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FA-31906 / Keyboard interactions / Open access

Release-completed dot chord keyboard: Rolling dot chord forgets earlier dots or removes a repeated dot · case 01

The event trace violates the accumulate dot rule and produces incorrect keyboard state or command output.

Verified by executionVariant 1 · 11 checks per implementationDownload source bundle ↓JSON ↗

ROOT CAUSE

Rolling dot chord forgets earlier dots or removes a repeated dot.

VERIFIED REPAIR

Use the contract transition `chord.add(dot)` at the accumulate dot fault site; preserve the other state transitions.

Unsuccessful approach: The partial repair changes this transition to chord.symmetric_difference_update({dot}), which still violates the model contract on the explicit regression traces.

Case contract

Events [kind,dot]. Dot values 1..8. Down adds a dot to held and accumulated chord; repeated down does not add another dot. Up releases a held dot and commits sorted accumulated dots only when the final held dot is released. Cancel clears held/chord without output; separator commits pending chord then emits empty dot list and resets. Return committed dot lists, held and accumulated sets. 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):
        held=set(); chord=set(); out=[]; ignored=0
        for kind,dot in c:
            if kind in ('down','up') and not 1<=dot<=8:
                ignored+=1
                continue
            if kind=='down':
                held.add(dot)
                chord={dot}
            elif kind=='up' and dot in held:
                held.discard(dot)
                if not held and chord:
                    out.append(sorted(chord))
                    chord.clear()
            elif kind=='up': ignored+=1
            elif kind=='cancel':
                held.clear(); chord.clear()
            elif kind=='separator':
                if chord: out.append(sorted(chord))
                out.append([])
                held.clear(); chord.clear()
        return [out,sorted(held),sorted(chord),ignored]
    return [run(c) for c in cases]
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
check('braille-chord scenario 0', solve([[]] * N), [[[], [], [], 0]] * N)
check('braille-chord scenario 1', solve([[['down', 1], ['down', 2]]] * N), [[[], [1, 2], [1, 2], 0]] * N)
check('braille-chord scenario 2', solve([[['down', 1], ['down', 8], ['up', 1], ['up', 8]]] * N), [[[[1, 8]], [], [], 0]] * N)
check('braille-chord scenario 3', solve([[['down', 2], ['down', 2], ['up', 2]]] * N), [[[[2]], [], [], 0]] * N)
check('braille-chord scenario 4', solve([[['down', 1], ['down', 2], ['up', 1]]] * N), [[[], [2], [1, 2], 0]] * N)
check('braille-chord scenario 5', solve([[['down', 1], ['up', 1], ['down', 2], ['up', 2]]] * N), [[[[1], [2]], [], [], 0]] * N)
check('braille-chord scenario 6', solve([[['down', 2], ['up', 3]]] * N), [[[], [2], [2], 1]] * N)
check('braille-chord scenario 7', solve([[['down', 0], ['up', 0], ['down', 9]]] * N), [[[], [], [], 3]] * N)
check('braille-chord scenario 8', solve([[['down', 1], ['down', 2], ['separator', 0]]] * N), [[[[1, 2], []], [], [], 0]] * N)
check('braille-chord scenario 9', solve([[['separator', 0]]] * N), [[[[]], [], [], 0]] * N)
check('braille-chord scenario 10', solve([[['down', 1], ['cancel', 0], ['up', 1]]] * N), [[[], [], [], 1]] * 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
braille-chord scenario 0[[[], [], [], 0]][[[], [], [], 0]]Passed
braille-chord scenario 1[[[], [1, 2], [2], 0]][[[], [1, 2], [1, 2], 0]]Failed
braille-chord scenario 2[[[[8]], [], [], 0]][[[[1, 8]], [], [], 0]]Failed
braille-chord scenario 3[[[[2]], [], [], 0]][[[[2]], [], [], 0]]Passed
braille-chord scenario 4[[[], [2], [2], 0]][[[], [2], [1, 2], 0]]Failed
braille-chord scenario 5[[[[1], [2]], [], [], 0]][[[[1], [2]], [], [], 0]]Passed
braille-chord scenario 6[[[], [2], [2], 1]][[[], [2], [2], 1]]Passed
braille-chord scenario 7[[[], [], [], 3]][[[], [], [], 3]]Passed
braille-chord scenario 8[[[[2], []], [], [], 0]][[[[1, 2], []], [], [], 0]]Failed
braille-chord scenario 9[[[[]], [], [], 0]][[[[]], [], [], 0]]Passed
braille-chord scenario 10[[[], [], [], 1]][[[], [], [], 1]]Passed

