], [[2040, 3, 28], [2040, 6, 28]]]], [['regression pre-issue guard 1', [[2014, 12, 10], [[2015, 12, 31], [2016, 6, 30]], [2015, 11, 4]], [[2014, 12, 10], [2015, 12, 31]]], ['regression pre-issue guard 2', [[2016, 2, 8], [[2017, 2, 24], [2017, 5, 24], [2017, 8, 24], [2017, 11, 24], [2018, 2, 24], [2018, 5, 24]], [2016, 8, 10]], [[2016, 2, 8], [2017, 2, 24]]], ['partial repair probe 1', [[2010, 2, 12], [[2011, 1, 28], [2011, 7, 28], [2012, 1, 28], [2012, 7, 28], [2013, 1, 28]], [2010, 2, 12]], [[2010, 2, 12], [2011, 1, 28]]], ['partial repair probe 2', [[2032, 1, 15], [[2032, 12, 27], [2033, 3, 27], [2033, 6, 27], [2033, 9, 27]], [2032, 1, 15]], [[2032, 1, 15], [2032, 12, 27]]], ['normal control 1', [[2026, 12, 12], [[2027, 2, 11], [2027, 5, 11], [2027, 8, 11], [2027, 11, 11], [2028, 2, 11], [2028, 5, 11]], [2027, 2, 11]], [[2027, 2, 11], [2027, 5, 11]]], ['normal control 2', [[2016, 6, 2], [[2017, 1, 28], [2017, 7, 28], [2018, 1, 28], [2018, 7, 28], [2019, 1, 28]], [2016, 5, 28]], 'not issued'], ['normal control 3', [[2020, 6, 5], [[2021, 6, 30], [2021, 9, 30], [2021, 12, 30], [2022, 3, 30], [2022, 6, 30]], [2021, 7, 25]], [[2021, 6, 30], [2021, 9, 30]]], ['normal control 4', [[2034, 11, 1], [[2034, 11, 30], [2035, 5, 30], [2035, 11, 30], [2036, 5, 30]], [2035, 9, 9]], [[2035, 5, 30], [2035, 11, 30]]]], [['regression pre-issue guard 1', [[2019, 5, 4], [[2020, 3, 28], [2021, 3, 28], [2022, 3, 28]], [2019, 9, 1]], [[2019, 5, 4], [2020, 3, 28]]], ['regression pre-issue guard 2', [[2026, 11, 3], [[2027, 7, 31], [2028, 7, 31]], [2027, 3, 28]], [[2026, 11, 3], [2027, 7, 31]]], ['partial repair probe 1', [[2019, 6, 27], [[2019, 12, 31], [2020, 6, 30]], [2019, 6, 27]], [[2019, 6, 27], [2019, 12, 31]]], ['partial repair probe 2', [[2011, 1, 3], [[2011, 1, 13], [2011, 7, 13]], [2011, 1, 3]], [[2011, 1, 3], [2011, 1, 13]]], ['normal control 1', [[2038, 10, 4], [[2039, 1, 25], [2039, 7, 25], [2040, 1, 25]], [2039, 10, 20]], [[2039, 7, 25], [2040, 1, 25]]], ['normal control 2', [[2024, 4, 22], [[2024, 7, 20], [2025, 7, 20], [2026, 7, 20], [2027, 7, 20], [2028, 7, 20]], [2024, 4, 21]], 'not issued'], ['normal control 3', [[2018, 6, 22], [[2019, 7, 26], [2020, 1, 26], [2020, 7, 26], [2021, 1, 26], [2021, 7, 26], [2022, 1, 26]], [2020, 6, 1]], [[2020, 1, 26], [2020, 7, 26]]], ['normal control 4', [[2031, 1, 4], [[2031, 3, 29], [2031, 9, 29], [2032, 3, 29], [2032, 9, 29], [2033, 3, 29]], [2031, 4, 8]], [[2031, 3, 29], [2031, 9, 29]]]], [['regression pre-issue guard 1', [[2012, 11, 11], [[2013, 4, 20], [2013, 7, 20], [2013, 10, 20], [2014, 1, 20]], [2012, 12, 1]], [[2012, 11, 11], [2013, 4, 20]]], ['regression pre-issue guard 2', [[2021, 2, 3], [[2021, 12, 31], [2022, 6, 30], [2022, 12, 31], [2023, 6, 30]], [2021, 5, 9]], [[2021, 2, 3], [2021, 12, 31]]], ['partial repair probe 1', [[2038, 1, 19], [[2038, 11, 29], [2039, 2, 28], [2039, 5, 29]], [2038, 1, 19]], [[2038, 1, 19], [2038, 11, 29]]], ['partial repair probe 2', [[2008, 5, 10], [[2009, 3, 31], [2009, 