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FA-31116 / Keyboard interactions / Open access

Tap versus hold command arbitration: The pending state does not record that a hold has already dispatched · case 01

The event trace violates the mark emitted rule and produces incorrect keyboard state or command output.

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

ROOT CAUSE

The pending state does not record that a hold has already dispatched.

THE FAILURE

The pending state does not record that a hold has already dispatched.

Unsuccessful approach: The partial repair changes this transition to pending[k][0]=now, 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]=False
            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'], ['hold', 'A']], []]][[[['hold', 'A']], []]]Failed
hold-threshold scenario 5[[[['hold', 'A']], [['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[[[['hold', 'B']], [['B', 11, False]]]][[[['hold', 'B']], [['B', 11, True]]]]Failed
hold-threshold scenario 8[[[], []]][[[], []]]Passed

SHA-256 / 8b68ed66fc951378bc063c09da0f8c40e06e4ee8c5b7f2daf9759826350c55a6

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-start>=threshold:
                        output.append(['hold',k])
                        pending[k][0]=now
            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'], ['tap', 'A']], []]][[[['hold', 'A']], []]]Failed
hold-threshold scenario 5[[[['hold', 'A']], [['A', 15, 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[[[['hold', 'B']], [['B', 16, False]]]][[[['hold', 'B']], [['B', 11, True]]]]Failed
hold-threshold scenario 8[[[], []]][[[], []]]Passed

SHA-256 / c97248e2671ac804c1a6d68588c5fe45b4dfe379352778aa6a3e7c246da213fc

HELD IN THE MEMBER ARCHIVE

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

This mechanism has 9 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 2026-09-29T14:41:59.313471+00:00.

Case digest / e6e97813ce0407b18bd38548718f33766eb62704c43b1f6bb27ff1695ac43f78