{"abstract":"Later-year payments grow linearly instead of compounding.","category":"Loan amortization schedules","checks":7,"contract":"x = {'principal', 'rate_bp', 'months', 'initial_payment', 'step_bp', 'steps'}. Month m (1-based) is in year t = (m-1)//12. For t < steps+1 the year payment starts at initial_payment and each new year multiplies the previous year payment by (10000+step_bp)/10000, rounded half-up. At the start of year steps+1 (if the loan runs that long) the payment is re-leveled on the balance over the remaining months (exact annuity, half-up) and stays fixed. Interest round_half_up(balance*bp/120000); balance += interest - payment (it may grow). Return {'year_payments', 'peak_balance', 'end_balance'}.","contract_signature":"x","evaluation_group":"w2-loan-amortization-schedules-graduated-payment-steps","failed_approach":"Compounding the unrounded initial payment differs from compounding the rounded yearly payments.","family":"w2-loan-amortization-schedules-graduated-payment-steps-step-compounding-base","id":"FA-58816","implementations":{"attempt":{"sha256":"9d2f0344fdac15d28756dc9708410c847d3a74a6aa90d455932efea89a624c98","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\nimport math\nfrom fractions import Fraction\nN = 1\nobservations = []\ndef solve(x):\n    def rnd(n, d):\n        q, r = divmod(n, d)\n        return q + (1 if 2 * r >= d else 0)\n    def level(P, n):\n        if n <= 0 or P <= 0:\n            return 0\n        if bp == 0:\n            exact = Fraction(P, n)\n        else:\n            r = Fraction(bp, 120000)\n            exact = P * r / (1 - (1 + r) ** -n)\n        return math.floor(exact + Fraction(1, 2))\n    bp = x['rate_bp']\n    n = x['months']\n    bal = x['principal']\n    pay = x['initial_payment']\n    years = [pay]\n    peak = bal\n    for m in range(1, n + 1):\n        t = (m - 1) // 12\n        if m > 1 and (m - 1) % 12 == 0:\n            if t <= x['steps']:\n                pay = rnd(x['initial_payment'] * (10000 + x['step_bp']) ** t, 10000 ** t)\n            elif t == x['steps'] + 1:\n                pay = level(bal, n - m + 1)\n            years.append(pay)\n        interest = rnd(bal * bp, 120000)\n        bal += interest - pay\n        peak = max(peak, bal)\n    return {'year_payments': years, 'peak_balance': peak, 'end_balance': bal}\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\nfixtures = [[['regression: step compounding base', {'principal': 1000000, 'rate_bp': 600, 'months': 36, 'initial_payment': 20000, 'step_bp': 750, 'steps': 2}, {'year_payments': [20000, 21500, 23113], 'peak_balance': 1000000, 'end_balance': 351915}], ['regression: step compounding base, partial-repair probe', {'principal': 100000, 'rate_bp': 900, 'months': 36, 'initial_payment': 500, 'step_bp': 250, 'steps': 2}, {'year_payments': [500, 513, 526], 'peak_balance': 109781, 'end_balance': 109781}], ['control 1', {'principal': 250000, 'rate_bp': 600, 'months': 24, 'initial_payment': 3000, 'step_bp': 250, 'steps': 3}, {'year_payments': [3000, 3075], 'peak_balance': 250000, 'end_balance': 204568}], ['control 2', {'principal': 250000, 'rate_bp': 900, 'months': 36, 'initial_payment': 8000, 'step_bp': 250, 'steps': 0}, {'year_payments': [8000, 7921, 7921], 'peak_balance': 