6, 30]], [2008, 5, 10]], [[2008, 5, 10], [2009, 3, 31]]], ['normal control 1', [[2031, 3, 25], [[2031, 9, 29], [2032, 9, 29], [2033, 9, 29], [2034, 9, 29]], [2031, 3, 23]], 'not issued'], ['normal control 2', [[2009, 6, 7], [[2010, 5, 29], [2010, 8, 29], [2010, 11, 29]], [2010, 11, 29]], 'matured'], ['normal control 3', [[2032, 5, 17], [[2032, 10, 31], [2033, 10, 31], [2034, 10, 31], [2035, 10, 31], [2036, 10, 31]], [2034, 12, 25]], [[2034, 10, 31], [2035, 10, 31]]], ['normal control 4', [[2008, 12, 16], [[2009, 7, 31], [2009, 10, 31], [2010, 1, 31], [2010, 4, 30], [2010, 7, 31], [2010, 10, 31]], [2010, 3, 13]], [[2010, 1, 31], [2010, 4, 30]]]]]
for label, args, expected in fixtures[N-1]:
    check(label, 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 fixture	Actual	Expected	Outcome
regression pre-issue guard 1	`not issued`	`[[2024, 4, 9], [2024, 6, 16]]`	Failed
regression pre-issue guard 2	`not issued`	`[[2026, 4, 22], [2027, 3, 22]]`	Failed
partial repair probe 1	`not issued`	`[[2020, 2, 21], [2020, 3, 30]]`	Failed
partial repair probe 2	`not issued`	`[[2019, 4, 25], [2019, 12, 11]]`	Failed
normal control 1	`not issued`	`not issued`	Passed
normal control 2	`[[2038, 5, 30], [2038, 8, 30]]`	`[[2038, 5, 30], [2038, 8, 30]]`	Passed
normal control 3	`[[2006, 7, 31], [2006, 10, 31]]`	`[[2006, 7, 31], [2006, 10, 31]]`	Passed
normal control 4	`matured`	`matured`	Passed

SHA-256 / a74eee60bd097e03a6f00dfa734af7ff4baf0f62a805024234e51ec77f23b4b8

2 / The unsuccessful fix

Exit 1

"""Failure Map reference implementation. Python standard library only."""
import json
import datetime
import bisect
N = 1
observations = []
def solve(issue, schedule, settle):
    I = datetime.date(*issue)
    dates = [datetime.date(*d) for d in schedule]
    S = datetime.date(*settle)
    if S <= I:
        return 'not issued'
    if S >= dates[-1]:
        return 'matured'
    i = bisect.bisect_right(dates, S)
    prev = dates[i - 1] if i > 0 else I
    nxt = dates[i]
    return [[prev.year, prev.month, prev.day], [nxt.year, nxt.month, nxt.day]]
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
fixtures = [[['regression pre-issue guard 1', [[2024, 4, 9], [[2024, 6, 16], [2025, 6, 16]], [2024, 5, 16]], [[2024, 4, 9], [2024, 6, 16]]], ['regression pre-issue guard 2', [[2026, 4, 22], [[2027, 3, 22], [2027, 9, 22]], [2026, 7, 12]], [[2026, 4, 22], [2027, 3, 22]]], ['partial repair probe 1', [[2020, 2, 21], [[2020, 3, 30], [2020, 6, 30], [2020, 9, 30]], [2020, 2, 21]], [[2020, 2, 21], [2020, 3, 30]]], ['partial repair probe 2', [[2019, 4, 25], [[2019, 12, 11], [2020, 3, 11], [2020, 6, 11], [2020, 9, 11], [2020, 12, 11]], [2019, 4, 25]], [[2019, 4, 25], [2019, 12, 11]]], ['normal control 1', [[2023, 5, 23], [[2023, 9, 30], [2024, 3, 30], [2024, 9, 30], [2025, 3, 30]], [2023, 5, 19]], 'not issued'], ['normal control 2', [[2037, 8, 30], [[2037, 11, 30], [2038, 2, 28], [2038, 5, 30], [2038, 8, 30], [2038, 11, 30]], [2038, 7, 31]], [[2038, 5, 30], [2038, 8, 30]]], ['normal