FAILURE MAP
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FA-86226 / Game economy crafting balance / Open access

Currency exchange desk: Change ignores the fee · case 01

Change returned is computed before deducting the fee.

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

ROOT CAUSE

The copper change is taken from the gross value.

VERIFIED REPAIR

Restore `net % rates[to_cur]` at the change remainder step.

Unsuccessful approach: Subtracting the coin count mixes units.

Case contract

rates map currency -> copper value. Same currency returns [amount, 0] without fee. Otherwise value = amount*rate[from]; fee = ceil(value*fee_bp/10000), at least 1 copper when value > 0 and fee_bp > 0 and 0 otherwise; net = value - fee; return [net // rate[to], net % rate[to]] (change in copper).

Why this case matters

Game economies leak or destroy currency when one crafting or pricing rule is off by one boundary, rounding stage or state update; the defect is observable in exact integer outcomes.

1 / The failure

Exit 1
"""Failure Map reference implementation. Python standard library only."""
import json

N = 1
observations = []
def solve(amount, from_cur, to_cur, rates, fee_bp):
    if from_cur == to_cur:
        return [amount, 0]
    value = amount * rates[from_cur]
    fee = -(-value * fee_bp // 10000)
    if value > 0 and fee_bp > 0:
        fee = max(fee, 1)
    net = value - fee
    return [net // rates[to_cur], value % rates[to_cur]]
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
cases = [[('fee rounds up #1', [3, 'gem', 'silver', {'copper': 1, 'silver': 100, 'gem': 250}, 25], [7, 48]),
  ('regression change remainder #1',
   [1, 'gem', 'token', {'copper': 1, 'silver': 100, 'gold': 10000, 'gem': 250, 'token': 100}, 1],
   [2, 49]),
  ('regression change remainder #2',
   [1291, 'gold', 'token', {'copper': 1, 'silver': 100, 'gold': 10000, 'gem': 250, 'token': 100}, 25],
   [128777, 25]),
  ('regression change remainder #3',
   [3, 'token', 'silver', {'copper': 1, 'silver': 100, 'gold': 10000, 'gem': 250, 'token': 100}, 25],
   [2, 99]),
  ('regression change remainder #4',
   [3, 'gem', 'silver', {'copper': 1, 'silver': 100, 'gold': 10000, 'gem': 250, 'token': 100}, 50],
   [7, 46]),
  ('same currency no fee #1',
   [5, 'gold', 'gold', {'copper': 1, 'silver': 100, 'gold': 10000, 'gem': 250}, 150],
   [5, 0]),
  ('zero amount with fee #1', [0, 'gem', 'silver', {'copper': 1, 'silver': 100, 'gem': 250}, 50], [0, 0]),
