FAILURE MAP
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FA-83346 / Card game rule engines / Open access

A high off-suit discard wins the trick · case 01

Discarding an ace of another suit steals a trick won by a lower card of the led suit.

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

ROOT CAUSE

Cards of a different non-trump suit are compared by rank.

VERIFIED REPAIR

Only a card of the current winning suit or a first trump can take over.

Unsuccessful approach: Excluding only the case where a trump is currently winning still lets off-suit discards beat the led suit.

Case contract

Input [cards_in_play_order, leader_seat, trump_or_None, seats]. The highest trump wins; with no trump played the highest card of the led suit wins (A high). Off-suit non-trump cards never win. Return the winning seat, counting clockwise from the leader.

Why this case matters

Card-game engines, scoring apps and online tables apply this rule automatically on every hand.

1 / The failure

Exit 1
"""Failure Map reference implementation. Python standard library only."""
import json

N = 1
observations = []
def solve(x):
    cards, leader, trump, seats = x
    order = '23456789TJQKA'
    best = 0
    for i in range(1, len(cards)):
        card, top = cards[i], cards[best]
        if card[1] == top[1]:
            if order.index(card[0]) > order.index(top[0]):
                best = i
        elif card[1] == trump or order.index(card[0]) > order.index(top[0]):
            best = i
    return (leader + best) % seats
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
fixtures = [[[[['KD', 'AC', '5D', 'JH'], 2, 'S', 4], 2], [[['KC', 'AC', '8H', '8D'], 2, None, 4], 3], [[['3H', '9S', 'QD', '5H'], 3, 'D', 4], 1], [[['KD', '2H', '9D', '2D', '6C'], 4, None, 5], 4], [[['QH', '4D', 'TS', '5D', '2S'], 4, None, 5], 4], [[['8H', 'TS', '7D', 'JS'], 2, None, 4], 2], [[['8S', 'AD', 'KC'], 0, None, 3], 0], [[['TD', '5D', 'QS', 'AC', 'KS'], 1, None, 5], 1]], [[[['8H', 'TS', '7D', 'JS'], 2, None, 4], 2], [[['9C', '7D', '8D', '2S', 'TD'], 4, 'D', 5], 3], [[['JD', '2H', 'KD', '5D', 'QS'], 0, None, 5], 2], [[['2D', 'QC', '3S', '3H'], 3, 'S', 4], 1], [[['5C', '6H', '3C', 'AC'], 2, 'D', 4], 1], [[['4D', '6S', 'TH'], 2, 'D', 3], 2], [[['9H', 'KS', '7S', '9C'], 0, 'D', 4], 0], [[['2S', '3C', '9S', 'KH'], 2, None, 4], 0]], [[[['4D', '6S', 'TH'], 2, 'D', 3], 2], [[['5D', 'AD', '8H'], 1, None, 3], 2], [[['TD', '5D', 'QS', 'AC', 'KS'], 1, None, 5], 1], [[['8H', 'QC', 'JS'], 2, 'C', 3], 0], [[['KC', '6C', '4S'], 0, 'D', 3], 0], [[['3S', '6C', 'QS'], 0, 'S', 3], 2], [[['JH', '5H', 'JS'], 2, None, 3], 2], [[['9S', 'QD', '4S'], 2, 'C', 3], 2]], [[[['8S', '5S', 'KS'], 2, 'H', 3], 1], [[['3D', 'QD', '8S', '6D', 'TS'], 2, None, 5], 3], [[['6D', '2H', '4D', '5S', '7S'], 4, 'H', 5], 0], [[['8C', '5H', '6H', '9C'], 2, None, 4], 1], [[['AH', 'TD', '4H', '3S', 'KD'], 1, None, 5], 1], [[['6H', 'AS', '7H', 'JD'], 2, 'D', 4], 1], [[['7H', '3C', '6D', '5C'], 3, 'H', 4], 3], [[['TH', '8D', 'TD', 'JD'], 2, 'C', 4], 2]], [[[['7S', '4S', '8D'], 1, 'S', 3], 1], [[['3S', 'JS', 'TC', '5D', '3H'], 2, 'D', 5], 0], [[['9H', '6H', '3D'], 1, 'S', 3], 1], [[['3H', '8D', '3C'], 0, 'H', 3], 0], [[['AD', 'JH', '8D', '5D'], 1, 'H', 4], 2], [[['8C', '8S', 'AC'], 1, None, 3], 0], [[['6D', 'AS', 'AD'], 1, 'H', 3], 0], [[['6S', 'TD', '6H'], 1, 'C', 3], 1]]]
for i, (args, expected) in enumerate(fixtures[N-1]):
    check("trick case %d" % 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
trick case 032Failed
trick case 133Passed
trick case 211Passed
trick case 344Passed
trick case 444Passed
trick case 512Failed
trick case 610Failed
trick case 741Failed

