FA-8701 / Overlay interactions / Open access

Overlay dismissal stack: Unmounting one layer retains only the removed layer · case 01

Unmounting one layer retains only the removed layer.

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

ROOT CAUSE

The remove id operation uses `x['id'] == target` where the contract requires `x['id'] != target`.

VERIFIED REPAIR

Implement the remove id operation as `x['id'] != target`.

Unsuccessful approach: Clearing all layers destroys unrelated overlays.

Case contract

Only the topmost overlay handles Escape/outside policy; inside descendants are exempt; explicit unmount removes only its identity.

Why this case matters

A deterministic model of overlay dismissal stack; this isolates one interface invariant without requiring a browser.

1 / The failure

Exit 1

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

N = 1
observations = []
def solve(layers, event, target):
    layers = [dict(x) for x in layers]
    if not layers: return layers
    active = layers[-1]
    if event == 'escape' and active['escape']: return layers[:-1]
    if event == 'outside' and active['outside'] and target not in active['inside']: return layers[:-1]
    if event == 'remove': return [x for x in layers if x['id'] == target]
    return layers
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
check('topmost', solve([dict(id='a',escape=False,outside=False,inside=['a']),dict(id='z',escape=True,outside=True,inside=['z'])], 'escape', None), [{'id': 'a', 'escape': False, 'outside': False, 'inside': ['a']}])
check('protected escape', solve([dict(id='a',escape=False,outside=False,inside=['a'])], 'escape', None), [{'id': 'a', 'escape': False, 'outside': False, 'inside': ['a']}])
check('protected outside', solve([dict(id='a',escape=True,outside=False,inside=['a'])], 'outside', 'x'), [{'id': 'a', 'escape': True, 'outside': False, 'inside': ['a']}])
check('inside child', solve([dict(id='a',escape=True,outside=True,inside=['a','child'])], 'outside', 'child'), [{'id': 'a', 'escape': True, 'outside': True, 'inside': ['a', 'child']}])
check('outside', solve([dict(id='a',escape=True,outside=True,inside=['a'])], 'outside', 'x'), [])
check('remove', solve([dict(id='a',escape=True,outside=True,inside=['a']),dict(id='b',escape=True,outside=True,inside=['b'])], 'remove', 'a'), [{'id': 'b', 'escape': True, 'outside': True, 'inside': ['b']}])
check('parameterized stack depth', solve([dict(id=str(i),escape=True,outside=True,inside=[str(i)]) for i in range(N)],'escape',None), [dict(id=str(i),escape=True,outside=True,inside=[str(i)]) for i in range(N-1)])
for repetition in range(N):
    check('repeat remove', solve([dict(id='a',escape=True,outside=True,inside=['a']),dict(id='b',escape=True,outside=True,inside=['b'])], 'remove', 'a'), [{'id': 'b', 'escape': True, 'outside': True, 'inside': ['b']}])
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
topmost	`[{'escape': False, 'id': 'a', 'inside': ['a'], 'outside': False}]`	`[{'escape': False, 'id': 'a', 'inside': ['a'], 'outside': False}]`	Passed
protected escape	`[{'escape': False, 'id': 'a', 'inside': ['a'], 'outside': False}]`	`[{'escape': False, 'id': 'a', 'inside': ['a'], 'outside': False}]`	Passed
protected outside	`[{'escape': True, 'id': 'a', 'inside': ['a'], 'outside': False}]`	`[{'escape': True, 'id': 'a', 'inside': ['a'], 'outside': False}]`	Passed
inside child	`[{'escape': True, 'id': 'a', 'inside': ['a', 'child'], 'outside': True}]`	`[{'escape': True, 'id': 'a', 'inside': ['a', 'child'], 'outside': True}]`	Passed
outside	`[]`	`[]`	Passed
remove	`[{'escape': True, 'id': 'a', 'inside': ['a'], 'outside': True}]`	`[{'escape': True, 'id': 'b', 'inside': ['b'], 'outside': True}]`	Failed
parameterized stack depth	`[]`	`[]`	Passed
repeat remove	`[{'escape': True, 'id': 'a', 'inside': ['a'], 'outside': True}]`	`[{'escape': True, 'id': 'b', 'inside': ['b'], 'outside': True}]`	Failed

