FA-83751 / Card game rule engines / Open access

Pairs are compared by their lowest suit · case 01

5D-5S cannot beat 5C-5H.

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

ROOT CAUSE

Combinations are compared on their minimum key.

VERIFIED REPAIR

Compare the highest card of each combination.

Unsuccessful approach: Comparing the first card as listed depends on input order.

Case contract

Input [current_combination, play]. Ranks 3 low to 2 high; suits D<C<H<S. A play is 1-3 cards of one rank. On an empty table any valid play is "ok"; otherwise it must have the same size and its highest card must outrank the current highest card (rank, then suit). Empty play is "pass". Return "ok", "invalid" or "pass".

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):
    cur, play = x
    order = '3456789TJQKA2'
    suits = 'DCHS'
    def key(c):
        return (order.index(c[0]), suits.index(c[1]))
    if not play:
        return 'pass'
    if len(set(c[0] for c in play)) != 1 or len(play) > 3:
        return 'invalid'
    if not cur:
        return 'ok'
    if len(play) != len(cur):
        return 'invalid'
    if min(key(c) for c in play) > min(key(c) for c in cur):
        return 'ok'
    return 'invalid'
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
fixtures = [[[[[], ['KD']], 'ok'], [[['KC', 'KD'], ['KH', 'KS']], 'ok'], [[['8S', '8C', '8H'], ['KD', 'KC', 'KS']], 'ok'], [[['6S'], ['6H']], 'invalid'], [[['9C'], ['6S']], 'invalid'], [[[], ['3H', '3S', '3C']], 'ok'], [[['3C', '3H'], ['3S', '3D']], 'ok'], [[['9D', '9H', '9C'], ['9D', '9H', '9S']], 'ok']], [[[['8D', '8H'], ['8S', '8D', '8H', '8C']], 'invalid'], [[['AS'], ['AH', 'AC', 'AD']], 'invalid'], [[[], ['3C']], 'ok'], [[['QD'], ['QH']], 'ok'], [[['JD', 'JS'], ['TD', 'TS', 'TC', 'TH']], 'invalid'], [[['9S', '9H'], ['8S', '8C']], 'invalid'], [[['6C', '6H'], ['6D', '6S']], 'ok'], [[['KD', 'KS'], ['KS', 'KC']], 'invalid']], [[[['9D', '9C'], ['9D', '9C']], 'invalid'], [[['KD'], ['AH']], 'ok'], [[[], ['KS', 'KD']], 'ok'], [[['JC'], ['7C']], 'invalid'], [[['5S'], ['5H']], 'invalid'], [[['2S'], ['5D']], 'invalid'], [[['JH', 'JS', 'JD'], ['JS', 'JD', 'JH']], 'invalid'], [[['7C', '7S', '7D'], ['7S', '7H', '7C']], 'invalid']], [[[['JH', 'JC'], ['JC', 'JS']], 'ok'], [[['7C'], ['2D']], 'ok'], [[['2H'], ['2H']], 'invalid'], [[['TH', 'TD'], ['8D', '2S']], 'invalid'], [[['5H', '5D'], ['JS', 'JC']], 'ok'], [[[], ['QC', 'QH']], 'ok'], [[['QD', 'QS'], ['QH', 'QD']], 'invalid'], [[['3C', '3H'], ['3S', '3C']], 'ok']], [[[['6C', '6H'], ['AH', '4D']], 'invalid'], [[['3D', '3H', '3C'], ['3S', '3D', '3H', 'AC']], 'invalid'], [[['5S'], ['3S']], 'invalid'], [[['9C'], ['9C']], 'invalid'], [[['7C', '7S', '7D'], ['3D', '3S', '3C']], 'invalid'], [[['3H', '3C'], ['3D', '3C', '3S', '3H']], 'invalid'], [[['5C', '5H'], ['5D', '5S']], 'ok'], [[['5D', '5S'], ['5C', '5H']], 'invalid']]]
for i, (args, expected) in enumerate(fixtures[N-1]):
    check("play 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 fixture	Actual	Expected	Outcome
play case 0	`ok`	`ok`	Passed
play case 1	`ok`	`ok`	Passed
play case 2	`ok`	`ok`	Passed
play case 3	`invalid`	`invalid`	Passed
play case 4	`invalid`	`invalid`	Passed
play case 5	`ok`	`ok`	Passed
play case 6	`invalid`	`ok`	Failed
play case 7	`invalid`	`ok`	Failed

