FAILURE MAP
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FA-60821 / Loyalty points ledgers / Open access

Household pool redemption draw: contribution cap · case 01

A member who limited their pool contribution is drawn beyond their limit.

Verified by executionVariant 1 · 7 checks per implementationDownload source bundle ↓JSON ↗

ROOT CAUSE

Usable points of other members ignore their contribution caps.

THE FAILURE

Usable points of other members ignore their contribution caps.

Unsuccessful approach: Applying caps to the requester as well blocks them from spending their own points.

Case contract

Input {balances:{member:pts}, caps:{member:max contribution}, requester, pts}. The requester contributes their full balance first (caps never apply to the requester). Other members contribute up to min(balance, cap), in descending order of that usable amount, ties by name. If total usable points are short return {"error":"insufficient"}. Return {draws:[[member,pts]]} with zero draws omitted.

Why this case matters

Member point balances, statements and the program liability depend on this ledger rule.

1 / The failure

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

N = 1
observations = []
def solve(x):
    bal = x['balances']
    caps = x['caps']
    rq = x['requester']
    usable = lambda m: bal[m]
    if x['pts'] > sum(usable(m) for m in bal):
        return {'error': 'insufficient'}
    others = sorted([m for m in bal if m != rq], key=lambda m: (-usable(m), m))
    need = x['pts']
    draws = []
    for m in [rq] + others:
        t = min(need, usable(m))
        if t > 0:
            draws.append([m, t])
            need -= t
    return {'draws': draws}
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
fixtures = [[['requester first', {'balances': {'ann': 300, 'bob': 900, 'cy': 400}, 'caps': {}, 'requester': 'ann', 'pts': 1001}, {'draws': [['ann', 300], ['bob', 701]]}], ['capped contributor', {'balances': {'ann': 100, 'bob': 5000, 'cy': 400}, 'caps': {'bob': 201}, 'requester': 'ann', 'pts': 600}, {'draws': [['ann', 100], ['cy', 400], ['bob', 100]]}], ['insufficient with caps', {'balances': {'ann': 100, 'bob': 5000}, 'caps': {'bob': 100}, 'requester': 'ann', 'pts': 301}, {'error': 'insufficient'}], ['requester cap ignored', {'balances': {'ann': 800, 'bob': 100}, 'caps': {'ann': 10}, 'requester': 'ann', 'pts': 701}, {'draws': [['ann', 701]]}], ['order by usable', {'balances': {'ann': 0, 'bob': 5000, 'cy': 600, 'dee': 500}, 'caps': {'bob': 50}, 'requester': 'ann', 'pts': 701}, {'draws': [['cy', 600], ['dee', 101]]}], ['ties by name', {'balances': {'zed': 0, 'amy': 300, 'max': 300}, 'caps': {}, 'requester': 'zed', 