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FA-85401 / Ride-hailing fare and surge pricing / Open access

Surged fare truncated instead of rounded · case 01

A 1.5x fare on 12.35 shows 18.52 instead of 18.53.

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

ROOT CAUSE

The surge product is floor-divided.

THE FAILURE

The surge product is floor-divided.

Unsuccessful approach: Python round() sends exact half cents to the even cent, so half of them still round down.

Case contract

Cents throughout. Surge (tenths) multiplies only base+distance+time, rounded half up. A percentage promo discounts the surged amount (floor), capped at promo cap cents. The booking fee is added after the discount. Tax (basis points, rounded half up) applies to surged - discount + booking fee; tolls and airport fees are passed through untaxed and unsurged.

Why this case matters

Ride-hailing prices are computed per trip at scale; ordering, unit and boundary slips become systematic over- or under-charging.

1 / The failure

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

N = 1
observations = []
def solve(parts, surge, promo, tax_bp):
    def half_up(num, den):
        return (num * 2 + den) // (den * 2)
    core = parts['base'] + parts['distance'] + parts['time']
    surged = core * surge // 10
    disc = 0
    if promo:
        disc = min(surged * promo['pct'] // 100, promo['cap'])
    sub = surged - disc + parts['booking_fee']
    tax = half_up(sub * tax_bp, 10000)
    total = sub + tax + parts['tolls'] + parts['airport_fee']
    return {'surged': surged, 'discount': disc, 'tax': tax, 'total': total}
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
fixtures = [[('regression: surge product rounding',
   [{'airport_fee': 0, 'base': 250, 'booking_fee': 0, 'distance': 1133, 'time': 346, 'tolls': 690}, 25,
    {'cap': 1000, 'pct': 50}, 625],
   {'discount': 1000, 'surged': 4323, 'tax': 208, 'total': 4221}),
  ('partial repair probe: surge product rounding',
   [{'airport_fee': 0, 'base': 150, 'booking_fee': 175, 'distance': 2672, 'time': 63, 'tolls': 0}, 25, None,
    625],
   {'discount': 0, 'surged': 7213, 'tax': 462, 'total': 7850}),
  ('second regression',
   [{'airport_fee': 0, 'base': 150, 'booking_fee': 245, 'distance': 915, 'time': 814, 'tolls': 375}, 12,
    {'cap': 500, 'pct': 20}, 1000],
   {'discount': 451, 'surged': 2255, 'tax': 205, 'total': 2629}),
  ('normal control 1',
   [{'airport_fee': 0, 'base': 150, 'booking_fee': 0, 'distance': 1078, 'time': 847, 'tolls': 690}, 12,
    {'cap': 500, 'pct': 20}, 1000],
   {'discount': 498, 'surged': 2490, 'tax': 199, 'total': 2881}),
  ('normal control 2',