250000, 'end_balance': 9}], ['control 3', {'principal': 100000, 'rate_bp': 600, 'months': 24, 'initial_payment': 500, 'step_bp': 250, 'steps': 0}, {'year_payments': [500, 8607], 'peak_balance': 100000, 'end_balance': -4}], ['control 4', {'principal': 250000, 'rate_bp': 900, 'months': 60, 'initial_payment': 8000, 'step_bp': 250, 'steps': 1}, {'year_payments': [8000, 8200, 2770, 2770, 2770], 'peak_balance': 250000, 'end_balance': -23}], ['control 5', {'principal': 250000, 'rate_bp': 1200, 'months': 60, 'initial_payment': 20000, 'step_bp': 250, 'steps': 1}, {'year_payments': [20000, 20500, 0, 0, 0], 'peak_balance': 250000, 'end_balance': -326758}]], [['regression: step compounding base', {'principal': 1000000, 'rate_bp': 600, 'months': 60, 'initial_payment': 500, 'step_bp': 250, 'steps': 2}, {'year_payments': [500, 513, 526, 52144, 52144], 'peak_balance': 1176523, 'end_balance': 4}], ['control 1', {'principal': 250000, 'rate_bp': 1200, 'months': 24, 'initial_payment': 3000, 'step_bp': 250, 'steps': 2}, {'year_payments': [3000, 3075], 'peak_balance': 250000, 'end_balance': 235565}], ['control 2', {'principal': 250000, 'rate_bp': 600, 'months': 24, 'initial_payment': 3000, 'step_bp': 1000, 'steps': 1}, {'year_payments': [3000, 3300], 'peak_balance': 250000, 'end_balance': 201795}], ['control 3', {'principal': 100000, 'rate_bp': 900, 'months': 24, 'initial_payment': 500, 'step_bp': 1000, 'steps': 3}, {'year_payments': [500, 550], 'peak_balance': 105921, 'end_balance': 105921}], ['control 4', {'principal': 250000, 'rate_bp': 900, 'months': 60, 'initial_payment': 500, 'step_bp': 250, 'steps': 1}, {'year_payments': [500, 513, 9090, 9090, 9090], 'peak_balance': 285848, 'end_balance': -7}], ['control 5', {'principal': 250000, 'rate_bp': 1200, 'months': 36, 'initial_payment': 8000, 'step_bp': 250, 'steps': 0}, {'year_payments': [8000, 8485, 8485], 'peak_balance': 250000, 'end_balance': -6}], ['control 6', {'principal': 100000, 'rate_bp': 1200, 'months': 36, 'initial_payment': 500, 'step_bp': 250, 'steps': 0}, {'year_payments': [500, 5006, 5006], 'peak_balance': 106341, 'end_balance': -5}]], [['regression: step compounding base', {'principal': 1000000, 'rate_bp': 1200, 'months': 60, 'initial_payment': 8000, 'step_bp': 250, 'steps': 2}, {'year_payments': [8000, 8200, 8405, 50753, 50753], 'peak_balance': 1078159, 'end_balance': -8}], ['regression: step compounding base, partial-repair probe', {'principal': 100000, 'rate_bp': 600, 'months': 60, 'initial_payment': 500, 'step_bp': 250, 'steps': 3}, {'year_payments': [500, 513, 526, 539, 8520], 'peak_balance': 100000, 'end_balance': 6}], ['control 1', {'principal': 1000000, 'rate_bp': 900, 'months': 36, 'initial_payment': 3000, 'step_bp': 750, 'steps': 1}, {'year_payments': [3000, 3225, 97511], 'peak_balance': 1115035, 'end_balance': 6}], ['control 2', {'principal': 250000, 'rate_bp': 900, 'months': 24, 'initial_payment': 3000, 'step_bp': 750, 'steps': 1}, {'year_payments': [3000, 3225], 'peak_balance': 250000, 'end_balance': 217726}], ['control 3', {'principal': 1000000, 'rate_bp': 900, 'months': 36, 'initial_payment': 20000, 'step_bp': 1000, 'steps': 1}, {'year_payments': [20000, 22000, 56636], 'peak_balance': 1000000, 'end_balance': 0}], ['control 4', {'principal': 