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FA-85461 / Ride-hailing fare and surge pricing / Open access

ETA improvement treated as driver lateness · case 01

Riders are charged although the ETA ballooned by ten minutes.

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

ROOT CAUSE

The ETA change is subtracted in the wrong order.

THE FAILURE

The ETA change is subtracted in the wrong order.

Unsuccessful approach: Using the absolute change also waives fees when the driver got closer.

Case contract

Decide a cancellation charge [cents, reason]. Driver cancellations are free. A rider cancelling at or after driver arrival pays the no-show fee if at least noshow_wait seconds passed since arrival, else the regular fee. Before arrival, cancelling within free_window seconds of acceptance is free; it is also free if the ETA grew by more than late_margin since acceptance, or if the driver is more than late_margin past the ETA promised at acceptance; otherwise the regular fee applies.

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(ev, policy):
    if ev['cancel_by'] == 'driver':
        return [0, 'driver']
    if ev['arrived_t'] is not None and ev['cancel_t'] >= ev['arrived_t']:
        if ev['cancel_t'] - ev['arrived_t'] >= policy['noshow_wait']:
            return [policy['noshow_fee'], 'no_show']
        return [policy['fee'], 'after_arrival']
    if ev['cancel_t'] - ev['accept_t'] <= policy['free_window']:
        return [0, 'free_window']
    if ev['eta_at_accept'] - ev['eta_latest'] > policy['late_margin']:
        return [0, 'driver_late']
    if ev['cancel_t'] > ev['accept_t'] + ev['eta_at_accept'] + policy['late_margin']:
        return [0, 'driver_late']
    return [policy['fee'], 'late_cancel']
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
fixtures = [[('regression: eta growth direction',
   [{'accept_t': 1000,
     'arrived_t': None,
     'cancel_by': 'rider',
     'cancel_t': 1300,
     'eta_at_accept': 240,
     'eta_latest': -160},
    {'fee': 500, 'free_window': 120, 'late_margin': 300, 'noshow_fee': 700, 'noshow_wait': 300}],
   [500, 'late_cancel']),
  ('partial repair probe: eta growth direction',
   [{'accept_t': 1000,
     'arrived_t': None,
     'cancel_by': 'rider',
     'cancel_t': 1600,
     'eta_at_accept': 300,
     'eta_latest': -100},
    {'fee': 500, 'free_window': 120, 'late_margin': 300, 'noshow_fee': 700, 'noshow_wait': 300}],
   [500, 'late_cancel']),
  ('second regression',
   [{'accept_t': 1000,
     'arrived_t': 2100,
     'cancel_by': 'rider',
     'cancel_t': 1300,
     'eta_at_accept': 900,
     'eta_latest': 1201},
    {'fee': 500, 'free_window': 120, 'late_margin': 300, 'noshow_fee': 700, 'noshow_wait': 300}],
   [0, 'driver_late']),
  ('normal control 1',
   [{'accept_t': 1000,
     'arrived_t': 1680,
     'cancel_by': 'driver',
     'cancel_t': 1300,
     'eta_at_accept': 480,
     'eta_latest': 480},
    {'fee': 500, 'free_window': 120, 'late_margin': 300, 'noshow_fee': 700, 'noshow_wait': 300}],
   [0, 'driver']),
  ('normal control 2',
   [{'accept_t': 1000,
     'arrived_t': 1480,
     'cancel_by': 'rider',
     'cancel_t': 1781,
     'eta_at_accept': 480,
     'eta_latest': 360},