SHA-256 / aa23b5f9ea5c914625394cfa6bb3b1ce1426a5886ef303102e4db2bb8eb48f76

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):
        held=set(); chord=set(); out=[]; ignored=0
        for kind,dot in c:
            if kind in ('down','up') and not 1<=dot<=8:
                ignored+=1
                continue
            if kind=='down':
                held.add(dot)
                chord.symmetric_difference_update({dot})
            elif kind=='up' and dot in held:
                held.discard(dot)
                if not held and chord:
                    out.append(sorted(chord))
                    chord.clear()
            elif kind=='up': ignored+=1
            elif kind=='cancel':
                held.clear(); chord.clear()
            elif kind=='separator':
                if chord: out.append(sorted(chord))
                out.append([])
                held.clear(); chord.clear()
        return [out,sorted(held),sorted(chord),ignored]
    return [run(c) for c in cases]
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
check('braille-chord scenario 0', solve([[]] * N), [[[], [], [], 0]] * N)
check('braille-chord scenario 1', solve([[['down', 1], ['down', 2]]] * N), [[[], [1, 2], [1, 2], 0]] * N)
check('braille-chord scenario 2', solve([[['down', 1], ['down', 8], ['up', 1], ['up', 8]]] * N), [[[[1, 8]], [], [], 0]] * N)
check('braille-chord scenario 3', solve([[['down', 2], ['down', 2], ['up', 2]]] * N), [[[[2]], [], [], 0]] * N)
check('braille-chord scenario 4', solve([[['down', 1], ['down', 2], ['up', 1]]] * N), [[[], [2], [1, 2], 0]] * N)
check('braille-chord scenario 5', solve([[['down', 1], ['up', 1], ['down', 2], ['up', 2]]] * N), [[[[1], [2]], [], [], 0]] * N)
check('braille-chord scenario 6', solve([[['down', 2], ['up', 3]]] * N), [[[], [2], [2], 1]] * N)
check('braille-chord scenario 7', solve([[['down', 0], ['up', 0], ['down', 9]]] * N), [[[], [], [], 3]] * N)
check('braille-chord scenario 8', solve([[['down', 1], ['down', 2], ['separator', 0]]] * N), [[[[1, 2], []], [], [], 0]] * N)
check('braille-chord scenario 9', solve([[['separator', 0]]] * N), [[[[]], [], [], 0]] * N)
check('braille-chord scenario 10', solve([[['down', 1], ['cancel', 0], ['up', 1]]] * N), [[[], [], [], 1]] * 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
braille-chord scenario 0[[[], [], [], 0]][[[], [], [], 0]]Passed
braille-chord scenario 1[[[], [1, 2], [1, 2], 0]][[[], [1, 2], [1, 2], 0]]Passed
braille-chord scenario 2[[[[1, 8]], [], [], 0]][[[[1, 8]], [], [], 0]]Passed
braille-chord scenario 3[[[], [], [], 0]][[[[2]], [], [], 0]]Failed
braille-chord scenario 4[[[], [2], [1, 2], 0]][[[], [2], [1, 2], 0]]Passed
braille-chord scenario 5[[[[1], [2]], [], [], 0]][[[[1], [2]], [], [], 0]]Passed
braille-chord scenario 6[[[], [2], [2], 1]][[[], [2], [2], 1]]Passed
braille-chord scenario 7[[[], [], [], 3]][[[], [], [], 3]]Passed
braille-chord scenario 8[[[[1, 2], []], [], [], 0]][[[[1, 2], []], [], [], 0]]Passed
braille-chord scenario 9[[[[]], [], [], 0]][[[[]], [], [], 0]]Passed
braille-chord scenario 10[[[], [], [], 1]][[[], [], [], 1]]Passed