100000, 'rate_bp': 900, 'months': 24, 'initial_payment': 3000, 'step_bp': 750, 'steps': 0}, {'year_payments': [3000, 6284], 'peak_balance': 100000, 'end_balance': -2}], ['control 5', {'principal': 250000, 'rate_bp': 1200, 'months': 60, 'initial_payment': 20000, 'step_bp': 250, 'steps': 0}, {'year_payments': [20000, 739, 739, 739, 739], 'peak_balance': 250000, 'end_balance': -10}]], [['regression: step compounding base', {'principal': 100000, 'rate_bp': 1200, 'months': 36, 'initial_payment': 3000, 'step_bp': 1000, 'steps': 2}, {'year_payments': [3000, 3300, 3630], 'peak_balance': 100000, 'end_balance': 1568}], ['regression: step compounding base, partial-repair probe', {'principal': 250000, 'rate_bp': 600, 'months': 36, 'initial_payment': 500, 'step_bp': 250, 'steps': 3}, {'year_payments': [500, 513, 526], 'peak_balance': 279010, 'end_balance': 279010}], ['control 1', {'principal': 100000, 'rate_bp': 900, 'months': 24, 'initial_payment': 20000, 'step_bp': 750, 'steps': 3}, {'year_payments': [20000, 21500], 'peak_balance': 100000, 'end_balance': -422889}], ['control 2', {'principal': 1000000, 'rate_bp': 900, 'months': 36, 'initial_payment': 8000, 'step_bp': 250, 'steps': 1}, {'year_payments': [8000, 8200, 86087], 'peak_balance': 1000000, 'end_balance': 5}], ['control 3', {'principal': 1000000, 'rate_bp': 900, 'months': 60, 'initial_payment': 500, 'step_bp': 250, 'steps': 0}, {'year_payments': [500, 27064, 27064, 27064, 27064], 'peak_balance': 1087553, 'end_balance': -13}], ['control 4', {'principal': 250000, 'rate_bp': 900, 'months': 36, 'initial_payment': 20000, 'step_bp': 750, 'steps': 1}, {'year_payments': [20000, 21500, 0], 'peak_balance': 250000, 'end_balance': -266261}], ['control 5', {'principal': 1000000, 'rate_bp': 600, 'months': 60, 'initial_payment': 8000, 'step_bp': 1000, 'steps': 0}, {'year_payments': [8000, 22616, 22616, 22616, 22616], 'peak_balance': 1000000, 'end_balance': 0}]], [['regression: step compounding base', {'principal': 100000, 'rate_bp': 600, 'months': 60, 'initial_payment': 500, 'step_bp': 1000, 'steps': 3}, {'year_payments': [500, 550, 605, 666, 8252], 'peak_balance': 100000, 'end_balance': 1}], ['regression: step compounding base, partial-repair probe', {'principal': 100000, 'rate_bp': 1200, 'months': 36, 'initial_payment': 500, 'step_bp': 250, 'steps': 2}, {'year_payments': [500, 513, 526], 'peak_balance': 121021, 'end_balance': 121021}], ['control 1', {'principal': 1000000, 'rate_bp': 600, 'months': 60, 'initial_payment': 20000, 'step_bp': 750, 'steps': 1}, {'year_payments': [20000, 21500, 18254, 18254, 18254], 'peak_balance': 1000000, 'end_balance': -11}], ['control 2', {'principal': 1000000, 'rate_bp': 900, 'months': 60, 'initial_payment': 3000, 'step_bp': 1000, 'steps': 1}, {'year_payments': [3000, 3300, 35428, 35428, 35428], 'peak_balance': 1114096, 'end_balance': -5}], ['control 3', {'principal': 250000, 'rate_bp': 1200, 'months': 24, 'initial_payment': 3000, 'step_bp': 250, 'steps': 1}, {'year_payments': [3000, 3075], 'peak_balance': 250000, 'end_balance': 235565}], ['control 4', {'principal': 1000000, 'rate_bp': 600, 'months': 36, 'initial_payment': 3000, 'step_bp': 1000, 'steps': 1}, {'year_payments': [3000, 3300, 90126], 'peak_balance': 1047163, 'end_balance': -6}], ['control 5', {'principal': 100000, 'rate_bp': 1200, 'months': 24, 'initial_payment': 500, 'step_bp': 250, 'steps': 0}, {'year_payments': [500, 9448], 'peak_balance': 106341, 'end_balance': 5}]]]\nfor label, args, expected in fixtures[N-1]:\n    try:\n        actual = solve(args)\n    except Exception as exc:\n        actual = 'raised ' + type(exc).