FA-53601 / Accessibility interaction semantics / Open access

Retired accessibility proxies accept new pins · case 01

Retired accessibility proxies accept new pins.

Verified by executionVariant 1 · 8 checks per implementationDownload source bundle ↓JSON ↗

ROOT CAUSE

The dead pin decision in the proxy lifetime adapter violates its declared contract.

VERIFIED REPAIR

Apply the exact contract at the dead pin decision: kind == 'pin' and old[1]

Unsuccessful approach: The local repair substitutes kind == 'pin' and old[3] == 0 but still mishandles the regression fixtures.

Case contract

Bounded accessibility proxy registry: input operations [kind,id,generation,value]. create installs a nonnegative generation only if newer than existing generation; retired generations remain recorded. destroy only applies to matching generation. get returns value only for matching generation live proxy. set changes matching live proxy and never creates objects. pin/unpin maintain nonnegative reference count; destroying a pinned proxy immediately makes reads unavailable but keeps tombstone until unpinned. Each operation returns a snapshot [id,generation,live,value,pins] for its ID, or None when absent; dead value is always None. Unknown operations do nothing.

Why this case matters

Offline accessibility bridge model with explicit policy; useful for testing semantic API adapters independently of browser implementations.

1 / The failure

Exit 1

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

N = 1
observations = []
def solve(data):
    state = {}
    result = []
    for kind,ident,generation,value in data:
        old = state.get(ident)
        if kind == 'create' and generation >= 0 and (old is None or generation > old[0]):
            state[ident] = [generation,True,value,0]
        elif old is not None and generation == old[0]:
            if kind == 'destroy': old[1],old[2] = False,None
            elif kind == 'set' and old[1]: old[2] = value
            elif kind == 'pin': old[3] += 1
            elif kind == 'unpin': old[3] = max(0,old[3]-1)
        row = state.get(ident)
        result.append((ident,list(row)) if row is not None else None)
    return [([entry[0]]+entry[1]) if entry is not None else None for entry in result]
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
check('newer proxy preserves stale isolation', solve([['create','a',N,'x'],['create','a',N+1,'y'],['set','a',N,'stale'],['destroy','a',N,None]],), [['a',N,True,'x',0],['a',N+1,True,'y',0],['a',N+1,True,'y',0],['a',N+1,True,'y',0]])
check('equal generation no reset', solve([['create','a',N,'x'],['pin','a',N,None],['create','a',N,'y']],), [['a',N,True,'x',0],['a',N,True,'x',1],['a',N,True,'x',1]])
