Anthropic · llm model

Claude Fable 5.1

Claude Fable 5.1 is an Anthropic language model released Sep 15, 2026; Anthropic's newest language model in our dataset is Claude Haiku 5.5. Proprietary, API access only. Anthropic's top-priced generally available Claude model, announced alongside the access-limited Claude Mythos on Sep 15, 2026. Verified against vendor sources on Oct 26, 2026.

Reported Last verified Oct 26, 2026 · All models · JSON · Markdown

ReleasedSep 15, 2026
Context window1M1,000,000 tokens
Max output128K128,000 tokens
LicenceProprietaryProprietary (API)

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Key facts

Claude Fable 5.1: key facts with sources
Fact	Value	Source
Vendor	Anthropic	n/a
Released	Sep 15, 2026 Date of the Anthropic announcement "Introducing Claude Mythos and Fable 5.1".	source
Status	generally available	n/a
API id	claude-fable-5-1	source
Context window	1,000,000 tokens (1M)	source
Max output	128,000 tokens	source
Input	text, image	source
Output	text	source
Licence	Proprietary (API)	source
Pricing	$10 in / $50 out per 1M tokens	source

Where Claude Fable 5.1 sits in our data

Released Sep 15, 2026 (week 38 of 2026), in September 2026. Other models in our data released that month: GPT-6.1 Sol, Claude Sonnet 5.5, Claude Opus 5.5, Gemini 3.8 Flash TTS, Gemini 3.8 Flash-Lite TTS, GPT-6 Luna.
The previous Anthropic model we track is Claude Mythos 5.1 (Sep 1, 2026), 14 days earlier.
Of the 60 models in our data with a published context window, Claude Fable 5.1 has the number 28 largest (1M tokens). Our data is not every model on the market.
Anthropic tools we cover: Claude Code, Claude.
All releases by date: AI model releases by month · new AI models this week. Choosing for code: best LLM for coding.

How Claude Fable 5.1 differs from Claude Mythos 5.1

Read from the recorded facts of the two models, not from a head-to-head test. We have not run either.

Listed price is the same as Claude Mythos 5.1: $10 in and $50 out (per 1M tokens).
Both list a 1M-token context window.
Status is generally available, against limited access.
Claude Fable 5.1 came out 14 days after Claude Mythos 5.1.
Facts for the other model: Claude Mythos 5.1.

What we tested

Nothing yet. We have not run Claude Fable 5.1 ourselves, so every fact on this page is Reported from the sources below. When we do test it, the scope will be stated here and in our test logs. See methodology.

Not verified, left out

We could not confirm these on a vendor page, so we do not state them.

Claude Mythos 5.1 is listed by Anthropic with access limited to verification programs; we did not verify its specifications, so it has no entry.