  ('control #1',
   [751, 'silver', 'silver', {'copper': 1, 'silver': 100, 'gold': 10000, 'gem': 250, 'token': 100}, 1],
   [751, 0])],
 [('fee rounds up #1', [3, 'gem', 'silver', {'copper': 1, 'silver': 100, 'gem': 250}, 25], [7, 48]),
  ('regression change remainder #1',
   [1291, 'gold', 'token', {'copper': 1, 'silver': 100, 'gold': 10000, 'gem': 250, 'token': 100}, 25],
   [128777, 25]),
  ('fault site change remainder #1',
   [3, 'copper', 'silver', {'copper': 1, 'silver': 100, 'gold': 10000, 'gem': 250, 'token': 100}, 333],
   [0, 2]),
  ('regression change remainder #2',
   [3, 'token', 'silver', {'copper': 1, 'silver': 100, 'gold': 10000, 'gem': 250, 'token': 100}, 25],
   [2, 99]),
  ('regression change remainder #3',
   [3, 'gem', 'silver', {'copper': 1, 'silver': 100, 'gold': 10000, 'gem': 250, 'token': 100}, 50],
   [7, 46]),
  ('same currency no fee #1',
   [5, 'gold', 'gold', {'copper': 1, 'silver': 100, 'gold': 10000, 'gem': 250}, 150],
   [5, 0]),
  ('zero amount with fee #1', [0, 'gem', 'silver', {'copper': 1, 'silver': 100, 'gem': 250}, 50], [0, 0]),
  ('control #1',
   [751, 'silver', 'silver', {'copper': 1, 'silver': 100, 'gold': 10000, 'gem': 250, 'token': 100}, 1],
   [751, 0])],
 [('fee rounds up #1', [3, 'gem', 'silver', {'copper': 1, 'silver': 100, 'gem': 250}, 25], [7, 48]),
  ('fault site change remainder #1',
   [1, 'copper', 'gold', {'copper': 1, 'silver': 100, 'gold': 10000, 'gem': 250, 'token': 100}, 333],
   [0, 0]),
  ('regression change remainder #1',
   [3, 'token', 'silver', {'copper': 1, 'silver': 100, 'gold': 10000, 'gem': 250, 'token': 100}, 25],
   [2, 99]),
  ('regression change remainder #2',
   [3, 'gem', 'silver', {'copper': 1, 'silver': 100, 'gold': 10000, 'gem': 250, 'token': 100}, 50],
   [7, 46]),
  ('regression change remainder #3',
   [7, 'silver', 'token', {'copper': 1, 'silver': 100, 'gold': 10000, 'gem': 250, 'token': 100}, 150],
   [6, 89]),
  ('same currency no fee #1',
   [5, 'gold', 'gold', {'copper': 1, 'silver': 100, 'gold': 10000, 'gem': 250}, 150],
   [5, 0]),
  ('zero amount with fee #1', [0, 'gem', 'silver', {'copper': 1, 'silver': 100, 'gem': 250}, 50], [0, 0]),
  ('control #1',
   [751, 'silver', 'silver', {'copper': 1, 'silver': 100, 'gold': 10000, 'gem': 250, 'token': 100}, 1],
   [751, 0])],
 [('fee rounds up #1', [3, 'gem', 'silver', {'copper': 1, 'silver': 100, 'gem': 250}, 25], [7, 48]),
  ('regression change remainder #1',
   [3, 'gem', 'silver', {'copper': 1, 'silver': 100, 'gold': 10000, 'gem': 250, 'token': 100}, 50],
