# Anthropic — Claude Fable 5.1

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- This model's page: https://forck.live/models/claude-fable-5-1
- Anthropic's page: https://forck.live/company/anthropic
- Every model: https://forck.live/models
- Catalogue: https://forck.live/llms.txt

## Model

- Name: Claude Fable 5.1
- Company: Anthropic (anthropic.com)
- Launch post: Introducing Claude Mythos and Fable 5.1 — https://forck.live/items/7275-introducing-claude-mythos-and-fable-5-1
- Announced: 2026-09-01
- Launch source: https://www.anthropic.com/claude-fable-and-mythos-5-1
- Launch chosen by: a person, pinned in the model registry
- Released (per models.dev): 2026-09-01
- Listed (per OpenRouter): 2026-09-01
- Open weights: no
- Posts about it: 2
- Outlets named under its posts: 6
- Also written: Fable 5.1; Fable
- OpenRouter id: anthropic/claude-fable-5.1 — https://openrouter.ai/anthropic/claude-fable-5.1
- Price: cost an estimated 25% less than Fable 5 for typical workloads — from https://forck.live/items/7275-introducing-claude-mythos-and-fable-5-1

## Posts about it

_Anthropic's own posts whose title names Claude Fable 5.1, and its launch post, in the record's order: dated newest first, undated last. The record reads the newest 50 first-party posts mentioning the model, every company's together, so a model mentioned more often than that lists the newest of them._

Every entry is one first-party announcement, and carries the same eight fields
in this order before any others:

    Company · Announced · Category · Coverage · Announcement · Group · Source · Record

`Source` is the company's own page the announcement was traced to and `Record`
is this site's page for it. Both are safe to cite.

`Coverage` is a number of outlets, or `not counted` — which means this record
reached no count of its own, never that nobody wrote about it.

`Category` is this tracker's own analysis, and is authoritative wherever it is
stated. `not stated` means either that nothing has analysed the post yet or
that the analysis placed it outside this taxonomy; neither is a verdict about
the announcement.

`Announcement` is whether the post is news of something the company did, rather
than a how-to, a customer story, a changelog listing or a staffing note.

`Group` is which of this record's groups the entry falls in, carried on the
entry itself so it holds where the groups are headings and where they are not.
One of: `models`, `covered`, `announcements`, `routine`.

Anything after `Record` is held detail that only some announcements carry.

### Anthropic — How Block orchestrates Claude Fable across thousands of pull requests

- Company: Anthropic (anthropic.com)
- Announced: 2026-10-08
- Category: not stated
- Coverage: not counted
- Announcement: no
- Group: routine
- Source: https://claude.com/resources/articles/how-block-orchestrates-claude-fable-across-thousands-of-pull-requests
- Record: https://forck.live/items/17144-how-block-orchestrates-claude-fable-across-thousands-of-pull-requests
- Subject: Claude

Block is using Anthropic's Claude Fable 5 to orchestrate company-wide code migrations spanning thousands of pull requests across multiple repositories. A human engineer handles high-level design while Fable directs dozens of smaller models like Opus and Sonnet to make file edits and run tests. Early results show the orchestrator using frontier tokens for complex planning before routing most tokens to cheaper worker models without quality loss. Block runs the setup on Buzz, its open-source workspace where humans and AI agents collaborate in shared channels and threads.

### Anthropic — Introducing Claude Mythos and Fable 5.1

- Company: Anthropic (anthropic.com)
- Announced: 2026-09-01
- Category: new-model
- Coverage: not counted
- Announcement: yes
- Group: models
- Source: https://www.anthropic.com/claude-fable-and-mythos-5-1
- Record: https://forck.live/items/7275-introducing-claude-mythos-and-fable-5-1
- Subject: Claude

Anthropic announces two new models: Claude Fable 5.1 (generally available) and Claude Mythos 5.1 (restricted access). They are the same model with different safeguards, offering improved performance in coding, knowledge work, and scientific research, with lower pricing and enhanced privacy and safety features.

## Who reported on it

_Outlets this record can name and link, under the first-party post each one covered. Their number is `Outlets named under its posts` above, and the rows are not totalled again. A post's own `Coverage` can be higher: it counts outlets the signal saw that this record cannot name and link._

### On: Introducing Claude Mythos and Fable 5.1

Record: https://forck.live/items/7275-introducing-claude-mythos-and-fable-5-1

- QbitAI — Claude最强Fable 5.1发布！8项屠榜，最高降价45%，反蒸馏机制上线 (2026-09-02T02:18:12+00:00): https://www.qbitai.com/2026/09/482652.html
- TestingCatalog — Anthropic launches Claude Fable 5.1 and Mythos 5.1 (2026-09-01T23:59:59+00:00): https://www.testingcatalog.com/anthropic-launches-claude-fable-5-1-and-mythos-5-1/
- The Verge — Anthropic launches Claude Fable 5.1 and says it’s up to 45 percent cheaper for agentic work (2026-09-01T22:01:36+00:00): https://www.theverge.com/ai-artificial-intelligence/987830/anthropic-claude-fable-mythos-5-1
- Moneycontrol — Anthropic launches Claude Fable 5.1 and Mythos 5.1 with improved coding, research capabilities and lower pricing: https://moneycontrol.com/technology/anthropic-launches-claude-fable-5-1-and-mythos-5-1-with-improved-coding-research-capabilities-and-lower-pricing-article-14020859.html
- Silicon Republic — Anthropic launches Claude Fable 5.1 and Mythos 5.1: https://siliconrepublic.com/machines/anthropic-launches-claude-fable-5-1-and-mythos-5-1
- The Deep View — In Fable 5.1, AI's cost war comes for Anthropic: https://thedeepview.com/articles/in-fable-5-1-ai-s-cost-war-comes-for-anthropic

## Where it runs

_Other companies' own announcements naming Claude Fable 5.1 and Anthropic — each is that company's post, not Anthropic's._

### Amazon — Introducing Claude Fable 5.1 on AWS

- Company: Amazon (amazon.com)
- Announced: 2026-09-01T19:12:43+00:00
- Category: new-model
- Coverage: not counted
- Announcement: yes
- Group: models
- Source: https://aws.amazon.com/blogs/machine-learning/introducing-claude-fable-5-1-on-aws/
- Record: https://forck.live/items/7272-introducing-claude-fable-5-1-on-aws
- Subject: Bedrock / Nova

Amazon announces the availability of Claude Fable 5.1 on Amazon Bedrock, a new model with improved reasoning, agentic coding, autonomous operation, and scientific research capabilities. It is designated as a Covered Model with data retention policies and is available with Enterprise Frontier Safeguards for eligible customers.

### GitHub — Claude Fable 5.1 is generally available in GitHub Copilot

- Company: GitHub (github.com)
- Announced: 2026-09-01T14:29:23+00:00
- Category: availability-change
- Coverage: not counted
- Announcement: yes
- Group: announcements
- Source: https://github.blog/changelog/2026-09-01-claude-fable-5-1-generally-available-in-github-copilot
- Record: https://forck.live/items/7295-claude-fable-5-1-is-generally-available-in-github-copilot
- Subject: Copilot

Claude Fable 5.1 from Anthropic is now generally available in GitHub Copilot. It requires data retention by default for safety classifiers, with zero data retention available for eligible enterprise customers. The model is available to Copilot Pro+, Max, Business, and Enterprise users.

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