FA-59896 / Inventory cost layering / Open access

Periodic LIFO year-end layering: increment exhaustion stop · case 01

The increment layer absorbs units from every purchase even after the increment is satisfied.

Verified by executionVariant 1 · 9 checks per implementationDownload source bundle ↓JSON ↗

ROOT CAUSE

The purchase walk stops only when the purchase list ends, and the per-purchase take ignores the remaining increment.

THE FAILURE

The purchase walk stops only when the purchase list ends, and the per-purchase take ignores the remaining increment.

Unsuccessful approach: Capping each take at the total increment instead of the remaining increment still overfills when several purchases are used.

Case contract

Input {begin:[[qty,unit]] oldest first, purchases:[[qty,unit]] chronological, ending_qty}. Ending inventory keeps the oldest units: if ending_qty covers the base, all base layers stay and one increment layer is priced at the EARLIEST purchases of the year; otherwise the newest base layers are liquidated. ending_qty outside [0, available] returns {"error"}. Return {layers:[[qty,value]], ending_value, cogs}.

Why this case matters

Inventory valuation and cost-of-goods decisions depend on this rule.

1 / The failure

Exit 1

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

N = 1
observations = []
def solve(x):
    begin = [list(l) for l in x['begin']]
    purchases = x['purchases']
    end_q = x['ending_qty']
    base_q = sum(l[0] for l in begin)
    buy_q = sum(p[0] for p in purchases)
    avail = base_q + buy_q
    if end_q < 0 or end_q > avail:
        return {'error': 'invalid ending quantity'}
    layers = []
    if end_q >= base_q:
        layers = [[q, q * c] for q, c in begin]
        inc = end_q - base_q
        new_q = 0
        new_v = 0
        for q, c in purchases:
            if inc == 0:
                break
            take = q
            new_q += take
            new_v += take * c
            inc -= take
        if new_q > 0:
            layers.append([new_q, new_v])
    else:
        rem = end_q
        for bq, bc in begin:
            take = min(rem, bq)
            if take > 0:
                layers.append([take, take * bc])
            rem -= take
    begin_value = sum(q * c for q, c in begin)
    buy_value = sum(q * c for q, c in purchases)
    ending_value = sum(v for q, v in layers)
    return {'layers': layers, 'ending_value': ending_value, 'cogs': begin_value + buy_value - ending_value}
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
fixtures = [[['increment layer', {'begin': [[10, 5], [4, 6]], 'purchases': [[6, 7], [8, 10]], 'ending_qty': 18}, {'layers': [[10, 50], [4, 24], [4, 28]], 'ending_value': 102, 'cogs': 94}], ['liquidation', {'begin': [[10, 5], [4, 6]], 'purchases': [[6, 7]], 'ending_qty': 10}, {'layers': [[10, 50]], 'ending_value': 50, 'cogs': 66}], ['deep liquidation', {'begin': [[3, 2], [3, 4], [3, 6]], 'purchases': [[2, 8]], 'ending_qty': 1}, {'layers': [[1, 2]], 'ending_value': 2, 'cogs': 50}], ['over available', {'begin': [[2, 3]], 'purchases': [[3, 4]], 'ending_qty': 6}, {'error': 'invalid ending quantity'}], ['negative ending', {'begin': [[2, 3]], 'purchases': [[3, 4]], 'ending_qty': -1}, {'error': 'invalid ending quantity'}], ['count of minus one', {'begin': [[3, 3]], 'purchases': [[3, 4]], 'ending_qty': -1}, {'error': 'invalid ending