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FA-31441 / Keyboard interactions / Open access

Overlapping keyboard sequence matcher: Cancelling a key sequence leaves either its prefix or timeout origin live · case 01

The event trace violates the cancel clock rule and produces incorrect keyboard state or command output.

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

ROOT CAUSE

Cancelling a key sequence leaves either its prefix or timeout origin live.

THE FAILURE

Cancelling a key sequence leaves either its prefix or timeout origin live.

Unsuccessful approach: The partial repair changes this transition to if kind=='cancel': last=None, which still violates the model contract on the explicit regression traces.

Case contract

Case [sequence,timeout,events]. Nonempty sequence is list of key names. Events [kind,key,time,repeat]. Only nonrepeat down feeds matcher. Accepted downs more than timeout after the previous accepted down discard the prefix; tick likewise expires it. Cancel resets prefix and clock. Keep longest suffix matching a sequence prefix, and after a match retain the longest proper overlapping prefix. Return match timestamps, partial prefix and last accepted time. 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):
        sequence,timeout,events=c
        buffer=[]; last=None; matches=[]
        for kind,key,now,repeat in events:
            if kind=='cancel': buffer=[]
            elif kind=='tick':
                if last is not None and now-last>timeout: buffer=[]; last=None
            elif kind=='down' and not repeat:
                if last is not None and now-last>timeout: buffer=[]
                candidate=buffer+[key]
                last=now
                buffer=[]
                for size in range(min(len(sequence),len(candidate)),0,-1):
                    if candidate[-size:]==sequence[:size]:
                        buffer=candidate[-size:]
                        break
                if buffer==sequence:
                    matches.append(now)
                    buffer=[]
                    for size in range(len(sequence)-1,0,-1):
                        if sequence[-size:]==sequence[:size]:
                            buffer=sequence[:size]
                            break
        return [matches,buffer,last]
    return [run(c) for c in cases]
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
check('sequence-prefix scenario 0', solve([[['A', 'B'], 5, []]] * N), [[[], [], None]] * N)
check('sequence-prefix scenario 1', solve([[['A', 'B'], 5, [['down', 'A', 10, False], ['down', 'B', 15, False]]]] * N), [[[15], [], 15]] * N)
check('sequence-prefix scenario 2', solve([[['A', 'B'], 5, [['down', 'A', 10, False], ['tick', '', 15, False]]]] * N), [[[], ['A'], 10]] * N)
check('sequence-prefix scenario 3', solve([[['A', 'B'], 5, [['down', 'A', 10, False], ['down', 'B', 16, False]]]] * N), [[[], [], 16]] * N)
check('sequence-prefix scenario 4', solve([[['A', 'B'], 5, [['down', 'A', 10, False], ['down', 'B', 11, True], ['up', 'B', 12, False]]]] * N), [[[], ['A'], 10]] * N)
check('sequence-prefix scenario 5', solve([[['A', 'B'], 5, [['down', 'A', 10, False], ['cancel', '', 11, False]]]] * N), [[[], [], None]] * N)
check('sequence-prefix scenario 6', solve([[['A', 'B', 'A'], 5, [['down', 'A', 10, False], ['down', 'B', 11, False], ['down', 'A', 12, False], ['down', 'B', 13, False], ['down', 'A', 14, False]]]] * N), [[[12, 14], ['A'], 14]] * N)
check('sequence-prefix scenario 7', solve([[['A', 'B', 'A', 'B'], 5, [['down', 'A', 10, False], ['down', 'B', 11, False], ['down', 'A', 12, False], ['down', 'B', 13, False], ['down', 'A', 14, False], ['down', 'B', 15, False]]]] * N), [[[13, 15], ['A', 'B'], 15]] * N)
check('sequence-prefix scenario 8', solve([[['A', 'A', 'B'], 5, [['down', 'A', 10, False], ['down', 'A', 11, False], ['down', 'A', 12, False], ['down', 'B', 13, False]]]] * N), [[[13], [], 13]] * N)
check('sequence-prefix scenario 9', solve([[['A', 'B', 'C'], 5, [['down', 'A', 10, False], ['down', 'X', 11, False], ['down', 'A', 12, False], ['down', 'B', 13, False], ['down', 'C', 14, False]]]] * N), [[[14], [], 14]] * 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
sequence-prefix scenario 0[[[], [], None]][[[], [], None]]Passed
sequence-prefix scenario 1[[[15], [], 15]][[[15], [], 15]]Passed
sequence-prefix scenario 2[[[], ['A'], 10]][[[], ['A'], 10]]Passed
sequence-prefix scenario 3[[[], [], 16]][[[], [], 16]]Passed
sequence-prefix scenario 4[[[], ['A'], 10]][[[], ['A'], 10]]Passed
sequence-prefix scenario 5[[[], [], 10]][[[], [], None]]Failed
sequence-prefix scenario 6[[[12, 14], ['A'], 14]][[[12, 14], ['A'], 14]]Passed
sequence-prefix scenario 7[[[13, 15], ['A', 'B'], 15]][[[13, 15], ['A', 'B'], 15]]Passed
sequence-prefix scenario 8[[[13], [], 13]][[[13], [], 13]]Passed
sequence-prefix scenario 9[[[14], [], 14]][[[14], [], 14]]Passed

