FA-81946 / Poker hand evaluation / Open access

Four-card run accepted as a straight · case 01

9-T-J-Q with no eight or king is reported as a queen-high straight.

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

ROOT CAUSE

The window mask has four bits set, so any four consecutive ranks match.

VERIFIED REPAIR

Use a five-bit window 0b11111 shifted so its top bit is the candidate top rank.

Unsuccessful approach: Keeping five bits but shifting by top-5 reports each straight one rank low.

Case contract

Input: 5 to 7 distinct cards "Rs". Build a rank bitmask (bit r for rank value r, 2..14; the ace also sets bit 1). Return the top rank of the highest five-card straight contained in the ranks (5 for the wheel), or 0 if none.

Why this case matters

Bitmask evaluators are the standard fast path for seven-card hold'em straights.

1 / The failure

Exit 1

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

N = 1
observations = []
def solve(x):
    R='23456789TJQKA'
    m=0
    for c in x:
        m|=1<<(R.index(c[0])+2)
    if m & (1<<14): m|=1<<1
    for top in range(14,4,-1):
        need=0b1111<<(top-3)
        if m & need == need: return top
    return 0
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
fixtures = [[('wheel in seven', ['Ah', '2d', '3c', '4s', '5h', 'Kd', 'Kc'], 5),
  ('broadway', ['Th', 'Jd', 'Qc', 'Ks', 'Ah', '2c', '2d'], 14),
  ('six-high over wheel', ['Ah', '2d', '3c', '4s', '5h', '6d', 'Jc'], 6),
  ('four-straight only', ['9h', 'Td', 'Jc', 'Qs', '2h', '2d', '3c'], 0),
  ('paired straight', ['5h', '5d', '6c', '7s', '8h', '9d', 'Kc'], 9),
  ('no straight', ['2h', '5d', '7c', '9s', 'Jh', 'Kd', 'Ac'], 0),
  ('gap straight', ['2h', '3d', '4c', '6s', '7h', '8d', '9c'], 0),
  ('no straight low cards', ['2h', '3d', '4c', '8s', '9h', 'Qd', 'Qc'], 0)],
 [('broadway', ['Th', 'Jd', 'Qc', 'Ks', 'Ah', '2c', '2d'], 14),
  ('six-high over wheel', ['Ah', '2d', '3c', '4s', '5h', '6d', 'Jc'], 6),
  ('four-straight only', ['9h', 'Td', 'Jc', 'Qs', '2h', '2d', '3c'], 0),
  ('paired straight', ['5h', '5d', '6c', '7s', '8h', '9d', 'Kc'], 9),
  ('trips inside straight', ['5h', '5d', '5c', '6s', '7h', '8d', '9c'], 9),
  ('seven-card long straight', ['4h', '5d', '6c', '7s', '8h', '9d', 'Tc'], 10),
  ('gap straight', ['2h', '3d', '4c', '6s', '7h', '8d', '9c'], 0),
