FA-31661 / Keyboard interactions / Open access

Per-switch keyboard scan debounce: Debounce dwell time is measured from the epoch or the first-ever contact transition · case 01

The event trace violates the timer origin rule and produces incorrect keyboard state or command output.

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

ROOT CAUSE

Debounce dwell time is measured from the epoch or the first-ever contact transition.

THE FAILURE

Debounce dwell time is measured from the epoch or the first-ever contact transition.

Unsuccessful approach: The partial repair changes this transition to since.setdefault(key,now), which still violates the model contract on the explicit regression traces.

Case contract

Case [threshold,scans]. Each scan is [time,sorted_pressed_keys] and times increase. A raw transition starts a candidate timer; a candidate becomes stable after continuously present for threshold time including exact boundary. Each scan considers every known or raw key. Emit [key,down_or_up,time] on stable transitions; return emissions plus stable pressed keys. Missing keys are raw up. 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,scans=c
        stable={}; candidate={}; since={}; output=[]
        for now,pressed in scans:
            raw=set(pressed)
            keys=sorted(set(stable)|set(candidate)|raw)
            for key in keys:
                value=key in raw
                if key not in candidate or candidate[key]!=value:
                    candidate[key]=value
                    since[key]=0
                if now-since[key]>=threshold and stable.get(key,False)!=value:
                    stable[key]=value
                    output.append([key,'down' if value else 'up',now])
        return [output,sorted(k for k,v in stable.items() if v)]
    return [run(c) for c in cases]
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
check('key-debounce scenario 0', solve([[3, []]] * N), [[[], []]] * N)
check('key-debounce scenario 1', solve([[3, [[10, ['A']], [12, ['A']], [13, ['A']], [14, ['A']]]]] * N), [[[['A', 'down', 13]], ['A']]] * N)
check('key-debounce scenario 2', solve([[3, [[10, ['A']], [13, ['A']], [14, []], [17, []]]]] * N), [[[['A', 'down', 13], ['A', 'up', 17]], []]] * N)
check('key-debounce scenario 3', solve([[3, [[10, ['A']], [11, []], [12, ['A']], [14, ['A']], [15, ['A']]]]] * N), [[[['A', 'down', 15]], ['A']]] * N)
check('key-debounce scenario 4', solve([[3, [[10, ['A']], [13, ['A']], [14, ['B']], [17, ['B']]]]] * N), [[[['A', 'down', 13], ['A', 'up', 17], ['B', 'down', 17]], ['B']]] * N)
check('key-debounce scenario 5', solve([[3, [[10, ['A']], [11, []], [14, []]]]] * N), [[[], []]] * N)
check('key-debounce scenario 6', solve([[3, [[10, []], [20, ['A', 'B']], [23, ['A', 'B']], [24, ['B']], [27, ['B']]]]] * N), [[[['A', 'down', 23], ['B', 'down', 23], ['A', 'up', 27]], ['B']]] * N)
check('key-debounce scenario 7', solve([[3, [[10, ['A']], [13, ['A']], [14, []], [15, ['A']], [18, ['A']]]]] * N), [[[['A', 'down', 13]], ['A']]] * 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 fixture	Actual	Expected	Outcome
key-debounce scenario 0	`[[[], []]]`	`[[[], []]]`	Passed
key-debounce scenario 1	`[[[['A', 'down', 10]], ['A']]]`	`[[[['A', 'down', 13]], ['A']]]`	Failed
key-debounce scenario 2	`[[[['A', 'down', 10], ['A', 'up', 14]], []]]`	`[[[['A', 'down', 13], ['A', 'up', 17]], []]]`	Failed
key-debounce scenario 3	`[[[['A', 'down', 10], ['A', 'up', 11], ['A', 'down', 12]], ['A']]]`	`[[[['A', 'down', 15]], ['A']]]`	Failed
key-debounce scenario 4	`[[[['A', 'down', 10], ['A', 'up', 14], ['B', 'down', 14]], ['B']]]`	`[[[['A', 'down', 13], ['A', 'up', 17], ['B', 'down', 17]], ['B']]]`	Failed
key-debounce scenario 5	`[[[['A', 'down', 10], ['A', 'up', 11]], []]]`	`[[[], []]]`	Failed
key-debounce scenario 6	`[[[['A', 'down', 20], ['B', 'down', 20], ['A', 'up', 24]], ['B']]]`	`[[[['A', 'down', 23], ['B', 'down', 23], ['A', 'up', 27]], ['B']]]`	Failed
key-debounce scenario 7	`[[[['A', 'down', 10], ['A', 'up', 14], ['A', 'down', 15]], ['A']]]`	`[[[['A', 'down', 13]], ['A']]]`	Failed

