Compare / Claude Opus 5.5 vs grok-4-fast-reasoning
Claude Opus 5.5 vs grok-4-fast-reasoning
12 results from 3 sources that measured both models. Each row is in the source's own units; there is no overall winner.
| Benchmark | Metric | Claude Opus 5.5 | grok-4-fast-reasoning |
|---|---|---|---|
| Arena (formerly LMArena)reported | Business, management and financeArena rating | 1,499 | 1,403 |
| Arena (formerly LMArena)reported | Creative writingArena rating | 1,521 | 1,383 |
| Arena (formerly LMArena)reported | Expert promptsArena rating | 1,556 | 1,421 |
| Arena (formerly LMArena)reported | Instruction followingArena rating | 1,516 | 1,389 |
| Arena (formerly LMArena)reported | OverallArena rating | 1,509 | 1,405 |
| Arena (formerly LMArena)reported | Writing, literature and languageArena rating | 1,520 | 1,388 |
| Artificial Analysisreported | Artificial Analysis Intelligence Indexindex score | 57.6 | 17.9 |
| Artificial Analysisreported | Humanity's Last Exam% of questions | 61.4% | 19.1% |
| Artificial Analysisreported | Long-context reasoning (AA-LCR)% of questions | 84.7% | 73.7% |
| UGI Leaderboardreported | Requested-length error% off the requested word count | 2.0% | 23.0% |
| UGI Leaderboardreported | Style adherencescore from 0 to 1 | 0.43 | 0.33 |
| UGI Leaderboardreported | Writing scorescore out of 100 | 70.0 | 53.4 |
Bold green marks the better value on that metric. Where a source reports ranges that overlap, the difference may not be meaningful; see the benchmark page for ranges.