FA-83231 / Go territory scoring / Open access

Two passes by the same player end the game · case 01

A player passing twice in a row (e.g. during free placement) ends the game.

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

ROOT CAUSE

The end test only requires any pending pass.

VERIFIED REPAIR

Require the pending pass to be by the other player.

Unsuccessful approach: Requiring at least two earlier moves rejects an immediate pass-pass ending.

Case contract

Input list of "C:action" tokens. Two consecutive passes by different players end the game ["score", None, index]; any board move clears a pending pass; "resign"/"timeout" end it with the opponent as winner ["resign"/"time", winner, index]. Otherwise ["playing", None, len(moves)].

Why this case matters

Go servers and scoring tools compute this value automatically; a wrong answer changes a game result.

1 / The failure

Exit 1

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

N = 1
observations = []
def solve(x):
    moves = x
    prev_pass = None
    for idx, mv in enumerate(moves):
        who, _, act = mv.partition(':')
        other = 'W' if who == 'B' else 'B'
        if act == 'resign':
            return ['resign', other, idx]
        if act == 'timeout':
            return ['time', other, idx]
        if act == 'pass':
            if prev_pass is not None:
                return ['score', None, idx]
            prev_pass = who
        else:
            prev_pass = None
    return ['playing', None, len(moves)]
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
fixtures = [[[['W:qq', 'W:dd', 'W:pass', 'W:pass'], ['playing', None, 4]], [['B:resign', 'W:pass', 'W:resign', 'B:resign', 'B:qq', 'W:cc'], ['resign', 'W', 0]], [['B:timeout', 'W:pass', 'B:cc', 'B:cc'], ['time', 'W', 0]], [['B:timeout', 'W:pass', 'W:pass', 'W:pass'], ['time', 'W', 0]], [['B:timeout', 'W:cc'], ['time', 'W', 0]], [['B:timeout', 'W:resign'], ['time', 'W', 0]], [['B:pass'], ['playing', None, 1]], [['B:pass', 'W:pass', 'B:pass', 'W:resign', 'B:pass', 'W:dd'], ['score', None, 1]]], [[['B:pass', 'W:dd'], ['playing', None, 2]], [['W:cc', 'B:pass', 'B:dd', 'W:cc', 'B:resign'], ['resign', 'W', 4]], [['B:pass'], ['playing', None, 1]], [['B:resign'], ['resign', 'W', 0]], [['B:resign', 'B:cc', 'W:timeout', 'W:pass', 