quantity'}], ['all sold', {'begin': [[5, 3]], 'purchases': [[5, 4]], 'ending_qty': 0}, {'layers': [], 'ending_value': 0, 'cogs': 35}], ['exact base', {'begin': [[4, 10]], 'purchases': [[1, 11], [2, 12]], 'ending_qty': 4}, {'layers': [[4, 40]], 'ending_value': 40, 'cogs': 35}], ['spans purchases', {'begin': [[2, 1]], 'purchases': [[2, 3], [5, 5]], 'ending_qty': 7}, {'layers': [[2, 2], [5, 21]], 'ending_value': 23, 'cogs': 10}]], [['increment layer', {'begin': [[10, 5], [4, 6]], 'purchases': [[6, 7], [8, 11]], 'ending_qty': 19}, {'layers': [[10, 50], [4, 24], [5, 35]], 'ending_value': 109, 'cogs': 95}], ['liquidation', {'begin': [[10, 5], [4, 6]], 'purchases': [[6, 7]], 'ending_qty': 11}, {'layers': [[10, 50], [1, 6]], 'ending_value': 56, 'cogs': 60}], ['deep liquidation', {'begin': [[3, 2], [3, 4], [3, 6]], 'purchases': [[2, 8]], 'ending_qty': 2}, {'layers': [[2, 4]], 'ending_value': 4, 'cogs': 48}], ['over available', {'begin': [[2, 3]], 'purchases': [[3, 4]], 'ending_qty': 7}, {'error': 'invalid ending quantity'}], ['negative ending', {'begin': [[2, 3]], 'purchases': [[3, 4]], 'ending_qty': -2}, {'error': 'invalid ending quantity'}], ['count of minus one', {'begin': [[4, 3]], 'purchases': [[3, 4]], 'ending_qty': -1}, {'error': 'invalid ending quantity'}], ['all sold', {'begin': [[5, 3]], 'purchases': [[5, 4]], 'ending_qty': 0}, {'layers': [], 'ending_value': 0, 'cogs': 35}], ['exact base', {'begin': [[4, 10]], 'purchases': [[2, 11], [2, 12]], 'ending_qty': 4}, {'layers': [[4, 40]], 'ending_value': 40, 'cogs': 46}], ['spans purchases', {'begin': [[2, 1]], 'purchases': [[2, 3], [5, 6]], 'ending_qty': 7}, {'layers': [[2, 2], [5, 24]], 'ending_value': 26, 'cogs': 12}]], [['increment layer', {'begin': [[10, 5], [4, 6]], 'purchases': [[6, 7], [8, 12]], 'ending_qty': 17}, {'layers': [[10, 50], [4, 24], [3, 21]], 'ending_value': 95, 'cogs': 117}], ['liquidation', {'begin': [[10, 5], [4, 6]], 'purchases': [[6, 7]], 'ending_qty': 10}, {'layers': [[10, 50]], 'ending_value': 50, 'cogs': 66}], ['deep liquidation', {'begin': [[3, 2], [3, 4], [3, 6]], 'purchases': [[2, 8]], 'ending_qty': 3}, {'layers': [[3, 6]], 'ending_value': 6, 'cogs': 46}], ['over available', {'begin': [[2, 3]], 'purchases': [[3, 4]], 'ending_qty': 8}, {'error': 'invalid ending quantity'}], ['negative ending', {'begin': [[2, 3]], 'purchases': [[3, 4]], 'ending_qty': -3}, {'error': 'invalid ending quantity'}], ['count of minus one', {'begin': [[5, 3]], 'purchases': [[3, 4]], 'ending_qty': -1}, {'error': 'invalid ending quantity'}], ['all sold', {'begin': [[5, 3]], 'purchases': [[5, 4]], 'ending_qty': 0}, {'layers': [], 'ending_value': 0, 'cogs': 35}], ['exact base', {'begin': [[4, 10]], 'purchases': [[3, 11], [2, 12]], 'ending_qty': 4}, {'layers': [[4, 40]], 'ending_value': 40, 'cogs': 57}], ['spans purchases', {'begin': [[2, 1]], 'purchases': [[2, 3], [5, 7]], 'ending_qty': 7}, {'layers': [[2, 2], [5, 27]], 'ending_value': 29, 'cogs': 14}]], [['increment layer', {'begin': [[10, 5], [4, 6]], 'purchases': [[6, 7], [8, 13]], 'ending_qty': 18}, {'layers': [[10, 50], [4, 24], [4, 28]], 'ending_value': 102, 'cogs': 118}], ['liquidation', {'begin': [[10, 5], [4, 6]], 'purchases': [[6, 7]], 'ending_qty': 11}, {'layers': [[10, 50], [1, 6]], 'ending_value': 56, 'cogs': 60}], ['deep liquidation', {'begin': [[3, 2], [3, 4], [3, 6]], 'purchases': [[2, 8]], 'ending_qty': 