FA-83546 / Card game rule engines / Open access

The crib scores a four-card flush · case 01

A crib whose four cards share a suit but not the starter scores 4.

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

ROOT CAUSE

The four-card flush branch ignores the crib flag.

VERIFIED REPAIR

The crib needs all five cards in one suit.

Unsuccessful approach: Blocking the five-card flush for the crib too loses a legitimate crib flush.

Case contract

Input [four_card_hand, starter, is_crib]. Fifteens (any 2-5 cards, A=1, T/J/Q/K=10) score 2; each pair 2; runs score their length for every distinct combination of the longest run length; a four-card hand flush scores 4 (+1 with the starter) but the crib scores only a five-card flush; a hand jack matching the starter suit scores 1. Return the total.

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
import itertools
N = 1
observations = []
def solve(x):
    hand, starter, crib = x
    order = 'A23456789TJQK'
    cards = hand + [starter]
    def val(c):
        return min(order.index(c[0]) + 1, 10)
    score = 0
    for k in range(2, 6):
        for combo in itertools.combinations(cards, k):
            if sum(val(c) for c in combo) == 15:
                score += 2
    for a, b in itertools.combinations(cards, 2):
        if a[0] == b[0]:
            score += 2
    ranks = sorted(order.index(c[0]) for c in cards)
    for size in (5, 4, 3):
        runs = 0
        for combo in itertools.combinations(ranks, size):
            if all(combo[i + 1] == combo[i] + 1 for i in range(size - 1)):
                runs += 1
        if runs:
            score += runs * size
            break
    suits = [c[1] for c in hand]
    if len(set(suits)) == 1:
        if starter[1] == suits[0]:
            score += 5
        else:
            score += 4
    for c in hand:
        if c[0] == 'J' and c[1] == starter[1]:
            score += 1
    return score
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
fixtures = [[[[['AC', '9C', '4C', 'TC'], '5S', True], 6], [[['KD', 'AH', '4S', '8D'], 'QH', False], 4], [[['3C', '3S', '4S', '5H'], '2D', False], 12], [[['5H', '9S', '6S', '2S'], 'AH', False], 4], [[['3S', '3H', '5H', 'JH'], 'QS', False], 6], [[['4C', 'QC', 'AC', '6C'], '5D', True], 9], [[['AD', 'AH', '2S', '3H'], 'KC', False], 12], [[['4H', '5H', '6H', '7H'], '8H', True], 14]], [[[['6S', '8D', 'JD', '9C'], '6D', False], 7], [[['4S', '5D', '9D', 'TC'], 'QH', True], 4], [[['5H', 'KC', '2H', '3S'], '6H', True], 4], [[['9H', '7H', 'QH', 'TH'], 'JH', False], 9], [[['2C', '2S', '3S', '4H'], 'KD', False], 12], [[['4S', '3S', '9S', 'TD'], '7C', False], 0], [[['9C', 'TC', '7C', '3C'], '5S', True], 4], [[['4H', '5H', '6H', '7H'], '8H', True], 14]], [[[['3H', 'QS', '3C', '6S'], '8D', False], 2], [[['JH', '9H', '9S', 'TD'], '3H', False], 9], [[['6C', '2C', '7C', 'AC'], '4H', True], 2], [[['4D', 'AS', '7H', 'QD'], '9S', False], 2], [[['6S', '5S', 'QS', '8C'], 'AC', False], 4], [[['8S', 'QS', 'TH', '9C'], 'QC', False], 5], [[['4S', 'QS', 'KS', 'AS'], '4C', True], 10], [[['4H', '5H', '6H', '7H'], '8H', True], 14]], [[[['AC', '9C', '4C', 'TC'], '5S', True], 6], [[['AS', '9S', 'TS', '2S'], '4C', False], 8], [[['TD', 'KS', 'TH', 'TS'], 'JC', False], 6], [[['KS', '5D', '3H', '8D'], 'KD', True], 6], [[['2S', '8S', 'TC', 'JS'], 'QH', False], 3], [[['9H', '7S', 'QH', '5H'], '3D', False], 4], [[['KH', '3C', '5H', '5C'], '8S', False], 6], [[['4H', '5H', '6H', '7H'], '8H', True], 14]], [[[['8D', '8C', '9S', 'TH'], 'AH', True], 8], [[['2H', '5H', 'AC', '3S'], '8C', False], 5], [[['AD', '4S', '9D', '4H'], 'TH', False], 6], [[['9S', '9C', 'JH', 'KS'], '3H', False], 3], [[['KD', 'TC', 'QS', '4D'], 'TH', True], 2], [[['QD', '8S', 'JC', '5H'], '6C', False], 5], [[['9C', 'TC', '7C', '3C'], '5S', True], 4], [[['4H', '5H', '6H', '7H'], '8H', True], 14]]]
for i, (args, expected) in enumerate(fixtures[N-1]):
    check("hand score 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
hand score case 0	`10`	`6`	Failed
hand score case 1	`4`	`4`	Passed
hand score case 2	`12`	`12`	Passed
hand score case 3	`4`	`4`	Passed
hand score case 4	`6`	`6`	Passed
hand score case 5	`13`	`9`	Failed
hand score case 6	`12`	`12`	Passed
hand score case 7	`14`	`14`	Passed

