Claude Fable 5.1
Anthropic · released 2026-09-01 · route claude-fable-5-1 · Model profile
Opening gap: +109 (95%: -121 to +339). The interval includes zero, so we can't yet say whether it performs differently across the variants.
Standard
- Rating
- 1,16295%: 998 to 1,325
- Record
- 12 won, 0 drawn, 12 lost of 24
- Accuracy (open positions)
- 85.0
- Accuracy (all moves)
- 87.6
- Average centipawn loss
- 74
- Blunders / mistakes / inaccuracies per 100 moves
- 6.8 / 4.4 / 8.6
- Matched Stockfish's first choice
- 39%
- In Stockfish's top three
- 61%
- Legal on the first try
- 95.2%
- Illegal / invalid
- 36 of 757 answers
- Forfeits
- 0
- Adjudicated games
- 19
- API-equivalent cost per game
- $2.37
- API-equivalent cost per move
- $0.079
- Seconds per move
- 20.4
- Model minutes per game
- 10.2
- Tokens per move (in / out)
- 1,052 / 1,162
- Reasoning tokens per move
- 1,142
- Aborted on our side (not counted)
- 0
By phase
| Phase | Moves | Accuracy | Centipawn loss | Blunders /100 | Engine match |
|---|---|---|---|---|---|
| Opening | 240 | 92.6 | 28 | 2.9 | 50% |
| Middlegame | 328 | 78.9 | 103 | 9.4 | 32% |
| Endgame | 153 | 80.7 | 83 | 7.2 | 36% |
Chess960
- Rating
- 1,05295%: 891 to 1,214
- Record
- 12 won, 0 drawn, 12 lost of 24
- Accuracy (open positions)
- 82.9
- Accuracy (all moves)
- 86.4
- Average centipawn loss
- 83
- Blunders / mistakes / inaccuracies per 100 moves
- 8.0 / 4.3 / 8.2
- Matched Stockfish's first choice
- 31%
- In Stockfish's top three
- 54%
- Legal on the first try
- 88.2%
- Illegal / invalid
- 92 of 815 answers
- Forfeits
- 0
- Adjudicated games
- 16
- API-equivalent cost per game
- $3.42
- API-equivalent cost per move
- $0.114
- Seconds per move
- 29.8
- Model minutes per game
- 15.0
- Tokens per move (in / out)
- 1,177 / 1,802
- Reasoning tokens per move
- 1,788
- Aborted on our side (not counted)
- 1
By phase
| Phase | Moves | Accuracy | Centipawn loss | Blunders /100 | Engine match |
|---|---|---|---|---|---|
| Opening | 240 | 85.2 | 56 | 7.5 | 25% |
| Middlegame | 369 | 80.5 | 104 | 9.2 | 35% |
| Endgame | 114 | 83.1 | 73 | 5.3 | 28% |
Games
Standard as blackWon vs Skill 0, 25% random moves36 plies · adjudicated: decisive advantage · $1.19Chess960 as blackWon vs Skill 0, 25% random moves40 plies · adjudicated: decisive advantage · $1.47Standard as whiteLost vs Stockfish 150036 plies · checkmate · $1.08Chess960 as whiteLost vs Stockfish Skill 053 plies · adjudicated: decisive advantage · $2.81Standard as blackLost vs Skill 0, 10% random moves47 plies · checkmate · $1.74Chess960 as blackWon vs Skill 0, 10% random moves82 plies · adjudicated: decisive advantage · $3.89Standard as whiteWon vs Skill 0, 10% random moves59 plies · adjudicated: decisive advantage · $1.77Chess960 as whiteLost vs Skill 0, 25% random moves46 plies · checkmate · $2.61Standard as blackLost vs Stockfish 132082 plies · adjudicated: decisive advantage · $4.32Chess960 as blackLost vs Stockfish 1320130 plies · adjudicated: decisive advantage · $7.20Standard as whiteWon vs Skill 0, 10% random moves35 plies · adjudicated: decisive advantage · $0.887Chess960 as whiteLost vs Skill 0, 10% random moves26 plies · checkmate · $1.24Standard as whiteLost vs Stockfish 1500177 