ReleaseBytes
github GitHub Changelog ·

Claude Fable 5.1 now generally available in GitHub Copilot

aigaengineer
feature announcement

Anthropic's Claude Fable 5.1, an advanced AI model designed for long-horizon coding and knowledge tasks, is now generally available within GitHub Copilot. This model demonstrated strong performance in complex coding workflows and deep codebase research during internal testing. Unlike other Claude models in Copilot, Fable 5.1 requires data retention by default for safety classifiers, although zero data retention is available for eligible enterprise customers. It is accessible to Copilot Pro+, Max, Business, and Enterprise users, requiring administrator enablement for business and enterprise plans.

  • →Claude Fable 5.1 generally available in GitHub Copilot
  • →Default data retention for Claude Fable 5.1
  • →Zero data retention options for eligible enterprises
  • →Availability and administrator enablement
Features (1) ›
  • Claude Fable 5.1 generally available in GitHub Copilot

    Anthropic's Claude Fable 5.1, the latest Mythos-class model, is now integrated into GitHub Copilot. Designed for long-horizon, autonomous coding and knowledge-work tasks, the model showed strong performance in substantial coding tasks, including deep codebase research and complex agentic workflows.

Notes (3) ›
  • Default data retention for Claude Fable 5.1

    Claude Fable 5.1 requires data retention by default for Anthropic’s safety classifiers, meaning prompts and outputs are retained, though not used to train Anthropic’s models. This differs from other Claude models in GitHub Copilot, which continue to operate under zero data retention (ZDR).

  • Zero data retention options for eligible enterprises

    Eligible enterprise customers can use Claude Fable 5.1 and Fable 5 with zero data retention until the end of the calendar year. This temporary exemption is in place while Anthropic rolls out Enterprise Frontier Safeguards (EFS), which will provide automated safety monitoring and more flexible data retention options.

  • Availability and administrator enablement

    Claude Fable 5.1 is available to Copilot Pro+, Max, Business, and Enterprise users across various platforms including Visual Studio Code, JetBrains IDEs, and GitHub Mobile. Copilot Enterprise and Business plan administrators must enable the Claude Fable 5.1 policy in Copilot settings, as it is off by default.

Read the original announcement →

https://github.blog/changelog/2026-09-01-claude-fable-5-1-generally-available-in-github-copilot

Related releases