    {'fee': 500, 'free_window': 120, 'late_margin': 300, 'noshow_fee': 700, 'noshow_wait': 300}],
   [700, 'no_show']),
  ('normal control 3',
   [{'accept_t': 1000,
     'arrived_t': 1900,
     'cancel_by': 'driver',
     'cancel_t': 2199,
     'eta_at_accept': 900,
     'eta_latest': 900},
    {'fee': 500, 'free_window': 120, 'late_margin': 300, 'noshow_fee': 700, 'noshow_wait': 300}],
   [0, 'driver']),
  ('normal control 4',
   [{'accept_t': 1000,
     'arrived_t': None,
     'cancel_by': 'driver',
     'cancel_t': 1060,
     'eta_at_accept': 480,
     'eta_latest': 360},
    {'fee': 500, 'free_window': 120, 'late_margin': 300, 'noshow_fee': 700, 'noshow_wait': 300}],
   [0, 'driver'])],
 [('regression: eta growth direction',
   [{'accept_t': 1000,
     'arrived_t': 1440,
     'cancel_by': 'rider',
     'cancel_t': 1121,
     'eta_at_accept': 240,
     'eta_latest': -160},
    {'fee': 500, 'free_window': 120, 'late_margin': 300, 'noshow_fee': 700, 'noshow_wait': 300}],
   [500, 'late_cancel']),
  ('partial repair probe: eta growth direction',
   [{'accept_t': 1000,
     'arrived_t': 1480,
     'cancel_by': 'rider',
     'cancel_t': 1121,
     'eta_at_accept': 480,
     'eta_latest': 80},
    {'fee': 500, 'free_window': 120, 'late_margin': 300, 'noshow_fee': 700, 'noshow_wait': 300}],
   [500, 'late_cancel']),
  ('second regression',
   [{'accept_t': 1000,
     'arrived_t': None,
     'cancel_by': 'rider',
     'cancel_t': 1121,
     'eta_at_accept': 480,
     'eta_latest': 781},
    {'fee': 500, 'free_window': 120, 'late_margin': 300, 'noshow_fee': 700, 'noshow_wait': 300}],
   [0, 'driver_late']),
  ('normal control 1',
   [{'accept_t': 1000,
     'arrived_t': None,
     'cancel_by': 'rider',
     'cancel_t': 2200,
     'eta_at_accept': 300,
     'eta_latest': 300},
    {'fee': 500, 'free_window': 120, 'late_margin': 300, 'noshow_fee': 700, 'noshow_wait': 300}],
   [0, 'driver_late']),
  ('normal control 2',
   [{'accept_t': 1000,
     'arrived_t': 1900,
     'cancel_by': 'driver',
     'cancel_t': 1121,
     'eta_at_accept': 900,
     'eta_latest': 900},
    {'fee': 500, 'free_window': 120, 'late_margin': 300, 'noshow_fee': 700, 'noshow_wait': 300}],
   [0, 'driver']),
  ('normal control 3',
   [{'accept_t': 1000,
     'arrived_t': 1900,
     'cancel_by': 'rider',
     'cancel_t': 2199,
     'eta_at_accept': 900,
     'eta_latest': 1200},
    {'fee': 500, 'free_window': 120, 'late_margin': 300, 'noshow_fee': 700, 'noshow_wait': 300}],
   [500, 'after_arrival']),
  ('normal control 4',
   [{'accept_t': 1000,
     'arrived_t': None,
     'cancel_by': 'rider',
     'cancel_t': 1601,
     'eta_at_accept': 480,
     'eta_latest': 480},
    {'fee': 500, 'free_window': 120, 'late_margin': 300, 'noshow_fee': 700, 'noshow_wait': 300}],
   [500, 'late_cancel'])],
 [('regression: eta growth direction',
   [{'accept_t': 1000,
     'arrived_t': None,
     'cancel_by': 'rider',
     'cancel_t': 1300,
     'eta_at_accept': 900,
     'eta_latest': 1500},
    {'fee': 500, 'free_window': 120, 'late_margin': 300, 'noshow_fee': 700, 'noshow_wait': 300}],
   [0, 'driver_late']),
  ('partial repair probe: eta growth direction',
   [{'accept_t': 1000,