__name__\n    check(label, actual, expected)\nprint(json.dumps({\"observations\": observations, \"passed\": all(x[\"passed\"] for x in observations)}, ensure_ascii=False))\nraise SystemExit(0 if all(x[\"passed\"] for x in observations) else 1)\n"},"broken":{"sha256":"a3e6acc373903cfcaf2b9cee26b224e755a3e112f94c97c1cc8e5db129f2c29c","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\nimport math\nfrom fractions import Fraction\nN = 1\nobservations = []\ndef solve(x):\n    def rnd(n, d):\n        q, r = divmod(n, d)\n        return q + (1 if 2 * r >= d else 0)\n    def level(P, n):\n        if n <= 0 or P <= 0:\n            return 0\n        if bp == 0:\n            exact = Fraction(P, n)\n        else:\n            r = Fraction(bp, 120000)\n            exact = P * r / (1 - (1 + r) ** -n)\n        return math.floor(exact + Fraction(1, 2))\n    bp = x['rate_bp']\n    n = x['months']\n    bal = x['principal']\n    pay = x['initial_payment']\n    years = [pay]\n    peak = bal\n    for m in range(1, n + 1):\n        t = (m - 1) // 12\n        if m > 1 and (m - 1) % 12 == 0:\n            if t <= x['steps']:\n                pay = rnd(x['initial_payment'] * (10000 + x['step_bp'] * t), 10000)\n            elif t == x['steps'] + 1:\n                pay = level(bal, n - m + 1)\n            years.append(pay)\n        interest = rnd(bal * bp, 120000)\n        bal += interest - pay\n        peak = max(peak, bal)\n    return {'year_payments': years, 'peak_balance': peak, 'end_balance': bal}\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\nfixtures = [[['regression: step compounding base', {'principal': 1000000, 'rate_bp': 600, 'months': 36, 'initial_payment': 20000, 'step_bp': 750, 'steps': 2}, {'year_payments': [20000, 21500, 23113], 'peak_balance': 1000000, 'end_balance': 351915}], ['regression: step compounding base, partial-repair probe', {'principal': 100000, 'rate_bp': 900, 'months': 36, 'initial_payment': 500, 'step_bp': 250, 'steps': 2}, {'year_payments': [500, 513, 526], 'peak_balance': 109781, 'end_balance': 109781}], ['control 1', {'principal': 250000, 'rate_bp': 600, 'months': 24, 'initial_payment': 3000, 'step_bp': 250, 'steps': 3}, {'year_payments': [3000, 3075], 'peak_balance': 250000, 'end_balance': 204568}], ['control 2', {'principal': 250000, 'rate_bp': 900, 'months': 36, 'initial_payment': 8000, 'step_bp': 250, 'steps': 0}, {'year_payments': [8000, 7921, 7921], 'peak_balance': 250000, 'end_balance': 9}], ['control 3', {'principal': 100000, 'rate_bp': 600, 'months': 24, 'initial_payment': 500, 'step_bp': 250, 'steps': 0}, {'year_payments': [500, 8607], 'peak_balance': 100000, 'end_balance': -4}], ['control 4', {'principal': 250000, 'rate_bp': 900, 'months': 60, 'initial_payment': 8000, 'step_bp': 250, 'steps': 1}, {'year_payments': [8000, 8200, 2770, 2770, 2770], 'peak_balance': 250000, 'end_balance': -23}], ['control 5', {'principal': 250000, 