4}, {'layers': [[3, 6], [1, 4]], 'ending_value': 10, 'cogs': 42}], ['over available', {'begin': [[2, 3]], 'purchases': [[3, 4]], 'ending_qty': 9}, {'error': 'invalid ending quantity'}], ['negative ending', {'begin': [[2, 3]], 'purchases': [[3, 4]], 'ending_qty': -4}, {'error': 'invalid ending quantity'}], ['count of minus one', {'begin': [[6, 3]], 'purchases': [[3, 4]], 'ending_qty': -1}, {'error': 'invalid ending quantity'}], ['all sold', {'begin': [[5, 3]], 'purchases': [[5, 4]], 'ending_qty': 0}, {'layers': [], 'ending_value': 0, 'cogs': 35}], ['exact base', {'begin': [[4, 10]], 'purchases': [[4, 11], [2, 12]], 'ending_qty': 4}, {'layers': [[4, 40]], 'ending_value': 40, 'cogs': 68}], ['spans purchases', {'begin': [[2, 1]], 'purchases': [[2, 3], [5, 8]], 'ending_qty': 7}, {'layers': [[2, 2], [5, 30]], 'ending_value': 32, 'cogs': 16}]], [['increment layer', {'begin': [[10, 5], [4, 6]], 'purchases': [[6, 7], [8, 14]], 'ending_qty': 19}, {'layers': [[10, 50], [4, 24], [5, 35]], 'ending_value': 109, 'cogs': 119}], ['liquidation', {'begin': [[10, 5], [4, 6]], 'purchases': [[6, 7]], 'ending_qty': 10}, {'layers': [[10, 50]], 'ending_value': 50, 'cogs': 66}], ['deep liquidation', {'begin': [[3, 2], [3, 4], [3, 6]], 'purchases': [[2, 8]], 'ending_qty': 5}, {'layers': [[3, 6], [2, 8]], 'ending_value': 14, 'cogs': 38}], ['over available', {'begin': [[2, 3]], 'purchases': [[3, 4]], 'ending_qty': 10}, {'error': 'invalid ending quantity'}], ['negative ending', {'begin': [[2, 3]], 'purchases': [[3, 4]], 'ending_qty': -5}, {'error': 'invalid ending quantity'}], ['count of minus one', {'begin': [[7, 3]], 'purchases': [[3, 4]], 'ending_qty': -1}, {'error': 'invalid ending quantity'}], ['all sold', {'begin': [[5, 3]], 'purchases': [[5, 4]], 'ending_qty': 0}, {'layers': [], 'ending_value': 0, 'cogs': 35}], ['exact base', {'begin': [[4, 10]], 'purchases': [[5, 11], [2, 12]], 'ending_qty': 4}, {'layers': [[4, 40]], 'ending_value': 40, 'cogs': 79}], ['spans purchases', {'begin': [[2, 1]], 'purchases': [[2, 3], [5, 9]], 'ending_qty': 7}, {'layers': [[2, 2], [5, 33]], 'ending_value': 35, 'cogs': 18}]]]
for label, args, expected in fixtures[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 fixture	Actual	Expected	Outcome
increment layer	`{'cogs': 0, 'ending_value': 196, 'layers': [[10, 50], [4, 24], [14, 122]]}`	`{'cogs': 94, 'ending_value': 102, 'layers': [[10, 50], [4, 24], [4, 28]]}`	Failed
liquidation	`{'cogs': 66, 'ending_value': 50, 'layers': [[10, 50]]}`	`{'cogs': 66, 'ending_value': 50, 'layers': [[10, 50]]}`	Passed
deep liquidation	`{'cogs': 50, 'ending_value': 2, 'layers': [[1, 2]]}`	`{'cogs': 50, 'ending_value': 2, 'layers': [[1, 2]]}`	Passed
over available	`{'error': 'invalid ending quantity'}`	`{'error': 'invalid ending quantity'}`	Passed
negative ending	`{'error': 'invalid ending quantity'}`	`{'error': 'invalid ending quantity'}`	Passed
count of minus one	`{'error': 'invalid ending quantity'}`	`{'error': 'invalid ending quantity'}`	Passed
all sold	`{'cogs': 35, 'ending_value': 0, 'layers': []}`	`{'cogs': 35, 'ending_value': 0, 'layers': []}`	Passed
exact base	`{'cogs': 35, 'ending_value': 40, 'layers': [[4, 40]]}`	`{'cogs': 35, 'ending_value': 40, 'layers': [[4, 40]]}`	Passed
spans purchases	`{'cogs': 0, 'ending_value': 33, 'layers': [[2, 2], [7, 31]]}`	`{'cogs': 10, 'ending_value': 23, 'layers': [[2, 2], [5, 21]]}`	Failed