   [{'airport_fee': 0, 'base': 250, 'booking_fee': 245, 'distance': 1178, 'time': 825, 'tolls': 0}, 17,
    {'cap': 5, 'pct': 15}, 0],
   {'discount': 5, 'surged': 3830, 'tax': 0, 'total': 4070}),
  ('normal control 3',
   [{'airport_fee': 0, 'base': 150, 'booking_fee': 0, 'distance': 651, 'time': 574, 'tolls': 375}, 12,
    {'cap': 1000, 'pct': 50}, 1000],
   {'discount': 825, 'surged': 1650, 'tax': 83, 'total': 1283}),
  ('normal control 4',
   [{'airport_fee': 0, 'base': 150, 'booking_fee': 0, 'distance': 2422, 'time': 315, 'tolls': 375}, 10, None,
    825],
   {'discount': 0, 'surged': 2887, 'tax': 238, 'total': 3500})],
 [('regression: surge product rounding',
   [{'airport_fee': 0, 'base': 150, 'booking_fee': 0, 'distance': 1959, 'time': 269, 'tolls': 0}, 17, None,
    625],
   {'discount': 0, 'surged': 4043, 'tax': 253, 'total': 4296}),
  ('partial repair probe: surge product rounding',
   [{'airport_fee': 0, 'base': 250, 'booking_fee': 175, 'distance': 227, 'time': 722, 'tolls': 0}, 15,
    {'cap': 5, 'pct': 15}, 625],
   {'discount': 5, 'surged': 1799, 'tax': 123, 'total': 2092}),
  ('second regression',
   [{'airport_fee': 500, 'base': 250, 'booking_fee': 0, 'distance': 670, 'time': 311, 'tolls': 0}, 25,
    {'cap': 500, 'pct': 20}, 1000],
   {'discount': 500, 'surged': 3078, 'tax': 258, 'total': 3336}),
  ('normal control 1',
   [{'airport_fee': 500, 'base': 150, 'booking_fee': 175, 'distance': 2869, 'time': 310, 'tolls': 0}, 10,
    {'cap': 5, 'pct': 15}, 825],
   {'discount': 5, 'surged': 3329, 'tax': 289, 'total': 4288}),
  ('normal control 2',
   [{'airport_fee': 500, 'base': 250, 'booking_fee': 175, 'distance': 2735, 'time': 367, 'tolls': 690}, 12,
    {'cap': 500, 'pct': 20}, 825],
   {'discount': 500, 'surged': 4022, 'tax': 305, 'total': 5192}),
  ('normal control 3',
   [{'airport_fee': 0, 'base': 150, 'booking_fee': 245, 'distance': 1129, 'time': 187, 'tolls': 0}, 12, None,
    625],
   {'discount': 0, 'surged': 1759, 'tax': 125, 'total': 2129}),
  ('normal control 4',
   [{'airport_fee': 500, 'base': 150, 'booking_fee': 0, 'distance': 2184, 'time': 136, 'tolls': 0}, 17,
    {'cap': 1000, 'pct': 50}, 0],
   {'discount': 1000, 'surged': 4199, 'tax': 0, 'total': 3699})],
 [('regression: surge product rounding',
   [{'airport_fee': 500, 'base': 150, 'booking_fee': 245, 'distance': 1137, 'time': 394, 'tolls': 0}, 15,
    {'cap': 1000, 'pct': 50}, 625],
   {'discount': 1000, 'surged': 2522, 'tax': 110, 'total': 2377}),
  ('partial repair probe: surge product rounding',
   [{'airport_fee': 0, 'base': 250, 'booking_fee': 245, 'distance': 1239, 'time': 362, 'tolls': 375}, 15,
    None, 625],
   {'discount': 0, 'surged': 2777, 'tax': 189, 'total': 3586}),
  ('second regression',