'rate_bp': 1200, 'months': 60, 'initial_payment': 20000, 'step_bp': 250, 'steps': 1}, {'year_payments': [20000, 20500, 0, 0, 0], 'peak_balance': 250000, 'end_balance': -326758}]], [['regression: step compounding base', {'principal': 1000000, 'rate_bp': 600, 'months': 60, 'initial_payment': 500, 'step_bp': 250, 'steps': 2}, {'year_payments': [500, 513, 526, 52144, 52144], 'peak_balance': 1176523, 'end_balance': 4}], ['control 1', {'principal': 250000, 'rate_bp': 1200, 'months': 24, 'initial_payment': 3000, 'step_bp': 250, 'steps': 2}, {'year_payments': [3000, 3075], 'peak_balance': 250000, 'end_balance': 235565}], ['control 2', {'principal': 250000, 'rate_bp': 600, 'months': 24, 'initial_payment': 3000, 'step_bp': 1000, 'steps': 1}, {'year_payments': [3000, 3300], 'peak_balance': 250000, 'end_balance': 201795}], ['control 3', {'principal': 100000, 'rate_bp': 900, 'months': 24, 'initial_payment': 500, 'step_bp': 1000, 'steps': 3}, {'year_payments': [500, 550], 'peak_balance': 105921, 'end_balance': 105921}], ['control 4', {'principal': 250000, 'rate_bp': 900, 'months': 60, 'initial_payment': 500, 'step_bp': 250, 'steps': 1}, {'year_payments': [500, 513, 9090, 9090, 9090], 'peak_balance': 285848, 'end_balance': -7}], ['control 5', {'principal': 250000, 'rate_bp': 1200, 'months': 36, 'initial_payment': 8000, 'step_bp': 250, 'steps': 0}, {'year_payments': [8000, 8485, 8485], 'peak_balance': 250000, 'end_balance': -6}], ['control 6', {'principal': 100000, 'rate_bp': 1200, 'months': 36, 'initial_payment': 500, 'step_bp': 250, 'steps': 0}, {'year_payments': [500, 5006, 5006], 'peak_balance': 106341, 'end_balance': -5}]], [['regression: step compounding base', {'principal': 1000000, 'rate_bp': 1200, 'months': 60, 'initial_payment': 8000, 'step_bp': 250, 'steps': 2}, {'year_payments': [8000, 8200, 8405, 50753, 50753], 'peak_balance': 1078159, 'end_balance': -8}], ['regression: step compounding base, partial-repair probe', {'principal': 100000, 'rate_bp': 600, 'months': 60, 'initial_payment': 500, 'step_bp': 250, 'steps': 3}, {'year_payments': [500, 513, 526, 539, 8520], 'peak_balance': 100000, 'end_balance': 6}], ['control 1', {'principal': 1000000, 'rate_bp': 900, 'months': 36, 'initial_payment': 3000, 'step_bp': 750, 'steps': 1}, {'year_payments': [3000, 3225, 97511], 'peak_balance': 1115035, 'end_balance': 6}], ['control 2', {'principal': 250000, 'rate_bp': 900, 'months': 24, 'initial_payment': 3000, 'step_bp': 750, 'steps': 1}, {'year_payments': [3000, 3225], 'peak_balance': 250000, 'end_balance': 217726}], ['control 3', {'principal': 1000000, 'rate_bp': 900, 'months': 36, 'initial_payment': 20000, 'step_bp': 1000, 'steps': 1}, {'year_payments': [20000, 22000, 56636], 'peak_balance': 1000000, 'end_balance': 0}], ['control 4', {'principal': 100000, 'rate_bp': 900, 'months': 24, 'initial_payment': 3000, 'step_bp': 750, 'steps': 0}, {'year_payments': [3000, 6284], 'peak_balance': 100000, 'end_balance': -2}], ['control 5', {'principal': 250000, 'rate_bp': 1200, 'months': 60, 'initial_payment': 20000, 'step_bp': 250, 'steps': 0}, {'year_payments': [20000, 739, 739, 739, 739], 'peak_balance': 250000, 'end_balance': -10}]], [['regression: step compounding base', {'principal': 100000, 'rate_bp': 1200, 'months': 