AdvancedOptionCategoryEnabled returned _advancedOptionCategoryEnabled (the
panel's own mutable bool[]) directly. Any caller holding the returned
IReadOnlyList<bool> could cast it back to bool[] and flip category flags
without going through ToggleAdvancedOptionCategoryAt — bypassing the
clamp/cache-refresh that action performs. The property now returns a
ReadOnlyCollection<bool> view built once over the same backing array
(built once since the array's own reference never changes, only its
elements, so no re-allocation is needed on every read): a cast back to
bool[] now throws InvalidCastException instead of handing out a mutable
reference.
Mutation named: reverted the property to return the raw array and
confirmed the new
AdvancedOptionCategoryEnabledIsNotTheMutableBackingArray pin fails (no
exception thrown) before restoring the fix.
MossTank suite 677 -> 678 (one new pin). Full solution build green; App
markup/plugin filter 203/203.
Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
23d4376cc3