Tournament commentary · 30
Qualified by half a point: Yang Dingxin's seven-point lead nearly slipped to Tan Xiao
In the deciding round of the Chinese qualifier for the 2nd Shinhan Bank World Kisen, Yang Dingxin beat Tan Xiao with Black by half a point and took the main-event place. A move-by-move KataGo rerun shows Black once led by seven points, lost most of it when Black 77 failed to capture the stone at J18, and was briefly overtaken in the endgame before Tan Xiao gave it back.
White 44 to 48: three moves at the top give the lead away
November 4, 2026, the deciding round of the qualifier: the winner goes to the main event, the loser is out. Yang Dingxin had Black and Tan Xiao White, 6.5 komi. The first forty-odd moves were even. Then White 44 at G16 (first choice J17), White 46 at P18 (first choice N16), and White 48 at L16 (first choice K17) took Black's win rate from 47% to 86% and the score from Black 0.5 behind to 4.4 ahead. By move 72 Black led by about 7.1 points.
The position before White 48, comparing the played L16 with KataGo's first choice K17, with White 44, 46, and 48 listed alongside. Black 77: the stone that was not captured
Black 77 was the largest score loss of the game. The White stone at J18 had a single liberty at J19, and KataGo's first choice was to capture it there, continuing J19, E13, H16, D12. Black instead played E13 on the left, and White 78 escaped at J19 at once. Black's lead shrank from 6.6 points to 1.1 and the win rate fell from 92% to 65%. In KataGo's line Black captures first and lets White have E13, and that is still the better deal.
The position before Black 77, comparing the played E13 with KataGo's first choice J19. The middle game: back and forth
Once the lead had shrunk, both sides made errors and the curve swung back and forth. Black 85 at P3 (first choice Q4) dropped Black to 40%. White 88 at F10 (first choice M9) brought it back to 63%. White 132 at L3 (first choice R2) lifted Black from 35% to 72%. None of these swings moved the score by as much as 2.5 points. After move 160 the score stayed within ±0.8 points, and the endgame would decide it.
The position before White 88, comparing the played F10 with KataGo's first choice M9, with Black 85, White 88, and White 132 listed alongside. The endgame: Tan Xiao goes ahead, then gives it back
Black 189 at C1 and Black 191 at B6 both passed over KataGo's first choice, L12. After move 191 White's win rate was about 72%: Tan Xiao had turned the game around. Then White 192 at L1 (first choice T15), White 194 at T15 (first choice T16), and White 198 at A15 (first choice S13) lifted Black to 42%, 59%, and 90% in turn. By move 202 Black stood at 96%, and nothing changed after that.
The position before White 198, comparing the played A15 with KataGo's first choice S13, with five of moves 189 to 198 listed alongside. Win rate in a half-point game
The win rate swung violently in the endgame while the score never moved far from half a point: around White 198 Black's lead went only from 0.5 to 0.4 points, yet the win rate jumped from 59% to 90%. In a half-point game the order of a single endgame move can decide the result, and the win rate reflects that uncertainty rather than any one move collapsing. At the end KataGo put Black about 0.6 points ahead, consistent with Black's half-point win.
Tournament reports
Four judgements about this game
- Black's lead of about seven points came mainly from White's three moves from 44 to 48.
- Black 77 failed to capture the J18 stone, and the lead shrank from 6.6 points to 1.1.
- After move 191 Tan Xiao had actually turned the game around, with White at about 72%.
- The last few endgame moves handed the game back to Black; KataGo's final estimate is Black ahead by about 0.6 points.