   [{'airport_fee': 0, 'base': 250, 'booking_fee': 175, 'distance': 2998, 'time': 169, 'tolls': 0}, 15,
    {'cap': 5, 'pct': 15}, 625],
   {'discount': 5, 'surged': 5126, 'tax': 331, 'total': 5627}),
  ('normal control 1',
   [{'airport_fee': 0, 'base': 150, 'booking_fee': 0, 'distance': 978, 'time': 114, 'tolls': 690}, 25, None,
    825],
   {'discount': 0, 'surged': 3105, 'tax': 256, 'total': 4051}),
  ('normal control 2',
   [{'airport_fee': 0, 'base': 150, 'booking_fee': 0, 'distance': 2383, 'time': 160, 'tolls': 0}, 17,
    {'cap': 5, 'pct': 15}, 625],
   {'discount': 5, 'surged': 4578, 'tax': 286, 'total': 4859}),
  ('normal control 3',
   [{'airport_fee': 0, 'base': 150, 'booking_fee': 175, 'distance': 1266, 'time': 570, 'tolls': 0}, 17,
    {'cap': 5, 'pct': 15}, 0],
   {'discount': 5, 'surged': 3376, 'tax': 0, 'total': 3546}),
  ('normal control 4',
   [{'airport_fee': 0, 'base': 150, 'booking_fee': 245, 'distance': 2592, 'time': 644, 'tolls': 0}, 10,
    {'cap': 500, 'pct': 20}, 1000],
   {'discount': 500, 'surged': 3386, 'tax': 313, 'total': 3444})],
 [('regression: surge product rounding',
   [{'airport_fee': 0, 'base': 150, 'booking_fee': 0, 'distance': 343, 'time': 325, 'tolls': 0}, 12,
    {'cap': 500, 'pct': 20}, 625],
   {'discount': 196, 'surged': 982, 'tax': 49, 'total': 835}),
  ('partial repair probe: surge product rounding',
   [{'airport_fee': 500, 'base': 250, 'booking_fee': 245, 'distance': 401, 'time': 180, 'tolls': 375}, 15,
    {'cap': 1000, 'pct': 50}, 1000],
   {'discount': 623, 'surged': 1247, 'tax': 87, 'total': 1831}),
  ('second regression',
   [{'airport_fee': 500, 'base': 150, 'booking_fee': 175, 'distance': 1525, 'time': 734, 'tolls': 690}, 15,
    None, 625],
   {'discount': 0, 'surged': 3614, 'tax': 237, 'total': 5216}),
  ('normal control 1',
   [{'airport_fee': 0, 'base': 250, 'booking_fee': 245, 'distance': 1417, 'time': 611, 'tolls': 375}, 25,
    {'cap': 500, 'pct': 20}, 825],
   {'discount': 500, 'surged': 5695, 'tax': 449, 'total': 6264}),
  ('normal control 2',
   [{'airport_fee': 0, 'base': 250, 'booking_fee': 0, 'distance': 2189, 'time': 343, 'tolls': 375}, 10,
    {'cap': 1000, 'pct': 50}, 825],
   {'discount': 1000, 'surged': 2782, 'tax': 147, 'total': 2304}),
  ('normal control 3',
   [{'airport_fee': 0, 'base': 150, 'booking_fee': 175, 'distance': 986, 'time': 383, 'tolls': 375}, 10,
    {'cap': 5, 'pct': 15}, 0],
   {'discount': 5, 'surged': 1519, 'tax': 0, 'total': 2064}),
  ('normal control 4',
   [{'airport_fee': 500, 'base': 150, 'booking_fee': 175, 'distance': 556, 'time': 727, 'tolls': 375}, 10,
    {'cap': 500, 'pct': 20}, 625],
   {'discount': 286, 'surged': 1433, 'tax': 83, 'total': 2280})],
