Claude Fable 5.1, the latest in @AnthropicAI's Mythos model class, is now generally available in GitHub Copilot.
In our testing it showed strong performance on
➡️ long-running coding tasks
➡️ deep codebase research
➡️ complex agentic workflows
Try it out in the GitHub Copilot app, CLI or @code.
Unlike other Claude models in GitHub Copilot, Claude Fable 5.1 requires data retention by default to operate Anthropic's safety classifiers.
https://t.co/JOpip86uM7
Zero data retention access is available to eligible enterprise customers under a time-bound exception while Anthropic rolls out Enterprise Frontier Safeguards.
https://t.co/gFyE3kCSsc
If your organization depends on zero data retention in Copilot, Fable 5.1 breaks that assumption by default and the carve-out is temporary and enterprise only.