36, 'initial_payment': 3000, 'step_bp': 1000, 'steps': 2}, {'year_payments': [3000, 3300, 3630], 'peak_balance': 100000, 'end_balance': 1568}], ['regression: step compounding base, partial-repair probe', {'principal': 250000, 'rate_bp': 600, 'months': 36, 'initial_payment': 500, 'step_bp': 250, 'steps': 3}, {'year_payments': [500, 513, 526], 'peak_balance': 279010, 'end_balance': 279010}], ['control 1', {'principal': 100000, 'rate_bp': 900, 'months': 24, 'initial_payment': 20000, 'step_bp': 750, 'steps': 3}, {'year_payments': [20000, 21500], 'peak_balance': 100000, 'end_balance': -422889}], ['control 2', {'principal': 1000000, 'rate_bp': 900, 'months': 36, 'initial_payment': 8000, 'step_bp': 250, 'steps': 1}, {'year_payments': [8000, 8200, 86087], 'peak_balance': 1000000, 'end_balance': 5}], ['control 3', {'principal': 1000000, 'rate_bp': 900, 'months': 60, 'initial_payment': 500, 'step_bp': 250, 'steps': 0}, {'year_payments': [500, 27064, 27064, 27064, 27064], 'peak_balance': 1087553, 'end_balance': -13}], ['control 4', {'principal': 250000, 'rate_bp': 900, 'months': 36, 'initial_payment': 20000, 'step_bp': 750, 'steps': 1}, {'year_payments': [20000, 21500, 0], 'peak_balance': 250000, 'end_balance': -266261}], ['control 5', {'principal': 1000000, 'rate_bp': 600, 'months': 60, 'initial_payment': 8000, 'step_bp': 1000, 'steps': 0}, {'year_payments': [8000, 22616, 22616, 22616, 22616], 'peak_balance': 1000000, 'end_balance': 0}]], [['regression: step compounding base', {'principal': 100000, 'rate_bp': 600, 'months': 60, 'initial_payment': 500, 'step_bp': 1000, 'steps': 3}, {'year_payments': [500, 550, 605, 666, 8252], 'peak_balance': 100000, 'end_balance': 1}], ['regression: step compounding base, partial-repair probe', {'principal': 100000, 'rate_bp': 1200, 'months': 36, 'initial_payment': 500, 'step_bp': 250, 'steps': 2}, {'year_payments': [500, 513, 526], 'peak_balance': 121021, 'end_balance': 121021}], ['control 1', {'principal': 1000000, 'rate_bp': 600, 'months': 60, 'initial_payment': 20000, 'step_bp': 750, 'steps': 1}, {'year_payments': [20000, 21500, 18254, 18254, 18254], 'peak_balance': 1000000, 'end_balance': -11}], ['control 2', {'principal': 1000000, 'rate_bp': 900, 'months': 60, 'initial_payment': 3000, 'step_bp': 1000, 'steps': 1}, {'year_payments': [3000, 3300, 35428, 35428, 35428], 'peak_balance': 1114096, 'end_balance': -5}], ['control 3', {'principal': 250000, 'rate_bp': 1200, 'months': 24, 'initial_payment': 3000, 'step_bp': 250, 'steps': 1}, {'year_payments': [3000, 3075], 'peak_balance': 250000, 'end_balance': 235565}], ['control 4', {'principal': 1000000, 'rate_bp': 600, 'months': 36, 'initial_payment': 3000, 'step_bp': 1000, 'steps': 1}, {'year_payments': [3000, 3300, 90126], 'peak_balance': 1047163, 'end_balance': -6}], ['control 5', {'principal': 100000, 'rate_bp': 1200, 'months': 24, 'initial_payment': 500, 'step_bp': 250, 'steps': 0}, {'year_payments': [500, 9448], 'peak_balance': 106341, 'end_balance': 5}]]]\nfor label, args, expected in fixtures[N-1]:\n    try:\n        actual = solve(args)\n    except Exception as exc:\n        actual = 'raised ' + type(exc).