control 3', [[2006, 5, 24], [[2006, 7, 31], [2006, 10, 31], [2007, 1, 31]], [2006, 8, 31]], [[2006, 7, 31], [2006, 10, 31]]], ['normal control 4', [[2033, 10, 20], [[2034, 1, 12], [2034, 7, 12], [2035, 1, 12]], [2035, 1, 12]], 'matured']], [['regression pre-issue guard 1', [[2038, 7, 13], [[2039, 6, 30], [2040, 6, 30], [2041, 6, 30], [2042, 6, 30], [2043, 6, 30]], [2038, 8, 30]], [[2038, 7, 13], [2039, 6, 30]]], ['regression pre-issue guard 2', [[2019, 9, 14], [[2020, 9, 29], [2021, 3, 29], [2021, 9, 29], [2022, 3, 29], [2022, 9, 29]], [2020, 3, 16]], [[2019, 9, 14], [2020, 9, 29]]], ['partial repair probe 1', [[2008, 7, 7], [[2008, 9, 15], [2008, 12, 15]], [2008, 7, 7]], [[2008, 7, 7], [2008, 9, 15]]], ['partial repair probe 2', [[2022, 1, 3], [[2022, 7, 31], [2023, 1, 31], [2023, 7, 31], [2024, 1, 31], [2024, 7, 31]], [2022, 1, 3]], [[2022, 1, 3], [2022, 7, 31]]], ['normal control 1', [[2004, 8, 30], [[2005, 5, 30], [2005, 11, 30], [2006, 5, 30]], [2005, 5, 30]], [[2005, 5, 30], [2005, 11, 30]]], ['normal control 2', [[2021, 4, 1], [[2021, 6, 30], [2022, 6, 30]], [2021, 9, 29]], [[2021, 6, 30], [2022, 6, 30]]], ['normal control 3', [[2035, 6, 6], [[2036, 6, 2], [2036, 12, 2]], [2036, 7, 30]], [[2036, 6, 2], [2036, 12, 2]]], ['normal control 4', [[2039, 11, 18], [[2040, 3, 28], [2040, 6, 28], [2040, 9, 28], [2040, 12, 28], [2041, 3, 28]], [2040, 4, 5]], [[2040, 3, 28], [2040, 6, 28]]]], [['regression pre-issue guard 1', [[2014, 12, 10], [[2015, 12, 31], [2016, 6, 30]], [2015, 11, 4]], [[2014, 12, 10], [2015, 12, 31]]], ['regression pre-issue guard 2', [[2016, 2, 8], [[2017, 2, 24], [2017, 5, 24], [2017, 8, 24], [2017, 11, 24], [2018, 2, 24], [2018, 5, 24]], [2016, 8, 10]], [[2016, 2, 8], [2017, 2, 24]]], ['partial repair probe 1', [[2010, 2, 12], [[2011, 1, 28], [2011, 7, 28], [2012, 1, 28], [2012, 7, 28], [2013, 1, 28]], [2010, 2, 12]], [[2010, 2, 12], [2011, 1, 28]]], ['partial repair probe 2', [[2032, 1, 15], [[2032, 12, 27], [2033, 3, 27], [2033, 6, 27], [2033, 9, 27]], [2032, 1, 15]], [[2032, 1, 15], [2032, 12, 27]]], ['normal control 1', [[2026, 12, 12], [[2027, 2, 11], [2027, 5, 11], [2027, 8, 11], [2027, 11, 11], [2028, 2, 11], [2028, 5, 11]], [2027, 2, 11]], [[2027, 2, 11], [2027, 5, 11]]], ['normal control 2', [[2016, 6, 2], [[2017, 1, 28], [2017, 7, 28], [2018, 1, 28], [2018, 7, 28], [2019, 1, 28]], [2016, 5, 28]], 'not issued'], ['normal control 3', [[2020, 6, 5], [[2021, 6, 30], [2021, 9, 30], [2021, 12, 30], [2022, 3, 30], [2022, 6, 30]], [2021, 7, 25]], [[2021, 6, 30], [2021, 9, 30]]], ['normal control 4', [[2034, 11, 1], [[2034, 11, 30], [2035, 5, 30], [2035, 11, 30], [2036, 5, 30]], [2035, 9, 9]], [[2035, 5, 30], [2035, 11, 30]]]], [['regression pre-issue guard 1', [[2019, 5, 4], [[2020, 3, 28], [2021, 3, 28], [2022, 3, 28]], [2019, 9, 1]], [[2019, 5, 4], [2020, 3, 28]]], ['regression pre-issue guard 2', [[2026, 11, 3], [[2027, 7, 31], [2028, 7, 31]], [2027, 3, 28]], [[2026, 11, 3], [2027, 7, 31]]], ['partial repair