   [7, 46]),
  ('regression change remainder #2',
   [7, 'silver', 'token', {'copper': 1, 'silver': 100, 'gold': 10000, 'gem': 250, 'token': 100}, 150],
   [6, 89]),
  ('regression change remainder #3',
   [40, 'gold', 'token', {'copper': 1, 'silver': 100, 'gold': 10000, 'gem': 250, 'token': 100}, 1],
   [3999, 60]),
  ('regression change remainder #4',
   [7, 'gold', 'silver', {'copper': 1, 'silver': 100, 'gold': 10000, 'gem': 250, 'token': 100}, 25],
   [698, 25]),
  ('same currency no fee #1',
   [5, 'gold', 'gold', {'copper': 1, 'silver': 100, 'gold': 10000, 'gem': 250}, 150],
   [5, 0]),
  ('zero amount with fee #1', [0, 'gem', 'silver', {'copper': 1, 'silver': 100, 'gem': 250}, 50], [0, 0]),
  ('control #1',
   [7, 'gold', 'copper', {'copper': 1, 'silver': 100, 'gold': 10000, 'gem': 250, 'token': 100}, 333],
   [67669, 0])],
 [('fee rounds up #1', [3, 'gem', 'silver', {'copper': 1, 'silver': 100, 'gem': 250}, 25], [7, 48]),
  ('regression change remainder #1',
   [40, 'gold', 'token', {'copper': 1, 'silver': 100, 'gold': 10000, 'gem': 250, 'token': 100}, 1],
   [3999, 60]),
  ('fault site change remainder #1',
   [1, 'token', 'silver', {'copper': 1, 'silver': 100, 'gold': 10000, 'gem': 250, 'token': 100}, 25],
   [0, 99]),
  ('regression change remainder #2',
   [7, 'gem', 'token', {'copper': 1, 'silver': 100, 'gold': 10000, 'gem': 250, 'token': 100}, 50],
   [17, 41]),
  ('regression change remainder #3',
   [40, 'silver', 'token', {'copper': 1, 'silver': 100, 'gold': 10000, 'gem': 250, 'token': 100}, 150],
   [39, 40]),
  ('same currency no fee #1',
   [5, 'gold', 'gold', {'copper': 1, 'silver': 100, 'gold': 10000, 'gem': 250}, 150],
   [5, 0]),
  ('zero amount with fee #1', [0, 'gem', 'silver', {'copper': 1, 'silver': 100, 'gem': 250}, 50], [0, 0]),
  ('control #1',
   [1, 'copper', 'copper', {'copper': 1, 'silver': 100, 'gold': 10000, 'gem': 250, 'token': 100}, 50],
   [1, 0])]]
for label, args, expected in cases[N-1]:
    check(label, 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 fixtureActualExpectedOutcome
fee rounds up #1[7, 50][7, 48]Failed
regression change remainder #1[2, 50][2, 49]Failed
regression change remainder #2[128777, 0][128777, 25]Failed
regression change remainder #3[2, 0][2, 99]Failed
regression change remainder #4[7, 50][7, 46]Failed
same currency no fee #1[5, 0][5, 0]Passed
zero amount with fee #1[0, 0][0, 0]Passed
control #1[751, 0][751, 0]Passed

