semelis: I disagree with ogee.
This way it's seki.
caranthir: I agree with semelis. It's gote seki for the attacker when after B19, defender leaves the position as is. I kept the variation, though, because if attacker is lacking ko threats, then the option "gote seki but leaving defender the option to live with points before the external liberty is removed but in a ko for life where attacker takes first" could be optimal.
Usually in Life&Death problems, seki is considered false if attacker can create a ko.