SHA-256 / dcdb21ab550994ee5bc373e60f0ec14dc29c7551132a9623896304ccb26d087c

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):
        held=set(); chord=set(); out=[]; ignored=0
        for kind,dot in c:
            if kind in ('down','up') and not 1<=dot<=8:
                ignored+=1
                continue
            if kind=='down':
                held.add(dot)
                chord.add(dot)
            elif kind=='up' and dot in held:
                held.discard(dot)
                if not held and chord:
                    out.append(sorted(chord))
                    chord.clear()
            elif kind=='up': ignored+=1
            elif kind=='cancel':
                held.clear(); chord.clear()
            elif kind=='separator':
                if chord: out.append(sorted(chord))
                out.append([])
                held.clear(); chord.clear()
        return [out,sorted(held),sorted(chord),ignored]
    return [run(c) for c in cases]
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
check('braille-chord scenario 0', solve([[]] * N), [[[], [], [], 0]] * N)
check('braille-chord scenario 1', solve([[['down', 1], ['down', 2]]] * N), [[[], [1, 2], [1, 2], 0]] * N)
check('braille-chord scenario 2', solve([[['down', 1], ['down', 8], ['up', 1], ['up', 8]]] * N), [[[[1, 8]], [], [], 0]] * N)
check('braille-chord scenario 3', solve([[['down', 2], ['down', 2], ['up', 2]]] * N), [[[[2]], [], [], 0]] * N)
check('braille-chord scenario 4', solve([[['down', 1], ['down', 2], ['up', 1]]] * N), [[[], [2], [1, 2], 0]] * N)
check('braille-chord scenario 5', solve([[['down', 1], ['up', 1], ['down', 2], ['up', 2]]] * N), [[[[1], [2]], [], [], 0]] * N)
check('braille-chord scenario 6', solve([[['down', 2], ['up', 3]]] * N), [[[], [2], [2], 1]] * N)
check('braille-chord scenario 7', solve([[['down', 0], ['up', 0], ['down', 9]]] * N), [[[], [], [], 3]] * N)
check('braille-chord scenario 8', solve([[['down', 1], ['down', 2], ['separator', 0]]] * N), [[[[1, 2], []], [], [], 0]] * N)
check('braille-chord scenario 9', solve([[['separator', 0]]] * N), [[[[]], [], [], 0]] * N)
check('braille-chord scenario 10', solve([[['down', 1], ['cancel', 0], ['up', 1]]] * N), [[[], [], [], 1]] * 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
braille-chord scenario 0[[[], [], [], 0]][[[], [], [], 0]]Passed
braille-chord scenario 1[[[], [1, 2], [1, 2], 0]][[[], [1, 2], [1, 2], 0]]Passed
braille-chord scenario 2[[[[1, 8]], [], [], 0]][[[[1, 8]], [], [], 0]]Passed
braille-chord scenario 3[[[[2]], [], [], 0]][[[[2]], [], [], 0]]Passed
braille-chord scenario 4[[[], [2], [1, 2], 0]][[[], [2], [1, 2], 0]]Passed
braille-chord scenario 5[[[[1], [2]], [], [], 0]][[[[1], [2]], [], [], 0]]Passed
braille-chord scenario 6[[[], [2], [2], 1]][[[], [2], [2], 1]]Passed
braille-chord scenario 7[[[], [], [], 3]][[[], [], [], 3]]Passed
braille-chord scenario 8[[[[1, 2], []], [], [], 0]][[[[1, 2], []], [], [], 0]]Passed
braille-chord scenario 9[[[[]], [], [], 0]][[[[]], [], [], 0]]Passed
braille-chord scenario 10[[[], [], [], 1]][[[], [], [], 1]]Passed

SHA-256 / 735ecc8729791f83b2cb4eba105e3d1253081696e146da62e4ac323c322955dd

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 2026-09-29T14:42:06.756971+00:00.

Case digest / 378a18b8d726359320220db9655e29e7af6c719fc6d5e72fb9498ad1dac9348c