'pts': 401}, {'draws': [['amy', 300], ['max', 101]]}], ['requester covers', {'balances': {'ann': 5000, 'bob': 9000}, 'caps': {}, 'requester': 'ann', 'pts': 4001}, {'draws': [['ann', 4001]]}]], [['requester first', {'balances': {'ann': 300, 'bob': 900, 'cy': 400}, 'caps': {}, 'requester': 'ann', 'pts': 1002}, {'draws': [['ann', 300], ['bob', 702]]}], ['capped contributor', {'balances': {'ann': 100, 'bob': 5000, 'cy': 400}, 'caps': {'bob': 202}, 'requester': 'ann', 'pts': 600}, {'draws': [['ann', 100], ['cy', 400], ['bob', 100]]}], ['insufficient with caps', {'balances': {'ann': 100, 'bob': 5000}, 'caps': {'bob': 100}, 'requester': 'ann', 'pts': 302}, {'error': 'insufficient'}], ['requester cap ignored', {'balances': {'ann': 800, 'bob': 100}, 'caps': {'ann': 10}, 'requester': 'ann', 'pts': 702}, {'draws': [['ann', 702]]}], ['order by usable', {'balances': {'ann': 0, 'bob': 5000, 'cy': 600, 'dee': 500}, 'caps': {'bob': 50}, 'requester': 'ann', 'pts': 702}, {'draws': [['cy', 600], ['dee', 102]]}], ['ties by name', {'balances': {'zed': 0, 'amy': 300, 'max': 300}, 'caps': {}, 'requester': 'zed', 'pts': 402}, {'draws': [['amy', 300], ['max', 102]]}], ['requester covers', {'balances': {'ann': 5000, 'bob': 9000}, 'caps': {}, 'requester': 'ann', 'pts': 4002}, {'draws': [['ann', 4002]]}]], [['requester first', {'balances': {'ann': 300, 'bob': 900, 'cy': 400}, 'caps': {}, 'requester': 'ann', 'pts': 1003}, {'draws': [['ann', 300], ['bob', 703]]}], ['capped contributor', {'balances': {'ann': 100, 'bob': 5000, 'cy': 400}, 'caps': {'bob': 203}, 'requester': 'ann', 'pts': 600}, {'draws': [['ann', 100], ['cy', 400], ['bob', 100]]}], ['insufficient with caps', {'balances': {'ann': 100, 'bob': 5000}, 'caps': {'bob': 100}, 'requester': 'ann', 'pts': 303}, {'error': 'insufficient'}], ['requester cap ignored', {'balances': {'ann': 800, 'bob': 100}, 'caps': {'ann': 10}, 'requester': 'ann', 'pts': 703}, {'draws': [['ann', 703]]}], ['order by usable', {'balances': {'ann': 0, 'bob': 5000, 'cy': 600, 'dee': 500}, 'caps': {'bob': 50}, 'requester': 'ann', 'pts': 703}, {'draws': [['cy', 600], ['dee', 103]]}], ['ties by name', {'balances': {'zed': 0, 'amy': 300, 'max': 300}, 'caps': {}, 'requester': 'zed', 'pts': 403}, {'draws': [['amy', 300], ['max', 103]]}], ['requester covers', {'balances': {'ann': 5000, 'bob': 9000}, 'caps': {}, 'requester': 'ann', 'pts': 4003}, {'draws': [['ann', 4003]]}]], [['requester first', {'balances': {'ann': 300, 'bob': 900, 'cy': 400}, 'caps': {}, 'requester': 'ann', 'pts': 1004}, {'draws': [['ann', 300], ['bob', 704]]}], ['capped contributor', {'balances': {'ann': 100, 'bob': 5000, 'cy': 400}, 'caps': {'bob': 204}, 'requester': 