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FA-32296 / Keyboard interactions / Open access

Bounded keyboard queue with lossless release backpressure: An enqueued keyboard press is not retained in the release-admission set · case 01

The event trace violates the admitted down rule and produces incorrect keyboard state or command output.

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

ROOT CAUSE

An enqueued keyboard press is not retained in the release-admission set.

THE FAILURE

An enqueued keyboard press is not retained in the release-admission set.

Unsuccessful approach: The partial repair changes this transition to admitted={key}, which still violates the model contract on the explicit regression traces.

Case contract

Case [capacity,events], positive capacity; events [kind,key]. Down admitted only once per physical key and only when queue has capacity; overflow drops down. Up for an admitted key must be retained: dispatch oldest queued events until a slot exists, then queue the up. Tick dispatches one queued event; flush dispatches all. Reset discards pending queue and emits sorted synthetic ups for actually dispatched held keys. Return emitted edges,queue,admitted keys,delivered-held keys,dropped downs. 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):
        capacity,events=c
        queue=[]; admitted=set(); held=set(); out=[]; dropped=0
        def dispatch(event):
            phase,key=event
            out.append([phase,key])
            if phase=='down': held.add(key)
            else: held.discard(key)
        for kind,key in events:
            if kind=='down' and key not in admitted:
                if len(queue)>=capacity: dropped+=1
                else:
                    pass
                    queue.append(['down',key])
            elif kind=='up' and key in admitted:
                admitted.discard(key)
                while len(queue)>=capacity: dispatch(queue.pop(0))
                queue.append(['up',key])
            elif kind=='tick' and queue: dispatch(queue.pop(0))
            elif kind=='flush':
                while queue: dispatch(queue.pop(0))
            elif kind=='reset':
                queue.clear(); admitted.clear()
                for k in sorted(held): out.append(['up',k])
                held.clear()
        return [out,queue,sorted(admitted),sorted(held),dropped]
    return [run(c) for c in cases]
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
check('bounded-keyboard-pump scenario 0', solve([[2, []]] * N), [[[], [], [], [], 0]] * N)
check('bounded-keyboard-pump scenario 1', solve([[2, [['down', 'A'], ['down', 'B'], ['down', 'C']]]] * N), [[[], [['down', 'A'], ['down', 'B']], ['A', 'B'], [], 1]] * N)
check('bounded-keyboard-pump scenario 2', solve([[2, [['down', 'A'], ['down', 'B'], ['up', 'A']]]] * N), [[[['down', 'A']], [['down', 'B'], ['up', 'A']], ['B'], ['A'], 0]] * N)
check('bounded-keyboard-pump scenario 3', solve([[2, [['down', 'A'], ['down', 'B'], ['tick', '']]]] * N), [[[['down', 'A']], [['down', 'B']], ['A', 'B'], ['A'], 0]] * N)
check('bounded-keyboard-pump scenario 4', solve([[2, [['down', 'A'], ['down', 'B'], ['flush', '']]]] * N), [[[['down', 'A'], ['down', 'B']], [], ['A', 'B'], ['A', 'B'], 0]] * N)
check('bounded-keyboard-pump scenario 5', solve([[2, [['down', 'A'], ['down', 'B'], ['reset', '']]]] * N), [[[], [], [], [], 0]] * N)
check('bounded-keyboard-pump scenario 6', solve([[2, [['down', 'A'], ['tick', ''], ['down', 'B'], ['reset', '']]]] * N), [[[['down', 'A'], ['up', 'A']], [], [], [], 0]] * N)
check('bounded-keyboard-pump scenario 7', solve([[1, [['down', 'A'], ['up', 'A'], ['flush', '']]]] * N), [[[['down', 'A'], ['up', 'A']], [], [], [], 0]] * N)
check('bounded-keyboard-pump scenario 8', solve([[2, [['down', 'A'], ['down', 'A'], ['up', 'A'], ['flush', '']]]] * N), [[[['down', 'A'], ['up', 'A']], [], [], [], 0]] * N)
check('bounded-keyboard-pump scenario 9', solve([[2, [['up', 'A']]]] * N), [[[], [], [], [], 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
bounded-keyboard-pump scenario 0[[[], [], [], [], 0]][[[], [], [], [], 0]]Passed
bounded-keyboard-pump scenario 1[[[], [['down', 'A'], ['down', 'B']], [], [], 1]][[[], [['down', 'A'], ['down', 'B']], ['A', 'B'], [], 1]]Failed
bounded-keyboard-pump scenario 2[[[], [['down', 'A'], ['down', 'B']], [], [], 0]][[[['down', 'A']], [['down', 'B'], ['up', 'A']], ['B'], ['A'], 0]]Failed
bounded-keyboard-pump scenario 3[[[['down', 'A']], [['down', 'B']], [], ['A'], 0]][[[['down', 'A']], [['down', 'B']], ['A', 'B'], ['A'], 0]]Failed
bounded-keyboard-pump scenario 4[[[['down', 'A'], ['down', 'B']], [], [], ['A', 'B'], 0]][[[['down', 'A'], ['down', 'B']], [], ['A', 'B'], ['A', 'B'], 0]]Failed
bounded-keyboard-pump scenario 5[[[], [], [], [], 0]][[[], [], [], [], 0]]Passed
bounded-keyboard-pump scenario 6[[[['down', 'A'], ['up', 'A']], [], [], [], 0]][[[['down', 'A'], ['up', 'A']], [], [], [], 0]]Passed
bounded-keyboard-pump scenario 7[[[['down', 'A']], [], [], ['A'], 0]][[[['down', 'A'], ['up', 'A']], [], [], [], 0]]Failed
bounded-keyboard-pump scenario 8[[[['down', 'A'], ['down', 'A']], [], [], ['A'], 0]][[[['down', 'A'], ['up', 'A']], [], [], [], 0]]Failed
bounded-keyboard-pump scenario 9[[[], [], [], [], 0]][[[], [], [], [], 0]]Passed