     'arrived_t': 1440,
     'cancel_by': 'rider',
     'cancel_t': 1274,
     'eta_at_accept': 240,
     'eta_latest': -160},
    {'fee': 500, 'free_window': 120, 'late_margin': 300, 'noshow_fee': 700, 'noshow_wait': 300}],
   [500, 'late_cancel']),
  ('second regression',
   [{'accept_t': 1000,
     'arrived_t': None,
     'cancel_by': 'rider',
     'cancel_t': 1900,
     'eta_at_accept': 900,
     'eta_latest': 1201},
    {'fee': 500, 'free_window': 120, 'late_margin': 300, 'noshow_fee': 700, 'noshow_wait': 300}],
   [0, 'driver_late']),
  ('normal control 1',
   [{'accept_t': 1000,
     'arrived_t': None,
     'cancel_by': 'rider',
     'cancel_t': 2344,
     'eta_at_accept': 900,
     'eta_latest': 780},
    {'fee': 500, 'free_window': 120, 'late_margin': 300, 'noshow_fee': 700, 'noshow_wait': 300}],
   [0, 'driver_late']),
  ('normal control 2',
   [{'accept_t': 1000,
     'arrived_t': None,
     'cancel_by': 'rider',
     'cancel_t': 1120,
     'eta_at_accept': 480,
     'eta_latest': 80},
    {'fee': 500, 'free_window': 120, 'late_margin': 300, 'noshow_fee': 700, 'noshow_wait': 300}],
   [0, 'free_window']),
  ('normal control 3',
   [{'accept_t': 1000,
     'arrived_t': 1480,
     'cancel_by': 'rider',
     'cancel_t': 2446,
     'eta_at_accept': 480,
     'eta_latest': 480},
    {'fee': 500, 'free_window': 120, 'late_margin': 300, 'noshow_fee': 700, 'noshow_wait': 300}],
   [700, 'no_show']),
  ('normal control 4',
   [{'accept_t': 1000,
     'arrived_t': 1680,
     'cancel_by': 'rider',
     'cancel_t': 1121,
     'eta_at_accept': 480,
     'eta_latest': 780},
    {'fee': 500, 'free_window': 120, 'late_margin': 300, 'noshow_fee': 700, 'noshow_wait': 300}],
   [500, 'late_cancel'])],
 [('regression: eta growth direction',
   [{'accept_t': 1000,
     'arrived_t': None,
     'cancel_by': 'rider',
     'cancel_t': 2200,
     'eta_at_accept': 900,
     'eta_latest': 1500},
    {'fee': 500, 'free_window': 120, 'late_margin': 300, 'noshow_fee': 700, 'noshow_wait': 300}],
   [0, 'driver_late']),
  ('partial repair probe: eta growth direction',
   [{'accept_t': 1000,
     'arrived_t': None,
     'cancel_by': 'rider',
     'cancel_t': 1300,
     'eta_at_accept': 300,
     'eta_latest': -100},
    {'fee': 500, 'free_window': 120, 'late_margin': 300, 'noshow_fee': 700, 'noshow_wait': 300}],
   [500, 'late_cancel']),
  ('second regression',
   [{'accept_t': 1000,
     'arrived_t': None,
     'cancel_by': 'rider',
     'cancel_t': 1121,
     'eta_at_accept': 300,
     'eta_latest': 601},
    {'fee': 500, 'free_window': 120, 'late_margin': 300, 'noshow_fee': 700, 'noshow_wait': 300}],
   [0, 'driver_late']),
  ('normal control 1',
   [{'accept_t': 1000,
     'arrived_t': 1500,
     'cancel_by': 'driver',
     'cancel_t': 1121,
     'eta_at_accept': 300,
     'eta_latest': -100},
    {'fee': 500, 'free_window': 120, 'late_margin': 300, 'noshow_fee': 700, 'noshow_wait': 300}],
   [0, 'driver']),
  ('normal control 2',
   [{'accept_t': 1000,
     'arrived_t': 1900,
     'cancel_by': 'driver',
     'cancel_t': 2199,
     'eta_at_accept': 900,
     'eta_latest': 1500},
    {'fee': 500, 'free_window': 120, 'late_margin': 300, 'noshow_fee': 700, 'noshow_wait': 300}],
