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FA-31951 / Keyboard interactions / Open access

Multi-tap keyboard character commit timing: Multi-tap character cycling saturates or moves backward instead of wrapping · case 01

The event trace violates the cycle wrap rule and produces incorrect keyboard state or command output.

Verified by executionVariant 1 · 10 checks per implementationDownload source bundle ↓JSON ↗

ROOT CAUSE

Multi-tap character cycling saturates or moves backward instead of wrapping.

THE FAILURE

Multi-tap character cycling saturates or moves backward instead of wrapping.

Unsuccessful approach: The partial repair changes this transition to (pending[1]-1)%len(mapping[value]), which still violates the model contract on the explicit regression traces.

Case contract

Case [map,window,events]. Map maps keys to nonempty character strings. Events [kind,value,time]. Valid press cycles the pending same-key character before deadline, otherwise commits previous and starts new. Tick at or past deadline commits. Backspace cancels pending character before deleting committed text. Space commits pending then adds space; cancel drops pending only. Unknown press is ignored. Return committed text and pending [key,index,deadline] or None. Inputs are finite ordered event traces; return the stated deterministic state. Batch entries are independent. N varies the number of independent input transactions.

Why this case matters

Controlled keyboard event processing model for debugging application event logic.

1 / The failure

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

N = 1
observations = []
def solve(cases):
    def run(c):
        mapping,window,events=c
        text=''; pending=None
        for kind,value,now in events:
            if kind=='press' and value in mapping:
                if pending is not None and now>=pending[2]:
                    text+=mapping[pending[0]][pending[1]]; pending=None
                if pending is not None and pending[0]==value:
                    pending[1]=min(pending[1]+1,len(mapping[value])-1)
                    pending[2]=now+window
                else:
                    if pending is not None: text+=mapping[pending[0]][pending[1]]
                    pending=[value,0,now+window]
            elif kind=='tick' and pending is not None and now>=pending[2]:
                text+=mapping[pending[0]][pending[1]]; pending=None
            elif kind=='backspace':
                if pending is not None: pending=None
                else: text=text[:-1]
            elif kind=='space':
                if pending is not None: text+=mapping[pending[0]][pending[1]]
                pending=None; text+=' '
            elif kind=='cancel': pending=None
        return [text,pending]
    return [run(c) for c in cases]
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
check('multi-tap-keypad scenario 0', solve([[{'2': 'abc', '3': 'de'}, 5, [['press', '2', 10], ['press', '2', 11]]]] * N), [['', ['2', 1, 16]]] * N)
check('multi-tap-keypad scenario 1', solve([[{'2': 'abc', '3': 'de'}, 5, []]] * N), [['', None]] * N)
check('multi-tap-keypad scenario 2', solve([[{'2': 'abc', '3': 'de'}, 5, [['press', '2', 10], ['press', '2', 11], ['press', '2', 12], ['press', '2', 13], ['tick', '', 18]]]] * N), [['a', None]] * N)
check('multi-tap-keypad scenario 3', solve([[{'2': 'abc', '3': 'de'}, 5, [['press', '2', 10], ['press', '2', 15]]]] * N), [['a', ['2', 0, 20]]] * N)
check('multi-tap-keypad scenario 4', solve([[{'2': 'abc', '3': 'de'}, 5, [['press', '2', 10], ['press', '3', 12], ['tick', '', 17]]]] * N), [['ad', None]] * N)
check('multi-tap-keypad scenario 5', solve([[{'2': 'abc', '3': 'de'}, 5, [['press', '2', 10], ['tick', '', 12]]]] * N), [['', ['2', 0, 15]]] * N)
check('multi-tap-keypad scenario 6', solve([[{'2': 'abc', '3': 'de'}, 5, [['press', '2', 10], ['tick', '', 15], ['press', '3', 16], ['backspace', '', 17]]]] * N), [['a', None]] * N)
check('multi-tap-keypad scenario 7', solve([[{'2': 'abc', '3': 'de'}, 5, [['press', '2', 10], ['press', '3', 11], ['space', '', 12], ['backspace', '', 13]]]] * N), [['ad', None]] * N)
check('multi-tap-keypad scenario 8', solve([[{'2': 'abc', '3': 'de'}, 5, [['press', '2', 10], ['space', '', 12]]]] * N), [['a ', None]] * N)
check('multi-tap-keypad scenario 9', solve([[{'2': 'abc', '3': 'de'}, 5, [['press', '?', 10], ['backspace', '', 11]]]] * N), [['', None]] * N)
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
multi-tap-keypad scenario 0[['', ['2', 1, 16]]][['', ['2', 1, 16]]]Passed
multi-tap-keypad scenario 1[['', None]][['', None]]Passed
multi-tap-keypad scenario 2[['c', None]][['a', None]]Failed
multi-tap-keypad scenario 3[['a', ['2', 0, 20]]][['a', ['2', 0, 20]]]Passed
multi-tap-keypad scenario 4[['ad', None]][['ad', None]]Passed
multi-tap-keypad scenario 5[['', ['2', 0, 15]]][['', ['2', 0, 15]]]Passed
multi-tap-keypad scenario 6[['a', None]][['a', None]]Passed
multi-tap-keypad scenario 7[['ad', None]][['ad', None]]Passed
multi-tap-keypad scenario 8[['a ', None]][['a ', None]]Passed
multi-tap-keypad scenario 9[['', None]][['', None]]Passed