'B:cc'], ['resign', 'W', 0]], [['B:cc', 'W:pass', 'B:dd', 'B:resign'], ['resign', 'W', 3]], [['B:pass', 'B:pass'], ['playing', None, 2]], [['B:pass', 'W:pass'], ['score', None, 1]]], [[['B:pass', 'W:qq'], ['playing', None, 2]], [['B:resign', 'W:pass'], ['resign', 'W', 0]], [['B:pass', 'W:cc', 'W:pass', 'B:cc'], ['playing', None, 4]], [['B:pass', 'W:qq'], ['playing', None, 2]], [['B:pass', 'B:dd', 'B:qq'], ['playing', None, 3]], [['W:pass'], ['playing', None, 1]], [['B:pass', 'B:pass', 'B:qq', 'W:pass'], ['playing', None, 4]], [['B:pass', 'W:pass', 'B:pass', 'W:timeout'], ['score', None, 1]]], [[['B:resign', 'W:pass', 'B:pass', 'W:dd'], ['resign', 'W', 0]], [['B:pass', 'W:qq', 'B:resign', 'W:pass', 'B:resign'], ['resign', 'W', 2]], [['B:dd', 'W:pass', 'B:pass', 'W:cc', 'B:cc'], ['score', None, 2]], [['B:dd', 'W:resign', 'B:dd', 'W:dd'], ['resign', 'B', 1]], [['W:qq', 'W:timeout', 'B:dd', 'W:pass', 'B:cc', 'W:qq'], ['time', 'B', 1]], [['B:dd'], ['playing', None, 1]], [['B:pass', 'W:pass', 'B:pass', 'B:dd', 'B:cc', 'W:timeout'], ['score', None, 1]], [['B:qq', 'B:pass', 'B:pass', 'W:pass'], ['score', None, 3]]], [[['W:cc', 'W:resign'], ['resign', 'B', 1]], [['B:dd', 'B:cc', 'B:cc', 'W:resign'], ['resign', 'B', 3]], [['W:pass', 'B:timeout', 'B:cc', 'W:dd'], ['time', 'W', 1]], [['B:timeout'], ['time', 'W', 0]], [['B:pass', 'W:pass', 'B:pass', 'W:resign', 'B:pass', 'W:dd'], ['score', None, 1]], [['W:timeout', 'W:cc', 'B:cc', 'W:pass', 'B:dd', 'W:qq'], ['time', 'B', 0]], [['B:pass', 'W:pass', 'B:resign', 'W:pass', 'B:pass', 'B:dd'], ['score', None, 1]], [['B:qq', 'W:qq', 'B:pass', 'B:pass', 'B:timeout', 'B:cc'], ['time', 'W', 4]]]]
for i, (args, expected) in enumerate(fixtures[N-1]):
    check("game end 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
game end case 0	`['score', None, 3]`	`['playing', None, 4]`	Failed
game end case 1	`['resign', 'W', 0]`	`['resign', 'W', 0]`	Passed
game end case 2	`['time', 'W', 0]`	`['time', 'W', 0]`	Passed
game end case 3	`['time', 'W', 0]`	`['time', 'W', 0]`	Passed
game end case 4	`['time', 'W', 0]`	`['time', 'W', 0]`	Passed
game end case 5	`['time', 'W', 0]`	`['time', 'W', 0]`	Passed
game end case 6	`['playing', None, 1]`	`['playing', None, 1]`	Passed
game end case 7	`['score', None, 1]`	`['score', None, 1]`	Passed