  ('ace-king-queen-jack only', ['Ah', 'Kd', 'Qc', 'Js', '9h'], 0)],
 [('six-high over wheel', ['Ah', '2d', '3c', '4s', '5h', '6d', 'Jc'], 6),
  ('paired straight', ['5h', '5d', '6c', '7s', '8h', '9d', 'Kc'], 9),
  ('trips inside straight', ['5h', '5d', '5c', '6s', '7h', '8d', '9c'], 9),
  ('seven-card long straight', ['4h', '5d', '6c', '7s', '8h', '9d', 'Tc'], 10),
  ('gap straight', ['2h', '3d', '4c', '6s', '7h', '8d', '9c'], 0),
  ('five cards straight', ['6h', '7d', '8c', '9s', 'Th'], 10),
  ('ace-king-queen-jack only', ['Ah', 'Kd', 'Qc', 'Js', '9h'], 0),
  ('king with low run', ['Kh', '2d', '3c', '4s', '5h', '9d'], 0)],
 [('four-straight only', ['9h', 'Td', 'Jc', 'Qs', '2h', '2d', '3c'], 0),
  ('paired straight', ['5h', '5d', '6c', '7s', '8h', '9d', 'Kc'], 9),
  ('trips inside straight', ['5h', '5d', '5c', '6s', '7h', '8d', '9c'], 9),
  ('gap straight', ['2h', '3d', '4c', '6s', '7h', '8d', '9c'], 0),
  ('five cards straight', ['6h', '7d', '8c', '9s', 'Th'], 10),
  ('ace-king-queen-jack only', ['Ah', 'Kd', 'Qc', 'Js', '9h'], 0),
  ('pair of fours with straight', ['3h', '4d', '4c', '5s', '6h', '7d', 'Ac'], 7),
  ('king with low run', ['Kh', '2d', '3c', '4s', '5h', '9d'], 0)],
 [('four-straight only', ['9h', 'Td', 'Jc', 'Qs', '2h', '2d', '3c'], 0),
  ('trips inside straight', ['5h', '5d', '5c', '6s', '7h', '8d', '9c'], 9),
  ('seven-card long straight', ['4h', '5d', '6c', '7s', '8h', '9d', 'Tc'], 10),
  ('gap straight', ['2h', '3d', '4c', '6s', '7h', '8d', '9c'], 0),
  ('pair of fours with straight', ['3h', '4d', '4c', '5s', '6h', '7d', 'Ac'], 7),
  ('two pair inside straight', ['8h', '8d', '9c', '9s', 'Th', 'Jd', 'Qc'], 12),
  ('king-high straight', ['9h', 'Td', 'Jc', 'Qs', 'Kh', '3d', '2c'], 13),
  ('wheel without king', ['Ah', '2d', '3c', '4s', '5h', '9d', 'Jc'], 5)]]
for label, args, expected in fixtures[N-1]:
    try:
        actual = solve(args)
    except Exception as exc:
        actual = 'error:' + type(exc).__name__
    check(label, actual, 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
wheel in seven	`5`	`5`	Passed
broadway	`14`	`14`	Passed
six-high over wheel	`6`	`6`	Passed
four-straight only	`12`	`0`	Failed
paired straight	`9`	`9`	Passed
no straight	`0`	`0`	Passed
gap straight	`9`	`0`	Failed
no straight low cards	`0`	`0`	Passed

