Head to head
Claude Opus 5.5 vs Claude Sonnet 5.5
Which is better, Claude Opus 5.5 or Claude Sonnet 5.5?
Claude Opus 5.5 finishes ahead of Claude Sonnet 5.5 on the index, 92.8 to 91.5. It is the stronger of the two on Craft, while Claude Sonnet 5.5 still leads on Speed and Value. Both are scored on the same rubric, in the same week, and neither placing is sponsored.
Updated
Claude Opus 5.5
01 of 73
92.8
Fable-level answers for less than the Opus it replaces. The new default.
Claude Sonnet 5.5
02 of 73
91.5
Nearly the strongest model in the index, at a mid-range price. Sonnet stopped being the compromise.
The four scores, side by side
| Score | Claude Opus 5.5 | Claude Sonnet 5.5 | Difference |
|---|---|---|---|
| Craft | 98 | 93 | +5 |
| Speed | 84 | 88 | +4 |
| Control | 91 | 90 | +1 |
| Value | 84 | 90 | +6 |
| Index score | 92.8 | 91.5 | +1.3 |
Which to pick
Pick Claude Opus 5.5 unless Speed and Value is what decides it for you, which is exactly where Claude Sonnet 5.5 is the better answer.
Claude Opus 5.5
Opus 5.5 reset the top of this index. Anthropic says it performs at the level of Fable 5.1 while costing less than Opus 5, and the independent leaderboards agree: it tops the Artificial Analysis index and sits second on the human-preference arena. It keeps the million-token window and runs long agent loops without drifting. If you want one paid model and no further decisions this quarter, this is it.
Where it shines
- Highest score on the Artificial Analysis index as of October 2026
- Matches the Fable tier on long agentic work at under half its price
- A fast mode for interactive work, in research preview
Claude Sonnet 5.5
Sonnet 5.5 is the surprise of the autumn releases. It costs the same as Sonnet 5 and scores second only to Opus 5.5 on the Artificial Analysis index, ahead of every OpenAI and Google model. Human voters rate it lower than its benchmarks suggest, which is why it sits below Opus on craft here. For coding agents, editor integrations and anything that runs all day, it is the best value at the top of the field.
Where it shines
- Second-highest Artificial Analysis score in the index, at a fifth of the Fable price
- Top-tier terminal and computer-use results
- Cheaper cached input since October, which helps long agent loops