SHA-256 / 1d52c25195abad31c9ed90f3caa5c6b85a427f3d1ef90b3b7adbfa5eceb02f2e

2 / The unsuccessful fix

Exit 1

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

N = 1
observations = []
def solve(x):
    moves = x
    prev_pass = None
    for idx, mv in enumerate(moves):
        who, _, act = mv.partition(':')
        other = 'W' if who == 'B' else 'B'
        if act == 'resign':
            return ['resign', other, idx]
        if act == 'timeout':
            return ['time', other, idx]
        if act == 'pass':
            if prev_pass is not None and prev_pass != who and idx >= 2:
                return ['score', None, idx]
            prev_pass = who
        else:
            prev_pass = None
    return ['playing', None, len(moves)]
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
fixtures = [[[['W:qq', 'W:dd', 'W:pass', 'W:pass'], ['playing', None, 4]], [['B:resign', 'W:pass', 'W:resign', 'B:resign', 'B:qq', 'W:cc'], ['resign', 'W', 0]], [['B:timeout', 'W:pass', 'B:cc', 'B:cc'], ['time', 'W', 0]], [['B:timeout', 'W:pass', 'W:pass', 'W:pass'], ['time', 'W', 0]], [['B:timeout', 'W:cc'], ['time', 'W', 0]], [['B:timeout', 'W:resign'], ['time', 'W', 0]], [['B:pass'], ['playing', None, 1]], [['B:pass', 'W:pass', 'B:pass', 'W:resign', 'B:pass', 'W:dd'], ['score', None, 1]]], [[['B:pass', 'W:dd'], ['playing', None, 2]], [['W:cc', 'B:pass', 'B:dd', 'W:cc', 'B:resign'], ['resign', 'W', 4]], [['B:pass'], ['playing', None, 1]], [['B:resign'], ['resign', 'W', 0]], [['B:resign', 'B:cc', 'W:timeout', 'W:pass', 'B:cc'], ['resign', 'W', 0]], [['B:cc', 'W:pass', 'B:dd', 'B:resign'], ['resign', 'W', 3]], [['B:pass', 'B:pass'], ['playing', None, 2]], [['B:pass', 'W:pass'], ['score', None, 1]]], [[['B:pass', 'W:qq'], ['playing', None, 2]], [['B:resign', 'W:pass'], ['resign', 'W', 0]], [['B:pass', 'W:cc', 'W:pass', 'B:cc'], ['playing', None, 4]], [['B:pass', 'W:qq'], ['playing', None, 2]], [['B:pass', 'B:dd', 'B:qq'], ['playing', None, 3]], [['W:pass'], ['playing', None, 1]], [['B:pass', 'B:pass', 'B:qq', 'W:pass'], ['playing', None, 4]], [['B:pass', 'W:pass', 'B:pass', 'W:timeout'], ['score', None, 1]]], [[['B:resign', 'W:pass', 'B:pass', 'W:dd'], ['resign', 'W', 0]], [['B:pass', 'W:qq', 'B:resign', 'W:pass', 'B:resign'], ['resign', 'W', 2]], [['B:dd', 'W:pass', 'B:pass', 'W:cc', 'B:cc'], ['score', None, 2]], [['B:dd', 'W:resign', 'B:dd', 'W:dd'], ['resign', 'B', 1]], [['W:qq', 'W:timeout', 'B:dd', 'W:pass', 'B:cc', 'W:qq'], ['time', 'B', 1]], [['B:dd'], ['playing', None, 1]], [['B:pass', 'W:pass', 'B:pass', 'B:dd', 'B:cc', 'W:timeout'], ['score', None, 1]], [['B:qq', 'B:pass', 'B:pass', 'W:pass'], ['score', None, 3]]], [[['W:cc', 'W:resign'], ['resign', 'B', 1]], [['B:dd', 'B:cc', 'B:cc', 'W:resign'], ['resign', 'B', 3]], [['W:pass', 'B:timeout', 'B:cc', 'W:dd'], ['time', 'W', 1]], [['B:timeout'], ['time', 'W', 0]], [['B:pass', 'W:pass', 'B:pass', 'W:resign', 'B:pass', 'W:dd'], ['score', None, 1]], [['W:timeout', 'W:cc', 'B:cc', 'W:pass', 'B:dd', 'W:qq'], ['time', 'B', 0]], [['B:pass', 'W:pass', 'B:resign', 'W:pass', 'B:pass', 'B:dd'], ['score', None, 1]], [['B:qq', 'W:qq', 'B:pass', 'B:pass', 'B:timeout', 'B:cc'], ['time', 'W', 4]]]]
for i, (args, expected) in enumerate(fixtures[N-1]):
    check("game end 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
game end case 0	`['playing', None, 4]`	`['playing', None, 4]`	Passed
game end case 1	`['resign', 'W', 0]`	`['resign', 'W', 0]`	Passed
game end case 2	`['time', 'W', 0]`	`['time', 'W', 0]`	Passed
game end case 3	`['time', 'W', 0]`	`['time', 'W', 0]`	Passed
game end case 4	`['time', 'W', 0]`	`['time', 'W', 0]`	Passed
game end case 5	`['time', 'W', 0]`	`['time', 'W', 0]`	Passed
game end case 6	`['playing', None, 1]`	`['playing', None, 1]`	Passed
game end case 7	`['score', None, 2]`	`['score', None, 1]`	Failed

