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FA-31101 / Keyboard interactions / Open access

Tap versus hold command arbitration: Hold eligibility uses an exclusive boundary or absolute timestamp · case 01

The event trace violates the tick threshold rule and produces incorrect keyboard state or command output.

Verified by executionVariant 1 · 9 checks per implementationDownload source bundle ↓JSON ↗

ROOT CAUSE

Hold eligibility uses an exclusive boundary or absolute timestamp.

VERIFIED REPAIR

Use the contract transition `now-start>=threshold: output` at the tick threshold fault site; preserve the other state transitions.

Unsuccessful approach: The partial repair changes this transition to now>=threshold: output, which still violates the model contract on the explicit regression traces.

Case contract

Case [threshold,events]. Events [kind,key,time]. Down arms an unarmed key. Tick emits hold once when age >= threshold. Up before threshold emits tap, at or after threshold emits hold if not yet emitted. Cancel removes just one key silently. Return output and pending [key,start,held] entries. 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):
        threshold,events=c
        pending={}; output=[]
        for kind,key,now in events:
            if kind=='down' and key not in pending:
                pending[key]=[now,False]
            elif kind=='tick':
                for k in sorted(pending):
                    start,sent=pending[k]
                    if not sent and now-start>threshold:
                        output.append(['hold',k])
                        pending[k][1]=True
            elif kind=='up' and key in pending:
                start,sent=pending[key]
                if not sent:
                    output.append(['hold' if now-start>=threshold else 'tap',key])
                del pending[key]
            elif kind=='cancel':
                pending.pop(key,None)
        return [output,sorted([[k]+v for k,v in pending.items()])]
    return [run(c) for c in cases]
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
check('hold-threshold scenario 0', solve([[5, []]] * N), [[[], []]] * N)
check('hold-threshold scenario 1', solve([[5, [['down', 'A', 10], ['tick', '', 12]]]] * N), [[[], [['A', 10, False]]]] * N)
check('hold-threshold scenario 2', solve([[5, [['down', 'A', 10], ['up', 'A', 12]]]] * N), [[[['tap', 'A']], []]] * N)
check('hold-threshold scenario 3', solve([[5, [['down', 'A', 10], ['up', 'A', 15]]]] * N), [[[['hold', 'A']], []]] * N)
check('hold-threshold scenario 4', solve([[5, [['down', 'A', 10], ['tick', '', 15], ['tick', '', 16], ['up', 'A', 17]]]] * N), [[[['hold', 'A']], []]] * N)
check('hold-threshold scenario 5', solve([[5, [['down', 'A', 10], ['down', 'A', 13], ['tick', '', 15]]]] * N), [[[['hold', 'A']], [['A', 10, True]]]] * N)
check('hold-threshold scenario 6', solve([[5, [['down', 'A', 10], ['down', 'B', 11], ['up', 'A', 12]]]] * N), [[[['tap', 'A']], [['B', 11, False]]]] * N)
check('hold-threshold scenario 7', solve([[5, [['down', 'A', 10], ['down', 'B', 11], ['cancel', 'A', 12], ['tick', '', 16]]]] * N), [[[['hold', 'B']], [['B', 11, True]]]] * N)
check('hold-threshold scenario 8', solve([[5, [['up', 'A', 100]]]] * N), [[[], []]] * 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
hold-threshold scenario 0[[[], []]][[[], []]]Passed
hold-threshold scenario 1[[[], [['A', 10, False]]]][[[], [['A', 10, False]]]]Passed
hold-threshold scenario 2[[[['tap', 'A']], []]][[[['tap', 'A']], []]]Passed
hold-threshold scenario 3[[[['hold', 'A']], []]][[[['hold', 'A']], []]]Passed
hold-threshold scenario 4[[[['hold', 'A']], []]][[[['hold', 'A']], []]]Passed
hold-threshold scenario 5[[[], [['A', 10, False]]]][[[['hold', 'A']], [['A', 10, True]]]]Failed
hold-threshold scenario 6[[[['tap', 'A']], [['B', 11, False]]]][[[['tap', 'A']], [['B', 11, False]]]]Passed
hold-threshold scenario 7[[[], [['B', 11, False]]]][[[['hold', 'B']], [['B', 11, True]]]]Failed
hold-threshold scenario 8[[[], []]][[[], []]]Passed