SHA-256 / cc5a5100748414008231507bca3474a4ec38fa855ecfd1fcbe7388dd331c6fa8

2 / The unsuccessful fix

Exit 1

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

N = 1
observations = []
def solve(x):
    cur, play = x
    order = '3456789TJQKA2'
    suits = 'DCHS'
    def key(c):
        return (order.index(c[0]), suits.index(c[1]))
    if not play:
        return 'pass'
    if len(set(c[0] for c in play)) != 1 or len(play) > 3:
        return 'invalid'
    if not cur:
        return 'ok'
    if len(play) != len(cur):
        return 'invalid'
    if key(play[0]) > key(cur[0]):
        return 'ok'
    return 'invalid'
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
fixtures = [[[[[], ['KD']], 'ok'], [[['KC', 'KD'], ['KH', 'KS']], 'ok'], [[['8S', '8C', '8H'], ['KD', 'KC', 'KS']], 'ok'], [[['6S'], ['6H']], 'invalid'], [[['9C'], ['6S']], 'invalid'], [[[], ['3H', '3S', '3C']], 'ok'], [[['3C', '3H'], ['3S', '3D']], 'ok'], [[['9D', '9H', '9C'], ['9D', '9H', '9S']], 'ok']], [[[['8D', '8H'], ['8S', '8D', '8H', '8C']], 'invalid'], [[['AS'], ['AH', 'AC', 'AD']], 'invalid'], [[[], ['3C']], 'ok'], [[['QD'], ['QH']], 'ok'], [[['JD', 'JS'], ['TD', 'TS', 'TC', 'TH']], 'invalid'], [[['9S', '9H'], ['8S', '8C']], 'invalid'], [[['6C', '6H'], ['6D', '6S']], 'ok'], [[['KD', 'KS'], ['KS', 'KC']], 'invalid']], [[[['9D', '9C'], ['9D', '9C']], 'invalid'], [[['KD'], ['AH']], 'ok'], [[[], ['KS', 'KD']], 'ok'], [[['JC'], ['7C']], 'invalid'], [[['5S'], ['5H']], 'invalid'], [[['2S'], ['5D']], 'invalid'], [[['JH', 'JS', 'JD'], ['JS', 'JD', 'JH']], 'invalid'], [[['7C', '7S', '7D'], ['7S', '7H', '7C']], 'invalid']], [[[['JH', 'JC'], ['JC', 'JS']], 'ok'], [[['7C'], ['2D']], 'ok'], [[['2H'], ['2H']], 'invalid'], [[['TH', 'TD'], ['8D', '2S']], 'invalid'], [[['5H', '5D'], ['JS', 'JC']], 'ok'], [[[], ['QC', 'QH']], 'ok'], [[['QD', 'QS'], ['QH', 'QD']], 'invalid'], [[['3C', '3H'], ['3S', '3C']], 'ok']], [[[['6C', '6H'], ['AH', '4D']], 'invalid'], [[['3D', '3H', '3C'], ['3S', '3D', '3H', 'AC']], 'invalid'], [[['5S'], ['3S']], 'invalid'], [[['9C'], ['9C']], 'invalid'], [[['7C', '7S', '7D'], ['3D', '3S', '3C']], 'invalid'], [[['3H', '3C'], ['3D', '3C', '3S', '3H']], 'invalid'], [[['5C', '5H'], ['5D', '5S']], 'ok'], [[['5D', '5S'], ['5C', '5H']], 'invalid']]]
for i, (args, expected) in enumerate(fixtures[N-1]):
    check("play 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 fixture	Actual	Expected	Outcome
play case 0	`ok`	`ok`	Passed
play case 1	`ok`	`ok`	Passed
play case 2	`ok`	`ok`	Passed
play case 3	`invalid`	`invalid`	Passed
play case 4	`invalid`	`invalid`	Passed
play case 5	`ok`	`ok`	Passed
play case 6	`ok`	`ok`	Passed
play case 7	`invalid`	`ok`	Failed