SHA-256 / 991507c896de77e97072deed3c4dce54f93490aeb70eb8fbd08406e761802e25

2 / The unsuccessful fix

Exit 1

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

N = 1
observations = []
def solve(x):
    R='23456789TJQKA'
    m=0
    for c in x:
        m|=1<<(R.index(c[0])+2)
    if m & (1<<14): m|=1<<1
    for top in range(14,4,-1):
        need=0b11111<<(top-5)
        if m & need == need: return top
    return 0
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
fixtures = [[('wheel in seven', ['Ah', '2d', '3c', '4s', '5h', 'Kd', 'Kc'], 5),
  ('broadway', ['Th', 'Jd', 'Qc', 'Ks', 'Ah', '2c', '2d'], 14),
  ('six-high over wheel', ['Ah', '2d', '3c', '4s', '5h', '6d', 'Jc'], 6),
  ('four-straight only', ['9h', 'Td', 'Jc', 'Qs', '2h', '2d', '3c'], 0),
  ('paired straight', ['5h', '5d', '6c', '7s', '8h', '9d', 'Kc'], 9),
  ('no straight', ['2h', '5d', '7c', '9s', 'Jh', 'Kd', 'Ac'], 0),
  ('gap straight', ['2h', '3d', '4c', '6s', '7h', '8d', '9c'], 0),
  ('no straight low cards', ['2h', '3d', '4c', '8s', '9h', 'Qd', 'Qc'], 0)],
 [('broadway', ['Th', 'Jd', 'Qc', 'Ks', 'Ah', '2c', '2d'], 14),
  ('six-high over wheel', ['Ah', '2d', '3c', '4s', '5h', '6d', 'Jc'], 6),
  ('four-straight only', ['9h', 'Td', 'Jc', 'Qs', '2h', '2d', '3c'], 0),
  ('paired straight', ['5h', '5d', '6c', '7s', '8h', '9d', 'Kc'], 9),
  ('trips inside straight', ['5h', '5d', '5c', '6s', '7h', '8d', '9c'], 9),
  ('seven-card long straight', ['4h', '5d', '6c', '7s', '8h', '9d', 'Tc'], 10),
  ('gap straight', ['2h', '3d', '4c', '6s', '7h', '8d', '9c'], 0),
  ('ace-king-queen-jack only', ['Ah', 'Kd', 'Qc', 'Js', '9h'], 0)],
 [('six-high over wheel', ['Ah', '2d', '3c', '4s', '5h', '6d', 'Jc'], 6),
  ('paired straight', ['5h', '5d', '6c', '7s', '8h', '9d', 'Kc'], 9),
  ('trips inside straight', ['5h', '5d', '5c', '6s', '7h', '8d', '9c'], 9),
  ('seven-card long straight', ['4h', '5d', '6c', '7s', '8h', '9d', 'Tc'], 10),
  ('gap straight', ['2h', '3d', '4c', '6s', '7h', '8d', '9c'], 0),
  ('five cards straight', ['6h', '7d', '8c', '9s', 'Th'], 10),
  ('ace-king-queen-jack only', ['Ah', 'Kd', 'Qc', 'Js', '9h'], 0),
  ('king with low run', ['Kh', '2d', '3c', '4s', '5h', '9d'], 0)],
 [('four-straight only', ['9h', 'Td', 'Jc', 'Qs', '2h', '2d', '3c'], 0),
  ('paired straight', ['5h', '5d', '6c', '7s', '8h', '9d', 'Kc'], 9),
  ('trips inside straight', ['5h', '5d', '5c', '6s', '7h', '8d', '9c'], 9),
  ('gap straight', ['2h', '3d', '4c', '6s', '7h', '8d', '9c'], 0),
  ('five cards straight', ['6h', '7d', '8c', '9s', 'Th'], 10),
  ('ace-king-queen-jack only', ['Ah', 'Kd', 'Qc', 'Js', '9h'], 0),
  ('pair of fours with straight', ['3h', '4d', '4c', '5s', '6h', '7d', 'Ac'], 7),
  ('king with low run', ['Kh', '2d', '3c', '4s', '5h', '9d'], 0)],
 [('four-straight only', ['9h', 'Td', 'Jc', 'Qs', '2h', '2d', '3c'], 0),
  ('trips inside straight', ['5h', '5d', '5c', '6s', '7h', '8d', '9c'], 9),
  ('seven-card long straight', ['4h', '5d', '6c', '7s', '8h', '9d', 'Tc'], 10),
  ('gap straight', ['2h', '3d', '4c', '6s', '7h', '8d', '9c'], 0),
  ('pair of fours with straight', ['3h', '4d', '4c', '5s', '6h', '7d', 'Ac'], 7),
  ('two pair inside straight', ['8h', '8d', '9c', '9s', 'Th', 'Jd', 'Qc'], 12),
  ('king-high straight', ['9h', 'Td', 'Jc', 'Qs', 'Kh', '3d', '2c'], 13),
  ('wheel without king', ['Ah', '2d', '3c', '4s', '5h', '9d', 'Jc'], 5)]]
for label, args, expected in fixtures[N-1]:
    try:
        actual = solve(args)
    except Exception as exc:
        actual = 'error:' + type(exc).__name__
    check(label, actual, 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
wheel in seven	`6`	`5`	Failed
broadway	`0`	`14`	Failed
six-high over wheel	`7`	`6`	Failed
four-straight only	`0`	`0`	Passed
paired straight	`10`	`9`	Failed
no straight	`0`	`0`	Passed
gap straight	`0`	`0`	Passed
no straight low cards	`0`	`0`	Passed

