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FA-85986 / Game economy crafting balance / Open access

Auction house fees: Auction cut truncates halves · case 01

Sales exactly on a half-copper cut pay too little fee.

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

ROOT CAUSE

The cut is floored rather than rounded half up.

THE FAILURE

The cut is floored rather than rounded half up.

Unsuccessful approach: Ceiling rounding overcharges every sale with any fractional cut.

Case contract

Deposit = per_block * (hours//12) where per_block = max(1, floor(stack_value*15/100)). Sold: net = price - cut with cut = 5% of price rounded half up (deposit refunded). Expired: net = -deposit. Cancelled: net = -deposit - floor(bid*5/100) (bid defaults to 0). Returns {deposit, net} 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(listing, outcome):
    blocks = listing['hours'] // 12
    per_block = max(1, listing['stack_value'] * 15 // 100)
    deposit = per_block * blocks
    status = outcome['status']
    if status == 'sold':
        cut = listing['price'] * 5 // 100
        net = listing['price'] - cut
    elif status == 'cancelled':
        net = -deposit - outcome.get('bid', 0) * 5 // 100
    else:
        net = -deposit
    return {'deposit': deposit, 'net': net}
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
cases = [[('half-up cut boundary #1',
   [{'price': 10, 'hours': 12, 'stack_value': 100}, {'status': 'sold'}],
   {'deposit': 15, 'net': 9}),
  ('fault site cut rounding #1',
   [{'price': 30, 'hours': 12, 'stack_value': 6}, {'status': 'sold'}],
   {'deposit': 1, 'net': 28}),
  ('fault site cut rounding #2',
   [{'price': 190, 'hours': 12, 'stack_value': 0}, {'status': 'sold'}],
   {'deposit': 1, 'net': 180}),
  ('partial repair boundary #1',
   [{'price': 1, 'hours': 24, 'stack_value': 7}, {'status': 'sold'}],
   {'deposit': 2, 'net': 1}),
  ('partial repair boundary #2',
   [{'price': 5141, 'hours': 12, 'stack_value': 13}, {'status': 'sold'}],
   {'deposit': 1, 'net': 4884}),
  ('long cheap listing #1',
   [{'price': 10, 'hours': 48, 'stack_value': 3}, {'status': 'expired'}],
   {'deposit': 4, 'net': -4}),
  ('cancel with bid #1',
   [{'price': 500, 'hours': 24, 'stack_value': 40}, {'status': 'cancelled', 'bid': 390}],
   {'deposit': 12, 'net': -31}),
  ('control #1',
   [{'price': 11, 'hours': 24, 'stack_value': 13}, {'status': 'cancelled', 'bid': 0}],
   {'deposit': 2, 'net': -2})],
 [('half-up cut boundary #1',
   [{'price': 10, 'hours': 12, 'stack_value': 100}, {'status': 'sold'}],
   {'deposit': 15, 'net': 9}),
  ('fault site cut rounding #1',
   [{'price': 190, 'hours': 12, 'stack_value': 0}, {'status': 'sold'}],
   {'deposit': 1, 'net': 180}),
  ('fault site cut rounding #2',
   [{'price': 30, 'hours': 24, 'stack_value': 1}, {'status': 'sold'}],
   {'deposit': 2, 'net': 28}),
  ('partial repair boundary #1',
   [{'price': 34146, 'hours': 48, 'stack_value': 3106}, {'status': 'sold'}],
   {'deposit': 1860, 'net': 32439}),
  ('partial repair boundary #2',
   [{'price': 9, 'hours': 48, 'stack_value': 1}, {'status': 'sold'}],
   {'deposit': 4, 'net': 9}),
  ('long cheap listing #1',
   [{'price': 10, 'hours': 48, 'stack_value': 3}, {'status': 'expired'}],
   {'deposit': 4, 'net': -4}),
  ('cancel with bid #1',
   [{'price': 500, 'hours': 24, 'stack_value': 40}, {'status': 'cancelled', 'bid': 390}],
   {'deposit': 12, 'net': -31}),
  ('control #1',
   [{'price': 11, 'hours': 24, 'stack_value': 13}, {'status': 'cancelled', 'bid': 0}],
   {'deposit': 2, 'net': -2})],
 [('half-up cut boundary #1',
   [{'price': 10, 'hours': 12, 'stack_value': 100}, {'status': 'sold'}],
   {'deposit': 15, 'net': 9}),
  ('fault site cut rounding #1',
   [{'price': 10, 'hours': 24, 'stack_value': 0}, {'status': 'sold'}],