SHA-256 / 1ab3f566128df4129482d347c9b833831754ae64f4db384dc01dc0e360103733

2 / The unsuccessful fix

Exit 1
"""Failure Map reference implementation. Python standard library only."""
import json

N = 1
observations = []
def solve(x):
    cards, leader, trump, seats = x
    order = '23456789TJQKA'
    best = 0
    for i in range(1, len(cards)):
        card, top = cards[i], cards[best]
        if card[1] == top[1]:
            if order.index(card[0]) > order.index(top[0]):
                best = i
        elif card[1] == trump or top[1] != trump and order.index(card[0]) > order.index(top[0]):
            best = i
    return (leader + best) % seats
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
fixtures = [[[[['KD', 'AC', '5D', 'JH'], 2, 'S', 4], 2], [[['KC', 'AC', '8H', '8D'], 2, None, 4], 3], [[['3H', '9S', 'QD', '5H'], 3, 'D', 4], 1], [[['KD', '2H', '9D', '2D', '6C'], 4, None, 5], 4], [[['QH', '4D', 'TS', '5D', '2S'], 4, None, 5], 4], [[['8H', 'TS', '7D', 'JS'], 2, None, 4], 2], [[['8S', 'AD', 'KC'], 0, None, 3], 0], [[['TD', '5D', 'QS', 'AC', 'KS'], 1, None, 5], 1]], [[[['8H', 'TS', '7D', 'JS'], 2, None, 4], 2], [[['9C', '7D', '8D', '2S', 'TD'], 4, 'D', 5], 3], [[['JD', '2H', 'KD', '5D', 'QS'], 0, None, 5], 2], [[['2D', 'QC', '3S', '3H'], 3, 'S', 4], 1], [[['5C', '6H', '3C', 'AC'], 2, 'D', 4], 1], [[['4D', '6S', 'TH'], 2, 'D', 3], 2], [[['9H', 'KS', '7S', '9C'], 0, 'D', 4], 0], [[['2S', '3C', '9S', 'KH'], 2, None, 4], 0]], [[[['4D', '6S', 'TH'], 2, 'D', 3], 2], [[['5D', 'AD', '8H'], 1, None, 3], 2], [[['TD', '5D', 'QS', 'AC', 'KS'], 1, None, 5], 1], [[['8H', 'QC', 'JS'], 2, 'C', 3], 0], [[['KC', '6C', '4S'], 0, 'D', 3], 0], [[['3S', '6C', 'QS'], 0, 'S', 3], 2], [[['JH', '5H', 'JS'], 2, None, 3], 2], [[['9S', 'QD', '4S'], 2, 'C', 3], 2]], [[[['8S', '5S', 'KS'], 2, 'H', 3], 1], [[['3D', 'QD', '8S', '6D', 'TS'], 2, None, 5], 3], [[['6D', '2H', '4D', '5S', '7S'], 4, 'H', 5], 0], [[['8C', '5H', '6H', '9C'], 2, None, 4], 1], [[['AH', 'TD', '4H', '3S', 'KD'], 1, None, 5], 1], [[['6H', 'AS', '7H', 'JD'], 2, 'D', 4], 1], [[['7H', '3C', '6D', '5C'], 3, 'H', 4], 3], [[['TH', '8D', 'TD', 'JD'], 2, 'C', 4], 2]], [[[['7S', '4S', '8D'], 1, 'S', 3], 1], [[['3S', 'JS', 'TC', '5D', '3H'], 2, 'D', 5], 0], [[['9H', '6H', '3D'], 1, 'S', 3], 1], [[['3H', '8D', '3C'], 0, 'H', 3], 0], [[['AD', 'JH', '8D', '5D'], 1, 'H', 4], 2], [[['8C', '8S', 'AC'], 1, None, 3], 0], [[['6D', 'AS', 'AD'], 1, 'H', 3], 0], [[['6S', 'TD', '6H'], 1, 'C', 3], 1]]]
for i, (args, expected) in enumerate(fixtures[N-1]):
    check("trick case %d" % 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
trick case 032Failed
trick case 133Passed
trick case 211Passed
trick case 344Passed
trick case 444Passed
trick case 512Failed
trick case 610Failed
trick case 741Failed