 [('regression: surge product rounding',
   [{'airport_fee': 0, 'base': 150, 'booking_fee': 245, 'distance': 1239, 'time': 898, 'tolls': 690}, 15,
    {'cap': 5, 'pct': 15}, 0],
   {'discount': 5, 'surged': 3431, 'tax': 0, 'total': 4361}),
  ('partial repair probe: surge product rounding',
   [{'airport_fee': 500, 'base': 150, 'booking_fee': 175, 'distance': 449, 'time': 856, 'tolls': 690}, 15,
    {'cap': 1000, 'pct': 50}, 0],
   {'discount': 1000, 'surged': 2183, 'tax': 0, 'total': 2548}),
  ('second regression',
   [{'airport_fee': 0, 'base': 250, 'booking_fee': 175, 'distance': 253, 'time': 50, 'tolls': 375}, 15,
    {'cap': 1000, 'pct': 50}, 1000],
   {'discount': 415, 'surged': 830, 'tax': 59, 'total': 1024}),
  ('normal control 1',
   [{'airport_fee': 500, 'base': 250, 'booking_fee': 0, 'distance': 288, 'time': 608, 'tolls': 690}, 12,
    {'cap': 5, 'pct': 15}, 0],
   {'discount': 5, 'surged': 1375, 'tax': 0, 'total': 2560}),
  ('normal control 2',
   [{'airport_fee': 0, 'base': 250, 'booking_fee': 0, 'distance': 1188, 'time': 261, 'tolls': 0}, 10,
    {'cap': 500, 'pct': 20}, 825],
   {'discount': 339, 'surged': 1699, 'tax': 112, 'total': 1472}),
  ('normal control 3',
   [{'airport_fee': 0, 'base': 150, 'booking_fee': 0, 'distance': 239, 'time': 770, 'tolls': 375}, 17,
    {'cap': 500, 'pct': 20}, 0],
   {'discount': 394, 'surged': 1970, 'tax': 0, 'total': 1951}),
  ('normal control 4',
   [{'airport_fee': 500, 'base': 150, 'booking_fee': 245, 'distance': 1284, 'time': 494, 'tolls': 690}, 10,
    {'cap': 1000, 'pct': 50}, 0],
   {'discount': 964, 'surged': 1928, 'tax': 0, 'total': 2399})]]
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
regression: surge product rounding{'discount': 1000, 'surged': 4322, 'tax': 208, 'total': 4220}{'discount': 1000, 'surged': 4323, 'tax': 208, 'total': 4221}Failed
partial repair probe: surge product rounding{'discount': 0, 'surged': 7212, 'tax': 462, 'total': 7849}{'discount': 0, 'surged': 7213, 'tax': 462, 'total': 7850}Failed
second regression{'discount': 450, 'surged': 2254, 'tax': 205, 'total': 2629}{'discount': 451, 'surged': 2255, 'tax': 205, 'total': 2629}Failed
normal control 1{'discount': 498, 'surged': 2490, 'tax': 199, 'total': 2881}{'discount': 498, 'surged': 2490, 'tax': 199, 'total': 2881}Passed
normal control 2{'discount': 5, 'surged': 3830, 'tax': 0, 'total': 4070}{'discount': 5, 'surged': 3830, 'tax': 0, 'total': 4070}Passed
normal control 3{'discount': 825, 'surged': 1650, 'tax': 83, 'total': 1283}{'discount': 825, 'surged': 1650, 'tax': 83, 'total': 1283}Passed
normal control 4{'discount': 0, 'surged': 2887, 'tax': 238, 'total': 3500}{'discount': 0, 'surged': 2887, 'tax': 238, 'total': 3500}Passed