   {'deposit': 2, 'net': 9}),
  ('fault site cut rounding #2',
   [{'price': 91070, 'hours': 24, 'stack_value': 7}, {'status': 'sold'}],
   {'deposit': 2, 'net': 86516}),
  ('partial repair boundary #1',
   [{'price': 72766, 'hours': 24, 'stack_value': 13}, {'status': 'sold'}],
   {'deposit': 2, 'net': 69128}),
  ('partial repair boundary #2',
   [{'price': 9, 'hours': 12, 'stack_value': 13}, {'status': 'sold'}],
   {'deposit': 1, 'net': 9}),
  ('long cheap listing #1',
   [{'price': 10, 'hours': 48, 'stack_value': 3}, {'status': 'expired'}],
   {'deposit': 4, 'net': -4}),
  ('cancel with bid #1',
   [{'price': 500, 'hours': 24, 'stack_value': 40}, {'status': 'cancelled', 'bid': 390}],
   {'deposit': 12, 'net': -31}),
  ('control #1',
   [{'price': 11, 'hours': 24, 'stack_value': 13}, {'status': 'cancelled', 'bid': 0}],
   {'deposit': 2, 'net': -2})],
 [('half-up cut boundary #1',
   [{'price': 10, 'hours': 12, 'stack_value': 100}, {'status': 'sold'}],
   {'deposit': 15, 'net': 9}),
  ('fault site cut rounding #1',
   [{'price': 30, 'hours': 24, 'stack_value': 7}, {'status': 'sold'}],
   {'deposit': 2, 'net': 28}),
  ('fault site cut rounding #2',
   [{'price': 190, 'hours': 12, 'stack_value': 1}, {'status': 'sold'}],
   {'deposit': 1, 'net': 180}),
  ('partial repair boundary #1',
   [{'price': 9, 'hours': 48, 'stack_value': 13}, {'status': 'sold'}],
   {'deposit': 4, 'net': 9}),
  ('partial repair boundary #2',
   [{'price': 74548, 'hours': 48, 'stack_value': 13}, {'status': 'sold'}],
   {'deposit': 4, 'net': 70821}),
  ('long cheap listing #1',
   [{'price': 10, 'hours': 48, 'stack_value': 3}, {'status': 'expired'}],
   {'deposit': 4, 'net': -4}),
  ('cancel with bid #1',
   [{'price': 500, 'hours': 24, 'stack_value': 40}, {'status': 'cancelled', 'bid': 390}],
   {'deposit': 12, 'net': -31}),
  ('control #1',
   [{'price': 10, 'hours': 48, 'stack_value': 0}, {'status': 'expired'}],
   {'deposit': 4, 'net': -4})],
 [('half-up cut boundary #1',
   [{'price': 10, 'hours': 12, 'stack_value': 100}, {'status': 'sold'}],
   {'deposit': 15, 'net': 9}),
  ('fault site cut rounding #1',
   [{'price': 30, 'hours': 12, 'stack_value': 1}, {'status': 'sold'}],
   {'deposit': 1, 'net': 28}),
  ('fault site cut rounding #2',
   [{'price': 70012, 'hours': 12, 'stack_value': 0}, {'status': 'sold'}],
   {'deposit': 1, 'net': 66511}),
  ('partial repair boundary #1',
   [{'price': 9, 'hours': 48, 'stack_value': 6}, {'status': 'sold'}],
   {'deposit': 4, 'net': 9}),
  ('partial repair boundary #2',
   [{'price': 1, 'hours': 48, 'stack_value': 1}, {'status': 'sold'}],
   {'deposit': 4, 'net': 1}),
  ('long cheap listing #1',
   [{'price': 10, 'hours': 48, 'stack_value': 3}, {'status': 'expired'}],
   {'deposit': 4, 'net': -4}),
  ('cancel with bid #1',
   [{'price': 500, 'hours': 24, 'stack_value': 40}, {'status': 'cancelled', 'bid': 390}],
   {'deposit': 12, 'net': -31}),
  ('control #1',
   [{'price': 50, 'hours': 24, 'stack_value': 6}, {'status': 'expired'}],
   {'deposit': 2, 'net': -2})]]
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
half-up cut boundary #1{'deposit': 15, 'net': 10}{'deposit': 15, 'net': 9}Failed
fault site cut rounding #1{'deposit': 1, 'net': 29}{'deposit': 1, 'net': 28}Failed
fault site cut rounding #2{'deposit': 1, 'net': 181}{'deposit': 1, 'net': 180}Failed
partial repair boundary #1{'deposit': 2, 'net': 1}{'deposit': 2, 'net': 1}Passed
partial repair boundary #2{'deposit': 1, 'net': 4884}{'deposit': 1, 'net': 4884}Passed
long cheap listing #1{'deposit': 4, 'net': -4}{'deposit': 4, 'net': -4}Passed
cancel with bid #1{'deposit': 12, 'net': -31}{'deposit': 12, 'net': -31}Passed
control #1{'deposit': 2, 'net': -2}{'deposit': 2, 'net': -2}Passed