'ann', 'pts': 600}, {'draws': [['ann', 100], ['cy', 400], ['bob', 100]]}], ['insufficient with caps', {'balances': {'ann': 100, 'bob': 5000}, 'caps': {'bob': 100}, 'requester': 'ann', 'pts': 304}, {'error': 'insufficient'}], ['requester cap ignored', {'balances': {'ann': 800, 'bob': 100}, 'caps': {'ann': 10}, 'requester': 'ann', 'pts': 704}, {'draws': [['ann', 704]]}], ['order by usable', {'balances': {'ann': 0, 'bob': 5000, 'cy': 600, 'dee': 500}, 'caps': {'bob': 50}, 'requester': 'ann', 'pts': 704}, {'draws': [['cy', 600], ['dee', 104]]}], ['ties by name', {'balances': {'zed': 0, 'amy': 300, 'max': 300}, 'caps': {}, 'requester': 'zed', 'pts': 404}, {'draws': [['amy', 300], ['max', 104]]}], ['requester covers', {'balances': {'ann': 5000, 'bob': 9000}, 'caps': {}, 'requester': 'ann', 'pts': 4004}, {'draws': [['ann', 4004]]}]], [['requester first', {'balances': {'ann': 300, 'bob': 900, 'cy': 400}, 'caps': {}, 'requester': 'ann', 'pts': 1005}, {'draws': [['ann', 300], ['bob', 705]]}], ['capped contributor', {'balances': {'ann': 100, 'bob': 5000, 'cy': 400}, 'caps': {'bob': 205}, 'requester': 'ann', 'pts': 600}, {'draws': [['ann', 100], ['cy', 400], ['bob', 100]]}], ['insufficient with caps', {'balances': {'ann': 100, 'bob': 5000}, 'caps': {'bob': 100}, 'requester': 'ann', 'pts': 305}, {'error': 'insufficient'}], ['requester cap ignored', {'balances': {'ann': 800, 'bob': 100}, 'caps': {'ann': 10}, 'requester': 'ann', 'pts': 705}, {'draws': [['ann', 705]]}], ['order by usable', {'balances': {'ann': 0, 'bob': 5000, 'cy': 600, 'dee': 500}, 'caps': {'bob': 50}, 'requester': 'ann', 'pts': 705}, {'draws': [['cy', 600], ['dee', 105]]}], ['ties by name', {'balances': {'zed': 0, 'amy': 300, 'max': 300}, 'caps': {}, 'requester': 'zed', 'pts': 405}, {'draws': [['amy', 300], ['max', 105]]}], ['requester covers', {'balances': {'ann': 5000, 'bob': 9000}, 'caps': {}, 'requester': 'ann', 'pts': 4005}, {'draws': [['ann', 4005]]}]]]
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 fixtureActualExpectedOutcome
requester first{'draws': [['ann', 300], ['bob', 701]]}{'draws': [['ann', 300], ['bob', 701]]}Passed
capped contributor{'draws': [['ann', 100], ['bob', 500]]}{'draws': [['ann', 100], ['cy', 400], ['bob', 100]]}Failed
insufficient with caps{'draws': [['ann', 100], ['bob', 201]]}{'error': 'insufficient'}Failed
requester cap ignored{'draws': [['ann', 701]]}{'draws': [['ann', 701]]}Passed
order by usable{'draws': [['bob', 701]]}{'draws': [['cy', 600], ['dee', 101]]}Failed
ties by name{'draws': [['amy', 300], ['max', 101]]}{'draws': [['amy', 300], ['max', 101]]}Passed
requester covers{'draws': [['ann', 4001]]}{'draws': [['ann', 4001]]}Passed