SHA-256 / 6869679994633d8703cf0acdabf453fd1ae4c1feb0715942791805325fdf6f22

2 / The unsuccessful fix

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

N = 1
observations = []
def solve(parts, surge, promo, tax_bp):
    def half_up(num, den):
        return (num * 2 + den) // (den * 2)
    core = parts['base'] + parts['distance'] + parts['time']
    surged = round(core * surge / 10)
    disc = 0
    if promo:
        disc = min(surged * promo['pct'] // 100, promo['cap'])
    sub = surged - disc + parts['booking_fee']
    tax = half_up(sub * tax_bp, 10000)
    total = sub + tax + parts['tolls'] + parts['airport_fee']
    return {'surged': surged, 'discount': disc, 'tax': tax, 'total': total}
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
fixtures = [[('regression: surge product rounding',
   [{'airport_fee': 0, 'base': 250, 'booking_fee': 0, 'distance': 1133, 'time': 346, 'tolls': 690}, 25,
    {'cap': 1000, 'pct': 50}, 625],
   {'discount': 1000, 'surged': 4323, 'tax': 208, 'total': 4221}),
  ('partial repair probe: surge product rounding',
   [{'airport_fee': 0, 'base': 150, 'booking_fee': 175, 'distance': 2672, 'time': 63, 'tolls': 0}, 25, None,
    625],
   {'discount': 0, 'surged': 7213, 'tax': 462, 'total': 7850}),
  ('second regression',
   [{'airport_fee': 0, 'base': 150, 'booking_fee': 245, 'distance': 915, 'time': 814, 'tolls': 375}, 12,
    {'cap': 500, 'pct': 20}, 1000],
   {'discount': 451, 'surged': 2255, 'tax': 205, 'total': 2629}),
  ('normal control 1',
   [{'airport_fee': 0, 'base': 150, 'booking_fee': 0, 'distance': 1078, 'time': 847, 'tolls': 690}, 12,
    {'cap': 500, 'pct': 20}, 1000],
   {'discount': 498, 'surged': 2490, 'tax': 199, 'total': 2881}),
  ('normal control 2',
   [{'airport_fee': 0, 'base': 250, 'booking_fee': 245, 'distance': 1178, 'time': 825, 'tolls': 0}, 17,
    {'cap': 5, 'pct': 15}, 0],
   {'discount': 5, 'surged': 3830, 'tax': 0, 'total': 4070}),
  ('normal control 3',
   [{'airport_fee': 0, 'base': 150, 'booking_fee': 0, 'distance': 651, 'time': 574, 'tolls': 375}, 12,
    {'cap': 1000, 'pct': 50}, 1000],
   {'discount': 825, 'surged': 1650, 'tax': 83, 'total': 1283}),
  ('normal control 4',
   [{'airport_fee': 0, 'base': 150, 'booking_fee': 0, 'distance': 2422, 'time': 315, 'tolls': 375}, 10, None,
    825],
   {'discount': 0, 'surged': 2887, 'tax': 238, 'total': 3500})],
 [('regression: surge product rounding',
   [{'airport_fee': 0, 'base': 150, 'booking_fee': 0, 'distance': 1959, 'time': 269, 'tolls': 0}, 17, None,
    625],
   {'discount': 0, 'surged': 4043, 'tax': 253, 'total': 4296}),
  ('partial repair probe: surge product rounding',
   [{'airport_fee': 0, 'base': 250, 'booking_fee': 175, 'distance': 227, 'time': 722, 'tolls': 0}, 15,
    {'cap': 5, 'pct': 15}, 625],
   {'discount': 5, 'surged': 1799, 'tax': 123, 'total': 2092}),
  ('second regression',
   [{'airport_fee': 500, 'base': 250, 'booking_fee': 0, 'distance': 670, 'time': 311, 'tolls': 0}, 25,
    {'cap': 500, 'pct': 20}, 1000],
   {'discount': 500, 'surged': 3078, 'tax': 258, 'total': 3336}),
  ('normal control 1',
   [{'airport_fee': 500, 'base': 150, 'booking_fee': 175, 'distance': 2869, 'time': 310, 'tolls': 0}, 10,
    {'cap': 5, 'pct': 15}, 825],
   {'discount': 5, 'surged': 3329, 'tax': 289, 'total': 4288}),
  ('normal control 2',
   [{'airport_fee': 500, 'base': 250, 'booking_fee': 175, 'distance': 2735, 'time': 367, 'tolls': 690}, 12,
