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FA-32166 / Keyboard interactions / Open access

Keyboard lock indicator request acknowledgements: A valid LED acknowledgment is rejected by the wrong ordering watermark · case 01

The event trace violates the ack watermark rule and produces incorrect keyboard state or command output.

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

ROOT CAUSE

A valid LED acknowledgment is rejected by the wrong ordering watermark.

VERIFIED REPAIR

Use the contract transition `value>accepted:` at the ack watermark fault site; preserve the other state transitions.

Unsuccessful approach: The partial repair changes this transition to value>serial:, which still violates the model contract on the explicit regression traces.

Case contract

Events [kind,value]. Toggle flips desired lock bit 0..2. Send creates monotonically numbered snapshot request only when desired differs applied. Ack for an in-flight id newer than accepted applies that request snapshot, advances accepted id and discards requests <= ack. Unknown or stale ack is ignored. Reset sets applied=0, clears in-flight requests and accepted watermark but preserves desired and increasing request serial. Return desired,applied,serial,accepted,in-flight and sent [id,mask]. 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):
        desired=0; applied=0; serial=0; accepted=0; inflight={}; sent=[]
        for kind,value in c:
            if kind=='toggle': desired^=1<<value
            elif kind=='send' and desired!=applied:
                serial+=1
                inflight[serial]=desired
                sent.append([serial,desired])
            elif kind=='ack' and value in inflight and value<accepted:
                applied=inflight[value]
                accepted=value
                inflight={k:v for k,v in inflight.items() if k>value}
            elif kind=='reset':
                applied=0; inflight={}; accepted=0
        return [desired,applied,serial,accepted,sorted([[k,v] for k,v in inflight.items()]),sent]
    return [run(c) for c in cases]
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
check('lock-led-ack scenario 0', solve([[]] * N), [[0, 0, 0, 0, [], []]] * N)
check('lock-led-ack scenario 1', solve([[['send', 0]]] * N), [[0, 0, 0, 0, [], []]] * N)
check('lock-led-ack scenario 2', solve([[['toggle', 0], ['toggle', 0], ['send', 0]]] * N), [[0, 0, 0, 0, [], []]] * N)
check('lock-led-ack scenario 3', solve([[['toggle', 2], ['send', 0], ['ack', 1]]] * N), [[4, 4, 1, 1, [], [[1, 4]]]] * N)
check('lock-led-ack scenario 4', solve([[['toggle', 0], ['send', 0], ['toggle', 1], ['send', 0], ['ack', 1]]] * N), [[3, 1, 2, 1, [[2, 3]], [[1, 1], [2, 3]]]] * N)
check('lock-led-ack scenario 5', solve([[['toggle', 0], ['send', 0], ['toggle', 1], ['send', 0], ['ack', 2], ['ack', 1]]] * N), [[3, 3, 2, 2, [], [[1, 1], [2, 3]]]] * N)
check('lock-led-ack scenario 6', solve([[['toggle', 1], ['send', 0], ['send', 0], ['ack', 1]]] * N), [[2, 2, 2, 1, [[2, 2]], [[1, 2], [2, 2]]]] * N)
check('lock-led-ack scenario 7', solve([[['toggle', 2], ['send', 0], ['reset', 0], ['send', 0]]] * N), [[4, 0, 2, 0, [[2, 4]], [[1, 4], [2, 4]]]] * N)
check('lock-led-ack scenario 8', solve([[['toggle', 0], ['send', 0], ['ack', 1], ['send', 0]]] * N), [[1, 1, 1, 1, [], [[1, 1]]]] * N)
check('lock-led-ack scenario 9', solve([[['ack', 999]]] * N), [[0, 0, 0, 0, [], []]] * 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
lock-led-ack scenario 0[[0, 0, 0, 0, [], []]][[0, 0, 0, 0, [], []]]Passed
lock-led-ack scenario 1[[0, 0, 0, 0, [], []]][[0, 0, 0, 0, [], []]]Passed
lock-led-ack scenario 2[[0, 0, 0, 0, [], []]][[0, 0, 0, 0, [], []]]Passed
lock-led-ack scenario 3[[4, 0, 1, 0, [[1, 4]], [[1, 4]]]][[4, 4, 1, 1, [], [[1, 4]]]]Failed
lock-led-ack scenario 4[[3, 0, 2, 0, [[1, 1], [2, 3]], [[1, 1], [2, 3]]]][[3, 1, 2, 1, [[2, 3]], [[1, 1], [2, 3]]]]Failed
lock-led-ack scenario 5[[3, 0, 2, 0, [[1, 1], [2, 3]], [[1, 1], [2, 3]]]][[3, 3, 2, 2, [], [[1, 1], [2, 3]]]]Failed
lock-led-ack scenario 6[[2, 0, 2, 0, [[1, 2], [2, 2]], [[1, 2], [2, 2]]]][[2, 2, 2, 1, [[2, 2]], [[1, 2], [2, 2]]]]Failed
lock-led-ack scenario 7[[4, 0, 2, 0, [[2, 4]], [[1, 4], [2, 4]]]][[4, 0, 2, 0, [[2, 4]], [[1, 4], [2, 4]]]]Passed
lock-led-ack scenario 8[[1, 0, 2, 0, [[1, 1], [2, 1]], [[1, 1], [2, 1]]]][[1, 1, 1, 1, [], [[1, 1]]]]Failed
lock-led-ack scenario 9[[0, 0, 0, 0, [], []]][[0, 0, 0, 0, [], []]]Passed