SHA-256 / ca4907e21c5456e2068b0820733e975017c7c582d4dd64c4797d3e1f4ab652ac

2 / The unsuccessful fix

Exit 1

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

N = 1
observations = []
def solve(layers, event, target):
    layers = [dict(x) for x in layers]
    if not layers: return layers
    active = layers[-1]
    if event == 'escape' and active['escape']: return layers[:-1]
    if event == 'outside' and active['outside'] and target not in active['inside']: return layers[:-1]
    if event == 'remove': return [x for x in layers if False]
    return layers
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
check('topmost', solve([dict(id='a',escape=False,outside=False,inside=['a']),dict(id='z',escape=True,outside=True,inside=['z'])], 'escape', None), [{'id': 'a', 'escape': False, 'outside': False, 'inside': ['a']}])
check('protected escape', solve([dict(id='a',escape=False,outside=False,inside=['a'])], 'escape', None), [{'id': 'a', 'escape': False, 'outside': False, 'inside': ['a']}])
check('protected outside', solve([dict(id='a',escape=True,outside=False,inside=['a'])], 'outside', 'x'), [{'id': 'a', 'escape': True, 'outside': False, 'inside': ['a']}])
check('inside child', solve([dict(id='a',escape=True,outside=True,inside=['a','child'])], 'outside', 'child'), [{'id': 'a', 'escape': True, 'outside': True, 'inside': ['a', 'child']}])
check('outside', solve([dict(id='a',escape=True,outside=True,inside=['a'])], 'outside', 'x'), [])
check('remove', solve([dict(id='a',escape=True,outside=True,inside=['a']),dict(id='b',escape=True,outside=True,inside=['b'])], 'remove', 'a'), [{'id': 'b', 'escape': True, 'outside': True, 'inside': ['b']}])
check('parameterized stack depth', solve([dict(id=str(i),escape=True,outside=True,inside=[str(i)]) for i in range(N)],'escape',None), [dict(id=str(i),escape=True,outside=True,inside=[str(i)]) for i in range(N-1)])
for repetition in range(N):
    check('repeat remove', solve([dict(id='a',escape=True,outside=True,inside=['a']),dict(id='b',escape=True,outside=True,inside=['b'])], 'remove', 'a'), [{'id': 'b', 'escape': True, 'outside': True, 'inside': ['b']}])
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
topmost	`[{'escape': False, 'id': 'a', 'inside': ['a'], 'outside': False}]`	`[{'escape': False, 'id': 'a', 'inside': ['a'], 'outside': False}]`	Passed
protected escape	`[{'escape': False, 'id': 'a', 'inside': ['a'], 'outside': False}]`	`[{'escape': False, 'id': 'a', 'inside': ['a'], 'outside': False}]`	Passed
protected outside	`[{'escape': True, 'id': 'a', 'inside': ['a'], 'outside': False}]`	`[{'escape': True, 'id': 'a', 'inside': ['a'], 'outside': False}]`	Passed
inside child	`[{'escape': True, 'id': 'a', 'inside': ['a', 'child'], 'outside': True}]`	`[{'escape': True, 'id': 'a', 'inside': ['a', 'child'], 'outside': True}]`	Passed
outside	`[]`	`[]`	Passed
remove	`[]`	`[{'escape': True, 'id': 'b', 'inside': ['b'], 'outside': True}]`	Failed
parameterized stack depth	`[]`	`[]`	Passed
repeat remove	`[]`	`[{'escape': True, 'id': 'b', 'inside': ['b'], 'outside': True}]`	Failed