   [0, 'driver']),
  ('normal control 3',
   [{'accept_t': 1000,
     'arrived_t': 1500,
     'cancel_by': 'driver',
     'cancel_t': 2000,
     'eta_at_accept': 300,
     'eta_latest': 300},
    {'fee': 500, 'free_window': 120, 'late_margin': 300, 'noshow_fee': 700, 'noshow_wait': 300}],
   [0, 'driver']),
  ('normal control 4',
   [{'accept_t': 1000,
     'arrived_t': None,
     'cancel_by': 'rider',
     'cancel_t': 2311,
     'eta_at_accept': 300,
     'eta_latest': 601},
    {'fee': 500, 'free_window': 120, 'late_margin': 300, 'noshow_fee': 700, 'noshow_wait': 300}],
   [0, 'driver_late'])],
 [('regression: eta growth direction',
   [{'accept_t': 1000,
     'arrived_t': None,
     'cancel_by': 'rider',
     'cancel_t': 1600,
     'eta_at_accept': 900,
     'eta_latest': 1500},
    {'fee': 500, 'free_window': 120, 'late_margin': 300, 'noshow_fee': 700, 'noshow_wait': 300}],
   [0, 'driver_late']),
  ('partial repair probe: eta growth direction',
   [{'accept_t': 1000,
     'arrived_t': None,
     'cancel_by': 'rider',
     'cancel_t': 1600,
     'eta_at_accept': 300,
     'eta_latest': -100},
    {'fee': 500, 'free_window': 120, 'late_margin': 300, 'noshow_fee': 700, 'noshow_wait': 300}],
   [500, 'late_cancel']),
  ('second regression',
   [{'accept_t': 1000,
     'arrived_t': 1900,
     'cancel_by': 'rider',
     'cancel_t': 1604,
     'eta_at_accept': 900,
     'eta_latest': 1201},
    {'fee': 500, 'free_window': 120, 'late_margin': 300, 'noshow_fee': 700, 'noshow_wait': 300}],
   [0, 'driver_late']),
  ('normal control 1',
   [{'accept_t': 1000,
     'arrived_t': None,
     'cancel_by': 'rider',
     'cancel_t': 1120,
     'eta_at_accept': 300,
     'eta_latest': -100},
    {'fee': 500, 'free_window': 120, 'late_margin': 300, 'noshow_fee': 700, 'noshow_wait': 300}],
   [0, 'free_window']),
  ('normal control 2',
   [{'accept_t': 1000,
     'arrived_t': None,
     'cancel_by': 'rider',
     'cancel_t': 1120,
     'eta_at_accept': 240,
     'eta_latest': 840},
    {'fee': 500, 'free_window': 120, 'late_margin': 300, 'noshow_fee': 700, 'noshow_wait': 300}],
   [0, 'free_window']),
  ('normal control 3',
   [{'accept_t': 1000,
     'arrived_t': 1440,
     'cancel_by': 'driver',
     'cancel_t': 1440,
     'eta_at_accept': 240,
     'eta_latest': 120},
    {'fee': 500, 'free_window': 120, 'late_margin': 300, 'noshow_fee': 700, 'noshow_wait': 300}],
   [0, 'driver']),
  ('normal control 4',
   [{'accept_t': 1000,
     'arrived_t': 1300,
     'cancel_by': 'driver',
     'cancel_t': 1601,
     'eta_at_accept': 300,
     'eta_latest': 900},
    {'fee': 500, 'free_window': 120, 'late_margin': 300, 'noshow_fee': 700, 'noshow_wait': 300}],
   [0, 'driver'])]]
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: eta growth direction[0, 'driver_late'][500, 'late_cancel']Failed
partial repair probe: eta growth direction[0, 'driver_late'][500, 'late_cancel']Failed
second regression[500, 'late_cancel'][0, 'driver_late']Failed
normal control 1[0, 'driver'][0, 'driver']Passed
normal control 2[700, 'no_show'][700, 'no_show']Passed
normal control 3[0, 'driver'][0, 'driver']Passed
normal control 4[0, 'driver'][0, 'driver']Passed

