FA-83416 / Card game rule engines / Open access

Doubled wagers lose the full stake to a dealer natural · case 01

The doubled portion is taken although the contract refunds it.

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

ROOT CAUSE

The dealer-natural branch returns the doubled stake.

THE FAILURE

The dealer-natural branch returns the doubled stake.

Unsuccessful approach: Refunding the whole wager on doubled hands loses nothing at all.

Case contract

Input [player_cards, dealer_cards, bet, doubled, from_split]. A natural is a two-card 21 not from a split. Player bust loses the stake (2*bet if doubled) first; both naturals push; player natural pays 3:2 on the bet; dealer natural takes only the original bet; dealer bust pays the stake; otherwise compare totals, equal totals push. Return net units.

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):
    p, d, bet, doubled, split = x
    def total(h):
        t = 0
        a = 0
        for c in h:
            if c[0] == 'A':
                a += 1
                t += 1
            elif c[0] in 'TJQK':
                t += 10
            else:
                t += int(c[0])
        if a and t + 10 <= 21:
            t += 10
        return t
    stake = bet * 2 if doubled else bet
    pt = total(p)
    dt = total(d)
    pn = pt == 21 and len(p) == 2 and not split
    dn = dt == 21 and len(d) == 2
    if pt > 21:
        return -stake
    if pn and dn:
        return 0
    if pn:
        return bet * 3 // 2
    if dn:
        return -stake
    if dt > 21:
        return stake
    if pt > dt:
        return stake
    if pt < dt:
        return -stake
    return 0
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
fixtures = [[[[['7D', '8C'], ['JC', '7S', 'QD'], 4, False, True], 4], [[['KH', '5D'], ['AD', 'JD'], 4, True, False], -4], [[['9H', '2H', '2D'], ['KC', '3C'], 10, False, False], 0], [[['7S', '6D'], ['4H', 'AC'], 20, False, False], -20], [[['6D', 'JC'], ['9H', '6C'], 4, True, False], 8], [[['7H', 'JS'], ['8S', '2D'], 20, True, False], 40], [[['6D', 'JS', '3D'], ['5D', '9H'], 4, True, True], 8], [[['9S', '8H'], ['AC', 'QD'], 10, True, False], -10]], [[[['JD', 'QC'], ['JC', '2D'], 20, False, False], 20], [[['3C', 'TH'], ['AC', '8C'], 4, False, True], -4], [[['9C', '2D', '5D', '8D'], ['6H', 'KH'], 20, False, False], -20], [[['2D', '6S'], ['6H', 'TC'], 4, False, False], -4], [[['4H', '7S', '2C'], ['JC', '4S'], 20, False, False], -20], [[['9C', '8S'], ['9S', '5H'], 4, False, False], 4], [[['7S', '4H', 'TC'], ['TC', 'AD'], 10, True, False], -10], [[['7S', '4H', 'TC'], ['TC', 'AD'], 10, True, False], -10]], [[[['KH', '5D'], ['AD', 'JD'], 4, True, False], -4], [[['4D', 'KS'], ['9D', 'JH', '9C'], 20, False, True], 20], [[['5H', '4D'], ['QH', '6D'], 2, False, False], -2], [[['5D', 'TC', '2C', '5S'], ['KD', 'QD'], 10, False, False], -10], [[['TH', '9S', '2H', '3H'], ['AS', 'QD'], 2, False, False], -2], [[['2D', '7C'], ['AC', 'TC'], 2, True, False], -2], [[['3H', 'TD'], ['8H', '5D'], 10, False, False], 0], [[['9S', '8H'], ['AC', 'QD'], 10, True, False], -10]], [[[['2D', '7C'], ['AC', 'TC'], 2, True, False], -2], [[['2D', '7C'], ['AC', 'TC'], 2, True, False], -2], [[['QS', '5S'], ['7S', '9C', '9S'], 2, False, True], 2], [[['4C', 'KH'], ['7H', 'TS'], 10, True, False], -20], [[['KH', '4D'], ['QD', '7S'], 2, False, False], -2], [[['TH', '3S', '5C', '8D'], ['8S', '6S'], 4, False, False], -4], [[['JC', '7S'], ['9D', 'JH', '6C'], 20, False, False], 20], [[['6S', 'AH'], ['8S', 'QC', '7D'], 4, False, False], 4]], [[[['KH', '5D'], ['AD', 'JD'], 4, True, False], -4], [[['7H', 'QH'], ['7S', '4C'], 10, False, False], 10], [[['AC', '7D'], ['4D', '4C'], 20, False, False], 20], [[['AS', '3C'], ['QD', '9C'], 4, False, False], -4], [[['KS', '8H', 'JD'], ['TS', 'AS'], 4, False, True], -4], [[['TD', 'QS', 'TH'], ['8H', 'TS'], 20, False, False], -20], [[['8D', 'JH', '2S', '6S'], ['JD', 'TS'], 10, False, False], -10], [[['9S', '8H'], ['AC', 'QD'], 10, True, False], -10]]]
for i, (args, expected) in enumerate(fixtures[N-1]):
    check("settlement 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
settlement case 0	`4`	`4`	Passed
settlement case 1	`-8`	`-4`	Failed
settlement case 2	`0`	`0`	Passed
settlement case 3	`-20`	`-20`	Passed
settlement case 4	`8`	`8`	Passed
settlement case 5	`40`	`40`	Passed
settlement case 6	`8`	`8`	Passed
settlement case 7	`-20`	`-10`	Failed