SHA-256 / 1ea3013807f0d4617edff601c833db5331b3dd77f1c2c1a550440f77af38c9bb

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):
        threshold,events=c
        pending={}; output=[]
        for kind,key,now in events:
            if kind=='down' and key not in pending:
                pending[key]=[now,False]
            elif kind=='tick':
                for k in sorted(pending):
                    start,sent=pending[k]
                    if not sent and now>=threshold:
                        output.append(['hold',k])
                        pending[k][1]=True
            elif kind=='up' and key in pending:
                start,sent=pending[key]
                if not sent:
                    output.append(['hold' if now-start>=threshold else 'tap',key])
                del pending[key]
            elif kind=='cancel':
                pending.pop(key,None)
        return [output,sorted([[k]+v for k,v in pending.items()])]
    return [run(c) for c in cases]
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
check('hold-threshold scenario 0', solve([[5, []]] * N), [[[], []]] * N)
check('hold-threshold scenario 1', solve([[5, [['down', 'A', 10], ['tick', '', 12]]]] * N), [[[], [['A', 10, False]]]] * N)
check('hold-threshold scenario 2', solve([[5, [['down', 'A', 10], ['up', 'A', 12]]]] * N), [[[['tap', 'A']], []]] * N)
check('hold-threshold scenario 3', solve([[5, [['down', 'A', 10], ['up', 'A', 15]]]] * N), [[[['hold', 'A']], []]] * N)
check('hold-threshold scenario 4', solve([[5, [['down', 'A', 10], ['tick', '', 15], ['tick', '', 16], ['up', 'A', 17]]]] * N), [[[['hold', 'A']], []]] * N)
check('hold-threshold scenario 5', solve([[5, [['down', 'A', 10], ['down', 'A', 13], ['tick', '', 15]]]] * N), [[[['hold', 'A']], [['A', 10, True]]]] * N)
check('hold-threshold scenario 6', solve([[5, [['down', 'A', 10], ['down', 'B', 11], ['up', 'A', 12]]]] * N), [[[['tap', 'A']], [['B', 11, False]]]] * N)
check('hold-threshold scenario 7', solve([[5, [['down', 'A', 10], ['down', 'B', 11], ['cancel', 'A', 12], ['tick', '', 16]]]] * N), [[[['hold', 'B']], [['B', 11, True]]]] * N)
check('hold-threshold scenario 8', solve([[5, [['up', 'A', 100]]]] * N), [[[], []]] * 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
hold-threshold scenario 0[[[], []]][[[], []]]Passed
hold-threshold scenario 1[[[['hold', 'A']], [['A', 10, True]]]][[[], [['A', 10, False]]]]Failed
hold-threshold scenario 2[[[['tap', 'A']], []]][[[['tap', 'A']], []]]Passed
hold-threshold scenario 3[[[['hold', 'A']], []]][[[['hold', 'A']], []]]Passed
hold-threshold scenario 4[[[['hold', 'A']], []]][[[['hold', 'A']], []]]Passed
hold-threshold scenario 5[[[['hold', 'A']], [['A', 10, True]]]][[[['hold', 'A']], [['A', 10, True]]]]Passed
hold-threshold scenario 6[[[['tap', 'A']], [['B', 11, False]]]][[[['tap', 'A']], [['B', 11, False]]]]Passed
hold-threshold scenario 7[[[['hold', 'B']], [['B', 11, True]]]][[[['hold', 'B']], [['B', 11, True]]]]Passed
hold-threshold scenario 8[[[], []]][[[], []]]Passed

