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Step 5 Preview
Claude Fable 5.1
Claude Fable 5.1 is a proprietary model from Anthropic, released Sep 1, 2026. It ranks #3 of 351 on the LMArena text leaderboard with a rating of 1513. It costs $10 per million input tokens and $50 per million output tokens, with a 1M-token context window.
- Developer
- Anthropic
- Released
- Sep 1, 2026
- Context window
- 1M
- Price in / out, per 1M tokens
- $10 / $50
- Weights
- Proprietary
- Inputs
- Text, Images, Files
- Reasoning
- Yes
- Tool use
- Yes
Benchmarks
| Benchmark | Score bar | Accuracy | Rank | Cost / test |
|---|---|---|---|---|
| Terminal-Bench 4.0Coding | 58.08% | 5 / 55 | $17.18 | |
| Vibe Code BenchCoding | 90.26% | 6 / 115 | $33.37 | |
| LiveCodeBenchCoding | 90.52% | 1 / 143 | $10 / $50 | |
| Tax Agent BenchFinance | 49.19% | 2 / 76 | $13.18 | |
| Legal Research BenchLaw | 55.29% | 3 / 85 | $23.06 | |
| MedCodeMedicine | 53.51% | 8 / 107 | $10 / $50 | |
| GPQA DiamondReasoning | 93.43% | 9 / 138 | $10 / $50 | |
| MMLU-ProReasoning | 92.38% | 1 / 138 | $10 / $50 | |
| MMMUReasoning | 90.64% | 1 / 93 | $10 / $50 | |
| Terminal-Bench ScienceReasoning | 40.00% | 6 / 42 | $38.01 |
Vals AI, as of Oct 24, 2026.
LMArena, by category
| Leaderboard | Rating | Rank | Votes |
|---|---|---|---|
| TextLMArena | 1513 | 3 / 351 | 16.3K |
| CodingLMArena | 1531 | 7 / 346 | 3.2K |
| MathLMArena | 1532 | 3 / 339 | 796 |
| Creative writingLMArena | 1510 | 3 / 349 | 3.7K |
| Instruction followingLMArena | 1519 | 4 / 351 | 4.9K |
| Hard promptsLMArena | 1528 | 3 / 351 | 9.5K |
| Multi-turnLMArena | 1495 | 12 / 349 | 2.2K |
| Long queriesLMArena | 1524 | 3 / 330 | 6.8K |
| ExpertLMArena | 1545 | 5 / 305 | 1.4K |
| Legal and governmentIndustries | 1512 | 7 / 325 | 1.3K |
| Medicine and healthcareIndustries | 1533 | 2 / 325 | 1.3K |
| Business and financeIndustries | 1492 | 7 / 344 | 2.9K |
| ChineseLanguages | 1584 | 2 / 328 | 1.3K |
| SpanishLanguages | 1519 | 2 / 249 | 546 |
| GermanLanguages | 1498 | 8 / 261 | 304 |
| FrenchLanguages | 1525 | 2 / 252 | 581 |
| JapaneseLanguages | 1560 | 1 / 236 | 299 |
| WebDevLMArena | 1743 | 5 / 124 | 8.1K |
| VisionLMArena | 1320 | 4 / 146 | 5K |
LMArena, CC BY 4.0, as of Oct 22, 2026. Where a model is rated at several effort levels, its best is shown.
Compare Claude Fable 5.1
Anthropic
An AI safety and research company that builds the Claude family of models, known for coding, long context and careful behaviour. Founded 2021, based in San Francisco. anthropic.com
Questions
Who makes Claude Fable 5.1?
Claude Fable 5.1 is made by Anthropic, founded 2021 and based in San Francisco.
How much does Claude Fable 5.1 cost?
$10 per million input tokens and $50 per million output tokens, at its provider’s list price.
What is Claude Fable 5.1’s context window?
1M tokens (1,000,000).
How does Claude Fable 5.1 rank?
#3 of 351 on LMArena’s text leaderboard, rated 1513 (95% interval 1507–1518) from 16,343 votes, as of Oct 22, 2026.
Is Claude Fable 5.1 open source?
No. Claude Fable 5.1 is proprietary and served through its provider’s API.