plies · adjudicated: decisive advantage · $10.64Standard as blackWon vs Skill 0, 25% random moves40 plies · adjudicated: decisive advantage · $1.20Chess960 as blackWon vs Skill 0, 25% random moves52 plies · adjudicated: decisive advantage · $3.31Chess960 as whiteLost vs Stockfish Skill 069 plies · adjudicated: decisive advantage · $5.26Standard as blackWon vs Skill 0, 10% random moves70 plies · adjudicated: decisive advantage · $2.31Chess960 as blackWon vs Skill 0, 10% random moves56 plies · adjudicated: decisive advantage · $2.32Standard as whiteWon vs Skill 0, 10% random moves45 plies · adjudicated: decisive advantage · $1.88Chess960 as whiteWon vs Skill 0, 25% random moves47 plies · adjudicated: decisive advantage · $2.46Standard as blackWon vs Stockfish 132042 plies · adjudicated: decisive advantage · $1.54Chess960 as blackLost vs Stockfish 132064 plies · adjudicated: decisive advantage · $5.01Standard as whiteLost vs Skill 0, 10% random moves87 plies · adjudicated: decisive advantage · $3.48Chess960 as whiteWon vs Skill 0, 10% random moves43 plies · checkmate · $2.15Standard as blackLost vs Skill 0, 25% random moves76 plies · adjudicated: decisive advantage · $4.25Chess960 as blackWon vs Skill 0, 25% random moves44 plies · adjudicated: decisive advantage · $2.29Chess960 as whiteLost vs Stockfish 1320109 plies · adjudicated: decisive advantage · $7.92Standard as whiteWon vs Stockfish Skill 043 plies · adjudicated: decisive advantage · $1.24Chess960 as blackWon vs Skill 0, 10% random moves114 plies · adjudicated: decisive advantage · $5.54Standard as blackWon vs Skill 0, 10% random moves62 plies · adjudicated: decisive advantage · $1.86Standard as whiteLost vs Skill 0, 10% random moves73 plies · adjudicated: decisive advantage · $2.72Chess960 as whiteWon vs Skill 0, 25% random moves33 plies · adjudicated: decisive advantage · $1.43Standard as blackLost vs Stockfish 132051 plies · checkmate · $2.19Chess960 as blackLost vs Skill 0, 10% random moves37 plies · checkmate · $2.34Standard as whiteWon vs Skill 0, 10% random moves19 plies · adjudicated: decisive advantage · $0.435Chess960 as whiteLost vs Skill 0, 10% random moves38 plies · checkmate · $2.58Standard as blackLost vs Skill 0, 10% random moves103 plies · checkmate · $4.49Chess960 as blackWon vs Skill 0, 25% random moves50 plies · adjudicated: decisive advantage · $2.76Standard as whiteLost vs Stockfish Skill 271 plies · adjudicated: decisive advantage · $2.77Chess960 as whiteLost vs Stockfish Skill 066 plies · checkmate · $4.39Standard as blackLost vs Stockfish Skill 023 plies · checkmate · $0.618Chess960 as blackWon vs Skill 0, 10% random moves60 plies · adjudicated: decisive advantage · $2.94Standard as whiteLost vs Stockfish 150067 plies · adjudicated: decisive advantage · $2.07Chess960 as whiteLost vs Skill 0, 10% random moves62 plies · checkmate · $3.68Standard as blackWon vs Stockfish Skill 064 plies · adjudicated: decisive advantage · $1.75Chess960 as blackLost vs Stockfish 132051 plies · checkmate · $3.20Chess960 as whiteWon vs Skill 0, 25% random moves69 plies · adjudicated: decisive advantage · $3.31Standard as whiteWon vs Skill 0, 25% random moves27 plies · adjudicated: decisive advantage · $0.436