SHA-256 / 680458c8a643e85dd817f213be6269018722c8b66debf23a5306c6633eff9fb5

2 / The unsuccessful fix

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

N = 1
observations = []
def solve(ev, policy):
    if ev['cancel_by'] == 'driver':
        return [0, 'driver']
    if ev['arrived_t'] is not None and ev['cancel_t'] >= ev['arrived_t']:
        if ev['cancel_t'] - ev['arrived_t'] >= policy['noshow_wait']:
            return [policy['noshow_fee'], 'no_show']
        return [policy['fee'], 'after_arrival']
    if ev['cancel_t'] - ev['accept_t'] <= policy['free_window']:
        return [0, 'free_window']
    if abs(ev['eta_latest'] - ev['eta_at_accept']) > policy['late_margin']:
        return [0, 'driver_late']
    if ev['cancel_t'] > ev['accept_t'] + ev['eta_at_accept'] + policy['late_margin']:
        return [0, 'driver_late']
    return [policy['fee'], 'late_cancel']
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
fixtures = [[('regression: eta growth direction',
   [{'accept_t': 1000,
     'arrived_t': None,
     'cancel_by': 'rider',
     'cancel_t': 1300,
     'eta_at_accept': 240,
     'eta_latest': -160},
    {'fee': 500, 'free_window': 120, 'late_margin': 300, 'noshow_fee': 700, 'noshow_wait': 300}],
   [500, 'late_cancel']),
  ('partial repair probe: eta growth direction',
   [{'accept_t': 1000,
     'arrived_t': None,
     'cancel_by': 'rider',
     'cancel_t': 1600,
     'eta_at_accept': 300,
     'eta_latest': -100},
    {'fee': 500, 'free_window': 120, 'late_margin': 300, 'noshow_fee': 700, 'noshow_wait': 300}],
   [500, 'late_cancel']),
  ('second regression',
   [{'accept_t': 1000,
     'arrived_t': 2100,
     'cancel_by': 'rider',
     'cancel_t': 1300,
     'eta_at_accept': 900,
     'eta_latest': 1201},
    {'fee': 500, 'free_window': 120, 'late_margin': 300, 'noshow_fee': 700, 'noshow_wait': 300}],
   [0, 'driver_late']),
  ('normal control 1',
   [{'accept_t': 1000,
     'arrived_t': 1680,
     'cancel_by': 'driver',
     'cancel_t': 1300,
     'eta_at_accept': 480,
     'eta_latest': 480},
    {'fee': 500, 'free_window': 120, 'late_margin': 300, 'noshow_fee': 700, 'noshow_wait': 300}],
   [0, 'driver']),
  ('normal control 2',
   [{'accept_t': 1000,
     'arrived_t': 1480,
     'cancel_by': 'rider',
     'cancel_t': 1781,
     'eta_at_accept': 480,
     'eta_latest': 360},
    {'fee': 500, 'free_window': 120, 'late_margin': 300, 'noshow_fee': 700, 'noshow_wait': 300}],
   [700, 'no_show']),
  ('normal control 3',
   [{'accept_t': 1000,
     'arrived_t': 1900,
     'cancel_by': 'driver',
     'cancel_t': 2199,
     'eta_at_accept': 900,
     'eta_latest': 900},
    {'fee': 500, 'free_window': 120, 'late_margin': 300, 'noshow_fee': 700, 'noshow_wait': 300}],
   [0, 'driver']),
  ('normal control 4',
   [{'accept_t': 1000,
     'arrived_t': None,
     'cancel_by': 'driver',
     'cancel_t': 1060,
     'eta_at_accept': 480,
     'eta_latest': 360},
    {'fee': 500, 'free_window': 120, 'late_margin': 300, 'noshow_fee': 700, 'noshow_wait': 300}],
   [0, 'driver'])],