SHA-256 / 8c26ed000f83a916fcf1d1d7c1b97352988faf367884f00efc8e40bfbbb58d03

2 / The unsuccessful fix

Exit 1
"""Failure Map reference implementation. Python standard library only."""
import json

N = 1
observations = []
def solve(amount, from_cur, to_cur, rates, fee_bp):
    if from_cur == to_cur:
        return [amount, 0]
    value = amount * rates[from_cur]
    fee = -(-value * fee_bp // 10000)
    if value > 0 and fee_bp > 0:
        fee = max(fee, 1)
    net = value - fee
    return [net // rates[to_cur], net - net // rates[to_cur]]
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
cases = [[('fee rounds up #1', [3, 'gem', 'silver', {'copper': 1, 'silver': 100, 'gem': 250}, 25], [7, 48]),
  ('regression change remainder #1',
   [1, 'gem', 'token', {'copper': 1, 'silver': 100, 'gold': 10000, 'gem': 250, 'token': 100}, 1],
   [2, 49]),
  ('regression change remainder #2',
   [1291, 'gold', 'token', {'copper': 1, 'silver': 100, 'gold': 10000, 'gem': 250, 'token': 100}, 25],
   [128777, 25]),
  ('regression change remainder #3',
   [3, 'token', 'silver', {'copper': 1, 'silver': 100, 'gold': 10000, 'gem': 250, 'token': 100}, 25],
   [2, 99]),
  ('regression change remainder #4',
   [3, 'gem', 'silver', {'copper': 1, 'silver': 100, 'gold': 10000, 'gem': 250, 'token': 100}, 50],
   [7, 46]),
  ('same currency no fee #1',
   [5, 'gold', 'gold', {'copper': 1, 'silver': 100, 'gold': 10000, 'gem': 250}, 150],
   [5, 0]),
  ('zero amount with fee #1', [0, 'gem', 'silver', {'copper': 1, 'silver': 100, 'gem': 250}, 50], [0, 0]),
  ('control #1',
   [751, 'silver', 'silver', {'copper': 1, 'silver': 100, 'gold': 10000, 'gem': 250, 'token': 100}, 1],
   [751, 0])],
 [('fee rounds up #1', [3, 'gem', 'silver', {'copper': 1, 'silver': 100, 'gem': 250}, 25], [7, 48]),
  ('regression change remainder #1',
   [1291, 'gold', 'token', {'copper': 1, 'silver': 100, 'gold': 10000, 'gem': 250, 'token': 100}, 25],
   [128777, 25]),
  ('fault site change remainder #1',
   [3, 'copper', 'silver', {'copper': 1, 'silver': 100, 'gold': 10000, 'gem': 250, 'token': 100}, 333],
   [0, 2]),
  ('regression change remainder #2',
   [3, 'token', 'silver', {'copper': 1, 'silver': 100, 'gold': 10000, 'gem': 250, 'token': 100}, 25],
   [2, 99]),
  ('regression change remainder #3',
   [3, 'gem', 'silver', {'copper': 1, 'silver': 100, 'gold': 10000, 'gem': 250, 'token': 100}, 50],
   [7, 46]),
  ('same currency no fee #1',
   [5, 'gold', 'gold', {'copper': 1, 'silver': 100, 'gold': 10000, 'gem': 250}, 150],
   [5, 0]),
  ('zero amount with fee #1', [0, 'gem', 'silver', {'copper': 1, 'silver': 100, 'gem': 250}, 50], [0, 0]),
  ('control #1',
   [751, 'silver', 'silver', {'copper': 1, 'silver': 100, 'gold': 10000, 'gem': 250, 'token': 100}, 1],
   [751, 0])],
 [('fee rounds up #1', [3, 'gem', 'silver', {'copper': 1, 'silver': 100, 'gem': 250}, 25], [7, 48]),
  ('fault site change remainder #1',
   [1, 'copper', 'gold', {'copper': 1, 'silver': 100, 'gold': 10000, 'gem': 250, 'token': 100}, 333],
   [0, 0]),
  ('regression change remainder #1',
   [3, 'token', 'silver', {'copper': 1, 'silver': 100, 'gold': 10000, 'gem': 250, 'token': 100}, 25],
   [2, 99]),
  ('regression change remainder #2',
   [3, 'gem', 'silver', {'copper': 1, 'silver': 100, 'gold': 10000, 'gem': 250, 'token': 100}, 50],