SHA-256 / d3d37b1054dc3d235a75d8b48c06d9e76d118c22082fcdcd531f8b9b5bc7c8cb

3 / The verified repair

Exit 0

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

N = 1
observations = []
def solve(layers, event, target):
    layers = [dict(x) for x in layers]
    if not layers: return layers
    active = layers[-1]
    if event == 'escape' and active['escape']: return layers[:-1]
    if event == 'outside' and active['outside'] and target not in active['inside']: return layers[:-1]
    if event == 'remove': return [x for x in layers if x['id'] != target]
    return layers
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
check('topmost', solve([dict(id='a',escape=False,outside=False,inside=['a']),dict(id='z',escape=True,outside=True,inside=['z'])], 'escape', None), [{'id': 'a', 'escape': False, 'outside': False, 'inside': ['a']}])
check('protected escape', solve([dict(id='a',escape=False,outside=False,inside=['a'])], 'escape', None), [{'id': 'a', 'escape': False, 'outside': False, 'inside': ['a']}])
check('protected outside', solve([dict(id='a',escape=True,outside=False,inside=['a'])], 'outside', 'x'), [{'id': 'a', 'escape': True, 'outside': False, 'inside': ['a']}])
check('inside child', solve([dict(id='a',escape=True,outside=True,inside=['a','child'])], 'outside', 'child'), [{'id': 'a', 'escape': True, 'outside': True, 'inside': ['a', 'child']}])
check('outside', solve([dict(id='a',escape=True,outside=True,inside=['a'])], 'outside', 'x'), [])
check('remove', solve([dict(id='a',escape=True,outside=True,inside=['a']),dict(id='b',escape=True,outside=True,inside=['b'])], 'remove', 'a'), [{'id': 'b', 'escape': True, 'outside': True, 'inside': ['b']}])
check('parameterized stack depth', solve([dict(id=str(i),escape=True,outside=True,inside=[str(i)]) for i in range(N)],'escape',None), [dict(id=str(i),escape=True,outside=True,inside=[str(i)]) for i in range(N-1)])
for repetition in range(N):
    check('repeat remove', solve([dict(id='a',escape=True,outside=True,inside=['a']),dict(id='b',escape=True,outside=True,inside=['b'])], 'remove', 'a'), [{'id': 'b', 'escape': True, 'outside': True, 'inside': ['b']}])
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
topmost	`[{'escape': False, 'id': 'a', 'inside': ['a'], 'outside': False}]`	`[{'escape': False, 'id': 'a', 'inside': ['a'], 'outside': False}]`	Passed
protected escape	`[{'escape': False, 'id': 'a', 'inside': ['a'], 'outside': False}]`	`[{'escape': False, 'id': 'a', 'inside': ['a'], 'outside': False}]`	Passed
protected outside	`[{'escape': True, 'id': 'a', 'inside': ['a'], 'outside': False}]`	`[{'escape': True, 'id': 'a', 'inside': ['a'], 'outside': False}]`	Passed
inside child	`[{'escape': True, 'id': 'a', 'inside': ['a', 'child'], 'outside': True}]`	`[{'escape': True, 'id': 'a', 'inside': ['a', 'child'], 'outside': True}]`	Passed
outside	`[]`	`[]`	Passed
remove	`[{'escape': True, 'id': 'b', 'inside': ['b'], 'outside': True}]`	`[{'escape': True, 'id': 'b', 'inside': ['b'], 'outside': True}]`	Passed
parameterized stack depth	`[]`	`[]`	Passed
repeat remove	`[{'escape': True, 'id': 'b', 'inside': ['b'], 'outside': True}]`	`[{'escape': True, 'id': 'b', 'inside': ['b'], 'outside': True}]`	Passed

SHA-256 / 15ba81ce96041653330d7722eb8d4b4ef5e335c8b061eb8bdf21fd3f701eb989

Verification & scope

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 2026-09-29T14:38:23.702969+00:00.

Case digest / 19845149b764ec49679623503f8570b596766ec32aab11c8481b3e76198a25a0