SHA-256 / 233e02c22780bdb41402321b82b13b28aab7751ec4cdab4a1ad1fc4c852c5e33

2 / The unsuccessful fix

Exit 1

"""Failure Map reference implementation. Python standard library only."""
import json
import itertools
N = 1
observations = []
def solve(x):
    hand, starter, crib = x
    order = 'A23456789TJQK'
    cards = hand + [starter]
    def val(c):
        return min(order.index(c[0]) + 1, 10)
    score = 0
    for k in range(2, 6):
        for combo in itertools.combinations(cards, k):
            if sum(val(c) for c in combo) == 15:
                score += 2
    for a, b in itertools.combinations(cards, 2):
        if a[0] == b[0]:
            score += 2
    ranks = sorted(order.index(c[0]) for c in cards)
    for size in (5, 4, 3):
        runs = 0
        for combo in itertools.combinations(ranks, size):
            if all(combo[i + 1] == combo[i] + 1 for i in range(size - 1)):
                runs += 1
        if runs:
            score += runs * size
            break
    suits = [c[1] for c in hand]
    if len(set(suits)) == 1:
        if starter[1] == suits[0] and not crib:
            score += 5
        elif not crib:
            score += 4
    for c in hand:
        if c[0] == 'J' and c[1] == starter[1]:
            score += 1
    return score
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
fixtures = [[[[['AC', '9C', '4C', 'TC'], '5S', True], 6], [[['KD', 'AH', '4S', '8D'], 'QH', False], 4], [[['3C', '3S', '4S', '5H'], '2D', False], 12], [[['5H', '9S', '6S', '2S'], 'AH', False], 4], [[['3S', '3H', '5H', 'JH'], 'QS', False], 6], [[['4C', 'QC', 'AC', '6C'], '5D', True], 9], [[['AD', 'AH', '2S', '3H'], 'KC', False], 12], [[['4H', '5H', '6H', '7H'], '8H', True], 14]], [[[['6S', '8D', 'JD', '9C'], '6D', False], 7], [[['4S', '5D', '9D', 'TC'], 'QH', True], 4], [[['5H', 'KC', '2H', '3S'], '6H', True], 4], [[['9H', '7H', 'QH', 'TH'], 'JH', False], 9], [[['2C', '2S', '3S', '4H'], 'KD', False], 12], [[['4S', '3S', '9S', 'TD'], '7C', False], 0], [[['9C', 'TC', '7C', '3C'], '5S', True], 4], [[['4H', '5H', '6H', '7H'], '8H', True], 14]], [[[['3H', 'QS', '3C', '6S'], '8D', False], 2], [[['JH', '9H', '9S', 'TD'], '3H', False], 9], [[['6C', '2C', '7C', 'AC'], '4H', True], 2], [[['4D', 'AS', '7H', 'QD'], '9S', False], 2], [[['6S', '5S', 'QS', '8C'], 'AC', False], 4], [[['8S', 'QS', 'TH', '9C'], 'QC', False], 5], [[['4S', 'QS', 'KS', 'AS'], '4C', True], 10], [[['4H', '5H', '6H', '7H'], '8H', True], 14]], [[[['AC', '9C', '4C', 'TC'], '5S', True], 6], [[['AS', '9S', 'TS', '2S'], '4C', False], 8], [[['TD', 'KS', 'TH', 'TS'], 'JC', False], 6], [[['KS', '5D', '3H', '8D'], 'KD', True], 6], [[['2S', '8S', 'TC', 'JS'], 'QH', False], 3], [[['9H', '7S', 'QH', '5H'], '3D', False], 4], [[['KH', '3C', '5H', '5C'], '8S', False], 6], [[['4H', '5H', '6H', '7H'], '8H', True], 14]], [[[['8D', '8C', '9S', 'TH'], 'AH', True], 8], [[['2H', '5H', 'AC', '3S'], '8C', False], 5], [[['AD', '4S', '9D', '4H'], 'TH', False], 6], [[['9S', '9C', 'JH', 'KS'], '3H', False], 3], [[['KD', 'TC', 'QS', '4D'], 'TH', True], 2], [[['QD', '8S', 'JC', '5H'], '6C', False], 5], [[['9C', 'TC', '7C', '3C'], '5S', True], 4], [[['4H', '5H', '6H', '7H'], '8H', True], 14]]]
for i, (args, expected) in enumerate(fixtures[N-1]):
    check("hand score 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
hand score case 0	`6`	`6`	Passed
hand score case 1	`4`	`4`	Passed
hand score case 2	`12`	`12`	Passed
hand score case 3	`4`	`4`	Passed
hand score case 4	`6`	`6`	Passed
hand score case 5	`9`	`9`	Passed
hand score case 6	`12`	`12`	Passed
hand score case 7	`9`	`14`	Failed