   [7, 46]),
  ('regression change remainder #3',
   [7, 'silver', 'token', {'copper': 1, 'silver': 100, 'gold': 10000, 'gem': 250, 'token': 100}, 150],
   [6, 89]),
  ('same currency no fee #1',
   [5, 'gold', 'gold', {'copper': 1, 'silver': 100, 'gold': 10000, 'gem': 250}, 150],
   [5, 0]),
  ('zero amount with fee #1', [0, 'gem', 'silver', {'copper': 1, 'silver': 100, 'gem': 250}, 50], [0, 0]),
  ('control #1',
   [751, 'silver', 'silver', {'copper': 1, 'silver': 100, 'gold': 10000, 'gem': 250, 'token': 100}, 1],
   [751, 0])],
 [('fee rounds up #1', [3, 'gem', 'silver', {'copper': 1, 'silver': 100, 'gem': 250}, 25], [7, 48]),
  ('regression change remainder #1',
   [3, 'gem', 'silver', {'copper': 1, 'silver': 100, 'gold': 10000, 'gem': 250, 'token': 100}, 50],
   [7, 46]),
  ('regression change remainder #2',
   [7, 'silver', 'token', {'copper': 1, 'silver': 100, 'gold': 10000, 'gem': 250, 'token': 100}, 150],
   [6, 89]),
  ('regression change remainder #3',
   [40, 'gold', 'token', {'copper': 1, 'silver': 100, 'gold': 10000, 'gem': 250, 'token': 100}, 1],
   [3999, 60]),
  ('regression change remainder #4',
   [7, 'gold', 'silver', {'copper': 1, 'silver': 100, 'gold': 10000, 'gem': 250, 'token': 100}, 25],
   [698, 25]),
  ('same currency no fee #1',
   [5, 'gold', 'gold', {'copper': 1, 'silver': 100, 'gold': 10000, 'gem': 250}, 150],
   [5, 0]),
  ('zero amount with fee #1', [0, 'gem', 'silver', {'copper': 1, 'silver': 100, 'gem': 250}, 50], [0, 0]),
  ('control #1',
   [7, 'gold', 'copper', {'copper': 1, 'silver': 100, 'gold': 10000, 'gem': 250, 'token': 100}, 333],
   [67669, 0])],
 [('fee rounds up #1', [3, 'gem', 'silver', {'copper': 1, 'silver': 100, 'gem': 250}, 25], [7, 48]),
  ('regression change remainder #1',
   [40, 'gold', 'token', {'copper': 1, 'silver': 100, 'gold': 10000, 'gem': 250, 'token': 100}, 1],
   [3999, 60]),
  ('fault site change remainder #1',
   [1, 'token', 'silver', {'copper': 1, 'silver': 100, 'gold': 10000, 'gem': 250, 'token': 100}, 25],
   [0, 99]),
  ('regression change remainder #2',
   [7, 'gem', 'token', {'copper': 1, 'silver': 100, 'gold': 10000, 'gem': 250, 'token': 100}, 50],
   [17, 41]),
  ('regression change remainder #3',
   [40, 'silver', 'token', {'copper': 1, 'silver': 100, 'gold': 10000, 'gem': 250, 'token': 100}, 150],
   [39, 40]),
  ('same currency no fee #1',
   [5, 'gold', 'gold', {'copper': 1, 'silver': 100, 'gold': 10000, 'gem': 250}, 150],
   [5, 0]),
  ('zero amount with fee #1', [0, 'gem', 'silver', {'copper': 1, 'silver': 100, 'gem': 250}, 50], [0, 0]),
  ('control #1',
   [1, 'copper', 'copper', {'copper': 1, 'silver': 100, 'gold': 10000, 'gem': 250, 'token': 100}, 50],
   [1, 0])]]
for label, args, expected in cases[N-1]:
    check(label, 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 fixtureActualExpectedOutcome
fee rounds up #1[7, 741][7, 48]Failed
regression change remainder #1[2, 247][2, 49]Failed
regression change remainder #2[128777, 12748948][128777, 25]Failed
regression change remainder #3[2, 297][2, 99]Failed
regression change remainder #4[7, 739][7, 46]Failed
same currency no fee #1[5, 0][5, 0]Passed
zero amount with fee #1[0, 0][0, 0]Passed
control #1[751, 0][751, 0]Passed

