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HEAD TO HEAD · UPDATED NOV 6, 2026
Claude Fable 5.1 vs Claude Sonnet 5.5
Two Anthropic models, on sourced numbers only. Green marks the higher (or cheaper) value on each row; the text below only calls a lead when the gap is bigger than measurement noise.
| Claude Fable 5.1 | Claude Sonnet 5.5 | |
|---|---|---|
| Arena Elo | 1504 source ↗ | 1477 source ↗ |
| GPQA Diamond | not published | 95.6% source ↗ |
| $ per 1M in / out | $10 / $50 source ↗ | $2 / $10 source ↗ |
| Blended $ per 1M (3:1) | $20.00 source ↗ | $4.00 source ↗ |
| Context window | 1M source ↗ | 1M source ↗ |
| Output speed | not published | 155 tok/s source ↗ |
| Released | Sep 1, 2026 source ↗ | Sep 28, 2026 source ↗ |
| Open weights | No source ↗ | No source ↗ |
| Reasoning effort tiers | low · medium · high · xhigh · max (default: high) | low · medium · high · xhigh · max (default: high) |
| API effort control | output_config={"effort": "low" | "medium" | "high" | "xhigh" | "max"} source ↗ | output_config={"effort": "low" | "medium" | "high" | "xhigh" | "max"} source ↗ |
| Additional benchmarks | Terminal-Bench 4.0: 55.8% source ↗ GDPval-AA v2.1: 1735 source ↗ AA Intelligence Index v5.0.1: 50 source ↗ | SWE-bench Pro: 81.3% source ↗ AA Intelligence Index v5.0.1: 55 source ↗ |
| Best for (workload) | Anthropic's most capable generally available model, for demanding reasoning and long-horizon agentic work (Anthropic). source ↗ | Fast (155 tok/s, Artificial Analysis) and strong on science: 95.6% GPQA Diamond at max effort (Epoch AI), above Opus 5.5's 90.6%. source ↗ |
Arena Elo from the arena.ai text leaderboard as of Oct 27, 2026 source ↗. Speed measured by Artificial Analysis and varies by provider.
Which one should I use?
For high-volume work where cost matters most, Claude Sonnet 5.5 is about 5.0 times cheaper per token. For overall answer quality as rated by people in blind tests, Claude Fable 5.1 leads clearly (1504 vs 1477 Arena Elo). Both are Anthropic models. Anthropic is at day 30 of a typical ~15-day gap between releases (PAST TYPICAL GAP).
Key differences from the sourced numbers
- Claude Sonnet 5.5 is the cheaper option: $4.00 vs $20.00 per 1M tokens at a 3:1 input-to-output mix (about 5.0 times less).
- Claude Fable 5.1 scores 27 Elo points higher (1504 vs 1477) on the Arena text leaderboard, where people vote on blind side-by-side answers.
- Claude Fable 5.1 pricing note: Same rate across the full 1M context window.
- Claude Sonnet 5.5 pricing note: Same rate across the full 1M context window.
Frequently asked questions
Is Claude Fable 5.1 or Claude Sonnet 5.5 better?
Claude Sonnet 5.5 is the cheaper option: $4.00 vs $20.00 per 1M tokens at a 3:1 input-to-output mix (about 5.0 times less). Claude Fable 5.1 scores 27 Elo points higher (1504 vs 1477) on the Arena text leaderboard, where people vote on blind side-by-side answers. Claude Fable 5.1 pricing note: Same rate across the full 1M context window. Claude Sonnet 5.5 pricing note: Same rate across the full 1M context window.
Which one should I use: Claude Fable 5.1 or Claude Sonnet 5.5?
For high-volume work where cost matters most, Claude Sonnet 5.5 is about 5.0 times cheaper per token. For overall answer quality as rated by people in blind tests, Claude Fable 5.1 leads clearly (1504 vs 1477 Arena Elo). Both are Anthropic models. Anthropic is at day 30 of a typical ~15-day gap between releases (PAST TYPICAL GAP).
How much does Claude Fable 5.1 cost compared with Claude Sonnet 5.5?
Claude Fable 5.1 lists at $10 / $50 per 1M input/output tokens ($20.00/1M blended at 3:1). Claude Sonnet 5.5 lists at $2 / $10 per 1M input/output tokens ($4.00/1M blended at 3:1).
Facts checked Nov 5, 2026 against official sources. Every number links to its source. Spotted an error? Email [email protected].