 [('regression: eta growth direction',
   [{'accept_t': 1000,
     'arrived_t': 1440,
     'cancel_by': 'rider',
     'cancel_t': 1121,
     'eta_at_accept': 240,
     'eta_latest': -160},
    {'fee': 500, 'free_window': 120, 'late_margin': 300, 'noshow_fee': 700, 'noshow_wait': 300}],
   [500, 'late_cancel']),
  ('partial repair probe: eta growth direction',
   [{'accept_t': 1000,
     'arrived_t': 1480,
     'cancel_by': 'rider',
     'cancel_t': 1121,
     'eta_at_accept': 480,
     'eta_latest': 80},
    {'fee': 500, 'free_window': 120, 'late_margin': 300, 'noshow_fee': 700, 'noshow_wait': 300}],
   [500, 'late_cancel']),
  ('second regression',
   [{'accept_t': 1000,
     'arrived_t': None,
     'cancel_by': 'rider',
     'cancel_t': 1121,
     'eta_at_accept': 480,
     'eta_latest': 781},
    {'fee': 500, 'free_window': 120, 'late_margin': 300, 'noshow_fee': 700, 'noshow_wait': 300}],
   [0, 'driver_late']),
  ('normal control 1',
   [{'accept_t': 1000,
     'arrived_t': None,
     'cancel_by': 'rider',
     'cancel_t': 2200,
     'eta_at_accept': 300,
     'eta_latest': 300},
    {'fee': 500, 'free_window': 120, 'late_margin': 300, 'noshow_fee': 700, 'noshow_wait': 300}],
   [0, 'driver_late']),
  ('normal control 2',
   [{'accept_t': 1000,
     'arrived_t': 1900,
     'cancel_by': 'driver',
     'cancel_t': 1121,
     'eta_at_accept': 900,
     'eta_latest': 900},
    {'fee': 500, 'free_window': 120, 'late_margin': 300, 'noshow_fee': 700, 'noshow_wait': 300}],
   [0, 'driver']),
  ('normal control 3',
   [{'accept_t': 1000,
     'arrived_t': 1900,
     'cancel_by': 'rider',
     'cancel_t': 2199,
     'eta_at_accept': 900,
     'eta_latest': 1200},
    {'fee': 500, 'free_window': 120, 'late_margin': 300, 'noshow_fee': 700, 'noshow_wait': 300}],
   [500, 'after_arrival']),
  ('normal control 4',
   [{'accept_t': 1000,
     'arrived_t': None,
     'cancel_by': 'rider',
     'cancel_t': 1601,
     'eta_at_accept': 480,
     'eta_latest': 480},
    {'fee': 500, 'free_window': 120, 'late_margin': 300, 'noshow_fee': 700, 'noshow_wait': 300}],
   [500, 'late_cancel'])],
 [('regression: eta growth direction',
   [{'accept_t': 1000,
     'arrived_t': None,
     'cancel_by': 'rider',
     'cancel_t': 1300,
     'eta_at_accept': 900,
     'eta_latest': 1500},
    {'fee': 500, 'free_window': 120, 'late_margin': 300, 'noshow_fee': 700, 'noshow_wait': 300}],
   [0, 'driver_late']),
  ('partial repair probe: eta growth direction',
   [{'accept_t': 1000,
     'arrived_t': 1440,
     'cancel_by': 'rider',
     'cancel_t': 1274,
     'eta_at_accept': 240,
     'eta_latest': -160},
    {'fee': 500, 'free_window': 120, 'late_margin': 300, 'noshow_fee': 700, 'noshow_wait': 300}],
   [500, 'late_cancel']),
  ('second regression',
   [{'accept_t': 1000,
     'arrived_t': None,
     'cancel_by': 'rider',
     'cancel_t': 1900,
     'eta_at_accept': 900,
     'eta_latest': 1201},
    {'fee': 500, 'free_window': 120, 'late_margin': 300, 'noshow_fee': 700, 'noshow_wait': 300}],
   [0, 'driver_late']),