SHA-256 / 213ad6954c3d34e378646759afa50c59fd89a2c972e02e521fd2fa823486882b

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):
        desired=0; applied=0; serial=0; accepted=0; inflight={}; sent=[]
        for kind,value in c:
            if kind=='toggle': desired^=1<<value
            elif kind=='send' and desired!=applied:
                serial+=1
                inflight[serial]=desired
                sent.append([serial,desired])
            elif kind=='ack' and value in inflight and value>serial:
                applied=inflight[value]
                accepted=value
                inflight={k:v for k,v in inflight.items() if k>value}
            elif kind=='reset':
                applied=0; inflight={}; accepted=0
        return [desired,applied,serial,accepted,sorted([[k,v] for k,v in inflight.items()]),sent]
    return [run(c) for c in cases]
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
check('lock-led-ack scenario 0', solve([[]] * N), [[0, 0, 0, 0, [], []]] * N)
check('lock-led-ack scenario 1', solve([[['send', 0]]] * N), [[0, 0, 0, 0, [], []]] * N)
check('lock-led-ack scenario 2', solve([[['toggle', 0], ['toggle', 0], ['send', 0]]] * N), [[0, 0, 0, 0, [], []]] * N)
check('lock-led-ack scenario 3', solve([[['toggle', 2], ['send', 0], ['ack', 1]]] * N), [[4, 4, 1, 1, [], [[1, 4]]]] * N)
check('lock-led-ack scenario 4', solve([[['toggle', 0], ['send', 0], ['toggle', 1], ['send', 0], ['ack', 1]]] * N), [[3, 1, 2, 1, [[2, 3]], [[1, 1], [2, 3]]]] * N)
check('lock-led-ack scenario 5', solve([[['toggle', 0], ['send', 0], ['toggle', 1], ['send', 0], ['ack', 2], ['ack', 1]]] * N), [[3, 3, 2, 2, [], [[1, 1], [2, 3]]]] * N)
check('lock-led-ack scenario 6', solve([[['toggle', 1], ['send', 0], ['send', 0], ['ack', 1]]] * N), [[2, 2, 2, 1, [[2, 2]], [[1, 2], [2, 2]]]] * N)
check('lock-led-ack scenario 7', solve([[['toggle', 2], ['send', 0], ['reset', 0], ['send', 0]]] * N), [[4, 0, 2, 0, [[2, 4]], [[1, 4], [2, 4]]]] * N)
check('lock-led-ack scenario 8', solve([[['toggle', 0], ['send', 0], ['ack', 1], ['send', 0]]] * N), [[1, 1, 1, 1, [], [[1, 1]]]] * N)
check('lock-led-ack scenario 9', solve([[['ack', 999]]] * N), [[0, 0, 0, 0, [], []]] * 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
lock-led-ack scenario 0[[0, 0, 0, 0, [], []]][[0, 0, 0, 0, [], []]]Passed
lock-led-ack scenario 1[[0, 0, 0, 0, [], []]][[0, 0, 0, 0, [], []]]Passed
lock-led-ack scenario 2[[0, 0, 0, 0, [], []]][[0, 0, 0, 0, [], []]]Passed
lock-led-ack scenario 3[[4, 0, 1, 0, [[1, 4]], [[1, 4]]]][[4, 4, 1, 1, [], [[1, 4]]]]Failed
lock-led-ack scenario 4[[3, 0, 2, 0, [[1, 1], [2, 3]], [[1, 1], [2, 3]]]][[3, 1, 2, 1, [[2, 3]], [[1, 1], [2, 3]]]]Failed
lock-led-ack scenario 5[[3, 0, 2, 0, [[1, 1], [2, 3]], [[1, 1], [2, 3]]]][[3, 3, 2, 2, [], [[1, 1], [2, 3]]]]Failed
lock-led-ack scenario 6[[2, 0, 2, 0, [[1, 2], [2, 2]], [[1, 2], [2, 2]]]][[2, 2, 2, 1, [[2, 2]], [[1, 2], [2, 2]]]]Failed
lock-led-ack scenario 7[[4, 0, 2, 0, [[2, 4]], [[1, 4], [2, 4]]]][[4, 0, 2, 0, [[2, 4]], [[1, 4], [2, 4]]]]Passed
lock-led-ack scenario 8[[1, 0, 2, 0, [[1, 1], [2, 1]], [[1, 1], [2, 1]]]][[1, 1, 1, 1, [], [[1, 1]]]]Failed
lock-led-ack scenario 9[[0, 0, 0, 0, [], []]][[0, 0, 0, 0, [], []]]Passed

