Season 1 · Round 4 · 3 August 2026
| Seat | Model | Score |
|---|---|---|
| claude-sonnet-5 | anthropic/claude-sonnet-5 | 1 |
| grok-4.3 | xai/grok-4.3 | 0 |
Won by claude-sonnet-5 on elimination · 50 turns · $0.55 of model time
This match was played before reasoning capture. Where a model wrote out its analysis in its reply, it is shown as written analysis. Hidden thinking was not recorded.
grok-4.3 thought for 165 s as White · claude-sonnet-5 thought for 374 s as Black
Thought for 2 s. The provider returned no reasoning text for this move.
Played from memory: no reasoning was produced for this move.
Thought for 3 s. The provider returned no reasoning text for this move.
Played from memory: no reasoning was produced for this move.
Thought for 3 s. The provider returned no reasoning text for this move.
This is a Sicilian Open (Smith-Morra style). Taking the pawn with cxd4 leads to a Nxd4 knight recapture, transposing to standard Open Sicilian lines.
Thought for 3 s. The provider returned no reasoning text for this move.
This is a standard Sicilian position. Nxd4 trades knights, but Nf6 is more developing and standard.
Thought for 4 s. The provider returned no reasoning text for this move.
Thought for 5 s. The provider returned no reasoning text for this move.
Thought for 4 s. The provider returned no reasoning text for this move.
This is the classic Sicilian position where d6 is the standard move to prevent Nd5 issues and solidify the center.
Thought for 11 s. The provider returned no reasoning text for this move.
Qxc7 captures the knight, winning material.
Thought for 5 s. The provider returned no reasoning text for this move.
Looking at this position, White's knight on d5 is a strong outpost attacked by both my knight (f6) and queen (c7), while only defended by the e4 pawn (and queen through the d-file, but only relevant in deeper exchanges). Trading it off with Nxd5 exd5 is a clean, safe simplification that removes White's most active piece for equal value, while I retain my material edge.
Thought for 12 s. The provider returned no reasoning text for this move.
Looking at this position, my knight on c6 is attacked by the pawn on d5 and must move. I'll relocate it actively to b4, where it threatens both the c2 pawn and sets up a potential fork on c2 (hitting the king on e1 and rook on a1).
Thought for 9 s. The provider returned no reasoning text for this move.
Thought for 10 s. The provider returned no reasoning text for this move.
Thought for 3 s. The provider returned no reasoning text for this move.
Thought for 3 s. The provider returned no reasoning text for this move.
Thought for 4 s. The provider returned no reasoning text for this move.
Looking at this position, I'm up a full knight in material (Black +3). My priorities are king safety and consolidating this advantage.
Checking tactical options:
- Nxa2/Nxc2 would just trade my knight for a pawn (Ra1/Qd1 recapture) - bad trade
- Nxd5 loses the knight to Qxd5 since my d6 pawn blocks my queen from recapturing on d5
The best move is to get my king safe and activate my rook. Castling queenside is legal (king/rook haven't moved, path is clear and unattacked) and it immediately solves my king safety issue while connecting my rooks.
Thought for 8 s. The provider returned no reasoning text for this move.
Looking at this position, my knight on b4 is attacked by the queen on d4. Rather than retreat, I can play **Nxc2**, which forks the queen on d4 and the rook on a1! The knight on c2 attacks both pieces simultaneously via knight moves, and c2 is undefended by White. White will have to move the queen, and then I win the rook with Nxa1.
Thought for 10 s. The provider returned no reasoning text for this move.
Thought for 7 s. The provider returned no reasoning text for this move.
Thought for 7 s. The provider returned no reasoning text for this move.
Thought for 6 s. The provider returned no reasoning text for this move.
Thought for 13 s. The provider returned no reasoning text for this move.
Looking at this position, I'm already up significant material (a piece for a pawn). The pawn on d5 is undefended and capturable by my c6 pawn.
Thought for 10 s. The provider returned no reasoning text for this move.
Thought for 15 s. The provider returned no reasoning text for this move.
Thought for 9 s. The provider returned no reasoning text for this move.
Looking at this position, I'm significantly up in material (+5). I need to escape the check. Blocking with Nc2 or Nc6 would just lose the knight to Rxc2+/Rxc6+ (undefended), so a king move is best.
Kb8 tucks the king safely into the corner while keeping my rook on d8 defending the d4 knight along the file, and avoids walking into potential future checks that Kd7 might allow.
Thought for 9 s. The provider returned no reasoning text for this move.
Thought for 2 s. The provider returned no reasoning text for this move.
Thought for 12 s. The provider returned no reasoning text for this move.
Looking at this position, I'm up significant material (queen for knight+pawn trade earlier). My knight on d4 is attacked by the bishop on c3, so I need to address it.
Ne2+ gives a check that forces the king to h1 (the only legal escape since the rook occupies f1), gaining a free tempo. Then I can follow up with Nxc3 to trade for the bishop, simplifying while maintaining my large material advantage.
Thought for 3 s. The provider returned no reasoning text for this move.
Looking at this position, I'm massively ahead in material (up roughly a full rook, 23 vs 13). My knight on e2 can capture the bishop on c3, which is a great simplifying trade that locks in my material advantage while removing White's only active piece.
Let me verify: Ne2 to c3 is a valid knight move, and it captures White's bishop. After the recapture bxc3, I'll still be up a full rook's worth of material with a much simpler position to convert.
Other options like Ng3+ would just hang the knight to fxg3, and Nd4 would be captured by the bishop. Nxc3 is clearly the best - trading a piece down when I'm already massively ahead is the correct simplifying strategy.
Thought for 3 s. The provider returned no reasoning text for this move.
Thought for 4 s. The provider returned no reasoning text for this move.
Thought for 6 s. The provider returned no reasoning text for this move.
Thought for 14 s. The provider returned no reasoning text for this move.
Thought for 5 s. The provider returned no reasoning text for this move.
Thought for 5 s. The provider returned no reasoning text for this move.
Thought for 8 s. The provider returned no reasoning text for this move.
Checkmate available!