__name__\n    check(label, actual, expected)\nprint(json.dumps({\"observations\": observations, \"passed\": all(x[\"passed\"] for x in observations)}, ensure_ascii=False))\nraise SystemExit(0 if all(x[\"passed\"] for x in observations) else 1)\n"}},"limitations":"A deterministic bounded teaching model with stipulated toy lending rules stated in the contract; money is integer cents and rates are basis points; it makes no claim of conformance to any regulation, servicing standard or product. 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.","method":"Deterministic executable model with adversarial boundary fixtures.","provenance":{"created_by":"Failure Map","dependencies":"Python standard library","family":"w2-loan-amortization-schedules-graduated-payment-steps-step-compounding-base","generated_at":"2026-09-29T14:46:30.235563+00:00","license":"CC0-1.0","python":"3.12.14","seed":1,"split":"open-access"},"relevance":"Amortization engines drive borrower statements, payoff quotes and investor remittances; a misplaced rounding step, boundary or ordering rule compounds across hundreds of periods.","root_cause":"Each step adds a simple percentage of the initial payment.","sha256":"40a97463be630543bd0017e60b1a2a246b087e21badea2adaeda7d41a274c2ec","title":"Graduated payment schedule: step compounding base · case 01","variant":1,"variant_policy":"Five numbered records share a model and may reuse boundary fixtures.","verified":true,"visibility":"public","verification":{"attempt":{"elapsed_ms":46.781,"exit_code":1,"observations":[{"actual":{"end_balance":351915,"peak_balance":1000000,"year_payments":[20000,21500,23113]},"check":"regression: step compounding base","expected":{"end_balance":351915,"peak_balance":1000000,"year_payments":[20000,21500,23113]},"passed":true},{"actual":{"end_balance":109794,"peak_balance":109794,"year_payments":[500,513,525]},"check":"regression: step compounding base, partial-repair probe","expected":{"end_balance":109781,"peak_balance":109781,"year_payments":[500,513,526]},"passed":false},{"actual":{"end_balance":204568,"peak_balance":250000,"year_payments":[3000,3075]},"check":"control 1","expected":{"end_balance":204568,"peak_balance":250000,"year_payments":[3000,3075]},"passed":true},{"actual":{"end_balance":9,"peak_balance":250000,"year_payments":[8000,7921,7921]},"check":"control 2","expected":{"end_balance":9,"peak_balance":250000,"year_payments":[8000,7921,7921]},"passed":true},{"actual":{"end_balance":-4,"peak_balance":100000,"year_payments":[500,8607]},"check":"control 3","expected":{"end_balance":-4,"peak_balance":100000,"year_payments":[500,8607]},"passed":true},{"actual":{"end_balance":-23,"peak_balance":250000,"year_payments":[8000,8200,2770,2770,2770]},"check":"control 4","expected":{"end_balance":-23,"peak_balance":250000,"year_payments":[8000,8200,2770,2770,2770]},"passed":true},{"actual":{"end_balance":-326758,"peak_balance":250000,"year_payments":[20000,20500,0,0,0]},"check":"control 5","expected":{"end_balance":-326758,"peak_balance":250000,"year_payments":[20000,20500,0,0,0]},"passed":true}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"regression: step compounding base\", \"actual\": {\"year_payments\": [20000, 21500, 23113], \"peak_balance\": 1000000, \"end_balance\": 351915}, \"expected\": {\"year_payments\": [20000, 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