Claude Sonnet 4 scores 18.7 on the Respan Index (#99), ahead of Grok 4 Fast Reasoning at 18.4 (#102). Grok 4 Fast Reasoning leads on 2 of the 3 benchmarks both report. Grok 4 Fast Reasoning is 22x cheaper per token at list price. Grok 4 Fast Reasoning has the larger context window (2M tokens).
| Benchmark | Claude Sonnet 4 | Grok 4 Fast Reasoning |
|---|---|---|
| GPQA Diamond | 79.2% | 85.7% |
| SAGE (Vals AI) | 35% | 29.8% |
| LMArena Elo | 1402 | 1405 |
Higher is better. Each score links to where it was published.
* Estimated: no published scores in that category. How the Respan Index works