check('stale create and pinned generation', solve([['create','a',N,'x'],['pin','a',N,None],['create','a',N+1,'y'],['create','a',N,'stale']],), [['a',N,True,'x',0],['a',N,True,'x',1],['a',N+1,True,'y',0],['a',N+1,True,'y',0]])
check('retired proxy cannot revive', solve([['create','a',N,'x'],['destroy','a',N,None],['set','a',N,'z'],['pin','a',N,None]],), [['a',N,True,'x',0],['a',N,False,None,0],['a',N,False,None,0],['a',N,False,None,0]])
check('pinned destroy immediate', solve([['create','a',N,'x'],['pin','a',N,None],['destroy','a',N,None],['unpin','a',N,None]],), [['a',N,True,'x',0],['a',N,True,'x',1],['a',N,False,None,1],['a',N,False,None,0]])
check('unpin lower bound', solve([['create','a',0,'x'],['unpin','a',0,None],['set','a',0,'y']],), [['a',0,True,'x',0],['a',0,True,'x',0],['a',0,True,'y',0]])
check('unknown and negative', solve([['set','missing',0,'x'],['create','bad',-1,'x'],['get','missing',0,None]],), [None,None,None])
check('separate proxy IDs', solve([['create','a',N,'x'],['create','b',N,'y']],), [['a',N,True,'x',0],['b',N,True,'y',0]])
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
newer proxy preserves stale isolation	`[['a', 1, True, 'x', 0], ['a', 2, True, 'y', 0], ['a', 2, True, 'y', 0], ['a', 2, True, 'y', 0]]`	`[['a', 1, True, 'x', 0], ['a', 2, True, 'y', 0], ['a', 2, True, 'y', 0], ['a', 2, True, 'y', 0]]`	Passed
equal generation no reset	`[['a', 1, True, 'x', 0], ['a', 1, True, 'x', 1], ['a', 1, True, 'x', 1]]`	`[['a', 1, True, 'x', 0], ['a', 1, True, 'x', 1], ['a', 1, True, 'x', 1]]`	Passed
stale create and pinned generation	`[['a', 1, True, 'x', 0], ['a', 1, True, 'x', 1], ['a', 2, True, 'y', 0], ['a', 2, True, 'y', 0]]`	`[['a', 1, True, 'x', 0], ['a', 1, True, 'x', 1], ['a', 2, True, 'y', 0], ['a', 2, True, 'y', 0]]`	Passed
retired proxy cannot revive	`[['a', 1, True, 'x', 0], ['a', 1, False, None, 0], ['a', 1, False, None, 0], ['a', 1, False, None, 1]]`	`[['a', 1, True, 'x', 0], ['a', 1, False, None, 0], ['a', 1, False, None, 0], ['a', 1, False, None, 0]]`	Failed
pinned destroy immediate	`[['a', 1, True, 'x', 0], ['a', 1, True, 'x', 1], ['a', 1, False, None, 1], ['a', 1, False, None, 0]]`	`[['a', 1, True, 'x', 0], ['a', 1, True, 'x', 1], ['a', 1, False, None, 1], ['a', 1, False, None, 0]]`	Passed
unpin lower bound	`[['a', 0, True, 'x', 0], ['a', 0, True, 'x', 0], ['a', 0, True, 'y', 0]]`	`[['a', 0, True, 'x', 0], ['a', 0, True, 'x', 0], ['a', 0, True, 'y', 0]]`	Passed
unknown and negative	`[None, None, None]`	`[None, None, None]`	Passed
separate proxy IDs	`[['a', 1, True, 'x', 0], ['b', 1, True, 'y', 0]]`	`[['a', 1, True, 'x', 0], ['b', 1, True, 'y', 0]]`	Passed