SHA-256 / 23513da1b1d0fe2e25a800794cdeb3e48c3a6ac03ff6f31bf63cbb9ae28e0c73

2 / The unsuccessful fix

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

N = 1
observations = []
def solve(cases):
    def run(c):
        mapping,window,events=c
        text=''; pending=None
        for kind,value,now in events:
            if kind=='press' and value in mapping:
                if pending is not None and now>=pending[2]:
                    text+=mapping[pending[0]][pending[1]]; pending=None
                if pending is not None and pending[0]==value:
                    pending[1]=(pending[1]-1)%len(mapping[value])
                    pending[2]=now+window
                else:
                    if pending is not None: text+=mapping[pending[0]][pending[1]]
                    pending=[value,0,now+window]
            elif kind=='tick' and pending is not None and now>=pending[2]:
                text+=mapping[pending[0]][pending[1]]; pending=None
            elif kind=='backspace':
                if pending is not None: pending=None
                else: text=text[:-1]
            elif kind=='space':
                if pending is not None: text+=mapping[pending[0]][pending[1]]
                pending=None; text+=' '
            elif kind=='cancel': pending=None
        return [text,pending]
    return [run(c) for c in cases]
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
check('multi-tap-keypad scenario 0', solve([[{'2': 'abc', '3': 'de'}, 5, [['press', '2', 10], ['press', '2', 11]]]] * N), [['', ['2', 1, 16]]] * N)
check('multi-tap-keypad scenario 1', solve([[{'2': 'abc', '3': 'de'}, 5, []]] * N), [['', None]] * N)
check('multi-tap-keypad scenario 2', solve([[{'2': 'abc', '3': 'de'}, 5, [['press', '2', 10], ['press', '2', 11], ['press', '2', 12], ['press', '2', 13], ['tick', '', 18]]]] * N), [['a', None]] * N)
check('multi-tap-keypad scenario 3', solve([[{'2': 'abc', '3': 'de'}, 5, [['press', '2', 10], ['press', '2', 15]]]] * N), [['a', ['2', 0, 20]]] * N)
check('multi-tap-keypad scenario 4', solve([[{'2': 'abc', '3': 'de'}, 5, [['press', '2', 10], ['press', '3', 12], ['tick', '', 17]]]] * N), [['ad', None]] * N)
check('multi-tap-keypad scenario 5', solve([[{'2': 'abc', '3': 'de'}, 5, [['press', '2', 10], ['tick', '', 12]]]] * N), [['', ['2', 0, 15]]] * N)
check('multi-tap-keypad scenario 6', solve([[{'2': 'abc', '3': 'de'}, 5, [['press', '2', 10], ['tick', '', 15], ['press', '3', 16], ['backspace', '', 17]]]] * N), [['a', None]] * N)
check('multi-tap-keypad scenario 7', solve([[{'2': 'abc', '3': 'de'}, 5, [['press', '2', 10], ['press', '3', 11], ['space', '', 12], ['backspace', '', 13]]]] * N), [['ad', None]] * N)
check('multi-tap-keypad scenario 8', solve([[{'2': 'abc', '3': 'de'}, 5, [['press', '2', 10], ['space', '', 12]]]] * N), [['a ', None]] * N)
check('multi-tap-keypad scenario 9', solve([[{'2': 'abc', '3': 'de'}, 5, [['press', '?', 10], ['backspace', '', 11]]]] * N), [['', None]] * N)
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
multi-tap-keypad scenario 0[['', ['2', 2, 16]]][['', ['2', 1, 16]]]Failed
multi-tap-keypad scenario 1[['', None]][['', None]]Passed
multi-tap-keypad scenario 2[['a', None]][['a', None]]Passed
multi-tap-keypad scenario 3[['a', ['2', 0, 20]]][['a', ['2', 0, 20]]]Passed
multi-tap-keypad scenario 4[['ad', None]][['ad', None]]Passed
multi-tap-keypad scenario 5[['', ['2', 0, 15]]][['', ['2', 0, 15]]]Passed
multi-tap-keypad scenario 6[['a', None]][['a', None]]Passed
multi-tap-keypad scenario 7[['ad', None]][['ad', None]]Passed
multi-tap-keypad scenario 8[['a ', None]][['a ', None]]Passed
multi-tap-keypad scenario 9[['', None]][['', None]]Passed

SHA-256 / 259779f3f3571b00db3d16471d81a598ba3d10297cb6ebc8b37cbe8cdf732b85

HELD IN THE MEMBER ARCHIVE

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

This mechanism has 10 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

Offline stipulated event model, not a browser implementation or web standard conformance claim. 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 2026-09-29T14:42:07.521250+00:00.

Case digest / a9689e35652622f2a9ac700a1e9d9b74a681bbf6ad331170621862cc6285aa90