Claude Sonnet 5.5 scores 68.5 on the Respan Index (#6), ahead of DeepSeek V4.1 Flash at 50.9 (#20). Claude Sonnet 5.5 leads on 12 of the 15 benchmarks both report. DeepSeek V4.1 Flash is 7.6x cheaper per token at list price.
* Estimated: no published scores in that category. How the Respan Index works
| LiveBench Data Analysis (LiveBench) |
| 78.6% |
| 79.3% |
| LiveBench Instruction Following (LiveBench) | 70.5% | 70% |
| LiveBench Language (LiveBench) | 83.4% | 81.2% |
| LiveBench Mathematics (LiveBench) | 96.7% | 93.3% |
| LiveBench Reasoning (LiveBench) | 91.6% | 86.7% |
| SAGE (Vals AI) | 51.8% | 47.9% |
| Terminal-Bench 4.0 (Vals AI) | 64.1% | 19.7% |
| LMArena Agent (LMArena) | 0.1252 | 0.0402 |
| LMArena Elo | 1471 | 1474 |
| LMArena WebDev (LMArena) | 1786 | 1620 |
| SimpleBench (SimpleBench) | 75.9% | 66.7% |
Higher is better. Each score links to where it was published.