SHA-256 / 683c48b7917a55cbca67e903deb643f22ade4c9fd18d7053512526cdc37bf4ce

2 / The unsuccessful fix

Exit 1

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

N = 1
observations = []
def solve(data):
    state = {}
    result = []
    for kind,ident,generation,value in data:
        old = state.get(ident)
        if kind == 'create' and generation >= 0 and (old is None or generation > old[0]):
            state[ident] = [generation,True,value,0]
        elif old is not None and generation == old[0]:
            if kind == 'destroy': old[1],old[2] = False,None
            elif kind == 'set' and old[1]: old[2] = value
            elif kind == 'pin' and old[3] == 0: old[3] += 1
            elif kind == 'unpin': old[3] = max(0,old[3]-1)
        row = state.get(ident)
        result.append((ident,list(row)) if row is not None else None)
    return [([entry[0]]+entry[1]) if entry is not None else None for entry in result]
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
check('newer proxy preserves stale isolation', solve([['create','a',N,'x'],['create','a',N+1,'y'],['set','a',N,'stale'],['destroy','a',N,None]],), [['a',N,True,'x',0],['a',N+1,True,'y',0],['a',N+1,True,'y',0],['a',N+1,True,'y',0]])
check('equal generation no reset', solve([['create','a',N,'x'],['pin','a',N,None],['create','a',N,'y']],), [['a',N,True,'x',0],['a',N,True,'x',1],['a',N,True,'x',1]])
check('stale create and pinned generation', solve([['create','a',N,'x'],['pin','a',N,None],['create','a',N+1,'y'],['create','a',N,'stale']],), [['a',N,True,'x',0],['a',N,True,'x',1],['a',N+1,True,'y',0],['a',N+1,True,'y',0]])
check('retired proxy cannot revive', solve([['create','a',N,'x'],['destroy','a',N,None],['set','a',N,'z'],['pin','a',N,None]],), [['a',N,True,'x',0],['a',N,False,None,0],['a',N,False,None,0],['a',N,False,None,0]])
check('pinned destroy immediate', solve([['create','a',N,'x'],['pin','a',N,None],['destroy','a',N,None],['unpin','a',N,None]],), [['a',N,True,'x',0],['a',N,True,'x',1],['a',N,False,None,1],['a',N,False,None,0]])
check('unpin lower bound', solve([['create','a',0,'x'],['unpin','a',0,None],['set','a',0,'y']],), [['a',0,True,'x',0],['a',0,True,'x',0],['a',0,True,'y',0]])
check('unknown and negative', solve([['set','missing',0,'x'],['create','bad',-1,'x'],['get','missing',0,None]],), [None,None,None])
check('separate proxy IDs', solve([['create','a',N,'x'],['create','b',N,'y']],), [['a',N,True,'x',0],['b',N,True,'y',0]])
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
newer proxy preserves stale isolation	`[['a', 1, True, 'x', 0], ['a', 2, True, 'y', 0], ['a', 2, True, 'y', 0], ['a', 2, True, 'y', 0]]`	`[['a', 1, True, 'x', 0], ['a', 2, True, 'y', 0], ['a', 2, True, 'y', 0], ['a', 2, True, 'y', 0]]`	Passed
equal generation no reset	`[['a', 1, True, 'x', 0], ['a', 1, True, 'x', 1], ['a', 1, True, 'x', 1]]`	`[['a', 1, True, 'x', 0], ['a', 1, True, 'x', 1], ['a', 1, True, 'x', 1]]`	Passed
stale create and pinned generation	`[['a', 1, True, 'x', 0], ['a', 1, True, 'x', 1], ['a', 2, True, 'y', 0], ['a', 2, True, 'y', 0]]`	`[['a', 1, True, 'x', 0], ['a', 1, True, 'x', 1], ['a', 2, True, 'y', 0], ['a', 2, True, 'y', 0]]`	Passed
retired proxy cannot revive	`[['a', 1, True, 'x', 0], ['a', 1, False, None, 0], ['a', 1, False, None, 0], ['a', 1, False, None, 1]]`	`[['a', 1, True, 'x', 0], ['a', 1, False, None, 0], ['a', 1, False, None, 0], ['a', 1, False, None, 0]]`	Failed
pinned destroy immediate	`[['a', 1, True, 'x', 0], ['a', 1, True, 'x', 1], ['a', 1, False, None, 1], ['a', 1, False, None, 0]]`	`[['a', 1, True, 'x', 0], ['a', 1, True, 'x', 1], ['a', 1, False, None, 1], ['a', 1, False, None, 0]]`	Passed
unpin lower bound	`[['a', 0, True, 'x', 0], ['a', 0, True, 'x', 0], ['a', 0, True, 'y', 0]]`	`[['a', 0, True, 'x', 0], ['a', 0, True, 'x', 0], ['a', 0, True, 'y', 0]]`	Passed
unknown and negative	`[None, None, None]`	`[None, None, None]`	Passed
separate proxy IDs	`[['a', 1, True, 'x', 0], ['b', 1, True, 'y', 0]]`	`[['a', 1, True, 'x', 0], ['b', 1, True, 'y', 0]]`	Passed