probe 1', [[2019, 6, 27], [[2019, 12, 31], [2020, 6, 30]], [2019, 6, 27]], [[2019, 6, 27], [2019, 12, 31]]], ['partial repair probe 2', [[2011, 1, 3], [[2011, 1, 13], [2011, 7, 13]], [2011, 1, 3]], [[2011, 1, 3], [2011, 1, 13]]], ['normal control 1', [[2038, 10, 4], [[2039, 1, 25], [2039, 7, 25], [2040, 1, 25]], [2039, 10, 20]], [[2039, 7, 25], [2040, 1, 25]]], ['normal control 2', [[2024, 4, 22], [[2024, 7, 20], [2025, 7, 20], [2026, 7, 20], [2027, 7, 20], [2028, 7, 20]], [2024, 4, 21]], 'not issued'], ['normal control 3', [[2018, 6, 22], [[2019, 7, 26], [2020, 1, 26], [2020, 7, 26], [2021, 1, 26], [2021, 7, 26], [2022, 1, 26]], [2020, 6, 1]], [[2020, 1, 26], [2020, 7, 26]]], ['normal control 4', [[2031, 1, 4], [[2031, 3, 29], [2031, 9, 29], [2032, 3, 29], [2032, 9, 29], [2033, 3, 29]], [2031, 4, 8]], [[2031, 3, 29], [2031, 9, 29]]]], [['regression pre-issue guard 1', [[2012, 11, 11], [[2013, 4, 20], [2013, 7, 20], [2013, 10, 20], [2014, 1, 20]], [2012, 12, 1]], [[2012, 11, 11], [2013, 4, 20]]], ['regression pre-issue guard 2', [[2021, 2, 3], [[2021, 12, 31], [2022, 6, 30], [2022, 12, 31], [2023, 6, 30]], [2021, 5, 9]], [[2021, 2, 3], [2021, 12, 31]]], ['partial repair probe 1', [[2038, 1, 19], [[2038, 11, 29], [2039, 2, 28], [2039, 5, 29]], [2038, 1, 19]], [[2038, 1, 19], [2038, 11, 29]]], ['partial repair probe 2', [[2008, 5, 10], [[2009, 3, 31], [2009, 6, 30]], [2008, 5, 10]], [[2008, 5, 10], [2009, 3, 31]]], ['normal control 1', [[2031, 3, 25], [[2031, 9, 29], [2032, 9, 29], [2033, 9, 29], [2034, 9, 29]], [2031, 3, 23]], 'not issued'], ['normal control 2', [[2009, 6, 7], [[2010, 5, 29], [2010, 8, 29], [2010, 11, 29]], [2010, 11, 29]], 'matured'], ['normal control 3', [[2032, 5, 17], [[2032, 10, 31], [2033, 10, 31], [2034, 10, 31], [2035, 10, 31], [2036, 10, 31]], [2034, 12, 25]], [[2034, 10, 31], [2035, 10, 31]]], ['normal control 4', [[2008, 12, 16], [[2009, 7, 31], [2009, 10, 31], [2010, 1, 31], [2010, 4, 30], [2010, 7, 31], [2010, 10, 31]], [2010, 3, 13]], [[2010, 1, 31], [2010, 4, 30]]]]]
for label, args, expected in fixtures[N-1]:
    check(label, 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 fixture	Actual	Expected	Outcome
regression pre-issue guard 1	`[[2024, 4, 9], [2024, 6, 16]]`	`[[2024, 4, 9], [2024, 6, 16]]`	Passed
regression pre-issue guard 2	`[[2026, 4, 22], [2027, 3, 22]]`	`[[2026, 4, 22], [2027, 3, 22]]`	Passed
partial repair probe 1	`not issued`	`[[2020, 2, 21], [2020, 3, 30]]`	Failed
partial repair probe 2	`not issued`	`[[2019, 4, 25], [2019, 12, 11]]`	Failed
normal control 1	`not issued`	`not issued`	Passed
normal control 2	`[[2038, 5, 30], [2038, 8, 30]]`	`[[2038, 5, 30], [2038, 8, 30]]`	Passed
normal control 3	`[[2006, 7, 31], [2006, 10, 31]]`	`[[2006, 7, 31], [2006, 10, 31]]`	Passed
normal control 4	`matured`	`matured`	Passed

SHA-256 / b25e6d6b1ca493a167c392d2215d0fe39849618ff332208c218acdbae4a54c58

3 / The verified repair

Exit 0

"""Failure Map reference implementation. Python standard library only."""
