Claude Fable 5.1
Anthropic's Claude Fable 5.1 is a new chatbot model for writing and answering questions, released alongside Claude Mythos 5.1 for developers online.
Key facts
- Released
- Sep 1, 2026
- What it does
- Text and chat: Writes, answers questions and holds a conversation.Thinks first: Can reason step by step before it answers: slower, but better at maths, code and tricky questions.Sees images: Understands pictures, screenshots and charts you share with it.Reads files: Reads documents such as PDFs.
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- Knowledge cutoff
- June 2026 · the latest events it learned about
- How
- For developers, through an API
- Announced as
- “Introducing Claude Fable 5.1 and Claude Mythos 5.1”
From trckr's archive of releases before it started watching. Date and details from Epoch AI's database of AI models (CC BY 4.0).
Price and limits
What developers pay to use it through the API: How developers plug a model into their own apps and pay per use. A model that's "in the API" can be used by programmers, even if it isn't in a chat app yet., per million Tokens: The small chunks of text a model reads and writes, about three-quarters of a word each. Prices and limits are counted in tokens. sent (input) or written back (output), and how much it can take in at once.
- Input
- $10.00
- per million tokensCached: $0.25
- Output
- $50.00
- per million tokens
- Context window: How much a model can keep in mind at once: your question, any files you share and its own replies. Measured in tokens; 1,000 tokens is about 750 words.
- 1M tokens
- about 750,000 words
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- Longest answer
- 128K tokens (about 96,000 words)
From the lab's own listing on models.dev and OpenRouter, checked .
How it scores
From independent testers, never the lab's own claims.
- Combined test score#5 of 235
- GPT-6 Astra169
- 2GPT-6.1 Sol169
- 3Claude Opus 5.5168
- 4GPT-6.1 Terra168
- 5Claude Fable 5.1167
Source: Epoch AI · Epoch Capabilities Index
- Chat answers, by people's votes#6 of 86
- Gemini 4 Carbon1,527
- 2Gemini 4 Argon1,522
- 5Claude Fable 51,504
- 6Claude Fable 5.11,503
- 7Claude Opus 4.61,503
Source: LMArena · LMArena text, adjusted for style
- Building apps, by people's votes#5 of 85
- Claude Opus 5.51,818
- 2Claude Sonnet 5.51,773
- 3Gemini 4 Carbon1,768
- 4GPT-6 Astra1,767
- 5Claude Fable 5.11,744
Source: LMArena · LMArena WebDev
Compare Claude Fable 5.1 with
It came out 39 days after Claude Opus 5, the lab's previous model.
The details
Claude Fable 5.1 is Anthropic's text model for language generation and question answering, released with Claude Mythos 5.1 and accessed through an API: How developers plug a model into their own apps and pay per use. A model that's "in the API" can be used by programmers, even if it isn't in a chat app yet. rather than as a download.
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