Claude Opus 5.5
ECI#4
169Claude Opus 5.5 is a closed-weights model from Anthropic, released September 22, 2026. It has an ECI score of 169 and ranks 4th of 240 tracked models. At the time of its release, it ranked 2nd of 226 tracked models.
Claude Opus 5.5 vs select alternatives
| Domain | Benchmark | Claude Opus 5.5 | |||
|---|---|---|---|---|---|
ECI scoreBest score 173 | 169 | 167 | 169 | 159 | |
| Ranking | #4 | #7 | #3 | #23 | |
| Games | SpireClimbBest score 34% | ||||
Chess PuzzlesBest score 79% | |||||
Mystery Game PuzzlesBest score 90% | |||||
Earthborne Rangers (EBR-bench)Best score 90% | |||||
| Mathematics | FrontierMath ErdősBest score 4% | ||||
FrontierMath Tier 4 (v2)Best score 100% | |||||
| Multimodal | Furniture Assembly BenchmarkBest score 90% | ||||
| Software engineering | MirrorCodeBest score 98% | ||||
| World knowledge | SimpleQA VerifiedBest score 94% |