SHA-256 / c3e235f809aa9fec7aecfb9334cfebf56b9eedf3f1713fe9610a96ece6c3ad4d

2 / The unsuccessful fix

Exit 1

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

N = 1
observations = []
def solve(x):
    p, d, bet, doubled, split = x
    def total(h):
        t = 0
        a = 0
        for c in h:
            if c[0] == 'A':
                a += 1
                t += 1
            elif c[0] in 'TJQK':
                t += 10
            else:
                t += int(c[0])
        if a and t + 10 <= 21:
            t += 10
        return t
    stake = bet * 2 if doubled else bet
    pt = total(p)
    dt = total(d)
    pn = pt == 21 and len(p) == 2 and not split
    dn = dt == 21 and len(d) == 2
    if pt > 21:
        return -stake
    if pn and dn:
        return 0
    if pn:
        return bet * 3 // 2
    if dn:
        return 0 if doubled else -bet
    if dt > 21:
        return stake
    if pt > dt:
        return stake
    if pt < dt:
        return -stake
    return 0
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
fixtures = [[[[['7D', '8C'], ['JC', '7S', 'QD'], 4, False, True], 4], [[['KH', '5D'], ['AD', 'JD'], 4, True, False], -4], [[['9H', '2H', '2D'], ['KC', '3C'], 10, False, False], 0], [[['7S', '6D'], ['4H', 'AC'], 20, False, False], -20], [[['6D', 'JC'], ['9H', '6C'], 4, True, False], 8], [[['7H', 'JS'], ['8S', '2D'], 20, True, False], 40], [[['6D', 'JS', '3D'], ['5D', '9H'], 4, True, True], 8], [[['9S', '8H'], ['AC', 'QD'], 10, True, False], -10]], [[[['JD', 'QC'], ['JC', '2D'], 20, False, False], 20], [[['3C', 'TH'], ['AC', '8C'], 4, False, True], -4], [[['9C', '2D', '5D', '8D'], ['6H', 'KH'], 20, False, False], -20], [[['2D', '6S'], ['6H', 'TC'], 4, False, False], -4], [[['4H', '7S', '2C'], ['JC', '4S'], 20, False, False], -20], [[['9C', '8S'], ['9S', '5H'], 4, False, False], 4], [[['7S', '4H', 'TC'], ['TC', 'AD'], 10, True, False], -10], [[['7S', '4H', 'TC'], ['TC', 'AD'], 10, True, False], -10]], [[[['KH', '5D'], ['AD', 'JD'], 4, True, False], -4], [[['4D', 'KS'], ['9D', 'JH', '9C'], 20, False, True], 20], [[['5H', '4D'], ['QH', '6D'], 2, False, False], -2], [[['5D', 'TC', '2C', '5S'], ['KD', 'QD'], 10, False, False], -10], [[['TH', '9S', '2H', '3H'], ['AS', 'QD'], 2, False, False], -2], [[['2D', '7C'], ['AC', 'TC'], 2, True, False], -2], [[['3H', 'TD'], ['8H', '5D'], 10, False, False], 0], [[['9S', '8H'], ['AC', 'QD'], 10, True, False], -10]], [[[['2D', '7C'], ['AC', 'TC'], 2, True, False], -2], [[['2D', '7C'], ['AC', 'TC'], 2, True, False], -2], [[['QS', '5S'], ['7S', '9C', '9S'], 2, False, True], 2], [[['4C', 'KH'], ['7H', 'TS'], 10, True, False], -20], [[['KH', '4D'], ['QD', '7S'], 2, False, False], -2], [[['TH', '3S', '5C', '8D'], ['8S', '6S'], 4, False, False], -4], [[['JC', '7S'], ['9D', 'JH', '6C'], 20, False, False], 20], [[['6S', 'AH'], ['8S', 'QC', '7D'], 4, False, False], 4]], [[[['KH', '5D'], ['AD', 'JD'], 4, True, False], -4], [[['7H', 'QH'], ['7S', '4C'], 10, False, False], 10], [[['AC', '7D'], ['4D', '4C'], 20, False, False], 20], [[['AS', '3C'], ['QD', '9C'], 4, False, False], -4], [[['KS', '8H', 'JD'], ['TS', 'AS'], 4, False, True], -4], [[['TD', 'QS', 'TH'], ['8H', 'TS'], 20, False, False], -20], [[['8D', 'JH', '2S', '6S'], ['JD', 'TS'], 10, False, False], -10], [[['9S', '8H'], ['AC', 'QD'], 10, True, False], -10]]]
for i, (args, expected) in enumerate(fixtures[N-1]):
    check("settlement 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
settlement case 0	`4`	`4`	Passed
settlement case 1	`0`	`-4`	Failed
settlement case 2	`0`	`0`	Passed
settlement case 3	`-20`	`-20`	Passed
settlement case 4	`8`	`8`	Passed
settlement case 5	`40`	`40`	Passed
settlement case 6	`8`	`8`	Passed
settlement case 7	`0`	`-10`	Failed

SHA-256 / ab3b5a41833a37650e8c5cc6ffa4e5240508304ecf79319fd8ac9d6b09baf9fd

HELD IN THE MEMBER ARCHIVE

The verified repair and its recorded checks are member-only.

This mechanism has 8 recorded checks per implementation. The open-access tier publishes the failure and the unsuccessful fix; the repaired source that passes every check, and the observations that prove it, are available to members.

Every case sharing this mechanism uses the same contract and the same repair, so this one record is held back for all of them.

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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 2026-09-29T14:50:21.343881+00:00.

Case digest / 17aa8c9b337a57c089ab9c534302a2c644b0492190febe662f1ccd0dae6f4bde