  ('normal control 1',
   [{'accept_t': 1000,
     'arrived_t': None,
     'cancel_by': 'rider',
     'cancel_t': 2344,
     'eta_at_accept': 900,
     'eta_latest': 780},
    {'fee': 500, 'free_window': 120, 'late_margin': 300, 'noshow_fee': 700, 'noshow_wait': 300}],
   [0, 'driver_late']),
  ('normal control 2',
   [{'accept_t': 1000,
     'arrived_t': None,
     'cancel_by': 'rider',
     'cancel_t': 1120,
     'eta_at_accept': 480,
     'eta_latest': 80},
    {'fee': 500, 'free_window': 120, 'late_margin': 300, 'noshow_fee': 700, 'noshow_wait': 300}],
   [0, 'free_window']),
  ('normal control 3',
   [{'accept_t': 1000,
     'arrived_t': 1480,
     'cancel_by': 'rider',
     'cancel_t': 2446,
     'eta_at_accept': 480,
     'eta_latest': 480},
    {'fee': 500, 'free_window': 120, 'late_margin': 300, 'noshow_fee': 700, 'noshow_wait': 300}],
   [700, 'no_show']),
  ('normal control 4',
   [{'accept_t': 1000,
     'arrived_t': 1680,
     'cancel_by': 'rider',
     'cancel_t': 1121,
     'eta_at_accept': 480,
     'eta_latest': 780},
    {'fee': 500, 'free_window': 120, 'late_margin': 300, 'noshow_fee': 700, 'noshow_wait': 300}],
   [500, 'late_cancel'])],
 [('regression: eta growth direction',
   [{'accept_t': 1000,
     'arrived_t': None,
     'cancel_by': 'rider',
     'cancel_t': 2200,
     'eta_at_accept': 900,
     'eta_latest': 1500},
    {'fee': 500, 'free_window': 120, 'late_margin': 300, 'noshow_fee': 700, 'noshow_wait': 300}],
   [0, 'driver_late']),
  ('partial repair probe: eta growth direction',
   [{'accept_t': 1000,
     'arrived_t': None,
     'cancel_by': 'rider',
     'cancel_t': 1300,
     'eta_at_accept': 300,
     'eta_latest': -100},
    {'fee': 500, 'free_window': 120, 'late_margin': 300, 'noshow_fee': 700, 'noshow_wait': 300}],
   [500, 'late_cancel']),
  ('second regression',
   [{'accept_t': 1000,
     'arrived_t': None,
     'cancel_by': 'rider',
     'cancel_t': 1121,
     'eta_at_accept': 300,
     'eta_latest': 601},
    {'fee': 500, 'free_window': 120, 'late_margin': 300, 'noshow_fee': 700, 'noshow_wait': 300}],
   [0, 'driver_late']),
  ('normal control 1',
   [{'accept_t': 1000,
     'arrived_t': 1500,
     'cancel_by': 'driver',
     'cancel_t': 1121,
     'eta_at_accept': 300,
     'eta_latest': -100},
    {'fee': 500, 'free_window': 120, 'late_margin': 300, 'noshow_fee': 700, 'noshow_wait': 300}],
   [0, 'driver']),
  ('normal control 2',
   [{'accept_t': 1000,
     'arrived_t': 1900,
     'cancel_by': 'driver',
     'cancel_t': 2199,
     'eta_at_accept': 900,
     'eta_latest': 1500},
    {'fee': 500, 'free_window': 120, 'late_margin': 300, 'noshow_fee': 700, 'noshow_wait': 300}],
   [0, 'driver']),
  ('normal control 3',
   [{'accept_t': 1000,
     'arrived_t': 1500,
     'cancel_by': 'driver',
     'cancel_t': 2000,
     'eta_at_accept': 300,
     'eta_latest': 300},
    {'fee': 500, 'free_window': 120, 'late_margin': 300, 'noshow_fee': 700, 'noshow_wait': 300}],
   [0, 'driver']),
  ('normal control 4',
   [{'accept_t': 1000,
     'arrived_t': None,