SHA-256 / e82c9262da03d0c89a08a5e0ff3c853ec6e9c882672579c35470e68da508ae7c

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):
        desired=0; applied=0; serial=0; accepted=0; inflight={}; sent=[]
        for kind,value in c:
            if kind=='toggle': desired^=1<<value
            elif kind=='send' and desired!=applied:
                serial+=1
                inflight[serial]=desired
                sent.append([serial,desired])
            elif kind=='ack' and value in inflight and value>accepted:
                applied=inflight[value]
                accepted=value
                inflight={k:v for k,v in inflight.items() if k>value}
            elif kind=='reset':
                applied=0; inflight={}; accepted=0
        return [desired,applied,serial,accepted,sorted([[k,v] for k,v in inflight.items()]),sent]
    return [run(c) for c in cases]
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
check('lock-led-ack scenario 0', solve([[]] * N), [[0, 0, 0, 0, [], []]] * N)
check('lock-led-ack scenario 1', solve([[['send', 0]]] * N), [[0, 0, 0, 0, [], []]] * N)
check('lock-led-ack scenario 2', solve([[['toggle', 0], ['toggle', 0], ['send', 0]]] * N), [[0, 0, 0, 0, [], []]] * N)
check('lock-led-ack scenario 3', solve([[['toggle', 2], ['send', 0], ['ack', 1]]] * N), [[4, 4, 1, 1, [], [[1, 4]]]] * N)
check('lock-led-ack scenario 4', solve([[['toggle', 0], ['send', 0], ['toggle', 1], ['send', 0], ['ack', 1]]] * N), [[3, 1, 2, 1, [[2, 3]], [[1, 1], [2, 3]]]] * N)
check('lock-led-ack scenario 5', solve([[['toggle', 0], ['send', 0], ['toggle', 1], ['send', 0], ['ack', 2], ['ack', 1]]] * N), [[3, 3, 2, 2, [], [[1, 1], [2, 3]]]] * N)
check('lock-led-ack scenario 6', solve([[['toggle', 1], ['send', 0], ['send', 0], ['ack', 1]]] * N), [[2, 2, 2, 1, [[2, 2]], [[1, 2], [2, 2]]]] * N)
check('lock-led-ack scenario 7', solve([[['toggle', 2], ['send', 0], ['reset', 0], ['send', 0]]] * N), [[4, 0, 2, 0, [[2, 4]], [[1, 4], [2, 4]]]] * N)
check('lock-led-ack scenario 8', solve([[['toggle', 0], ['send', 0], ['ack', 1], ['send', 0]]] * N), [[1, 1, 1, 1, [], [[1, 1]]]] * N)
check('lock-led-ack scenario 9', solve([[['ack', 999]]] * N), [[0, 0, 0, 0, [], []]] * 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
lock-led-ack scenario 0[[0, 0, 0, 0, [], []]][[0, 0, 0, 0, [], []]]Passed
lock-led-ack scenario 1[[0, 0, 0, 0, [], []]][[0, 0, 0, 0, [], []]]Passed
lock-led-ack scenario 2[[0, 0, 0, 0, [], []]][[0, 0, 0, 0, [], []]]Passed
lock-led-ack scenario 3[[4, 4, 1, 1, [], [[1, 4]]]][[4, 4, 1, 1, [], [[1, 4]]]]Passed
lock-led-ack scenario 4[[3, 1, 2, 1, [[2, 3]], [[1, 1], [2, 3]]]][[3, 1, 2, 1, [[2, 3]], [[1, 1], [2, 3]]]]Passed
lock-led-ack scenario 5[[3, 3, 2, 2, [], [[1, 1], [2, 3]]]][[3, 3, 2, 2, [], [[1, 1], [2, 3]]]]Passed
lock-led-ack scenario 6[[2, 2, 2, 1, [[2, 2]], [[1, 2], [2, 2]]]][[2, 2, 2, 1, [[2, 2]], [[1, 2], [2, 2]]]]Passed
lock-led-ack scenario 7[[4, 0, 2, 0, [[2, 4]], [[1, 4], [2, 4]]]][[4, 0, 2, 0, [[2, 4]], [[1, 4], [2, 4]]]]Passed
lock-led-ack scenario 8[[1, 1, 1, 1, [], [[1, 1]]]][[1, 1, 1, 1, [], [[1, 1]]]]Passed
lock-led-ack scenario 9[[0, 0, 0, 0, [], []]][[0, 0, 0, 0, [], []]]Passed

SHA-256 / bb24d5cbd4e88e19a3fe44978aca44a1aeb9947d0ca6de826c042ea0c22dca8b

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 2026-09-29T14:42:09.360354+00:00.

Case digest / 7d3fdc23124eac9420c796721fb8089a3068a978dfd759f0d88d5ad15d1f8e88