SHA-256 / 0700f11d97d1c83d375b2f67703fd6d11bf90c9453af9ed137a7e00628a9375d

2 / The unsuccessful fix

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

N = 1
observations = []
def solve(x):
    bal = x['balances']
    caps = x['caps']
    rq = x['requester']
    usable = lambda m: min(bal[m], caps.get(m, bal[m]))
    if x['pts'] > sum(usable(m) for m in bal):
        return {'error': 'insufficient'}
    others = sorted([m for m in bal if m != rq], key=lambda m: (-usable(m), m))
    need = x['pts']
    draws = []
    for m in [rq] + others:
        t = min(need, usable(m))
        if t > 0:
            draws.append([m, t])
            need -= t
    return {'draws': draws}
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
fixtures = [[['requester first', {'balances': {'ann': 300, 'bob': 900, 'cy': 400}, 'caps': {}, 'requester': 'ann', 'pts': 1001}, {'draws': [['ann', 300], ['bob', 701]]}], ['capped contributor', {'balances': {'ann': 100, 'bob': 5000, 'cy': 400}, 'caps': {'bob': 201}, 'requester': 'ann', 'pts': 600}, {'draws': [['ann', 100], ['cy', 400], ['bob', 100]]}], ['insufficient with caps', {'balances': {'ann': 100, 'bob': 5000}, 'caps': {'bob': 100}, 'requester': 'ann', 'pts': 301}, {'error': 'insufficient'}], ['requester cap ignored', {'balances': {'ann': 800, 'bob': 100}, 'caps': {'ann': 10}, 'requester': 'ann', 'pts': 701}, {'draws': [['ann', 701]]}], ['order by usable', {'balances': {'ann': 0, 'bob': 5000, 'cy': 600, 'dee': 500}, 'caps': {'bob': 50}, 'requester': 'ann', 'pts': 701}, {'draws': [['cy', 600], ['dee', 101]]}], ['ties by name', {'balances': {'zed': 0, 'amy': 300, 'max': 300}, 'caps': {}, 'requester': 'zed', 'pts': 401}, {'draws': [['amy', 300], ['max', 101]]}], ['requester covers', {'balances': {'ann': 5000, 'bob': 9000}, 'caps': {}, 'requester': 'ann', 'pts': 4001}, {'draws': [['ann', 4001]]}]], [['requester first', {'balances': {'ann': 300, 'bob': 900, 'cy': 400}, 'caps': {}, 'requester': 'ann', 'pts': 1002}, {'draws': [['ann', 300], ['bob', 702]]}], ['capped contributor', {'balances': {'ann': 100, 'bob': 5000, 'cy': 400}, 'caps': {'bob': 202}, 'requester': 'ann', 'pts': 600}, {'draws': [['ann', 100], ['cy', 400], ['bob', 100]]}], ['insufficient with caps', {'balances': {'ann': 100, 'bob': 5000}, 'caps': {'bob': 100}, 'requester': 'ann', 'pts': 302}, {'error': 'insufficient'}], ['requester cap ignored', {'balances': {'ann': 800, 'bob': 100}, 'caps': {'ann': 10}, 'requester': 'ann', 'pts': 702}, {'draws': [['ann', 702]]}], ['order by usable', {'balances': {'ann': 0, 'bob': 5000, 'cy': 600, 'dee': 500}, 'caps': {'bob': 50}, 'requester': 'ann', 'pts': 702}, {'draws': [['cy', 600], ['dee', 102]]}], ['ties by name', {'balances': {'zed': 0, 'amy': 300, 'max': 300}, 'caps': {}, 'requester': 'zed', 'pts': 402}, {'draws': [['amy', 300], ['max', 102]]}], ['requester covers', {'balances': {'ann': 5000, 'bob': 9000}, 'caps': {}, 'requester': 'ann', 'pts': 4002}, {'draws': [['ann', 4002]]}]], [['requester first', {'balances': {'ann': 300, 'bob': 900, 'cy': 400}, 'caps': {}, 'requester': 'ann', 'pts': 1003}, {'draws': [['ann', 300], ['bob', 703]]}], ['capped contributor', {'balances': {'ann': 100, 'bob': 5000, 'cy': 400}, 'caps': {'bob': 203}, 'requester': 'ann', 'pts': 600}, {'draws': [['ann', 100], ['cy', 400], ['bob', 100]]}], ['insufficient with caps', {'balances': {'ann': 100, 'bob': 5000}, 'caps': {'bob': 100}, 'requester': 'ann', 'pts': 303}, {'error': 'insufficient'}], ['requester cap ignored', {'balances': {'ann': 800, 'bob': 100}, 'caps': {'ann': 10}, 'requester': 'ann', 'pts': 703}, {'draws': [['ann', 703]]}], ['order by usable', {'balances': {'ann': 0, 'bob': 5000, 'cy': 600, 'dee': 500}, 'caps': {'bob': 50}, 'requester': 'ann', 'pts': 703}, {'draws': [['cy', 