    {'cap': 500, 'pct': 20}, 825],
   {'discount': 500, 'surged': 4022, 'tax': 305, 'total': 5192}),
  ('normal control 3',
   [{'airport_fee': 0, 'base': 150, 'booking_fee': 245, 'distance': 1129, 'time': 187, 'tolls': 0}, 12, None,
    625],
   {'discount': 0, 'surged': 1759, 'tax': 125, 'total': 2129}),
  ('normal control 4',
   [{'airport_fee': 500, 'base': 150, 'booking_fee': 0, 'distance': 2184, 'time': 136, 'tolls': 0}, 17,
    {'cap': 1000, 'pct': 50}, 0],
   {'discount': 1000, 'surged': 4199, 'tax': 0, 'total': 3699})],
 [('regression: surge product rounding',
   [{'airport_fee': 500, 'base': 150, 'booking_fee': 245, 'distance': 1137, 'time': 394, 'tolls': 0}, 15,
    {'cap': 1000, 'pct': 50}, 625],
   {'discount': 1000, 'surged': 2522, 'tax': 110, 'total': 2377}),
  ('partial repair probe: surge product rounding',
   [{'airport_fee': 0, 'base': 250, 'booking_fee': 245, 'distance': 1239, 'time': 362, 'tolls': 375}, 15,
    None, 625],
   {'discount': 0, 'surged': 2777, 'tax': 189, 'total': 3586}),
  ('second regression',
   [{'airport_fee': 0, 'base': 250, 'booking_fee': 175, 'distance': 2998, 'time': 169, 'tolls': 0}, 15,
    {'cap': 5, 'pct': 15}, 625],
   {'discount': 5, 'surged': 5126, 'tax': 331, 'total': 5627}),
  ('normal control 1',
   [{'airport_fee': 0, 'base': 150, 'booking_fee': 0, 'distance': 978, 'time': 114, 'tolls': 690}, 25, None,
    825],
   {'discount': 0, 'surged': 3105, 'tax': 256, 'total': 4051}),
  ('normal control 2',
   [{'airport_fee': 0, 'base': 150, 'booking_fee': 0, 'distance': 2383, 'time': 160, 'tolls': 0}, 17,
    {'cap': 5, 'pct': 15}, 625],
   {'discount': 5, 'surged': 4578, 'tax': 286, 'total': 4859}),
  ('normal control 3',
   [{'airport_fee': 0, 'base': 150, 'booking_fee': 175, 'distance': 1266, 'time': 570, 'tolls': 0}, 17,
    {'cap': 5, 'pct': 15}, 0],
   {'discount': 5, 'surged': 3376, 'tax': 0, 'total': 3546}),
  ('normal control 4',
   [{'airport_fee': 0, 'base': 150, 'booking_fee': 245, 'distance': 2592, 'time': 644, 'tolls': 0}, 10,
    {'cap': 500, 'pct': 20}, 1000],
   {'discount': 500, 'surged': 3386, 'tax': 313, 'total': 3444})],
 [('regression: surge product rounding',
   [{'airport_fee': 0, 'base': 150, 'booking_fee': 0, 'distance': 343, 'time': 325, 'tolls': 0}, 12,
    {'cap': 500, 'pct': 20}, 625],
   {'discount': 196, 'surged': 982, 'tax': 49, 'total': 835}),
  ('partial repair probe: surge product rounding',
   [{'airport_fee': 500, 'base': 250, 'booking_fee': 245, 'distance': 401, 'time': 180, 'tolls': 375}, 15,
    {'cap': 1000, 'pct': 50}, 1000],
   {'discount': 623, 'surged': 1247, 'tax': 87, 'total': 1831}),
  ('second regression',
   [{'airport_fee': 500, 'base': 150, 'booking_fee': 175, 'distance': 1525, 'time': 734, 'tolls': 690}, 15,
    None, 625],
   {'discount': 0, 'surged': 3614, 'tax': 237, 'total': 5216}),
  ('normal control 1',
   [{'airport_fee': 0, 'base': 250, 'booking_fee': 245, 'distance': 1417, 'time': 611, 'tolls': 375}, 25,
    {'cap': 500, 'pct': 20}, 825],
   {'discount': 500, 'surged': 5695, 'tax': 449, 'total': 6264}),
  ('normal control 2',
   [{'airport_fee': 0, 'base': 250, 'booking_fee': 0, 'distance': 2189, 'time': 343, 'tolls': 375}, 10,
    {'cap': 1000, 'pct': 50}, 825],
   {'discount': 1000, 'surged': 2782, 'tax': 147, 'total': 2304}),
  ('normal control 3',
   [{'airport_fee': 0, 'base': 150, 'booking_fee': 175, 'distance': 986, 'time': 383, 'tolls': 375}, 10,
    {'cap': 5, 'pct': 15}, 0],