import json
import datetime
import bisect
N = 1
observations = []
def solve(issue, schedule, settle):
    I = datetime.date(*issue)
    dates = [datetime.date(*d) for d in schedule]
    S = datetime.date(*settle)
    if S < I:
        return 'not issued'
    if S >= dates[-1]:
        return 'matured'
    i = bisect.bisect_right(dates, S)
    prev = dates[i - 1] if i > 0 else I
    nxt = dates[i]
    return [[prev.year, prev.month, prev.day], [nxt.year, nxt.month, nxt.day]]
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
fixtures = [[['regression pre-issue guard 1', [[2024, 4, 9], [[2024, 6, 16], [2025, 6, 16]], [2024, 5, 16]], [[2024, 4, 9], [2024, 6, 16]]], ['regression pre-issue guard 2', [[2026, 4, 22], [[2027, 3, 22], [2027, 9, 22]], [2026, 7, 12]], [[2026, 4, 22], [2027, 3, 22]]], ['partial repair probe 1', [[2020, 2, 21], [[2020, 3, 30], [2020, 6, 30], [2020, 9, 30]], [2020, 2, 21]], [[2020, 2, 21], [2020, 3, 30]]], ['partial repair probe 2', [[2019, 4, 25], [[2019, 12, 11], [2020, 3, 11], [2020, 6, 11], [2020, 9, 11], [2020, 12, 11]], [2019, 4, 25]], [[2019, 4, 25], [2019, 12, 11]]], ['normal control 1', [[2023, 5, 23], [[2023, 9, 30], [2024, 3, 30], [2024, 9, 30], [2025, 3, 30]], [2023, 5, 19]], 'not issued'], ['normal control 2', [[2037, 8, 30], [[2037, 11, 30], [2038, 2, 28], [2038, 5, 30], [2038, 8, 30], [2038, 11, 30]], [2038, 7, 31]], [[2038, 5, 30], [2038, 8, 30]]], ['normal control 3', [[2006, 5, 24], [[2006, 7, 31], [2006, 10, 31], [2007, 1, 31]], [2006, 8, 31]], [[2006, 7, 31], [2006, 10, 31]]], ['normal control 4', [[2033, 10, 20], [[2034, 1, 12], [2034, 7, 12], [2035, 1, 12]], [2035, 1, 12]], 'matured']], [['regression pre-issue guard 1', [[2038, 7, 13], [[2039, 6, 30], [2040, 6, 30], [2041, 6, 30], [2042, 6, 30], [2043, 6, 30]], [2038, 8, 30]], [[2038, 7, 13], [2039, 6, 30]]], ['regression pre-issue guard 2', [[2019, 9, 14], [[2020, 9, 29], [2021, 3, 29], [2021, 9, 29], [2022, 3, 29], [2022, 9, 29]], [2020, 3, 16]], [[2019, 9, 14], [2020, 9, 29]]], ['partial repair probe 1', [[2008, 7, 7], [[2008, 9, 15], [2008, 12, 15]], [2008, 7, 7]], [[2008, 7, 7], [2008, 9, 15]]], ['partial repair probe 2', [[2022, 1, 3], [[2022, 7, 31], [2023, 1, 31], [2023, 7, 31], [2024, 1, 31], [2024, 7, 31]], [2022, 1, 3]], [[2022, 1, 3], [2022, 7, 31]]], ['normal control 1', [[2004, 8, 30], [[2005, 5, 30], [2005, 11, 30], [2006, 5, 30]], [2005, 5, 30]], [[2005, 5, 30], [2005, 11, 30]]], ['normal control 2', [[2021, 4, 1], [[2021, 6, 30], [2022, 6, 30]], [2021, 9, 29]], [[2021, 6, 30], [2022, 6, 