SHA-256 / cb780edf5d5b51d8c971235da393003b94f52886b3473830109337da63faeb0c

3 / The verified repair

Exit 0
"""Failure Map reference implementation. Python standard library only."""
import json

N = 1
observations = []
def solve(amount, from_cur, to_cur, rates, fee_bp):
    if from_cur == to_cur:
        return [amount, 0]
    value = amount * rates[from_cur]
    fee = -(-value * fee_bp // 10000)
    if value > 0 and fee_bp > 0:
        fee = max(fee, 1)
    net = value - fee
    return [net // rates[to_cur], net % rates[to_cur]]
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
cases = [[('fee rounds up #1', [3, 'gem', 'silver', {'copper': 1, 'silver': 100, 'gem': 250}, 25], [7, 48]),
  ('regression change remainder #1',
   [1, 'gem', 'token', {'copper': 1, 'silver': 100, 'gold': 10000, 'gem': 250, 'token': 100}, 1],
   [2, 49]),
  ('regression change remainder #2',
   [1291, 'gold', 'token', {'copper': 1, 'silver': 100, 'gold': 10000, 'gem': 250, 'token': 100}, 25],
   [128777, 25]),
  ('regression change remainder #3',
   [3, 'token', 'silver', {'copper': 1, 'silver': 100, 'gold': 10000, 'gem': 250, 'token': 100}, 25],
   [2, 99]),
  ('regression change remainder #4',
   [3, 'gem', 'silver', {'copper': 1, 'silver': 100, 'gold': 10000, 'gem': 250, 'token': 100}, 50],
   [7, 46]),
  ('same currency no fee #1',
   [5, 'gold', 'gold', {'copper': 1, 'silver': 100, 'gold': 10000, 'gem': 250}, 150],
   [5, 0]),
  ('zero amount with fee #1', [0, 'gem', 'silver', {'copper': 1, 'silver': 100, 'gem': 250}, 50], [0, 0]),
  ('control #1',
   [751, 'silver', 'silver', {'copper': 1, 'silver': 100, 'gold': 10000, 'gem': 250, 'token': 100}, 1],
   [751, 0])],
 [('fee rounds up #1', [3, 'gem', 'silver', {'copper': 1, 'silver': 100, 'gem': 250}, 25], [7, 48]),
  ('regression change remainder #1',
   [1291, 'gold', 'token', {'copper': 1, 'silver': 100, 'gold': 10000, 'gem': 250, 'token': 100}, 25],
   [128777, 25]),
  ('fault site change remainder #1',
   [3, 'copper', 'silver', {'copper': 1, 'silver': 100, 'gold': 10000, 'gem': 250, 'token': 100}, 333],
   [0, 2]),
  ('regression change remainder #2',
   [3, 'token', 'silver', {'copper': 1, 'silver': 100, 'gold': 10000, 'gem': 250, 'token': 100}, 25],
   [2, 99]),
  ('regression change remainder #3',
   [3, 'gem', 'silver', {'copper': 1, 'silver': 100, 'gold': 10000, 'gem': 250, 'token': 100}, 50],
   [7, 46]),
  ('same currency no fee #1',
   [5, 'gold', 'gold', {'copper': 1, 'silver': 100, 'gold': 10000, 'gem': 250}, 150],
   [5, 0]),
  ('zero amount with fee #1', [0, 'gem', 'silver', {'copper': 1, 'silver': 100, 'gem': 250}, 50], [0, 0]),
  ('control #1',
   [751, 'silver', 'silver', {'copper': 1, 'silver': 100, 'gold': 10000, 'gem': 250, 'token': 100}, 1],
   [751, 0])],
 [('fee rounds up #1', [3, 'gem', 'silver', {'copper': 1, 'silver': 100, 'gem': 250}, 25], [7, 48]),
  ('fault site change remainder #1',
   [1, 'copper', 'gold', {'copper': 1, 'silver': 100, 'gold': 10000, 'gem': 250, 'token': 100}, 333],
   [0, 0]),
  ('regression change remainder #1',
   [3, 'token', 'silver', {'copper': 1, 'silver': 100, 'gold': 10000, 'gem': 250, 'token': 100}, 25],
   [2, 99]),
  ('regression change remainder #2',
   [3, 'gem', 'silver', {'copper': 1, 'silver': 100, 'gold': 10000, 'gem': 250, 'token': 100}, 50],
   [7, 46]),
  ('regression change remainder #3',
   [7, 'silver', 'token', {'copper': 1, 'silver': 100, 'gold': 10000, 'gem': 250, 'token': 100}, 150],