SHA-256 / 96085c0a3505a9669d7fa50c488755d636839202eb2ff0cf8e859bf8471b745d

3 / The verified repair

Exit 0

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

N = 1
observations = []
def solve(x):
    R='23456789TJQKA'
    m=0
    for c in x:
        m|=1<<(R.index(c[0])+2)
    if m & (1<<14): m|=1<<1
    for top in range(14,4,-1):
        need=0b11111<<(top-4)
        if m & need == need: return top
    return 0
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
fixtures = [[('wheel in seven', ['Ah', '2d', '3c', '4s', '5h', 'Kd', 'Kc'], 5),
  ('broadway', ['Th', 'Jd', 'Qc', 'Ks', 'Ah', '2c', '2d'], 14),
  ('six-high over wheel', ['Ah', '2d', '3c', '4s', '5h', '6d', 'Jc'], 6),
  ('four-straight only', ['9h', 'Td', 'Jc', 'Qs', '2h', '2d', '3c'], 0),
  ('paired straight', ['5h', '5d', '6c', '7s', '8h', '9d', 'Kc'], 9),
  ('no straight', ['2h', '5d', '7c', '9s', 'Jh', 'Kd', 'Ac'], 0),
  ('gap straight', ['2h', '3d', '4c', '6s', '7h', '8d', '9c'], 0),
  ('no straight low cards', ['2h', '3d', '4c', '8s', '9h', 'Qd', 'Qc'], 0)],
 [('broadway', ['Th', 'Jd', 'Qc', 'Ks', 'Ah', '2c', '2d'], 14),
  ('six-high over wheel', ['Ah', '2d', '3c', '4s', '5h', '6d', 'Jc'], 6),
  ('four-straight only', ['9h', 'Td', 'Jc', 'Qs', '2h', '2d', '3c'], 0),
  ('paired straight', ['5h', '5d', '6c', '7s', '8h', '9d', 'Kc'], 9),
  ('trips inside straight', ['5h', '5d', '5c', '6s', '7h', '8d', '9c'], 9),
  ('seven-card long straight', ['4h', '5d', '6c', '7s', '8h', '9d', 'Tc'], 10),
  ('gap straight', ['2h', '3d', '4c', '6s', '7h', '8d', '9c'], 0),
  ('ace-king-queen-jack only', ['Ah', 'Kd', 'Qc', 'Js', '9h'], 0)],
 [('six-high over wheel', ['Ah', '2d', '3c', '4s', '5h', '6d', 'Jc'], 6),
  ('paired straight', ['5h', '5d', '6c', '7s', '8h', '9d', 'Kc'], 9),
  ('trips inside straight', ['5h', '5d', '5c', '6s', '7h', '8d', '9c'], 9),
  ('seven-card long straight', ['4h', '5d', '6c', '7s', '8h', '9d', 'Tc'], 10),
  ('gap straight', ['2h', '3d', '4c', '6s', '7h', '8d', '9c'], 0),
  ('five cards straight', ['6h', '7d', '8c', '9s', 'Th'], 10),
  ('ace-king-queen-jack only', ['Ah', 'Kd', 'Qc', 'Js', '9h'], 0),
  ('king with low run', ['Kh', '2d', '3c', '4s', '5h', '9d'], 0)],
 [('four-straight only', ['9h', 'Td', 'Jc', 'Qs', '2h', '2d', '3c'], 0),
  ('paired straight', ['5h', '5d', '6c', '7s', '8h', '9d', 'Kc'], 9),
  ('trips inside straight', ['5h', '5d', '5c', '6s', '7h', '8d', '9c'], 9),
  ('gap straight', ['2h', '3d', '4c', '6s', '7h', '8d', '9c'], 0),
  ('five cards straight', ['6h', '7d', '8c', '9s', 'Th'], 10),
  ('ace-king-queen-jack only', ['Ah', 'Kd', 'Qc', 'Js', '9h'], 0),
  ('pair of fours with straight', ['3h', '4d', '4c', '5s', '6h', '7d', 'Ac'], 7),
  ('king with low run', ['Kh', '2d', '3c', '4s', '5h', '9d'], 0)],
 [('four-straight only', ['9h', 'Td', 'Jc', 'Qs', '2h', '2d', '3c'], 0),
  ('trips inside straight', ['5h', '5d', '5c', '6s', '7h', '8d', '9c'], 9),
  ('seven-card long straight', ['4h', '5d', '6c', '7s', '8h', '9d', 'Tc'], 10),
  ('gap straight', ['2h', '3d', '4c', '6s', '7h', '8d', '9c'], 0),
  ('pair of fours with straight', ['3h', '4d', '4c', '5s', '6h', '7d', 'Ac'], 7),
  ('two pair inside straight', ['8h', '8d', '9c', '9s', 'Th', 'Jd', 'Qc'], 12),
  ('king-high straight', ['9h', 'Td', 'Jc', 'Qs', 'Kh', '3d', '2c'], 13),
  ('wheel without king', ['Ah', '2d', '3c', '4s', '5h', '9d', 'Jc'], 5)]]
for label, args, expected in fixtures[N-1]:
    try:
        actual = solve(args)
    except Exception as exc:
        actual = 'error:' + type(exc).__name__
    check(label, actual, 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
wheel in seven	`5`	`5`	Passed
broadway	`14`	`14`	Passed
six-high over wheel	`6`	`6`	Passed
four-straight only	`0`	`0`	Passed
paired straight	`9`	`9`	Passed
no straight	`0`	`0`	Passed
gap straight	`0`	`0`	Passed
no straight low cards	`0`	`0`	Passed

SHA-256 / e3d3f3aee0ed9c03973e84436c263408b9e9fa8bd09850c74d2d464a161d19e0

Verification & scope

A deterministic toy model with an explicitly stated contract; card strings are rank+suit (for example "As", "Td", "10h"); no claim of conformance to any casino or tournament rulebook. 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 2026-09-29T14:50:07.620500+00:00.

Case digest / 9d4f550dacaf82c515b45a70f7a4d1a9e4b8b5be0199e560eb432df7e1eca0b4