SHA-256 / ec73a5793e7feb836deacc59434bf22b69615678a81d0d8c39dbd2d53c7c501e

2 / The unsuccessful fix

Exit 1

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

N = 1
observations = []
def solve(x):
    begin = [list(l) for l in x['begin']]
    purchases = x['purchases']
    end_q = x['ending_qty']
    base_q = sum(l[0] for l in begin)
    buy_q = sum(p[0] for p in purchases)
    avail = base_q + buy_q
    if end_q < 0 or end_q > avail:
        return {'error': 'invalid ending quantity'}
    layers = []
    if end_q >= base_q:
        layers = [[q, q * c] for q, c in begin]
        inc = end_q - base_q
        new_q = 0
        new_v = 0
        for q, c in purchases:
            if inc == 0:
                break
            take = min(end_q - base_q, q)
            new_q += take
            new_v += take * c
            inc -= take
        if new_q > 0:
            layers.append([new_q, new_v])
    else:
        rem = end_q
        for bq, bc in begin:
            take = min(rem, bq)
            if take > 0:
                layers.append([take, take * bc])
            rem -= take
    begin_value = sum(q * c for q, c in begin)
    buy_value = sum(q * c for q, c in purchases)
    ending_value = sum(v for q, v in layers)
    return {'layers': layers, 'ending_value': ending_value, 'cogs': begin_value + buy_value - ending_value}
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
fixtures = [[['increment layer', {'begin': [[10, 5], [4, 6]], 'purchases': [[6, 7], [8, 10]], 'ending_qty': 18}, {'layers': [[10, 50], [4, 24], [4, 28]], 'ending_value': 102, 'cogs': 94}], ['liquidation', {'begin': [[10, 5], [4, 6]], 'purchases': [[6, 7]], 'ending_qty': 10}, {'layers': [[10, 50]], 'ending_value': 50, 'cogs': 66}], ['deep liquidation', {'begin': [[3, 2], [3, 4], [3, 6]], 'purchases': [[2, 8]], 'ending_qty': 1}, {'layers': [[1, 2]], 'ending_value': 2, 'cogs': 50}], ['over available', {'begin': [[2, 3]], 'purchases': [[3, 4]], 'ending_qty': 6}, {'error': 'invalid ending quantity'}], ['negative ending', {'begin': [[2, 3]], 'purchases': [[3, 4]], 'ending_qty': -1}, {'error': 'invalid ending quantity'}], ['count of minus one', {'begin': [[3, 3]], 'purchases': [[3, 4]], 'ending_qty': -1}, {'error': 'invalid ending quantity'}], ['all sold', {'begin': [[5, 3]], 'purchases': [[5, 4]], 'ending_qty': 0}, {'layers': [], 'ending_value': 0, 'cogs': 35}], ['exact base', {'begin': [[4, 10]], 'purchases': [[1, 11], [2, 12]], 'ending_qty': 4}, {'layers': [[4, 40]], 'ending_value': 40, 'cogs': 35}], ['spans purchases', {'begin': [[2, 1]], 'purchases': [[2, 3], [5, 5]], 'ending_qty': 7}, {'layers': [[2, 2], [5, 21]], 'ending_value': 23, 'cogs': 10}]], [['increment layer', {'begin': [[10, 5], [4, 6]], 'purchases': [[6, 7], [8, 11]], 'ending_qty': 19}, {'layers': [[10, 50], [4, 24], [5, 35]], 'ending_value': 109, 'cogs': 95}], ['liquidation', {'begin': [[10, 5], [4, 6]], 'purchases': [[6, 7]], 'ending_qty': 11}, {'layers': [[10, 50], [1, 6]], 'ending_value': 56, 'cogs': 60}], ['deep liquidation', {'begin': [[3, 2], [3, 4], [3, 6]], 'purchases': [[2, 8]], 'ending_qty': 2}, {'layers': [[2, 4]], 'ending_value': 4, 'cogs': 48}], ['over