SHA-256 / 7e6c18aa1239fb3d328ecb409a17e8acf8f9bab5cce8099e05235e169fd2a623

2 / The unsuccessful fix

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

N = 1
observations = []
def solve(listing, outcome):
    blocks = listing['hours'] // 12
    per_block = max(1, listing['stack_value'] * 15 // 100)
    deposit = per_block * blocks
    status = outcome['status']
    if status == 'sold':
        cut = (listing['price'] * 5 + 99) // 100
        net = listing['price'] - cut
    elif status == 'cancelled':
        net = -deposit - outcome.get('bid', 0) * 5 // 100
    else:
        net = -deposit
    return {'deposit': deposit, 'net': net}
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
cases = [[('half-up cut boundary #1',
   [{'price': 10, 'hours': 12, 'stack_value': 100}, {'status': 'sold'}],
   {'deposit': 15, 'net': 9}),
  ('fault site cut rounding #1',
   [{'price': 30, 'hours': 12, 'stack_value': 6}, {'status': 'sold'}],
   {'deposit': 1, 'net': 28}),
  ('fault site cut rounding #2',
   [{'price': 190, 'hours': 12, 'stack_value': 0}, {'status': 'sold'}],
   {'deposit': 1, 'net': 180}),
  ('partial repair boundary #1',
   [{'price': 1, 'hours': 24, 'stack_value': 7}, {'status': 'sold'}],
   {'deposit': 2, 'net': 1}),
  ('partial repair boundary #2',
   [{'price': 5141, 'hours': 12, 'stack_value': 13}, {'status': 'sold'}],
   {'deposit': 1, 'net': 4884}),
  ('long cheap listing #1',
   [{'price': 10, 'hours': 48, 'stack_value': 3}, {'status': 'expired'}],
   {'deposit': 4, 'net': -4}),
  ('cancel with bid #1',
   [{'price': 500, 'hours': 24, 'stack_value': 40}, {'status': 'cancelled', 'bid': 390}],
   {'deposit': 12, 'net': -31}),
  ('control #1',
   [{'price': 11, 'hours': 24, 'stack_value': 13}, {'status': 'cancelled', 'bid': 0}],
   {'deposit': 2, 'net': -2})],
 [('half-up cut boundary #1',
   [{'price': 10, 'hours': 12, 'stack_value': 100}, {'status': 'sold'}],
   {'deposit': 15, 'net': 9}),
  ('fault site cut rounding #1',
   [{'price': 190, 'hours': 12, 'stack_value': 0}, {'status': 'sold'}],
   {'deposit': 1, 'net': 180}),
  ('fault site cut rounding #2',
   [{'price': 30, 'hours': 24, 'stack_value': 1}, {'status': 'sold'}],
   {'deposit': 2, 'net': 28}),
  ('partial repair boundary #1',
   [{'price': 34146, 'hours': 48, 'stack_value': 3106}, {'status': 'sold'}],
   {'deposit': 1860, 'net': 32439}),
  ('partial repair boundary #2',
   [{'price': 9, 'hours': 48, 'stack_value': 1}, {'status': 'sold'}],
   {'deposit': 4, 'net': 9}),
  ('long cheap listing #1',
   [{'price': 10, 'hours': 48, 'stack_value': 3}, {'status': 'expired'}],
   {'deposit': 4, 'net': -4}),
  ('cancel with bid #1',
   [{'price': 500, 'hours': 24, 'stack_value': 40}, {'status': 'cancelled', 'bid': 390}],
   {'deposit': 12, 'net': -31}),
  ('control #1',
   [{'price': 11, 'hours': 24, 'stack_value': 13}, {'status': 'cancelled', 'bid': 0}],
   {'deposit': 2, 'net': -2})],
 [('half-up cut boundary #1',
   [{'price': 10, 'hours': 12, 'stack_value': 100}, {'status': 'sold'}],
   {'deposit': 15, 'net': 9}),
  ('fault site cut rounding #1',
   [{'price': 10, 'hours': 24, 'stack_value': 0}, {'status': 'sold'}],
   {'deposit': 2, 'net': 9}),
  ('fault site cut rounding #2',
   [{'price': 91070, 'hours': 24, 'stack_value': 7}, {'status': 'sold'}],
   {'deposit': 2, 'net': 86516}),
  ('partial repair boundary #1',
   [{'price': 72766, 'hours': 24, 'stack_value': 13}, {'status': 'sold'}],
   {'deposit': 2, 'net': 69128}),
  ('partial repair boundary #2',
   [{'price': 9, 'hours': 12, 'stack_value': 13}, {'status': 'sold'}],
   {'deposit': 1, 'net': 9}),
