Claude Opus 5.5 vs Claude Fable 5.1
Claude Opus 5.5 scores higher on the Models at Work leaderboard (91 vs 80 out of 100). Claude Opus 5.5 is about 2.5× cheaper per blended million tokens ($8 vs $20). On Artificial Analysis' independent Intelligence Index, Claude Opus 5.5 leads 58 to 53.
| Claude Opus 5.5 · Anthropic | Claude Fable 5.1 · Anthropic | |
|---|---|---|
| Leaderboard rank | #1 | #6 |
| Score (0–100) | 91 | 80 |
| Tier | Frontier | Frontier |
| Price per 1M tokens | $4 in · $20 out | $10 in · $50 out |
| Context window | 1M | 1M |
| Open weights | No | No |
| Artificial Analysis Intelligence Index | 58 | 53 |
| Arena text score | 1507 | 1501 |
| Humanity's Last Exam, Diamond (Scale) | 55.0 | 51.3 |
| Epoch Capabilities Index | 167 | — |
| Best for | Agentic coding, Long-running agents, Enterprise knowledge work | Long-horizon agents, Problems Opus fails on, Demanding reasoning |
Choose Claude Opus 5.5 if…
- you need agentic coding
- you need long-running agents
- you need enterprise knowledge work
The model people actually ship agents on: top of the independent index, a price that does not need a budget meeting, and a community that complains mainly about how much it has to be used.
Caveats: Arena puts Gemini 4 Argon ahead on chat preference; the gap is inside two scores' error bars.
Choose Claude Fable 5.1 if…
- you need long-horizon agents
- you need problems opus fails on
- you need demanding reasoning
The specialist: Anthropic's own docs say to reach for it when Opus 5.5 at high effort still falls short, and the price says the same.
Caveats: Ten dollars per million input is the highest in this table alongside Astra.
What practitioners say
Claude Opus 5.5: The launch thread was the biggest Claude thread of the year on Hacker News, a port of the TypeScript compiler to Rust credited the model with a working build in ten hours, and a Vals AI materials-discovery run used it for agentic simulation. A 'has it been nerfed yet' tracker is the most-upvoted scepticism.
Questions people ask
Which is better, Claude Opus 5.5 or Claude Fable 5.1?
Claude Opus 5.5 scores higher on the Models at Work leaderboard (91 vs 80 out of 100). Claude Opus 5.5 is about 2.5× cheaper per blended million tokens ($8 vs $20). On Artificial Analysis' independent Intelligence Index, Claude Opus 5.5 leads 58 to 53.
When should I choose Claude Opus 5.5 over Claude Fable 5.1?
Choose Claude Opus 5.5 for agentic coding, long-running agents, enterprise knowledge work. The model people actually ship agents on: top of the independent index, a price that does not need a budget meeting, and a community that complains mainly about how much it has to be used.
When should I choose Claude Fable 5.1 over Claude Opus 5.5?
Choose Claude Fable 5.1 for long-horizon agents, problems opus fails on, demanding reasoning. The specialist: Anthropic's own docs say to reach for it when Opus 5.5 at high effort still falls short, and the price says the same.
Which is cheaper, Claude Opus 5.5 or Claude Fable 5.1?
Claude Opus 5.5 costs $4 per million input tokens and $20 per million output tokens on Anthropic's list price (Claude pricing, read Oct 10, 2026). Claude Fable 5.1 costs $10 per million input tokens and $50 per million output tokens on Anthropic's list price (Claude pricing, read Oct 10, 2026).
Scores come from the Models at Work leaderboard: Score is 0 to 100: 50% independent evals normalised within this table, 20% price-performance, 15% practitioner sentiment from Signals and community threads, 15% operational fit (context, speed, availability, open weights). Models within three points are a tie in practice. Vendor-published figures are labelled as such and never counted as independent. Prices are vendor list prices where published; blended figures assume three input tokens per output token.