FA-9026 / Keyboard interactions / Open access
Scoped keyboard shortcut dispatch: Shift-Undo dispatches undo instead of redo · case 01
Shift-Undo dispatches undo instead of redo.
ROOT CAUSE
The redo modifier operation uses `'undo'` where the contract requires `'redo' if shift else 'undo'`.
VERIFIED REPAIR
Implement the redo modifier operation as `'redo' if shift else 'undo'`.
Unsuccessful approach: Always redoing breaks the ordinary undo shortcut.
Case contract
Ignore prevented, repeated, and editable-origin events; use platform primary modifier; Alt blocks shortcuts; Shift-Z redoes, Z undoes, unshifted S saves.
Why this case matters
A deterministic model of scoped keyboard shortcut dispatch; this isolates one interface invariant without requiring a browser.
1 / The failure
Exit 1"""Failure Map reference implementation. Python standard library only."""
import json
N = 1
observations = []
def solve(key, ctrl, meta, alt, shift, platform, editable, repeat, prevented):
if prevented or repeat: return None
if editable: return None
primary = meta if platform == 'mac' else ctrl
if not primary or alt: return None
if key.lower() == 'z': return 'undo'
if key.lower() == 's' and not shift: return 'save'
return None
def check(label, actual, expected):
observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
check('prevented', solve('z', True, False, False, False, 'win', False, False, True), None)
check('repeat', solve('z', True, False, False, False, 'win', False, True, False), None)
check('editable', solve('z', True, False, False, False, 'win', True, False, False), None)
check('mac', solve('z', False, True, False, False, 'mac', False, False, False), 'undo')
check('win', solve('z', True, False, False, False, 'win', False, False, False), 'undo')
check('redo', solve('z', True, False, False, True, 'win', False, False, False), 'redo')
check('alt', solve('z', True, False, True, False, 'win', False, False, False), None)
check('parameterized target context', solve('z',True,False,False,False,'win',bool(N%2),False,False), None if N%2 else 'undo')
for repetition in range(N):
check('repeat alt', solve('z', True, False, True, False, 'win', False, False, False), None)
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 |
|---|---|---|---|
| prevented | None | None | Passed |
| repeat | None | None | Passed |
| editable | None | None | Passed |
| mac | undo | undo | Passed |
| win | undo | undo | Passed |
| redo | undo | redo | Failed |
| alt | None | None | Passed |
| parameterized target context | None | None | Passed |
| repeat alt | None | None | Passed |
SHA-256 / 421364f26b7443e914339cd19e908cb7c61a1b2bcc74ef6f693f6e3c203fdb86
2 / The unsuccessful fix
Exit 1"""Failure Map reference implementation. Python standard library only."""
import json
N = 1
observations = []
def solve(key, ctrl, meta, alt, shift, platform, editable, repeat, prevented):
if prevented or repeat: return None
if editable: return None
primary = meta if platform == 'mac' else ctrl
if not primary or alt: return None
if key.lower() == 'z': return 'redo'
if key.lower() == 's' and not shift: return 'save'
return None
def check(label, actual, expected):
observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
check('prevented', solve('z', True, False, False, False, 'win', False, False, True), None)
check('repeat', solve('z', True, False, False, False, 'win', False, True, False), None)
check('editable', solve('z', True, False, False, False, 'win', True, False, False), None)
check('mac', solve('z', False, True, False, False, 'mac', False, False, False), 'undo')
check('win', solve('z', True, False, False, False, 'win', False, False, False), 'undo')
check('redo', solve('z', True, False, False, True, 'win', False, False, False), 'redo')
check('alt', solve('z', True, False, True, False, 'win', False, False, False), None)
check('parameterized target context', solve('z',True,False,False,False,'win',bool(N%2),False,False), None if N%2 else 'undo')
for repetition in range(N):
check('repeat alt', solve('z', True, False, True, False, 'win', False, False, False), None)
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 |
|---|---|---|---|
| prevented | None | None | Passed |
| repeat | None | None | Passed |
| editable | None | None | Passed |
| mac | redo | undo | Failed |
| win | redo | undo | Failed |
| redo | redo | redo | Passed |
| alt | None | None | Passed |
| parameterized target context | None | None | Passed |
| repeat alt | None | None | Passed |
SHA-256 / 8d30794fad02bfc057cbbea61439fc485ccf07b3c1a85f622ce8f4f878b5f54c
3 / The verified repair
Exit 0"""Failure Map reference implementation. Python standard library only."""
import json
N = 1
observations = []
def solve(key, ctrl, meta, alt, shift, platform, editable, repeat, prevented):
if prevented or repeat: return None
if editable: return None
primary = meta if platform == 'mac' else ctrl
if not primary or alt: return None
if key.lower() == 'z': return 'redo' if shift else 'undo'
if key.lower() == 's' and not shift: return 'save'
return None
def check(label, actual, expected):
observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
check('prevented', solve('z', True, False, False, False, 'win', False, False, True), None)
check('repeat', solve('z', True, False, False, False, 'win', False, True, False), None)
check('editable', solve('z', True, False, False, False, 'win', True, False, False), None)
check('mac', solve('z', False, True, False, False, 'mac', False, False, False), 'undo')
check('win', solve('z', True, False, False, False, 'win', False, False, False), 'undo')
check('redo', solve('z', True, False, False, True, 'win', False, False, False), 'redo')
check('alt', solve('z', True, False, True, False, 'win', False, False, False), None)
check('parameterized target context', solve('z',True,False,False,False,'win',bool(N%2),False,False), None if N%2 else 'undo')
for repetition in range(N):
check('repeat alt', solve('z', True, False, True, False, 'win', False, False, False), None)
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 |
|---|---|---|---|
| prevented | None | None | Passed |
| repeat | None | None | Passed |
| editable | None | None | Passed |
| mac | undo | undo | Passed |
| win | undo | undo | Passed |
| redo | redo | redo | Passed |
| alt | None | None | Passed |
| parameterized target context | None | None | Passed |
| repeat alt | None | None | Passed |
SHA-256 / 57e8128ff05fe833f1456d79a412d1065dd2e5fcb142e213a048dee71ea1c567
Verification & scope
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 2026-09-29T14:38:26.451863+00:00.
Case digest / f4cbac5bafd96ac101b689cc0e71418fb2cf168980a699bd12aab9c6588800a5