SHA-256 / 4f252c7cf5613d4dd0e0b2ad4772a39c75073134c016ebb917eb85900d814f8e

3 / The verified repair

Exit 0

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

N = 1
observations = []
def solve(data):
    state = {}
    result = []
    for kind,ident,generation,value in data:
        old = state.get(ident)
        if kind == 'create' and generation >= 0 and (old is None or generation > old[0]):
            state[ident] = [generation,True,value,0]
        elif old is not None and generation == old[0]:
            if kind == 'destroy': old[1],old[2] = False,None
            elif kind == 'set' and old[1]: old[2] = value
            elif kind == 'pin' and old[1]: old[3] += 1
            elif kind == 'unpin': old[3] = max(0,old[3]-1)
        row = state.get(ident)
        result.append((ident,list(row)) if row is not None else None)
    return [([entry[0]]+entry[1]) if entry is not None else None for entry in result]
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
check('newer proxy preserves stale isolation', solve([['create','a',N,'x'],['create','a',N+1,'y'],['set','a',N,'stale'],['destroy','a',N,None]],), [['a',N,True,'x',0],['a',N+1,True,'y',0],['a',N+1,True,'y',0],['a',N+1,True,'y',0]])
check('equal generation no reset', solve([['create','a',N,'x'],['pin','a',N,None],['create','a',N,'y']],), [['a',N,True,'x',0],['a',N,True,'x',1],['a',N,True,'x',1]])
check('stale create and pinned generation', solve([['create','a',N,'x'],['pin','a',N,None],['create','a',N+1,'y'],['create','a',N,'stale']],), [['a',N,True,'x',0],['a',N,True,'x',1],['a',N+1,True,'y',0],['a',N+1,True,'y',0]])
check('retired proxy cannot revive', solve([['create','a',N,'x'],['destroy','a',N,None],['set','a',N,'z'],['pin','a',N,None]],), [['a',N,True,'x',0],['a',N,False,None,0],['a',N,False,None,0],['a',N,False,None,0]])
check('pinned destroy immediate', solve([['create','a',N,'x'],['pin','a',N,None],['destroy','a',N,None],['unpin','a',N,None]],), [['a',N,True,'x',0],['a',N,True,'x',1],['a',N,False,None,1],['a',N,False,None,0]])
check('unpin lower bound', solve([['create','a',0,'x'],['unpin','a',0,None],['set','a',0,'y']],), [['a',0,True,'x',0],['a',0,True,'x',0],['a',0,True,'y',0]])
check('unknown and negative', solve([['set','missing',0,'x'],['create','bad',-1,'x'],['get','missing',0,None]],), [None,None,None])
check('separate proxy IDs', solve([['create','a',N,'x'],['create','b',N,'y']],), [['a',N,True,'x',0],['b',N,True,'y',0]])
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
newer proxy preserves stale isolation	`[['a', 1, True, 'x', 0], ['a', 2, True, 'y', 0], ['a', 2, True, 'y', 0], ['a', 2, True, 'y', 0]]`	`[['a', 1, True, 'x', 0], ['a', 2, True, 'y', 0], ['a', 2, True, 'y', 0], ['a', 2, True, 'y', 0]]`	Passed
equal generation no reset	`[['a', 1, True, 'x', 0], ['a', 1, True, 'x', 1], ['a', 1, True, 'x', 1]]`	`[['a', 1, True, 'x', 0], ['a', 1, True, 'x', 1], ['a', 1, True, 'x', 1]]`	Passed
stale create and pinned generation	`[['a', 1, True, 'x', 0], ['a', 1, True, 'x', 1], ['a', 2, True, 'y', 0], ['a', 2, True, 'y', 0]]`	`[['a', 1, True, 'x', 0], ['a', 1, True, 'x', 1], ['a', 2, True, 'y', 0], ['a', 2, True, 'y', 0]]`	Passed
retired proxy cannot revive	`[['a', 1, True, 'x', 0], ['a', 1, False, None, 0], ['a', 1, False, None, 0], ['a', 1, False, None, 0]]`	`[['a', 1, True, 'x', 0], ['a', 1, False, None, 0], ['a', 1, False, None, 0], ['a', 1, False, None, 0]]`	Passed
pinned destroy immediate	`[['a', 1, True, 'x', 0], ['a', 1, True, 'x', 1], ['a', 1, False, None, 1], ['a', 1, False, None, 0]]`	`[['a', 1, True, 'x', 0], ['a', 1, True, 'x', 1], ['a', 1, False, None, 1], ['a', 1, False, None, 0]]`	Passed
unpin lower bound	`[['a', 0, True, 'x', 0], ['a', 0, True, 'x', 0], ['a', 0, True, 'y', 0]]`	`[['a', 0, True, 'x', 0], ['a', 0, True, 'x', 0], ['a', 0, True, 'y', 0]]`	Passed
unknown and negative	`[None, None, None]`	`[None, None, None]`	Passed
separate proxy IDs	`[['a', 1, True, 'x', 0], ['b', 1, True, 'y', 0]]`	`[['a', 1, True, 'x', 0], ['b', 1, True, 'y', 0]]`	Passed

SHA-256 / 77712f0bf52e23b28bf5b1b7774b7e7456ec7dd8b98bed4cdf22e5e7ee71edcb

Verification & scope

Stipulated finite adapter contract, not a claim of platform accessibility or ARIA conformance. 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 2026-09-29T14:45:40.582708+00:00.

Case digest / e7fc8cbd0d7c187a6cbd3078ea9f7c2eb74f26e51291cd0c02701b48f5cc9778