600], ['dee', 103]]}], ['ties by name', {'balances': {'zed': 0, 'amy': 300, 'max': 300}, 'caps': {}, 'requester': 'zed', 'pts': 403}, {'draws': [['amy', 300], ['max', 103]]}], ['requester covers', {'balances': {'ann': 5000, 'bob': 9000}, 'caps': {}, 'requester': 'ann', 'pts': 4003}, {'draws': [['ann', 4003]]}]], [['requester first', {'balances': {'ann': 300, 'bob': 900, 'cy': 400}, 'caps': {}, 'requester': 'ann', 'pts': 1004}, {'draws': [['ann', 300], ['bob', 704]]}], ['capped contributor', {'balances': {'ann': 100, 'bob': 5000, 'cy': 400}, 'caps': {'bob': 204}, 'requester': 'ann', 'pts': 600}, {'draws': [['ann', 100], ['cy', 400], ['bob', 100]]}], ['insufficient with caps', {'balances': {'ann': 100, 'bob': 5000}, 'caps': {'bob': 100}, 'requester': 'ann', 'pts': 304}, {'error': 'insufficient'}], ['requester cap ignored', {'balances': {'ann': 800, 'bob': 100}, 'caps': {'ann': 10}, 'requester': 'ann', 'pts': 704}, {'draws': [['ann', 704]]}], ['order by usable', {'balances': {'ann': 0, 'bob': 5000, 'cy': 600, 'dee': 500}, 'caps': {'bob': 50}, 'requester': 'ann', 'pts': 704}, {'draws': [['cy', 600], ['dee', 104]]}], ['ties by name', {'balances': {'zed': 0, 'amy': 300, 'max': 300}, 'caps': {}, 'requester': 'zed', 'pts': 404}, {'draws': [['amy', 300], ['max', 104]]}], ['requester covers', {'balances': {'ann': 5000, 'bob': 9000}, 'caps': {}, 'requester': 'ann', 'pts': 4004}, {'draws': [['ann', 4004]]}]], [['requester first', {'balances': {'ann': 300, 'bob': 900, 'cy': 400}, 'caps': {}, 'requester': 'ann', 'pts': 1005}, {'draws': [['ann', 300], ['bob', 705]]}], ['capped contributor', {'balances': {'ann': 100, 'bob': 5000, 'cy': 400}, 'caps': {'bob': 205}, 'requester': 'ann', 'pts': 600}, {'draws': [['ann', 100], ['cy', 400], ['bob', 100]]}], ['insufficient with caps', {'balances': {'ann': 100, 'bob': 5000}, 'caps': {'bob': 100}, 'requester': 'ann', 'pts': 305}, {'error': 'insufficient'}], ['requester cap ignored', {'balances': {'ann': 800, 'bob': 100}, 'caps': {'ann': 10}, 'requester': 'ann', 'pts': 705}, {'draws': [['ann', 705]]}], ['order by usable', {'balances': {'ann': 0, 'bob': 5000, 'cy': 600, 'dee': 500}, 'caps': {'bob': 50}, 'requester': 'ann', 'pts': 705}, {'draws': [['cy', 600], ['dee', 105]]}], ['ties by name', {'balances': {'zed': 0, 'amy': 300, 'max': 300}, 'caps': {}, 'requester': 'zed', 'pts': 405}, {'draws': [['amy', 300], ['max', 105]]}], ['requester covers', {'balances': {'ann': 5000, 'bob': 9000}, 'caps': {}, 'requester': 'ann', 'pts': 4005}, {'draws': [['ann', 4005]]}]]]
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 fixtureActualExpectedOutcome
requester first{'draws': [['ann', 300], ['bob', 701]]}{'draws': [['ann', 300], ['bob', 701]]}Passed
capped contributor{'draws': [['ann', 100], ['cy', 400], ['bob', 100]]}{'draws': [['ann', 100], ['cy', 400], ['bob', 100]]}Passed
insufficient with caps{'error': 'insufficient'}{'error': 'insufficient'}Passed
requester cap ignored{'error': 'insufficient'}{'draws': [['ann', 701]]}Failed
order by usable{'draws': [['cy', 600], ['dee', 101]]}{'draws': [['cy', 600], ['dee', 101]]}Passed
ties by name{'draws': [['amy', 300], ['max', 101]]}{'draws': [['amy', 300], ['max', 101]]}Passed
requester covers{'draws': [['ann', 4001]]}{'draws': [['ann', 4001]]}Passed

SHA-256 / a5d266e13d9488b5ea122c058280ec6c5680f406a60de9bbc44eea6909f41216

HELD IN THE MEMBER ARCHIVE

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

This mechanism has 7 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 loyalty-program model with explicit toy rules; not any real program terms. 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 2026-09-29T14:46:49.290539+00:00.

Case digest / f1a19aea71c53963aff713aa165d8ffea490585aeb4c0f30a3176408b0daba47