SHA-256 / 55109d83b978d87f391f99e9c46245fc262179539a5c627a46476ab9d123ff7e

3 / The verified repair

Exit 0

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

N = 1
observations = []
def solve(x):
    moves = x
    prev_pass = None
    for idx, mv in enumerate(moves):
        who, _, act = mv.partition(':')
        other = 'W' if who == 'B' else 'B'
        if act == 'resign':
            return ['resign', other, idx]
        if act == 'timeout':
            return ['time', other, idx]
        if act == 'pass':
            if prev_pass is not None and prev_pass != who:
                return ['score', None, idx]
            prev_pass = who
        else:
            prev_pass = None
    return ['playing', None, len(moves)]
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
fixtures = [[[['W:qq', 'W:dd', 'W:pass', 'W:pass'], ['playing', None, 4]], [['B:resign', 'W:pass', 'W:resign', 'B:resign', 'B:qq', 'W:cc'], ['resign', 'W', 0]], [['B:timeout', 'W:pass', 'B:cc', 'B:cc'], ['time', 'W', 0]], [['B:timeout', 'W:pass', 'W:pass', 'W:pass'], ['time', 'W', 0]], [['B:timeout', 'W:cc'], ['time', 'W', 0]], [['B:timeout', 'W:resign'], ['time', 'W', 0]], [['B:pass'], ['playing', None, 1]], [['B:pass', 'W:pass', 'B:pass', 'W:resign', 'B:pass', 'W:dd'], ['score', None, 1]]], [[['B:pass', 'W:dd'], ['playing', None, 2]], [['W:cc', 'B:pass', 'B:dd', 'W:cc', 'B:resign'], ['resign', 'W', 4]], [['B:pass'], ['playing', None, 1]], [['B:resign'], ['resign', 'W', 0]], [['B:resign', 'B:cc', 'W:timeout', 'W:pass', 'B:cc'], ['resign', 'W', 0]], [['B:cc', 'W:pass', 'B:dd', 'B:resign'], ['resign', 'W', 3]], [['B:pass', 'B:pass'], ['playing', None, 2]], [['B:pass', 'W:pass'], ['score', None, 1]]], [[['B:pass', 'W:qq'], ['playing', None, 2]], [['B:resign', 'W:pass'], ['resign', 'W', 0]], [['B:pass', 'W:cc', 'W:pass', 'B:cc'], ['playing', None, 4]], [['B:pass', 'W:qq'], ['playing', None, 2]], [['B:pass', 'B:dd', 'B:qq'], ['playing', None, 3]], [['W:pass'], ['playing', None, 1]], [['B:pass', 'B:pass', 'B:qq', 'W:pass'], ['playing', None, 4]], [['B:pass', 'W:pass', 'B:pass', 'W:timeout'], ['score', None, 1]]], [[['B:resign', 'W:pass', 'B:pass', 'W:dd'], ['resign', 'W', 0]], [['B:pass', 'W:qq', 'B:resign', 'W:pass', 'B:resign'], ['resign', 'W', 2]], [['B:dd', 'W:pass', 'B:pass', 'W:cc', 'B:cc'], ['score', None, 2]], [['B:dd', 'W:resign', 'B:dd', 'W:dd'], ['resign', 'B', 1]], [['W:qq', 'W:timeout', 'B:dd', 'W:pass', 'B:cc', 'W:qq'], ['time', 'B', 1]], [['B:dd'], ['playing', None, 1]], [['B:pass', 'W:pass', 'B:pass', 'B:dd', 'B:cc', 'W:timeout'], ['score', None, 1]], [['B:qq', 'B:pass', 'B:pass', 'W:pass'], ['score', None, 3]]], [[['W:cc', 'W:resign'], ['resign', 'B', 1]], [['B:dd', 'B:cc', 'B:cc', 'W:resign'], ['resign', 'B', 3]], [['W:pass', 'B:timeout', 'B:cc', 'W:dd'], ['time', 'W', 1]], [['B:timeout'], ['time', 'W', 0]], [['B:pass', 'W:pass', 'B:pass', 'W:resign', 'B:pass', 'W:dd'], ['score', None, 1]], [['W:timeout', 'W:cc', 'B:cc', 'W:pass', 'B:dd', 'W:qq'], ['time', 'B', 0]], [['B:pass', 'W:pass', 'B:resign', 'W:pass', 'B:pass', 'B:dd'], ['score', None, 1]], [['B:qq', 'W:qq', 'B:pass', 'B:pass', 'B:timeout', 'B:cc'], ['time', 'W', 4]]]]
for i, (args, expected) in enumerate(fixtures[N-1]):
    check("game end 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
game end case 0	`['playing', None, 4]`	`['playing', None, 4]`	Passed
game end case 1	`['resign', 'W', 0]`	`['resign', 'W', 0]`	Passed
game end case 2	`['time', 'W', 0]`	`['time', 'W', 0]`	Passed
game end case 3	`['time', 'W', 0]`	`['time', 'W', 0]`	Passed
game end case 4	`['time', 'W', 0]`	`['time', 'W', 0]`	Passed
game end case 5	`['time', 'W', 0]`	`['time', 'W', 0]`	Passed
game end case 6	`['playing', None, 1]`	`['playing', None, 1]`	Passed
game end case 7	`['score', None, 1]`	`['score', None, 1]`	Passed

SHA-256 / c71a8b1c5b0de42336e53d69dfc4c5753e2153d66b0e9f88e5d5b54224fcfbbd

Verification & scope

Small rectangular toy boards given as strings of B, W and dot; a bounded teaching model of one scoring or bookkeeping rule, not a complete rules engine or server implementation. 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 2026-09-29T14:50:19.623523+00:00.

Case digest / b29e9f533aa6280bb35a16d34e6697d8c9cfa4f281052d768a908637f7db3efe