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FA-54831 / Accessibility interaction semantics / Open access

Equal-stack semantic objects reverse native encounter precedence · case 01

Equal-stack semantic objects reverse native encounter precedence.

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

ROOT CAUSE

The stack tie decision in the platform hit adapter adapter violates its declared contract.

THE FAILURE

The stack tie decision in the platform hit adapter adapter violates its declared contract.

Unsuccessful approach: The local repair substitutes (z,index+1,proxy if proxy else ident) but still mishandles the regression fixtures.

Case contract

Input [window_origin,scroll,point,records,expected_window]. Pointer is screen coordinates. Convert to document coordinates by subtracting window_origin and adding scroll. Records [id,window,rect,z,exposed,transparent,clip,proxy,enabled]; rect and optional clip are [x0,y0,x1,y1], half-open. Zero/reversed rectangles never hit. Reject other windows or unexposed records. Transparent records do not themselves hit. Reject points outside clip. Among hits largest z wins, ties retain first input. Disabled semantics remain inspectable. Return proxy ID when nonempty, else own ID, plus [document_x,document_y]. None when no hit. This is semantic hit selection, not pixel rendering or focus navigation.

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):
    origin,scroll,point,records,window = data
    x,y = point[0]-origin[0]+scroll[0],point[1]-origin[1]+scroll[1]
    hits = []
    for index,(ident,owner,rect,z,exposed,transparent,clip,proxy,enabled) in enumerate(records):
        if owner != window or not exposed or transparent: continue
        x0,y0,x1,y1 = rect
        if not (x0 <= x < x1 and y0 <= y < y1): continue
        if clip is not None and not (clip[0] <= x < clip[2] and clip[1] <= y < clip[3]): continue
        hits.append((z,index,proxy if proxy else ident))
    if not hits: return None
    return [max(hits,key=lambda hit:(hit[0],hit[1]))[2],[x,y]]
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
check('contract fixture 1', solve([[N,10],[N+1,3],[N+1,11],[['a','w',[0,0,8,8],1,True,False,None,'',True]],'w'],), ['a',[N+2,4]])
check('contract fixture 2', solve([[0,0],[0,0],[1,1],[['back','w',[0,0,4,4],1,True,False,None,'',True],['front','w',[0,0,4,4],5,True,False,None,'proxy',False]],'w'],), ['proxy',[1,1]])
check('contract fixture 3', solve([[0,0],[0,0],[1,1],[['first','w',[0,0,4,4],2,True,False,None,'',True],['second','w',[0,0,4,4],2,True,False,None,'',True]],'w'],), ['first',[1,1]])
check('contract fixture 4', solve([[0,0],[0,0],[1,1],[['a','other',[0,0,4,4],1,True,False,None,'',True],['b','w',[0,0,4,4],2,False,False,None,'',True],['c','w',[0,0,4,4],3,True,True,None,'',True]],'w'],), None)
check('contract fixture 5', solve([[0,0],[0,0],[4,1],[['a','w',[0,0,4,4],1,True,False,None,'',True]],'w'],), None)
check('contract fixture 6', solve([[0,0],[0,0],[2,2],[['a','w',[0,0,4,4],1,True,False,[0,0,2,2],'',True]],'w'],), None)
check('contract fixture 7', solve([[0,0],[0,0],[0,0],[['a','w',[0,0,4,4],1,True,False,None,'',True]],'w'],), ['a',[0,0]])
check('contract fixture 8', solve([[0,0],[0,0],[1,1],[],'w'],), None)
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
contract fixture 1['a', [3, 4]]['a', [3, 4]]Passed
contract fixture 2['proxy', [1, 1]]['proxy', [1, 1]]Passed
contract fixture 3['second', [1, 1]]['first', [1, 1]]Failed
contract fixture 4NoneNonePassed
contract fixture 5NoneNonePassed
contract fixture 6NoneNonePassed
contract fixture 7['a', [0, 0]]['a', [0, 0]]Passed
contract fixture 8NoneNonePassed

SHA-256 / 6d4b1994f12b08804cb2d2ba602e26cbee2ce8a8ee30bacc3803a72b8225c24a

2 / The unsuccessful fix

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

N = 1
observations = []
def solve(data):
    origin,scroll,point,records,window = data
    x,y = point[0]-origin[0]+scroll[0],point[1]-origin[1]+scroll[1]
    hits = []
    for index,(ident,owner,rect,z,exposed,transparent,clip,proxy,enabled) in enumerate(records):
        if owner != window or not exposed or transparent: continue
        x0,y0,x1,y1 = rect
        if not (x0 <= x < x1 and y0 <= y < y1): continue
        if clip is not None and not (clip[0] <= x < clip[2] and clip[1] <= y < clip[3]): continue
        hits.append((z,index+1,proxy if proxy else ident))
    if not hits: return None
    return [max(hits,key=lambda hit:(hit[0],hit[1]))[2],[x,y]]
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
check('contract fixture 1', solve([[N,10],[N+1,3],[N+1,11],[['a','w',[0,0,8,8],1,True,False,None,'',True]],'w'],), ['a',[N+2,4]])
check('contract fixture 2', solve([[0,0],[0,0],[1,1],[['back','w',[0,0,4,4],1,True,False,None,'',True],['front','w',[0,0,4,4],5,True,False,None,'proxy',False]],'w'],), ['proxy',[1,1]])
check('contract fixture 3', solve([[0,0],[0,0],[1,1],[['first','w',[0,0,4,4],2,True,False,None,'',True],['second','w',[0,0,4,4],2,True,False,None,'',True]],'w'],), ['first',[1,1]])
check('contract fixture 4', solve([[0,0],[0,0],[1,1],[['a','other',[0,0,4,4],1,True,False,None,'',True],['b','w',[0,0,4,4],2,False,False,None,'',True],['c','w',[0,0,4,4],3,True,True,None,'',True]],'w'],), None)
check('contract fixture 5', solve([[0,0],[0,0],[4,1],[['a','w',[0,0,4,4],1,True,False,None,'',True]],'w'],), None)
check('contract fixture 6', solve([[0,0],[0,0],[2,2],[['a','w',[0,0,4,4],1,True,False,[0,0,2,2],'',True]],'w'],), None)
check('contract fixture 7', solve([[0,0],[0,0],[0,0],[['a','w',[0,0,4,4],1,True,False,None,'',True]],'w'],), ['a',[0,0]])
check('contract fixture 8', solve([[0,0],[0,0],[1,1],[],'w'],), None)
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
contract fixture 1['a', [3, 4]]['a', [3, 4]]Passed
contract fixture 2['proxy', [1, 1]]['proxy', [1, 1]]Passed
contract fixture 3['second', [1, 1]]['first', [1, 1]]Failed
contract fixture 4NoneNonePassed
contract fixture 5NoneNonePassed
contract fixture 6NoneNonePassed
contract fixture 7['a', [0, 0]]['a', [0, 0]]Passed
contract fixture 8NoneNonePassed

SHA-256 / cad0ff56ea598df1b6c3325c9e49920daebabdfe421a31eae73a23cc0aad20e7

HELD IN THE MEMBER ARCHIVE

The verified repair and its recorded checks are member-only.

This mechanism has 8 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

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 2026-09-29T14:45:52.055960+00:00.

Case digest / 49329e707fbd272efc8dc849a99c7c1bf9be761991229f224cec3abcd3fdb24e