SHA-256 / 721fd8793769d921c3e9833aaeb2586f9889fc7e4f384fe5a21d55217ea91247

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):
        sequence,timeout,events=c
        buffer=[]; last=None; matches=[]
        for kind,key,now,repeat in events:
            if kind=='cancel': last=None
            elif kind=='tick':
                if last is not None and now-last>timeout: buffer=[]; last=None
            elif kind=='down' and not repeat:
                if last is not None and now-last>timeout: buffer=[]
                candidate=buffer+[key]
                last=now
                buffer=[]
                for size in range(min(len(sequence),len(candidate)),0,-1):
                    if candidate[-size:]==sequence[:size]:
                        buffer=candidate[-size:]
                        break
                if buffer==sequence:
                    matches.append(now)
                    buffer=[]
                    for size in range(len(sequence)-1,0,-1):
                        if sequence[-size:]==sequence[:size]:
                            buffer=sequence[:size]
                            break
        return [matches,buffer,last]
    return [run(c) for c in cases]
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
check('sequence-prefix scenario 0', solve([[['A', 'B'], 5, []]] * N), [[[], [], None]] * N)
check('sequence-prefix scenario 1', solve([[['A', 'B'], 5, [['down', 'A', 10, False], ['down', 'B', 15, False]]]] * N), [[[15], [], 15]] * N)
check('sequence-prefix scenario 2', solve([[['A', 'B'], 5, [['down', 'A', 10, False], ['tick', '', 15, False]]]] * N), [[[], ['A'], 10]] * N)
check('sequence-prefix scenario 3', solve([[['A', 'B'], 5, [['down', 'A', 10, False], ['down', 'B', 16, False]]]] * N), [[[], [], 16]] * N)
check('sequence-prefix scenario 4', solve([[['A', 'B'], 5, [['down', 'A', 10, False], ['down', 'B', 11, True], ['up', 'B', 12, False]]]] * N), [[[], ['A'], 10]] * N)
check('sequence-prefix scenario 5', solve([[['A', 'B'], 5, [['down', 'A', 10, False], ['cancel', '', 11, False]]]] * N), [[[], [], None]] * N)
check('sequence-prefix scenario 6', solve([[['A', 'B', 'A'], 5, [['down', 'A', 10, False], ['down', 'B', 11, False], ['down', 'A', 12, False], ['down', 'B', 13, False], ['down', 'A', 14, False]]]] * N), [[[12, 14], ['A'], 14]] * N)
check('sequence-prefix scenario 7', solve([[['A', 'B', 'A', 'B'], 5, [['down', 'A', 10, False], ['down', 'B', 11, False], ['down', 'A', 12, False], ['down', 'B', 13, False], ['down', 'A', 14, False], ['down', 'B', 15, False]]]] * N), [[[13, 15], ['A', 'B'], 15]] * N)
check('sequence-prefix scenario 8', solve([[['A', 'A', 'B'], 5, [['down', 'A', 10, False], ['down', 'A', 11, False], ['down', 'A', 12, False], ['down', 'B', 13, False]]]] * N), [[[13], [], 13]] * N)
check('sequence-prefix scenario 9', solve([[['A', 'B', 'C'], 5, [['down', 'A', 10, False], ['down', 'X', 11, False], ['down', 'A', 12, False], ['down', 'B', 13, False], ['down', 'C', 14, False]]]] * N), [[[14], [], 14]] * 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
sequence-prefix scenario 0[[[], [], None]][[[], [], None]]Passed
sequence-prefix scenario 1[[[15], [], 15]][[[15], [], 15]]Passed
sequence-prefix scenario 2[[[], ['A'], 10]][[[], ['A'], 10]]Passed
sequence-prefix scenario 3[[[], [], 16]][[[], [], 16]]Passed
sequence-prefix scenario 4[[[], ['A'], 10]][[[], ['A'], 10]]Passed
sequence-prefix scenario 5[[[], ['A'], None]][[[], [], None]]Failed
sequence-prefix scenario 6[[[12, 14], ['A'], 14]][[[12, 14], ['A'], 14]]Passed
sequence-prefix scenario 7[[[13, 15], ['A', 'B'], 15]][[[13, 15], ['A', 'B'], 15]]Passed
sequence-prefix scenario 8[[[13], [], 13]][[[13], [], 13]]Passed
sequence-prefix scenario 9[[[14], [], 14]][[[14], [], 14]]Passed

SHA-256 / dab4077c15b9f950e344632dc11f7f599eefd4b71847925b33ba4b925efeb8cd

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 2026-09-29T14:42:02.567274+00:00.

Case digest / 26da4e66644da2af3d96763198c07e3d8a95c858484424d005f9fc03bd539c73