available', {'begin': [[2, 3]], 'purchases': [[3, 4]], 'ending_qty': 7}, {'error': 'invalid ending quantity'}], ['negative ending', {'begin': [[2, 3]], 'purchases': [[3, 4]], 'ending_qty': -2}, {'error': 'invalid ending quantity'}], ['count of minus one', {'begin': [[4, 3]], 'purchases': [[3, 4]], 'ending_qty': -1}, {'error': 'invalid ending quantity'}], ['all sold', {'begin': [[5, 3]], 'purchases': [[5, 4]], 'ending_qty': 0}, {'layers': [], 'ending_value': 0, 'cogs': 35}], ['exact base', {'begin': [[4, 10]], 'purchases': [[2, 11], [2, 12]], 'ending_qty': 4}, {'layers': [[4, 40]], 'ending_value': 40, 'cogs': 46}], ['spans purchases', {'begin': [[2, 1]], 'purchases': [[2, 3], [5, 6]], 'ending_qty': 7}, {'layers': [[2, 2], [5, 24]], 'ending_value': 26, 'cogs': 12}]], [['increment layer', {'begin': [[10, 5], [4, 6]], 'purchases': [[6, 7], [8, 12]], 'ending_qty': 17}, {'layers': [[10, 50], [4, 24], [3, 21]], 'ending_value': 95, 'cogs': 117}], ['liquidation', {'begin': [[10, 5], [4, 6]], 'purchases': [[6, 7]], 'ending_qty': 10}, {'layers': [[10, 50]], 'ending_value': 50, 'cogs': 66}], ['deep liquidation', {'begin': [[3, 2], [3, 4], [3, 6]], 'purchases': [[2, 8]], 'ending_qty': 3}, {'layers': [[3, 6]], 'ending_value': 6, 'cogs': 46}], ['over available', {'begin': [[2, 3]], 'purchases': [[3, 4]], 'ending_qty': 8}, {'error': 'invalid ending quantity'}], ['negative ending', {'begin': [[2, 3]], 'purchases': [[3, 4]], 'ending_qty': -3}, {'error': 'invalid ending quantity'}], ['count of minus one', {'begin': [[5, 3]], 'purchases': [[3, 4]], 'ending_qty': -1}, {'error': 'invalid ending quantity'}], ['all sold', {'begin': [[5, 3]], 'purchases': [[5, 4]], 'ending_qty': 0}, {'layers': [], 'ending_value': 0, 'cogs': 35}], ['exact base', {'begin': [[4, 10]], 'purchases': [[3, 11], [2, 12]], 'ending_qty': 4}, {'layers': [[4, 40]], 'ending_value': 40, 'cogs': 57}], ['spans purchases', {'begin': [[2, 1]], 'purchases': [[2, 3], [5, 7]], 'ending_qty': 7}, {'layers': [[2, 2], [5, 27]], 'ending_value': 29, 'cogs': 14}]], [['increment layer', {'begin': [[10, 5], [4, 6]], 'purchases': [[6, 7], [8, 13]], 'ending_qty': 18}, {'layers': [[10, 50], [4, 24], [4, 28]], 'ending_value': 102, 'cogs': 118}], ['liquidation', {'begin': [[10, 5], [4, 6]], 'purchases': [[6, 7]], 'ending_qty': 11}, {'layers': [[10, 50], [1, 6]], 'ending_value': 56, 'cogs': 60}], ['deep liquidation', {'begin': [[3, 2], [3, 4], [3, 6]], 'purchases': [[2, 8]], 'ending_qty': 4}, {'layers': [[3, 6], [1, 4]], 'ending_value': 10, 'cogs': 42}], ['over available', {'begin': [[2, 3]], 'purchases': [[3, 4]], 'ending_qty': 9}, {'error': 'invalid ending quantity'}], ['negative ending', {'begin': [[2, 3]], 'purchases': [[3, 4]], 'ending_qty': -4}, {'error': 'invalid ending quantity'}], ['count of minus one', {'begin': [[6, 3]], 'purchases': [[3, 4]], 'ending_qty': -1}, {'error': 'invalid ending quantity'}], ['all sold', {'begin': [[5, 3]], 'purchases': [[5, 4]], 'ending_qty': 0}, {'layers': [], 'ending_value': 0, 'cogs': 35}], ['exact base', {'begin': [[4, 10]], 'purchases': [[4, 11], [2, 12]], 'ending_qty': 4}, {'layers': [[4, 40]], 'ending_value': 40, 'cogs': 68}], ['spans