  ('long cheap listing #1',
   [{'price': 10, 'hours': 48, 'stack_value': 3}, {'status': 'expired'}],
   {'deposit': 4, 'net': -4}),
  ('cancel with bid #1',
   [{'price': 500, 'hours': 24, 'stack_value': 40}, {'status': 'cancelled', 'bid': 390}],
   {'deposit': 12, 'net': -31}),
  ('control #1',
   [{'price': 11, 'hours': 24, 'stack_value': 13}, {'status': 'cancelled', 'bid': 0}],
   {'deposit': 2, 'net': -2})],
 [('half-up cut boundary #1',
   [{'price': 10, 'hours': 12, 'stack_value': 100}, {'status': 'sold'}],
   {'deposit': 15, 'net': 9}),
  ('fault site cut rounding #1',
   [{'price': 30, 'hours': 24, 'stack_value': 7}, {'status': 'sold'}],
   {'deposit': 2, 'net': 28}),
  ('fault site cut rounding #2',
   [{'price': 190, 'hours': 12, 'stack_value': 1}, {'status': 'sold'}],
   {'deposit': 1, 'net': 180}),
  ('partial repair boundary #1',
   [{'price': 9, 'hours': 48, 'stack_value': 13}, {'status': 'sold'}],
   {'deposit': 4, 'net': 9}),
  ('partial repair boundary #2',
   [{'price': 74548, 'hours': 48, 'stack_value': 13}, {'status': 'sold'}],
   {'deposit': 4, 'net': 70821}),
  ('long cheap listing #1',
   [{'price': 10, 'hours': 48, 'stack_value': 3}, {'status': 'expired'}],
   {'deposit': 4, 'net': -4}),
  ('cancel with bid #1',
   [{'price': 500, 'hours': 24, 'stack_value': 40}, {'status': 'cancelled', 'bid': 390}],
   {'deposit': 12, 'net': -31}),
  ('control #1',
   [{'price': 10, 'hours': 48, 'stack_value': 0}, {'status': 'expired'}],
   {'deposit': 4, 'net': -4})],
 [('half-up cut boundary #1',
   [{'price': 10, 'hours': 12, 'stack_value': 100}, {'status': 'sold'}],
   {'deposit': 15, 'net': 9}),
  ('fault site cut rounding #1',
   [{'price': 30, 'hours': 12, 'stack_value': 1}, {'status': 'sold'}],
   {'deposit': 1, 'net': 28}),
  ('fault site cut rounding #2',
   [{'price': 70012, 'hours': 12, 'stack_value': 0}, {'status': 'sold'}],
   {'deposit': 1, 'net': 66511}),
  ('partial repair boundary #1',
   [{'price': 9, 'hours': 48, 'stack_value': 6}, {'status': 'sold'}],
   {'deposit': 4, 'net': 9}),
  ('partial repair boundary #2',
   [{'price': 1, 'hours': 48, 'stack_value': 1}, {'status': 'sold'}],
   {'deposit': 4, 'net': 1}),
  ('long cheap listing #1',
   [{'price': 10, 'hours': 48, 'stack_value': 3}, {'status': 'expired'}],
   {'deposit': 4, 'net': -4}),
  ('cancel with bid #1',
   [{'price': 500, 'hours': 24, 'stack_value': 40}, {'status': 'cancelled', 'bid': 390}],
   {'deposit': 12, 'net': -31}),
  ('control #1',
   [{'price': 50, 'hours': 24, 'stack_value': 6}, {'status': 'expired'}],
   {'deposit': 2, 'net': -2})]]
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
half-up cut boundary #1{'deposit': 15, 'net': 9}{'deposit': 15, 'net': 9}Passed
fault site cut rounding #1{'deposit': 1, 'net': 28}{'deposit': 1, 'net': 28}Passed
fault site cut rounding #2{'deposit': 1, 'net': 180}{'deposit': 1, 'net': 180}Passed
partial repair boundary #1{'deposit': 2, 'net': 0}{'deposit': 2, 'net': 1}Failed
partial repair boundary #2{'deposit': 1, 'net': 4883}{'deposit': 1, 'net': 4884}Failed
long cheap listing #1{'deposit': 4, 'net': -4}{'deposit': 4, 'net': -4}Passed
cancel with bid #1{'deposit': 12, 'net': -31}{'deposit': 12, 'net': -31}Passed
control #1{'deposit': 2, 'net': -2}{'deposit': 2, 'net': -2}Passed

SHA-256 / 579e4718cb5397efc631d094a725b31f89b852e3aec0fa1535647c8341125850

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

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 2026-09-29T14:50:45.448088+00:00.

Case digest / c8169499644ea88dc3a1ec7e59f912a779c59ded1cf184b0e8852d164054aa64