SHA-256 / 8c53f9144c8bbf3b5896fd7b12c55d55bc4aa22f2c71caac033b5cded8b0eeca

3 / The verified repair

Exit 0

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

N = 1
observations = []
def solve(x):
    cur, play = x
    order = '3456789TJQKA2'
    suits = 'DCHS'
    def key(c):
        return (order.index(c[0]), suits.index(c[1]))
    if not play:
        return 'pass'
    if len(set(c[0] for c in play)) != 1 or len(play) > 3:
        return 'invalid'
    if not cur:
        return 'ok'
    if len(play) != len(cur):
        return 'invalid'
    if max(key(c) for c in play) > max(key(c) for c in cur):
        return 'ok'
    return 'invalid'
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
fixtures = [[[[[], ['KD']], 'ok'], [[['KC', 'KD'], ['KH', 'KS']], 'ok'], [[['8S', '8C', '8H'], ['KD', 'KC', 'KS']], 'ok'], [[['6S'], ['6H']], 'invalid'], [[['9C'], ['6S']], 'invalid'], [[[], ['3H', '3S', '3C']], 'ok'], [[['3C', '3H'], ['3S', '3D']], 'ok'], [[['9D', '9H', '9C'], ['9D', '9H', '9S']], 'ok']], [[[['8D', '8H'], ['8S', '8D', '8H', '8C']], 'invalid'], [[['AS'], ['AH', 'AC', 'AD']], 'invalid'], [[[], ['3C']], 'ok'], [[['QD'], ['QH']], 'ok'], [[['JD', 'JS'], ['TD', 'TS', 'TC', 'TH']], 'invalid'], [[['9S', '9H'], ['8S', '8C']], 'invalid'], [[['6C', '6H'], ['6D', '6S']], 'ok'], [[['KD', 'KS'], ['KS', 'KC']], 'invalid']], [[[['9D', '9C'], ['9D', '9C']], 'invalid'], [[['KD'], ['AH']], 'ok'], [[[], ['KS', 'KD']], 'ok'], [[['JC'], ['7C']], 'invalid'], [[['5S'], ['5H']], 'invalid'], [[['2S'], ['5D']], 'invalid'], [[['JH', 'JS', 'JD'], ['JS', 'JD', 'JH']], 'invalid'], [[['7C', '7S', '7D'], ['7S', '7H', '7C']], 'invalid']], [[[['JH', 'JC'], ['JC', 'JS']], 'ok'], [[['7C'], ['2D']], 'ok'], [[['2H'], ['2H']], 'invalid'], [[['TH', 'TD'], ['8D', '2S']], 'invalid'], [[['5H', '5D'], ['JS', 'JC']], 'ok'], [[[], ['QC', 'QH']], 'ok'], [[['QD', 'QS'], ['QH', 'QD']], 'invalid'], [[['3C', '3H'], ['3S', '3C']], 'ok']], [[[['6C', '6H'], ['AH', '4D']], 'invalid'], [[['3D', '3H', '3C'], ['3S', '3D', '3H', 'AC']], 'invalid'], [[['5S'], ['3S']], 'invalid'], [[['9C'], ['9C']], 'invalid'], [[['7C', '7S', '7D'], ['3D', '3S', '3C']], 'invalid'], [[['3H', '3C'], ['3D', '3C', '3S', '3H']], 'invalid'], [[['5C', '5H'], ['5D', '5S']], 'ok'], [[['5D', '5S'], ['5C', '5H']], 'invalid']]]
for i, (args, expected) in enumerate(fixtures[N-1]):
    check("play 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 fixture	Actual	Expected	Outcome
play case 0	`ok`	`ok`	Passed
play case 1	`ok`	`ok`	Passed
play case 2	`ok`	`ok`	Passed
play case 3	`invalid`	`invalid`	Passed
play case 4	`invalid`	`invalid`	Passed
play case 5	`ok`	`ok`	Passed
play case 6	`ok`	`ok`	Passed
play case 7	`ok`	`ok`	Passed

SHA-256 / 63cfecfb3e4b8c7f658ab905e3bbd2663a5f7db065be3428a5512531f29f99bd

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 2026-09-29T14:50:24.579060+00:00.

Case digest / e1b4697d721f4f3558533a77c6ac97a964a41755ccb96289790a63ce2f0658c5