   [6, 89]),
  ('same currency no fee #1',
   [5, 'gold', 'gold', {'copper': 1, 'silver': 100, 'gold': 10000, 'gem': 250}, 150],
   [5, 0]),
  ('zero amount with fee #1', [0, 'gem', 'silver', {'copper': 1, 'silver': 100, 'gem': 250}, 50], [0, 0]),
  ('control #1',
   [751, 'silver', 'silver', {'copper': 1, 'silver': 100, 'gold': 10000, 'gem': 250, 'token': 100}, 1],
   [751, 0])],
 [('fee rounds up #1', [3, 'gem', 'silver', {'copper': 1, 'silver': 100, 'gem': 250}, 25], [7, 48]),
  ('regression change remainder #1',
   [3, 'gem', 'silver', {'copper': 1, 'silver': 100, 'gold': 10000, 'gem': 250, 'token': 100}, 50],
   [7, 46]),
  ('regression change remainder #2',
   [7, 'silver', 'token', {'copper': 1, 'silver': 100, 'gold': 10000, 'gem': 250, 'token': 100}, 150],
   [6, 89]),
  ('regression change remainder #3',
   [40, 'gold', 'token', {'copper': 1, 'silver': 100, 'gold': 10000, 'gem': 250, 'token': 100}, 1],
   [3999, 60]),
  ('regression change remainder #4',
   [7, 'gold', 'silver', {'copper': 1, 'silver': 100, 'gold': 10000, 'gem': 250, 'token': 100}, 25],
   [698, 25]),
  ('same currency no fee #1',
   [5, 'gold', 'gold', {'copper': 1, 'silver': 100, 'gold': 10000, 'gem': 250}, 150],
   [5, 0]),
  ('zero amount with fee #1', [0, 'gem', 'silver', {'copper': 1, 'silver': 100, 'gem': 250}, 50], [0, 0]),
  ('control #1',
   [7, 'gold', 'copper', {'copper': 1, 'silver': 100, 'gold': 10000, 'gem': 250, 'token': 100}, 333],
   [67669, 0])],
 [('fee rounds up #1', [3, 'gem', 'silver', {'copper': 1, 'silver': 100, 'gem': 250}, 25], [7, 48]),
  ('regression change remainder #1',
   [40, 'gold', 'token', {'copper': 1, 'silver': 100, 'gold': 10000, 'gem': 250, 'token': 100}, 1],
   [3999, 60]),
  ('fault site change remainder #1',
   [1, 'token', 'silver', {'copper': 1, 'silver': 100, 'gold': 10000, 'gem': 250, 'token': 100}, 25],
   [0, 99]),
  ('regression change remainder #2',
   [7, 'gem', 'token', {'copper': 1, 'silver': 100, 'gold': 10000, 'gem': 250, 'token': 100}, 50],
   [17, 41]),
  ('regression change remainder #3',
   [40, 'silver', 'token', {'copper': 1, 'silver': 100, 'gold': 10000, 'gem': 250, 'token': 100}, 150],
   [39, 40]),
  ('same currency no fee #1',
   [5, 'gold', 'gold', {'copper': 1, 'silver': 100, 'gold': 10000, 'gem': 250}, 150],
   [5, 0]),
  ('zero amount with fee #1', [0, 'gem', 'silver', {'copper': 1, 'silver': 100, 'gem': 250}, 50], [0, 0]),
  ('control #1',
   [1, 'copper', 'copper', {'copper': 1, 'silver': 100, 'gold': 10000, 'gem': 250, 'token': 100}, 50],
   [1, 0])]]
for label, args, expected in cases[N-1]:
    check(label, 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 fixtureActualExpectedOutcome
fee rounds up #1[7, 48][7, 48]Passed
regression change remainder #1[2, 49][2, 49]Passed
regression change remainder #2[128777, 25][128777, 25]Passed
regression change remainder #3[2, 99][2, 99]Passed
regression change remainder #4[7, 46][7, 46]Passed
same currency no fee #1[5, 0][5, 0]Passed
zero amount with fee #1[0, 0][0, 0]Passed
control #1[751, 0][751, 0]Passed

SHA-256 / e5eca149a8e21ef630619b25b7890e5b52be1ddf5757b58256ddeaaba37468c8

Verification & scope

Deterministic toy contract stipulated for this model; integer or exact arithmetic only, not a reproduction of any specific game engine. 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 2026-09-29T14:50:47.590944+00:00.

Case digest / b31d97f461750782aa55c12c921e5e3792c418ec47a9616296a55023109330dd