     'cancel_by': 'rider',
     'cancel_t': 2311,
     'eta_at_accept': 300,
     'eta_latest': 601},
    {'fee': 500, 'free_window': 120, 'late_margin': 300, 'noshow_fee': 700, 'noshow_wait': 300}],
   [0, 'driver_late'])],
 [('regression: eta growth direction',
   [{'accept_t': 1000,
     'arrived_t': None,
     'cancel_by': 'rider',
     'cancel_t': 1600,
     'eta_at_accept': 900,
     'eta_latest': 1500},
    {'fee': 500, 'free_window': 120, 'late_margin': 300, 'noshow_fee': 700, 'noshow_wait': 300}],
   [0, 'driver_late']),
  ('partial repair probe: eta growth direction',
   [{'accept_t': 1000,
     'arrived_t': None,
     'cancel_by': 'rider',
     'cancel_t': 1600,
     'eta_at_accept': 300,
     'eta_latest': -100},
    {'fee': 500, 'free_window': 120, 'late_margin': 300, 'noshow_fee': 700, 'noshow_wait': 300}],
   [500, 'late_cancel']),
  ('second regression',
   [{'accept_t': 1000,
     'arrived_t': 1900,
     'cancel_by': 'rider',
     'cancel_t': 1604,
     'eta_at_accept': 900,
     'eta_latest': 1201},
    {'fee': 500, 'free_window': 120, 'late_margin': 300, 'noshow_fee': 700, 'noshow_wait': 300}],
   [0, 'driver_late']),
  ('normal control 1',
   [{'accept_t': 1000,
     'arrived_t': None,
     'cancel_by': 'rider',
     'cancel_t': 1120,
     'eta_at_accept': 300,
     'eta_latest': -100},
    {'fee': 500, 'free_window': 120, 'late_margin': 300, 'noshow_fee': 700, 'noshow_wait': 300}],
   [0, 'free_window']),
  ('normal control 2',
   [{'accept_t': 1000,
     'arrived_t': None,
     'cancel_by': 'rider',
     'cancel_t': 1120,
     'eta_at_accept': 240,
     'eta_latest': 840},
    {'fee': 500, 'free_window': 120, 'late_margin': 300, 'noshow_fee': 700, 'noshow_wait': 300}],
   [0, 'free_window']),
  ('normal control 3',
   [{'accept_t': 1000,
     'arrived_t': 1440,
     'cancel_by': 'driver',
     'cancel_t': 1440,
     'eta_at_accept': 240,
     'eta_latest': 120},
    {'fee': 500, 'free_window': 120, 'late_margin': 300, 'noshow_fee': 700, 'noshow_wait': 300}],
   [0, 'driver']),
  ('normal control 4',
   [{'accept_t': 1000,
     'arrived_t': 1300,
     'cancel_by': 'driver',
     'cancel_t': 1601,
     'eta_at_accept': 300,
     'eta_latest': 900},
    {'fee': 500, 'free_window': 120, 'late_margin': 300, 'noshow_fee': 700, 'noshow_wait': 300}],
   [0, 'driver'])]]
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: eta growth direction[0, 'driver_late'][500, 'late_cancel']Failed
partial repair probe: eta growth direction[0, 'driver_late'][500, 'late_cancel']Failed
second regression[0, 'driver_late'][0, 'driver_late']Passed
normal control 1[0, 'driver'][0, 'driver']Passed
normal control 2[700, 'no_show'][700, 'no_show']Passed
normal control 3[0, 'driver'][0, 'driver']Passed
normal control 4[0, 'driver'][0, 'driver']Passed

SHA-256 / 739ec7c08f2a54aa01b95f11a16425cf9d174e3c4888567a2f7e094370cd9f79

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 2026-09-29T14:50:40.549438+00:00.

Case digest / 859e44f097b513700f7ec89132f0d4c04a117eedda4a31647f167cf41fa9da10