SHA-256 / f4020b15a90a712bad003b33ecc0abfa478f06b646200564dce88dd6082591ed

3 / The verified repair

Exit 0
"""Failure Map reference implementation. Python standard library only."""
import json

N = 1
observations = []
def solve(cases):
    def run(c):
        threshold,events=c
        pending={}; output=[]
        for kind,key,now in events:
            if kind=='down' and key not in pending:
                pending[key]=[now,False]
            elif kind=='tick':
                for k in sorted(pending):
                    start,sent=pending[k]
                    if not sent and now-start>=threshold:
                        output.append(['hold',k])
                        pending[k][1]=True
            elif kind=='up' and key in pending:
                start,sent=pending[key]
                if not sent:
                    output.append(['hold' if now-start>=threshold else 'tap',key])
                del pending[key]
            elif kind=='cancel':
                pending.pop(key,None)
        return [output,sorted([[k]+v for k,v in pending.items()])]
    return [run(c) for c in cases]
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
check('hold-threshold scenario 0', solve([[5, []]] * N), [[[], []]] * N)
check('hold-threshold scenario 1', solve([[5, [['down', 'A', 10], ['tick', '', 12]]]] * N), [[[], [['A', 10, False]]]] * N)
check('hold-threshold scenario 2', solve([[5, [['down', 'A', 10], ['up', 'A', 12]]]] * N), [[[['tap', 'A']], []]] * N)
check('hold-threshold scenario 3', solve([[5, [['down', 'A', 10], ['up', 'A', 15]]]] * N), [[[['hold', 'A']], []]] * N)
check('hold-threshold scenario 4', solve([[5, [['down', 'A', 10], ['tick', '', 15], ['tick', '', 16], ['up', 'A', 17]]]] * N), [[[['hold', 'A']], []]] * N)
check('hold-threshold scenario 5', solve([[5, [['down', 'A', 10], ['down', 'A', 13], ['tick', '', 15]]]] * N), [[[['hold', 'A']], [['A', 10, True]]]] * N)
check('hold-threshold scenario 6', solve([[5, [['down', 'A', 10], ['down', 'B', 11], ['up', 'A', 12]]]] * N), [[[['tap', 'A']], [['B', 11, False]]]] * N)
check('hold-threshold scenario 7', solve([[5, [['down', 'A', 10], ['down', 'B', 11], ['cancel', 'A', 12], ['tick', '', 16]]]] * N), [[[['hold', 'B']], [['B', 11, True]]]] * N)
check('hold-threshold scenario 8', solve([[5, [['up', 'A', 100]]]] * N), [[[], []]] * 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
hold-threshold scenario 0[[[], []]][[[], []]]Passed
hold-threshold scenario 1[[[], [['A', 10, False]]]][[[], [['A', 10, False]]]]Passed
hold-threshold scenario 2[[[['tap', 'A']], []]][[[['tap', 'A']], []]]Passed
hold-threshold scenario 3[[[['hold', 'A']], []]][[[['hold', 'A']], []]]Passed
hold-threshold scenario 4[[[['hold', 'A']], []]][[[['hold', 'A']], []]]Passed
hold-threshold scenario 5[[[['hold', 'A']], [['A', 10, True]]]][[[['hold', 'A']], [['A', 10, True]]]]Passed
hold-threshold scenario 6[[[['tap', 'A']], [['B', 11, False]]]][[[['tap', 'A']], [['B', 11, False]]]]Passed
hold-threshold scenario 7[[[['hold', 'B']], [['B', 11, True]]]][[[['hold', 'B']], [['B', 11, True]]]]Passed
hold-threshold scenario 8[[[], []]][[[], []]]Passed

SHA-256 / 3559c584388395b9ad7f21e5c69727bd641bfedebef31b5afa7ed39ccfc09a19

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 2026-09-29T14:41:59.006983+00:00.

Case digest / 0d3a4ff860602e21ffa79460189716401107508fa797eb829b20eca9253924fd