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HEAD TO HEAD · UPDATED NOV 6, 2026
Claude Opus 5.5 vs Claude Fable 5.1
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 Opus 5.5 | Claude Fable 5.1 | |
|---|---|---|
| Arena Elo | 1509 source ↗ | 1504 source ↗ |
| GPQA Diamond | 90.6% source ↗ | not published |
| $ per 1M in / out | $4 / $20 source ↗ | $10 / $50 source ↗ |
| Blended $ per 1M (3:1) | $8.00 source ↗ | $20.00 source ↗ |
| Context window | 1M source ↗ | 1M source ↗ |
| Output speed | 110 tok/s source ↗ | not published |
| Released | Sep 22, 2026 source ↗ | Sep 1, 2026 source ↗ |
| Open weights | No source ↗ | No source ↗ |
| Reasoning effort tiers | low · medium · high · xhigh · max (default: medium) | 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 | Arena WebDev: 1810 (#1) source ↗ SWE-bench Pro: 89.9% source ↗ Terminal-Bench 4.0: 66.4% (xhigh) source ↗ GDPval-AA v2.1: 1846 source ↗ CursorBench 4.0: 57.8% at max effort, 52.5% at default source ↗ AA Intelligence Index v5.0.1: 59 source ↗ | Terminal-Bench 4.0: 55.8% source ↗ GDPval-AA v2.1: 1735 source ↗ AA Intelligence Index v5.0.1: 50 source ↗ |
| Best for (workload) | Anthropic suggests starting with Opus 5.5 for most workloads. #1 on Arena WebDev (1810); 66.4% on Terminal-Bench 4.0 at xhigh effort (Anthropic). source ↗ | Anthropic's most capable generally available model, for demanding reasoning and long-horizon agentic work (Anthropic). 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 Opus 5.5 is about 2.5 times cheaper per token. 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 Opus 5.5 is the cheaper option: $8.00 vs $20.00 per 1M tokens at a 3:1 input-to-output mix (about 2.5 times less).
- On the Arena text leaderboard they are close (1509 vs 1504): a gap under 20 points is within the leaderboard's margin of error.
- Claude Opus 5.5 pricing note: Same rate across the full 1M context window.
- Claude Fable 5.1 pricing note: Same rate across the full 1M context window.
Frequently asked questions
Is Claude Opus 5.5 or Claude Fable 5.1 better?
Claude Opus 5.5 is the cheaper option: $8.00 vs $20.00 per 1M tokens at a 3:1 input-to-output mix (about 2.5 times less). On the Arena text leaderboard they are close (1509 vs 1504): a gap under 20 points is within the leaderboard's margin of error. Claude Opus 5.5 pricing note: Same rate across the full 1M context window. Claude Fable 5.1 pricing note: Same rate across the full 1M context window.
Which one should I use: Claude Opus 5.5 or Claude Fable 5.1?
For high-volume work where cost matters most, Claude Opus 5.5 is about 2.5 times cheaper per token. Both are Anthropic models. Anthropic is at day 30 of a typical ~15-day gap between releases (PAST TYPICAL GAP).
How much does Claude Opus 5.5 cost compared with Claude Fable 5.1?
Claude Opus 5.5 lists at $4 / $20 per 1M input/output tokens ($8.00/1M blended at 3:1). Claude Fable 5.1 lists at $10 / $50 per 1M input/output tokens ($20.00/1M blended at 3:1).
Facts checked Nov 5, 2026 against official sources. Every number links to its source. Spotted an error? Email [email protected].