SHA-256 / 6ddb1a3f5833cde6c21fed99d1fc4d0ffecb003a00c3c6bfd600aa4a524b79eb

3 / The verified repair

Exit 0
"""Failure Map reference implementation. Python standard library only."""
import json

N = 1
observations = []
def solve(x):
    cards, leader, trump, seats = x
    order = '23456789TJQKA'
    best = 0
    for i in range(1, len(cards)):
        card, top = cards[i], cards[best]
        if card[1] == top[1]:
            if order.index(card[0]) > order.index(top[0]):
                best = i
        elif card[1] == trump:
            best = i
    return (leader + best) % seats
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
fixtures = [[[[['KD', 'AC', '5D', 'JH'], 2, 'S', 4], 2], [[['KC', 'AC', '8H', '8D'], 2, None, 4], 3], [[['3H', '9S', 'QD', '5H'], 3, 'D', 4], 1], [[['KD', '2H', '9D', '2D', '6C'], 4, None, 5], 4], [[['QH', '4D', 'TS', '5D', '2S'], 4, None, 5], 4], [[['8H', 'TS', '7D', 'JS'], 2, None, 4], 2], [[['8S', 'AD', 'KC'], 0, None, 3], 0], [[['TD', '5D', 'QS', 'AC', 'KS'], 1, None, 5], 1]], [[[['8H', 'TS', '7D', 'JS'], 2, None, 4], 2], [[['9C', '7D', '8D', '2S', 'TD'], 4, 'D', 5], 3], [[['JD', '2H', 'KD', '5D', 'QS'], 0, None, 5], 2], [[['2D', 'QC', '3S', '3H'], 3, 'S', 4], 1], [[['5C', '6H', '3C', 'AC'], 2, 'D', 4], 1], [[['4D', '6S', 'TH'], 2, 'D', 3], 2], [[['9H', 'KS', '7S', '9C'], 0, 'D', 4], 0], [[['2S', '3C', '9S', 'KH'], 2, None, 4], 0]], [[[['4D', '6S', 'TH'], 2, 'D', 3], 2], [[['5D', 'AD', '8H'], 1, None, 3], 2], [[['TD', '5D', 'QS', 'AC', 'KS'], 1, None, 5], 1], [[['8H', 'QC', 'JS'], 2, 'C', 3], 0], [[['KC', '6C', '4S'], 0, 'D', 3], 0], [[['3S', '6C', 'QS'], 0, 'S', 3], 2], [[['JH', '5H', 'JS'], 2, None, 3], 2], [[['9S', 'QD', '4S'], 2, 'C', 3], 2]], [[[['8S', '5S', 'KS'], 2, 'H', 3], 1], [[['3D', 'QD', '8S', '6D', 'TS'], 2, None, 5], 3], [[['6D', '2H', '4D', '5S', '7S'], 4, 'H', 5], 0], [[['8C', '5H', '6H', '9C'], 2, None, 4], 1], [[['AH', 'TD', '4H', '3S', 'KD'], 1, None, 5], 1], [[['6H', 'AS', '7H', 'JD'], 2, 'D', 4], 1], [[['7H', '3C', '6D', '5C'], 3, 'H', 4], 3], [[['TH', '8D', 'TD', 'JD'], 2, 'C', 4], 2]], [[[['7S', '4S', '8D'], 1, 'S', 3], 1], [[['3S', 'JS', 'TC', '5D', '3H'], 2, 'D', 5], 0], [[['9H', '6H', '3D'], 1, 'S', 3], 1], [[['3H', '8D', '3C'], 0, 'H', 3], 0], [[['AD', 'JH', '8D', '5D'], 1, 'H', 4], 2], [[['8C', '8S', 'AC'], 1, None, 3], 0], [[['6D', 'AS', 'AD'], 1, 'H', 3], 0], [[['6S', 'TD', '6H'], 1, 'C', 3], 1]]]
for i, (args, expected) in enumerate(fixtures[N-1]):
    check("trick case %d" % 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
trick case 022Passed
trick case 133Passed
trick case 211Passed
trick case 344Passed
trick case 444Passed
trick case 522Passed
trick case 600Passed
trick case 711Passed

SHA-256 / 3667658441c1238ef80a472a08d519eead1d6edc4314f3d31d12e8f09e440211

Verification & scope

A bounded toy rule contract stated explicitly in the contract field; cards are two-character codes (rank, suit). Not a complete implementation of any published rulebook or casino table rules. 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 2026-09-29T14:50:20.691444+00:00.

Case digest / 7aa16f2d0aa333b46efeccc50e0d05ff7512d3510bbf4f2857c2237d987962fb