FA-24826 / Client state / Open access

A manual appearance choice is overwritten by a subsequent system preference event · case 01

A manual appearance choice is overwritten by a subsequent system preference event.

Verified by executionVariant 1 · 6 checks per implementationDownload source bundle ↓JSON ↗

ROOT CAUSE

The faulty implementation violates Appearance begins in system mode. A manual choice masks system changes without forgetting them; choosing system again reveals the latest system preference.

VERIFIED REPAIR

Appearance begins in system mode. A manual choice masks system changes without forgetting them; choosing system again reveals the latest system preference.

Unsuccessful approach: The partial repair still violates at least one explicit regression oracle.

Case contract

Appearance begins in system mode. A manual choice masks system changes without forgetting them; choosing system again reveals the latest system preference.

Why this case matters

A bounded offline client-state transition with explicit lifecycle inputs.

1 / The failure

Exit 1

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

N = 1
observations = []
def solve(events):
    return events[-1][1] if events else 'light'
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
check('manual shields system event', solve([('choose','dark'),('system','light')]), 'dark')
check('system mode follows', solve([('system','dark')]), 'dark')
check('return to system', solve([('system','dark'),('choose','light'),('choose','system')]), 'dark')
check('initial default', solve([]), 'light')
check('manual empty preference valid', solve([('choose',''),('system','dark')]), '')
check('parameterized repeated system events', solve([('choose','dark')]+[('system','light')]*N), 'dark')
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
manual shields system event	`light`	`dark`	Failed
system mode follows	`dark`	`dark`	Passed
return to system	`system`	`dark`	Failed
initial default	`light`	`light`	Passed
manual empty preference valid	`dark`		Failed
parameterized repeated system events	`light`	`dark`	Failed

SHA-256 / c262e5a18de55a292cb895aa2757d85254f438a6a345bd5aa22abfd3e9e42e60

2 / The unsuccessful fix

Exit 1

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

N = 1
observations = []
def solve(events):
    mode='light'
    for kind,value in events:
        if kind=='choose' and value!='system': mode=value
    return mode
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
check('manual shields system event', solve([('choose','dark'),('system','light')]), 'dark')
check('system mode follows', solve([('system','dark')]), 'dark')
check('return to system', solve([('system','dark'),('choose','light'),('choose','system')]), 'dark')
check('initial default', solve([]), 'light')
check('manual empty preference valid', solve([('choose',''),('system','dark')]), '')
check('parameterized repeated system events', solve([('choose','dark')]+[('system','light')]*N), 'dark')
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
manual shields system event	`dark`	`dark`	Passed
system mode follows	`light`	`dark`	Failed
return to system	`light`	`dark`	Failed
initial default	`light`	`light`	Passed
manual empty preference valid			Passed
parameterized repeated system events	`dark`	`dark`	Passed

SHA-256 / 1b1318c1e62d30cf970e8d3f0a48e0549e58678cd2e53c3015ba6066c7c442b2

3 / The verified repair

Exit 0

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

N = 1
observations = []
def solve(events):
    mode='system'; system='light'
    for kind,value in events:
        if kind=='choose': mode=value
        elif kind=='system': system=value
    return system if mode=='system' else mode
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
check('manual shields system event', solve([('choose','dark'),('system','light')]), 'dark')
check('system mode follows', solve([('system','dark')]), 'dark')
check('return to system', solve([('system','dark'),('choose','light'),('choose','system')]), 'dark')
check('initial default', solve([]), 'light')
check('manual empty preference valid', solve([('choose',''),('system','dark')]), '')
check('parameterized repeated system events', solve([('choose','dark')]+[('system','light')]*N), 'dark')
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
manual shields system event	`dark`	`dark`	Passed
system mode follows	`dark`	`dark`	Passed
return to system	`dark`	`dark`	Passed
initial default	`light`	`light`	Passed
manual empty preference valid			Passed
parameterized repeated system events	`dark`	`dark`	Passed

SHA-256 / 1650ef6b19abf5f9669dc96b6e7e9b886187933ebea4232d9a7952dbc6eb4800

Verification & scope

This models the stated application policy only; no browser or framework conformance is claimed. 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 2026-09-29T14:41:01.080782+00:00.

Case digest / 538528f101eee9f89bd90081288c6264294cce9f4f4f14caa91a940640acf1ab