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Claude Opus 5.5
Muse Wonder
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GLM-5.3
GPT-5.5
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DeepSeek-V4.1-Flash-20260910
Grok 4.20 Beta
amazon-nova-experimental-chat
Dola Seed 2.0 Pro
NVIDIA-Nemotron-3-Ultra-550B-A55B
Gemma 4 31B
Step 5 PreviewClaude Fable 5.1 vs Claude Opus 5
- Claude Fable 5.1 and Claude Opus 5 are level on LMArena’s text leaderboard (1513 and 1508).
- Claude Opus 5 is cheaper: $5 / $25 per million input / output tokens, against $10 / $50 for Claude Fable 5.1.
- On the 10 Vals AI benchmarks both have taken, Claude Fable 5.1 wins 7 and Claude Opus 5 wins 3 (Claude Fable 5.1: Terminal-Bench 4.0, Vibe Code Bench, LiveCodeBench).
Side by side
Models (2/6)
- Claude Fable 5.1
- Claude Opus 5
| Benchmark | Claude Fable 5.1 | Claude Opus 5 |
|---|---|---|
| The model | ||
| Lab | Anthropic | Anthropic |
| Released | 2026-09-01 | 2026-07-24 |
| Weights | Proprietary | Proprietary |
| Context window | 1M | 1M |
| Input, per 1M tokens | $10 | $5 |
| Output, per 1M tokens | $50 | $25 |
| LMArena, people’s votes | ||
| LMArena TextMillions of people compare two anonymous models side by side and vote for the better answer | 1513#3 of 351 | 1508#4 of 351 |
| LMArena WebDevPeople ask two anonymous models to build the same web app, try both and vote for the better one | 1743#5 of 124 | 1691#9 of 124 |
| LMArena VisionSide-by-side votes on prompts that include an image | 1320#4 of 146 | 1320#3 of 146 |
| LMArena CodingLMArena’s text votes on prompts that ask for code | 1531#7 of 346 | 1533#4 of 346 |
| LMArena MathLMArena’s text votes on math prompts | 1532#3 of 339 | 1533#2 of 339 |
| LMArena Creative writingLMArena’s text votes on stories, poems and other creative writing | 1510#3 of 349 | 1495#5 of 349 |
| LMArena Hard promptsLMArena’s text votes on the hardest prompts | 1528#3 of 351 | 1527#4 of 351 |
| LMArena Instruction followingLMArena’s text votes on prompts with specific instructions to follow | 1519#4 of 351 | 1518#5 of 351 |
| Vals AI, coding | ||
| Terminal-Bench 4.0Frontier-difficulty tasks an agent completes in a real terminal | 58.08%#5 of 55 | 53.53%#9 of 55 |
| SWE-benchReal GitHub issues from open-source projects | — | 97.00%#1 of 85 |
| Vibe Code BenchBuilding complete web apps from a plain-language brief, graded on whether the app works | 90.26%#6 of 115 | 88.40%#9 of 115 |
| LiveCodeBenchFresh competitive programming problems, collected after models’ training cut-offs to avoid contamination | 90.52%#1 of 143 | 89.03%#4 of 143 |
| Vals AI, finance | ||
| Tax Agent BenchAgentic research into US corporate tax questions | 49.19%#2 of 76 | 45.55%#4 of 76 |
| Vals AI, law | ||
| Legal Research BenchAgentic US legal research | 55.29%#3 of 85 | 55.29%#2 of 85 |
| Vals AI, medicine | ||
| MedCodeAssigning the right medical billing codes from clinical notes | 53.51%#8 of 107 | 63.57%#1 of 107 |
| Vals AI, reasoning | ||
| GPQA DiamondGraduate-level questions in biology, physics and chemistry that experts answer well and search does not | 93.43%#9 of 138 | 93.43%#8 of 138 |
| MMLU-ProHarder, reasoning-focused multiple choice across 14 subjects, from law to engineering | 92.38%#1 of 138 | 91.59%#2 of 138 |
| MMMUCollege-level questions that need both an image and text | 90.64%#1 of 93 | 89.88%#2 of 93 |
| Terminal-Bench ScienceExpert-written scientific research workflows, run by an agent in a terminal | 40.00%#6 of 42 | 27.14%#9 of 42 |
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Questions
Which is better, Claude Fable 5.1 or Claude Opus 5?
Claude Fable 5.1 and Claude Opus 5 are level on LMArena’s text leaderboard (1513 and 1508). Claude Opus 5 is cheaper: $5 / $25 per million input / output tokens, against $10 / $50 for Claude Fable 5.1. On the 10 Vals AI benchmarks both have taken, Claude Fable 5.1 wins 7 and Claude Opus 5 wins 3 (Claude Fable 5.1: Terminal-Bench 4.0, Vibe Code Bench, LiveCodeBench).
Which is cheaper, Claude Fable 5.1 or Claude Opus 5?
Claude Opus 5 is cheaper: $5 / $25 per million input / output tokens, against $10 / $50 for Claude Fable 5.1.