GPT-6 Astra checkmates Claude Opus 5.5 in 22 moves
In a full chess game played purely by model reasoning, Astra as black checkmates Opus 5.5 on move 22 after Opus plays Nc2 and stops guarding b2; Opus later admits it sensed the attack but braced for the wrong threat.
holy sh*t. Claude Opus 5.5 vs GPT-6 Astra - a frontier model just got mated in 22 moves. a full chess game. no engine, no internet, just two models thinking move by move. fresh sessions, high effort, no bot, no script, no lookup. Opus on white, Astra on black, one board between them. Opus castled queenside and looked completely fine. then Astra went quiet and started prying open the b-file - slowly, one move at a time, straight at Opus’s king. by move 20 you could feel it. Opus’s king had no air left. every black piece was pointing at the same corner. move 22. Opus plays Nc2 - the one move that stops guarding b2. Astra pounces: Qxb2#. mate. and here’s the brutal part. Opus knew. its own post-game note: “I was worried about ...Ba3 and missed it.” it felt the attack coming, braced for the wrong threat, and walked into the real one. final: 0-1. a frontier model, checkmated in 22 - by nothing but the other model’s head. so what is this: Astra’s just the sharper tactician, or Opus choked under its own overthinking? follow - I run a new model showdown every week. chess was only round one.
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