Claude Sonnet 5.5 vs Claude Fable 5.1
Claude Sonnet 5.5 scores higher on the Models at Work leaderboard (84 vs 80 out of 100). Claude Sonnet 5.5 is about 5.0× cheaper per blended million tokens ($4 vs $20). On Artificial Analysis' independent Intelligence Index, Claude Sonnet 5.5 leads 56 to 53.
| Claude Sonnet 5.5 · Anthropic | Claude Fable 5.1 · Anthropic | |
|---|---|---|
| Leaderboard rank | #4 | #6 |
| Score (0–100) | 84 | 80 |
| Tier | Workhorse | Frontier |
| Price per 1M tokens | $2 in · $10 out | $10 in · $50 out |
| Context window | 1M | 1M |
| Open weights | No | No |
| Artificial Analysis Intelligence Index | 56 | 53 |
| Arena text score | — | 1501 |
| Humanity's Last Exam, Diamond (Scale) | — | 51.3 |
| Best for | Production coding assistants, High-volume agents, Default model for most teams | Long-horizon agents, Problems Opus fails on, Demanding reasoning |
Choose Claude Sonnet 5.5 if…
- you need production coding assistants
- you need high-volume agents
- you need default model for most teams
The value pick of the table: second on the index at a fifth of the Opus price, and the fastest of the top five.
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 Sonnet 5.5: Less discussed than its siblings because it just works; the October cache-read price cut to $0.10 per million was the news.
Questions people ask
Which is better, Claude Sonnet 5.5 or Claude Fable 5.1?
Claude Sonnet 5.5 scores higher on the Models at Work leaderboard (84 vs 80 out of 100). Claude Sonnet 5.5 is about 5.0× cheaper per blended million tokens ($4 vs $20). On Artificial Analysis' independent Intelligence Index, Claude Sonnet 5.5 leads 56 to 53.
When should I choose Claude Sonnet 5.5 over Claude Fable 5.1?
Choose Claude Sonnet 5.5 for production coding assistants, high-volume agents, default model for most teams. The value pick of the table: second on the index at a fifth of the Opus price, and the fastest of the top five.
When should I choose Claude Fable 5.1 over Claude Sonnet 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 Sonnet 5.5 or Claude Fable 5.1?
Claude Sonnet 5.5 costs $2 per million input tokens and $10 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.