30]]], ['normal control 3', [[2035, 6, 6], [[2036, 6, 2], [2036, 12, 2]], [2036, 7, 30]], [[2036, 6, 2], [2036, 12, 2]]], ['normal control 4', [[2039, 11, 18], [[2040, 3, 28], [2040, 6, 28], [2040, 9, 28], [2040, 12, 28], [2041, 3, 28]], [2040, 4, 5]], [[2040, 3, 28], [2040, 6, 28]]]], [['regression pre-issue guard 1', [[2014, 12, 10], [[2015, 12, 31], [2016, 6, 30]], [2015, 11, 4]], [[2014, 12, 10], [2015, 12, 31]]], ['regression pre-issue guard 2', [[2016, 2, 8], [[2017, 2, 24], [2017, 5, 24], [2017, 8, 24], [2017, 11, 24], [2018, 2, 24], [2018, 5, 24]], [2016, 8, 10]], [[2016, 2, 8], [2017, 2, 24]]], ['partial repair probe 1', [[2010, 2, 12], [[2011, 1, 28], [2011, 7, 28], [2012, 1, 28], [2012, 7, 28], [2013, 1, 28]], [2010, 2, 12]], [[2010, 2, 12], [2011, 1, 28]]], ['partial repair probe 2', [[2032, 1, 15], [[2032, 12, 27], [2033, 3, 27], [2033, 6, 27], [2033, 9, 27]], [2032, 1, 15]], [[2032, 1, 15], [2032, 12, 27]]], ['normal control 1', [[2026, 12, 12], [[2027, 2, 11], [2027, 5, 11], [2027, 8, 11], [2027, 11, 11], [2028, 2, 11], [2028, 5, 11]], [2027, 2, 11]], [[2027, 2, 11], [2027, 5, 11]]], ['normal control 2', [[2016, 6, 2], [[2017, 1, 28], [2017, 7, 28], [2018, 1, 28], [2018, 7, 28], [2019, 1, 28]], [2016, 5, 28]], 'not issued'], ['normal control 3', [[2020, 6, 5], [[2021, 6, 30], [2021, 9, 30], [2021, 12, 30], [2022, 3, 30], [2022, 6, 30]], [2021, 7, 25]], [[2021, 6, 30], [2021, 9, 30]]], ['normal control 4', [[2034, 11, 1], [[2034, 11, 30], [2035, 5, 30], [2035, 11, 30], [2036, 5, 30]], [2035, 9, 9]], [[2035, 5, 30], [2035, 11, 30]]]], [['regression pre-issue guard 1', [[2019, 5, 4], [[2020, 3, 28], [2021, 3, 28], [2022, 3, 28]], [2019, 9, 1]], [[2019, 5, 4], [2020, 3, 28]]], ['regression pre-issue guard 2', [[2026, 11, 3], [[2027, 7, 31], [2028, 7, 31]], [2027, 3, 28]], [[2026, 11, 3], [2027, 7, 31]]], ['partial repair probe 1', [[2019, 6, 27], [[2019, 12, 31], [2020, 6, 30]], [2019, 6, 27]], [[2019, 6, 27], [2019, 12, 31]]], ['partial repair probe 2', [[2011, 1, 3], [[2011, 1, 13], [2011, 7, 13]], [2011, 1, 3]], [[2011, 1, 3], [2011, 1, 13]]], ['normal control 1', [[2038, 10, 4], [[2039, 1, 25], [2039, 7, 25], [2040, 1, 25]], [2039, 10, 20]], [[2039, 7, 25], [2040, 1, 25]]], ['normal control 2', [[2024, 4, 22], [[2024, 7, 20], [2025, 7, 20], [2026, 7, 20], [2027, 7, 20], [2028, 7, 20]], [2024, 4, 21]], 'not issued'], ['normal control 3', [[2018, 6, 22], [[2019, 7, 26], [2020, 1, 26], [2020, 7, 26], [2021, 1, 26], [2021, 7, 26], [2022, 1, 26]], [2020, 6, 1]], [[2020, 1, 26], [2020, 7, 26]]], ['normal