purchases', {'begin': [[2, 1]], 'purchases': [[2, 3], [5, 8]], 'ending_qty': 7}, {'layers': [[2, 2], [5, 30]], 'ending_value': 32, 'cogs': 16}]], [['increment layer', {'begin': [[10, 5], [4, 6]], 'purchases': [[6, 7], [8, 14]], 'ending_qty': 19}, {'layers': [[10, 50], [4, 24], [5, 35]], 'ending_value': 109, 'cogs': 119}], ['liquidation', {'begin': [[10, 5], [4, 6]], 'purchases': [[6, 7]], 'ending_qty': 10}, {'layers': [[10, 50]], 'ending_value': 50, 'cogs': 66}], ['deep liquidation', {'begin': [[3, 2], [3, 4], [3, 6]], 'purchases': [[2, 8]], 'ending_qty': 5}, {'layers': [[3, 6], [2, 8]], 'ending_value': 14, 'cogs': 38}], ['over available', {'begin': [[2, 3]], 'purchases': [[3, 4]], 'ending_qty': 10}, {'error': 'invalid ending quantity'}], ['negative ending', {'begin': [[2, 3]], 'purchases': [[3, 4]], 'ending_qty': -5}, {'error': 'invalid ending quantity'}], ['count of minus one', {'begin': [[7, 3]], 'purchases': [[3, 4]], 'ending_qty': -1}, {'error': 'invalid ending quantity'}], ['all sold', {'begin': [[5, 3]], 'purchases': [[5, 4]], 'ending_qty': 0}, {'layers': [], 'ending_value': 0, 'cogs': 35}], ['exact base', {'begin': [[4, 10]], 'purchases': [[5, 11], [2, 12]], 'ending_qty': 4}, {'layers': [[4, 40]], 'ending_value': 40, 'cogs': 79}], ['spans purchases', {'begin': [[2, 1]], 'purchases': [[2, 3], [5, 9]], 'ending_qty': 7}, {'layers': [[2, 2], [5, 33]], 'ending_value': 35, 'cogs': 18}]]]
for label, args, expected in fixtures[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 fixture	Actual	Expected	Outcome
increment layer	`{'cogs': 94, 'ending_value': 102, 'layers': [[10, 50], [4, 24], [4, 28]]}`	`{'cogs': 94, 'ending_value': 102, 'layers': [[10, 50], [4, 24], [4, 28]]}`	Passed
liquidation	`{'cogs': 66, 'ending_value': 50, 'layers': [[10, 50]]}`	`{'cogs': 66, 'ending_value': 50, 'layers': [[10, 50]]}`	Passed
deep liquidation	`{'cogs': 50, 'ending_value': 2, 'layers': [[1, 2]]}`	`{'cogs': 50, 'ending_value': 2, 'layers': [[1, 2]]}`	Passed
over available	`{'error': 'invalid ending quantity'}`	`{'error': 'invalid ending quantity'}`	Passed
negative ending	`{'error': 'invalid ending quantity'}`	`{'error': 'invalid ending quantity'}`	Passed
count of minus one	`{'error': 'invalid ending quantity'}`	`{'error': 'invalid ending quantity'}`	Passed
all sold	`{'cogs': 35, 'ending_value': 0, 'layers': []}`	`{'cogs': 35, 'ending_value': 0, 'layers': []}`	Passed
exact base	`{'cogs': 35, 'ending_value': 40, 'layers': [[4, 40]]}`	`{'cogs': 35, 'ending_value': 40, 'layers': [[4, 40]]}`	Passed
spans purchases	`{'cogs': 0, 'ending_value': 33, 'layers': [[2, 2], [7, 31]]}`	`{'cogs': 10, 'ending_value': 23, 'layers': [[2, 2], [5, 21]]}`	Failed

SHA-256 / 1d41877bd0967c93a26cda96842a3f3491e36d2475da6704ce4c29acfec35f31

HELD IN THE MEMBER ARCHIVE

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

This mechanism has 9 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

Stipulated bounded teaching model with explicit toy rules; not an accounting-standard 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 2026-09-29T14:46:40.590626+00:00.

Case digest / ec9fc35881fc3c780b1a3a74f5afd6609f1beef62f1b804a27812b869720daeb