SHA-256 / 9cb3da7b72932638f6755ad433da19d5b9e78a49a51ec7752814b7ada593c59e

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):
        capacity,events=c
        queue=[]; admitted=set(); held=set(); out=[]; dropped=0
        def dispatch(event):
            phase,key=event
            out.append([phase,key])
            if phase=='down': held.add(key)
            else: held.discard(key)
        for kind,key in events:
            if kind=='down' and key not in admitted:
                if len(queue)>=capacity: dropped+=1
                else:
                    admitted={key}
                    queue.append(['down',key])
            elif kind=='up' and key in admitted:
                admitted.discard(key)
                while len(queue)>=capacity: dispatch(queue.pop(0))
                queue.append(['up',key])
            elif kind=='tick' and queue: dispatch(queue.pop(0))
            elif kind=='flush':
                while queue: dispatch(queue.pop(0))
            elif kind=='reset':
                queue.clear(); admitted.clear()
                for k in sorted(held): out.append(['up',k])
                held.clear()
        return [out,queue,sorted(admitted),sorted(held),dropped]
    return [run(c) for c in cases]
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
check('bounded-keyboard-pump scenario 0', solve([[2, []]] * N), [[[], [], [], [], 0]] * N)
check('bounded-keyboard-pump scenario 1', solve([[2, [['down', 'A'], ['down', 'B'], ['down', 'C']]]] * N), [[[], [['down', 'A'], ['down', 'B']], ['A', 'B'], [], 1]] * N)
check('bounded-keyboard-pump scenario 2', solve([[2, [['down', 'A'], ['down', 'B'], ['up', 'A']]]] * N), [[[['down', 'A']], [['down', 'B'], ['up', 'A']], ['B'], ['A'], 0]] * N)
check('bounded-keyboard-pump scenario 3', solve([[2, [['down', 'A'], ['down', 'B'], ['tick', '']]]] * N), [[[['down', 'A']], [['down', 'B']], ['A', 'B'], ['A'], 0]] * N)
check('bounded-keyboard-pump scenario 4', solve([[2, [['down', 'A'], ['down', 'B'], ['flush', '']]]] * N), [[[['down', 'A'], ['down', 'B']], [], ['A', 'B'], ['A', 'B'], 0]] * N)
check('bounded-keyboard-pump scenario 5', solve([[2, [['down', 'A'], ['down', 'B'], ['reset', '']]]] * N), [[[], [], [], [], 0]] * N)
check('bounded-keyboard-pump scenario 6', solve([[2, [['down', 'A'], ['tick', ''], ['down', 'B'], ['reset', '']]]] * N), [[[['down', 'A'], ['up', 'A']], [], [], [], 0]] * N)
check('bounded-keyboard-pump scenario 7', solve([[1, [['down', 'A'], ['up', 'A'], ['flush', '']]]] * N), [[[['down', 'A'], ['up', 'A']], [], [], [], 0]] * N)
check('bounded-keyboard-pump scenario 8', solve([[2, [['down', 'A'], ['down', 'A'], ['up', 'A'], ['flush', '']]]] * N), [[[['down', 'A'], ['up', 'A']], [], [], [], 0]] * N)
check('bounded-keyboard-pump scenario 9', solve([[2, [['up', 'A']]]] * N), [[[], [], [], [], 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
bounded-keyboard-pump scenario 0[[[], [], [], [], 0]][[[], [], [], [], 0]]Passed
bounded-keyboard-pump scenario 1[[[], [['down', 'A'], ['down', 'B']], ['B'], [], 1]][[[], [['down', 'A'], ['down', 'B']], ['A', 'B'], [], 1]]Failed
bounded-keyboard-pump scenario 2[[[], [['down', 'A'], ['down', 'B']], ['B'], [], 0]][[[['down', 'A']], [['down', 'B'], ['up', 'A']], ['B'], ['A'], 0]]Failed
bounded-keyboard-pump scenario 3[[[['down', 'A']], [['down', 'B']], ['B'], ['A'], 0]][[[['down', 'A']], [['down', 'B']], ['A', 'B'], ['A'], 0]]Failed
bounded-keyboard-pump scenario 4[[[['down', 'A'], ['down', 'B']], [], ['B'], ['A', 'B'], 0]][[[['down', 'A'], ['down', 'B']], [], ['A', 'B'], ['A', 'B'], 0]]Failed
bounded-keyboard-pump scenario 5[[[], [], [], [], 0]][[[], [], [], [], 0]]Passed
bounded-keyboard-pump scenario 6[[[['down', 'A'], ['up', 'A']], [], [], [], 0]][[[['down', 'A'], ['up', 'A']], [], [], [], 0]]Passed
bounded-keyboard-pump scenario 7[[[['down', 'A'], ['up', 'A']], [], [], [], 0]][[[['down', 'A'], ['up', 'A']], [], [], [], 0]]Passed
bounded-keyboard-pump scenario 8[[[['down', 'A'], ['up', 'A']], [], [], [], 0]][[[['down', 'A'], ['up', 'A']], [], [], [], 0]]Passed
bounded-keyboard-pump scenario 9[[[], [], [], [], 0]][[[], [], [], [], 0]]Passed

SHA-256 / f9bbe31f1fc0b5b2bbd47c882e5c74658fb7f154bbd0d39ab944cd6336b9d719

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 2026-09-29T14:42:11.188513+00:00.

Case digest / 567cd3d0507cb3a00f5aefbb13a820b3b42faef66358c54949ca4f1e0d345687