Claude Opus 5.5 scores 72.4 on the Respan Index (#1), ahead of DeepSeek V4.1 Flash at 50.9 (#20). Claude Opus 5.5 leads on 11 of the 15 benchmarks both report. DeepSeek V4.1 Flash is 15x cheaper per token at list price.
* Estimated: no published scores in that category. How the Respan Index works
| LiveBench Data Analysis (LiveBench) |
| 80.3% |
| 79.3% |
| LiveBench Instruction Following (LiveBench) | 67% | 70% |
| LiveBench Language (LiveBench) | 86.3% | 81.2% |
| LiveBench Mathematics (LiveBench) | 97.1% | 93.3% |
| LiveBench Reasoning (LiveBench) | 92.2% | 86.7% |
| SAGE (Vals AI) | 45.8% | 47.9% |
| Terminal-Bench 4.0 (Vals AI) | 65.2% | 19.7% |
| LMArena Agent (LMArena) | 0.1382 | 0.0402 |
| LMArena Elo | 1504 | 1474 |
| LMArena WebDev (LMArena) | 1815 | 1620 |
| SimpleBench (SimpleBench) | 88.4% | 66.7% |
Higher is better. Each score links to where it was published.