SHA-256 / 6f15fda9ce7576c5ddc0be418da9e8187ee7ed603c4babf30d534cc7f336ae82

3 / The verified repair

Exit 0

"""Failure Map reference implementation. Python standard library only."""
import json
import itertools
N = 1
observations = []
def solve(x):
    hand, starter, crib = x
    order = 'A23456789TJQK'
    cards = hand + [starter]
    def val(c):
        return min(order.index(c[0]) + 1, 10)
    score = 0
    for k in range(2, 6):
        for combo in itertools.combinations(cards, k):
            if sum(val(c) for c in combo) == 15:
                score += 2
    for a, b in itertools.combinations(cards, 2):
        if a[0] == b[0]:
            score += 2
    ranks = sorted(order.index(c[0]) for c in cards)
    for size in (5, 4, 3):
        runs = 0
        for combo in itertools.combinations(ranks, size):
            if all(combo[i + 1] == combo[i] + 1 for i in range(size - 1)):
                runs += 1
        if runs:
            score += runs * size
            break
    suits = [c[1] for c in hand]
    if len(set(suits)) == 1:
        if starter[1] == suits[0]:
            score += 5
        elif not crib:
            score += 4
    for c in hand:
        if c[0] == 'J' and c[1] == starter[1]:
            score += 1
    return score
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
fixtures = [[[[['AC', '9C', '4C', 'TC'], '5S', True], 6], [[['KD', 'AH', '4S', '8D'], 'QH', False], 4], [[['3C', '3S', '4S', '5H'], '2D', False], 12], [[['5H', '9S', '6S', '2S'], 'AH', False], 4], [[['3S', '3H', '5H', 'JH'], 'QS', False], 6], [[['4C', 'QC', 'AC', '6C'], '5D', True], 9], [[['AD', 'AH', '2S', '3H'], 'KC', False], 12], [[['4H', '5H', '6H', '7H'], '8H', True], 14]], [[[['6S', '8D', 'JD', '9C'], '6D', False], 7], [[['4S', '5D', '9D', 'TC'], 'QH', True], 4], [[['5H', 'KC', '2H', '3S'], '6H', True], 4], [[['9H', '7H', 'QH', 'TH'], 'JH', False], 9], [[['2C', '2S', '3S', '4H'], 'KD', False], 12], [[['4S', '3S', '9S', 'TD'], '7C', False], 0], [[['9C', 'TC', '7C', '3C'], '5S', True], 4], [[['4H', '5H', '6H', '7H'], '8H', True], 14]], [[[['3H', 'QS', '3C', '6S'], '8D', False], 2], [[['JH', '9H', '9S', 'TD'], '3H', False], 9], [[['6C', '2C', '7C', 'AC'], '4H', True], 2], [[['4D', 'AS', '7H', 'QD'], '9S', False], 2], [[['6S', '5S', 'QS', '8C'], 'AC', False], 4], [[['8S', 'QS', 'TH', '9C'], 'QC', False], 5], [[['4S', 'QS', 'KS', 'AS'], '4C', True], 10], [[['4H', '5H', '6H', '7H'], '8H', True], 14]], [[[['AC', '9C', '4C', 'TC'], '5S', True], 6], [[['AS', '9S', 'TS', '2S'], '4C', False], 8], [[['TD', 'KS', 'TH', 'TS'], 'JC', False], 6], [[['KS', '5D', '3H', '8D'], 'KD', True], 6], [[['2S', '8S', 'TC', 'JS'], 'QH', False], 3], [[['9H', '7S', 'QH', '5H'], '3D', False], 4], [[['KH', '3C', '5H', '5C'], '8S', False], 6], [[['4H', '5H', '6H', '7H'], '8H', True], 14]], [[[['8D', '8C', '9S', 'TH'], 'AH', True], 8], [[['2H', '5H', 'AC', '3S'], '8C', False], 5], [[['AD', '4S', '9D', '4H'], 'TH', False], 6], [[['9S', '9C', 'JH', 'KS'], '3H', False], 3], [[['KD', 'TC', 'QS', '4D'], 'TH', True], 2], [[['QD', '8S', 'JC', '5H'], '6C', False], 5], [[['9C', 'TC', '7C', '3C'], '5S', True], 4], [[['4H', '5H', '6H', '7H'], '8H', True], 14]]]
for i, (args, expected) in enumerate(fixtures[N-1]):
    check("hand score 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
hand score case 0	`6`	`6`	Passed
hand score case 1	`4`	`4`	Passed
hand score case 2	`12`	`12`	Passed
hand score case 3	`4`	`4`	Passed
hand score case 4	`6`	`6`	Passed
hand score case 5	`9`	`9`	Passed
hand score case 6	`12`	`12`	Passed
hand score case 7	`14`	`14`	Passed

SHA-256 / 9c97fd848207ab7d792cd33f81c9528e42a2a904da2355338032fea724a316d6

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 2026-09-29T14:50:22.593499+00:00.

Case digest / 2968386565b7263d8e3f3e6ec9e9eebc8099accb5b4d315b286ac9c19aa220c5