SHA-256 / 15e351bfb1dcb14bc1fad6c7ca4719474a22e713f6c6f34ac1650f7e353165bd

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,scans=c
        stable={}; candidate={}; since={}; output=[]
        for now,pressed in scans:
            raw=set(pressed)
            keys=sorted(set(stable)|set(candidate)|raw)
            for key in keys:
                value=key in raw
                if key not in candidate or candidate[key]!=value:
                    candidate[key]=value
                    since.setdefault(key,now)
                if now-since[key]>=threshold and stable.get(key,False)!=value:
                    stable[key]=value
                    output.append([key,'down' if value else 'up',now])
        return [output,sorted(k for k,v in stable.items() if v)]
    return [run(c) for c in cases]
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
check('key-debounce scenario 0', solve([[3, []]] * N), [[[], []]] * N)
check('key-debounce scenario 1', solve([[3, [[10, ['A']], [12, ['A']], [13, ['A']], [14, ['A']]]]] * N), [[[['A', 'down', 13]], ['A']]] * N)
check('key-debounce scenario 2', solve([[3, [[10, ['A']], [13, ['A']], [14, []], [17, []]]]] * N), [[[['A', 'down', 13], ['A', 'up', 17]], []]] * N)
check('key-debounce scenario 3', solve([[3, [[10, ['A']], [11, []], [12, ['A']], [14, ['A']], [15, ['A']]]]] * N), [[[['A', 'down', 15]], ['A']]] * N)
check('key-debounce scenario 4', solve([[3, [[10, ['A']], [13, ['A']], [14, ['B']], [17, ['B']]]]] * N), [[[['A', 'down', 13], ['A', 'up', 17], ['B', 'down', 17]], ['B']]] * N)
check('key-debounce scenario 5', solve([[3, [[10, ['A']], [11, []], [14, []]]]] * N), [[[], []]] * N)
check('key-debounce scenario 6', solve([[3, [[10, []], [20, ['A', 'B']], [23, ['A', 'B']], [24, ['B']], [27, ['B']]]]] * N), [[[['A', 'down', 23], ['B', 'down', 23], ['A', 'up', 27]], ['B']]] * N)
check('key-debounce scenario 7', solve([[3, [[10, ['A']], [13, ['A']], [14, []], [15, ['A']], [18, ['A']]]]] * N), [[[['A', 'down', 13]], ['A']]] * 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 fixture	Actual	Expected	Outcome
key-debounce scenario 0	`[[[], []]]`	`[[[], []]]`	Passed
key-debounce scenario 1	`[[[['A', 'down', 13]], ['A']]]`	`[[[['A', 'down', 13]], ['A']]]`	Passed
key-debounce scenario 2	`[[[['A', 'down', 13], ['A', 'up', 14]], []]]`	`[[[['A', 'down', 13], ['A', 'up', 17]], []]]`	Failed
key-debounce scenario 3	`[[[['A', 'down', 14]], ['A']]]`	`[[[['A', 'down', 15]], ['A']]]`	Failed
key-debounce scenario 4	`[[[['A', 'down', 13], ['A', 'up', 14], ['B', 'down', 17]], ['B']]]`	`[[[['A', 'down', 13], ['A', 'up', 17], ['B', 'down', 17]], ['B']]]`	Failed
key-debounce scenario 5	`[[[], []]]`	`[[[], []]]`	Passed
key-debounce scenario 6	`[[[['A', 'down', 23], ['B', 'down', 23], ['A', 'up', 24]], ['B']]]`	`[[[['A', 'down', 23], ['B', 'down', 23], ['A', 'up', 27]], ['B']]]`	Failed
key-debounce scenario 7	`[[[['A', 'down', 13], ['A', 'up', 14], ['A', 'down', 15]], ['A']]]`	`[[[['A', 'down', 13]], ['A']]]`	Failed

SHA-256 / bdb3fd4265f98ad0ead64805eced3cbfd6d3876acc2b2f9a86e717d4c3a53bd2

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

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 2026-09-29T14:42:04.626076+00:00.

Case digest / ba0dde4c943b71a62ff7bd4705a72af3b59b48a302ac53f4424586feacae6682