Head to head
Claude Opus 5.5 vs Claude Fable 5.1
Which is better, Claude Opus 5.5 or Claude Fable 5.1?
Claude Opus 5.5 finishes ahead of Claude Fable 5.1 on the index, 92.8 to 87.9, and leads on all four scores: craft, speed, control 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 Fable 5.1
08 of 73
87.9
Anthropic's top tier for the longest, hardest runs, with a cheaper Opus now snapping at its heels.
The four scores, side by side
| Score | Claude Opus 5.5 | Claude Fable 5.1 | Difference |
|---|---|---|---|
| Craft | 98 | 95 | +3 |
| Speed | 84 | 76 | +8 |
| Control | 91 | 91 | — |
| Value | 84 | 72 | +12 |
| Index score | 92.8 | 87.9 | +4.9 |
Which to pick
Claude Opus 5.5 is the safer pick on every axis we score. Claude Fable 5.1 earns its place in the index, but nothing in these four numbers argues for it over Claude Opus 5.5.
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 Fable 5.1
Fable 5.1 is Anthropic's most expensive model and the one it positions for demanding reasoning and long-horizon agent work. It is a clear step up from Fable 5 and cuts the price of cached input by three quarters, which matters on long runs that re-read the same context. The trouble is Opus 5.5, which arrived three weeks later, scores higher on both independent leaderboards and costs well under half as much. Fable now earns its place only on work where you have measured the difference.
Where it shines
- Built and priced for hours-long agent runs that must not drift
- Cached input costs a quarter of what it did on Fable 5
- Strong on computer-use and terminal benchmarks