   {'discount': 5, 'surged': 1519, 'tax': 0, 'total': 2064}),
  ('normal control 4',
   [{'airport_fee': 500, 'base': 150, 'booking_fee': 175, 'distance': 556, 'time': 727, 'tolls': 375}, 10,
    {'cap': 500, 'pct': 20}, 625],
   {'discount': 286, 'surged': 1433, 'tax': 83, 'total': 2280})],
 [('regression: surge product rounding',
   [{'airport_fee': 0, 'base': 150, 'booking_fee': 245, 'distance': 1239, 'time': 898, 'tolls': 690}, 15,
    {'cap': 5, 'pct': 15}, 0],
   {'discount': 5, 'surged': 3431, 'tax': 0, 'total': 4361}),
  ('partial repair probe: surge product rounding',
   [{'airport_fee': 500, 'base': 150, 'booking_fee': 175, 'distance': 449, 'time': 856, 'tolls': 690}, 15,
    {'cap': 1000, 'pct': 50}, 0],
   {'discount': 1000, 'surged': 2183, 'tax': 0, 'total': 2548}),
  ('second regression',
   [{'airport_fee': 0, 'base': 250, 'booking_fee': 175, 'distance': 253, 'time': 50, 'tolls': 375}, 15,
    {'cap': 1000, 'pct': 50}, 1000],
   {'discount': 415, 'surged': 830, 'tax': 59, 'total': 1024}),
  ('normal control 1',
   [{'airport_fee': 500, 'base': 250, 'booking_fee': 0, 'distance': 288, 'time': 608, 'tolls': 690}, 12,
    {'cap': 5, 'pct': 15}, 0],
   {'discount': 5, 'surged': 1375, 'tax': 0, 'total': 2560}),
  ('normal control 2',
   [{'airport_fee': 0, 'base': 250, 'booking_fee': 0, 'distance': 1188, 'time': 261, 'tolls': 0}, 10,
    {'cap': 500, 'pct': 20}, 825],
   {'discount': 339, 'surged': 1699, 'tax': 112, 'total': 1472}),
  ('normal control 3',
   [{'airport_fee': 0, 'base': 150, 'booking_fee': 0, 'distance': 239, 'time': 770, 'tolls': 375}, 17,
    {'cap': 500, 'pct': 20}, 0],
   {'discount': 394, 'surged': 1970, 'tax': 0, 'total': 1951}),
  ('normal control 4',
   [{'airport_fee': 500, 'base': 150, 'booking_fee': 245, 'distance': 1284, 'time': 494, 'tolls': 690}, 10,
    {'cap': 1000, 'pct': 50}, 0],
   {'discount': 964, 'surged': 1928, 'tax': 0, 'total': 2399})]]
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
regression: surge product rounding{'discount': 1000, 'surged': 4322, 'tax': 208, 'total': 4220}{'discount': 1000, 'surged': 4323, 'tax': 208, 'total': 4221}Failed
partial repair probe: surge product rounding{'discount': 0, 'surged': 7212, 'tax': 462, 'total': 7849}{'discount': 0, 'surged': 7213, 'tax': 462, 'total': 7850}Failed
second regression{'discount': 451, 'surged': 2255, 'tax': 205, 'total': 2629}{'discount': 451, 'surged': 2255, 'tax': 205, 'total': 2629}Passed
normal control 1{'discount': 498, 'surged': 2490, 'tax': 199, 'total': 2881}{'discount': 498, 'surged': 2490, 'tax': 199, 'total': 2881}Passed
normal control 2{'discount': 5, 'surged': 3830, 'tax': 0, 'total': 4070}{'discount': 5, 'surged': 3830, 'tax': 0, 'total': 4070}Passed
normal control 3{'discount': 825, 'surged': 1650, 'tax': 83, 'total': 1283}{'discount': 825, 'surged': 1650, 'tax': 83, 'total': 1283}Passed
normal control 4{'discount': 0, 'surged': 2887, 'tax': 238, 'total': 3500}{'discount': 0, 'surged': 2887, 'tax': 238, 'total': 3500}Passed

SHA-256 / c88def712572838345d55390dc29ecf929f818229f044235eaa7703918ee20c4

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

A deterministic toy pricing contract stipulated for this example; it does not reproduce the pricing of any real ride-hailing operator or regulator. 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 2026-09-29T14:50:39.976039+00:00.

Case digest / 4b43f8bbd53bfe9121370f589d974936f8268fb1252f8cca593f40a6b4017091