surprising, isn’t it? 
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Indeed! Had re-read every variation a few times before I seriously considered that last move.
Here is one from a league game I played on January 1st:
I’m black and I just ran out the laddered stone (after quadruple checking that the ladder is currently good for me). In the game my opponent went for a ladder breaker at the triangle, which looks promising, but it turns out I could ignore it and get a good result.
Can you find a stronger move for white?
Hint 1
It’s not just some different spot in the lower left quadrant, all those can be ignored by black.
Hint 2
Squeezing is not good enough - the strongest move guarantees something to be captured.
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Thoughts
If white can get a stone at N15 in sente, then P12, O13, N12 is a geta that captures black.
I’d probably play N15. If black ignores with P12 then N18 looks not bad for white.
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Correct!
KataGo thinks allowing white N18 is bad, so black should respond to the atari and let white get a geta.
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In this game Black won by 5.5 but could White have tried something instead of passing?
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That’s evil if Black misses it.
K5 then L2 (or L2 then K5)
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Correct!
So Black must sacrifice the two stones K6, and this is enough for White to win the game!
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)
Guess
Cut the knight’s move with H8?
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From a game I saw on GoQuest:
Where should black play next? (Chinese rules)
Probably not very difficult when posed as a problem, but both players made mistakes in the actual continuation 
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Why doesn’t reversing the order of White’s moves work as a solution?
Black G2
White F5, Black G5 (or vice-versa)
White passes
Black G3 or G1
The game is finished.
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It does. It’s a mistake in the problem.
There’s also a slight mistake with black’s response: connecting gives 1 more ko threat.
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To be honest I don’t really understand how OGS scoring works. When I finish a game there is always an “accepting phase”. Are the players not allowed to agree on the life and death status of the groups, as we do in face-to-face go?
The Japanese rules used to be different, with groups being alive or dead “by shape”, but nowadays I think all rules agree that if a player can’t kill a group, then that group is alive. Or if both players agree that a group is alive, then that group is alive. If both players passed in this game, then they most likely agree that black is alive and white is dead. So what’s confusing about this situation?
In all games I’ve played on OGS, there was always an “accept” phase after passing. I don’t think I’ve had a disagreement yet, so I don’t know how it works exactly, but I assumed this was a regular player agreement about the status of groups.
The game you linked is marked as “annulled”, so I assume the players erroneously accepted a wrong scoring, then called a moderator who annulled the game?
Normally the auto-score provides an assessment (that is usually correct when there are no unsettled positions and no open borders). The players should then accept or correct if needed and then agree.
With bot games the auto-score is used exclusively because unfortunately trying to have the bots agree the score with their human opponents doesn’t work very well. The example was a bot game.
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I don’t see what game you’re referring to, so I don’t know what the ruleset was,
but under Chinese and AGA rules, the human should be allowed a resumption after
which almost-all stones on the board at the end will be scored as alive, since a clean
resolution of life-and-death disputes is most of the point of not using Japanese rules.
One could still score as dead the stones that, using pass-alive in the sense
that allows suicide even if the actual rules don’t allow suicide, are in a
[connected component of [intersections which are not
occupied by the opponent’s pass-alive stones] such that
[at most 2 of the component’s intersections are not adjacent to the opponent’s stones]
and [if there are 2 such intersections, then they are adjacent to each other]].
(The reason for for allowing suicide in that pass-alive even if the actual rules don’t, is so
the opponent’s stones will remain pass-alive even after capturing the player’s stones.)
It’s a game on OGS. The dragon would probably die if I were white. To my surprise, it’s winrate was more than 90%. I’m not sure if it serves as a good tsumego.
White to play
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