control 4', [[2031, 1, 4], [[2031, 3, 29], [2031, 9, 29], [2032, 3, 29], [2032, 9, 29], [2033, 3, 29]], [2031, 4, 8]], [[2031, 3, 29], [2031, 9, 29]]]], [['regression pre-issue guard 1', [[2012, 11, 11], [[2013, 4, 20], [2013, 7, 20], [2013, 10, 20], [2014, 1, 20]], [2012, 12, 1]], [[2012, 11, 11], [2013, 4, 20]]], ['regression pre-issue guard 2', [[2021, 2, 3], [[2021, 12, 31], [2022, 6, 30], [2022, 12, 31], [2023, 6, 30]], [2021, 5, 9]], [[2021, 2, 3], [2021, 12, 31]]], ['partial repair probe 1', [[2038, 1, 19], [[2038, 11, 29], [2039, 2, 28], [2039, 5, 29]], [2038, 1, 19]], [[2038, 1, 19], [2038, 11, 29]]], ['partial repair probe 2', [[2008, 5, 10], [[2009, 3, 31], [2009, 6, 30]], [2008, 5, 10]], [[2008, 5, 10], [2009, 3, 31]]], ['normal control 1', [[2031, 3, 25], [[2031, 9, 29], [2032, 9, 29], [2033, 9, 29], [2034, 9, 29]], [2031, 3, 23]], 'not issued'], ['normal control 2', [[2009, 6, 7], [[2010, 5, 29], [2010, 8, 29], [2010, 11, 29]], [2010, 11, 29]], 'matured'], ['normal control 3', [[2032, 5, 17], [[2032, 10, 31], [2033, 10, 31], [2034, 10, 31], [2035, 10, 31], [2036, 10, 31]], [2034, 12, 25]], [[2034, 10, 31], [2035, 10, 31]]], ['normal control 4', [[2008, 12, 16], [[2009, 7, 31], [2009, 10, 31], [2010, 1, 31], [2010, 4, 30], [2010, 7, 31], [2010, 10, 31]], [2010, 3, 13]], [[2010, 1, 31], [2010, 4, 30]]]]]
for label, args, expected in fixtures[N-1]:
    check(label, 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 fixture	Actual	Expected	Outcome
regression pre-issue guard 1	`[[2024, 4, 9], [2024, 6, 16]]`	`[[2024, 4, 9], [2024, 6, 16]]`	Passed
regression pre-issue guard 2	`[[2026, 4, 22], [2027, 3, 22]]`	`[[2026, 4, 22], [2027, 3, 22]]`	Passed
partial repair probe 1	`[[2020, 2, 21], [2020, 3, 30]]`	`[[2020, 2, 21], [2020, 3, 30]]`	Passed
partial repair probe 2	`[[2019, 4, 25], [2019, 12, 11]]`	`[[2019, 4, 25], [2019, 12, 11]]`	Passed
normal control 1	`not issued`	`not issued`	Passed
normal control 2	`[[2038, 5, 30], [2038, 8, 30]]`	`[[2038, 5, 30], [2038, 8, 30]]`	Passed
normal control 3	`[[2006, 7, 31], [2006, 10, 31]]`	`[[2006, 7, 31], [2006, 10, 31]]`	Passed
normal control 4	`matured`	`matured`	Passed

SHA-256 / 008ea6370cd4b4572f0b3a6d172d4c185a2eefe012e6e8b5ebb1efdcc6979ab2

Verification & scope

A deterministic toy contract stated explicitly in the contract field; no claim of conformance to any published convention text. 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 2026-09-29T14:46:54.208956+00:00.

Case digest / 3d34dfd8dab693166b38207af800ab59ac93c9cabdf2ad4de0a9cb1077eb016d