Microsoft is limiting employee access to Anthropic’s Claude Fable 5 while its legal teams review new data retention rules tied to the model.

Key Points:

• Microsoft has restricted internal employee access to Claude Fable 5.
• The concern centers on Anthropic’s 30-day retention of prompts and outputs.
• The model is still available to GitHub Copilot and Foundry customers.

Claude Restrictions

The Verge reported Jun. 10 that Claude Fable 5 is not available in the model picker used by Microsoft employees for internal GitHub Copilot versions.

The report said other Claude models remain available internally because they operate under Zero Data Retention rules, unlike Fable 5.

Microsoft has told employees that its legal teams are evaluating Anthropic’s retention terms, according to Tom Warren, with concerns focused on customer data and confidential information.

Fable 5 retains prompts and outputs for 30 days to support safety classifiers. Some flagged material can be stored for up to two years if it appears to violate policy.

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Anthropic Safety

Microsoft offered Fable 5 to GitHub Copilot and Foundry customers, but internal use faces a higher bar because employee tools can involve sensitive data.

Anthropic released Fable 5 as the first broadly available model from its Mythos class, weeks after saying that family was too capable at cybersecurity tasks for public release without stronger safeguards.

The dispute shows how frontier AI releases now hinge on legal and compliance terms, not only benchmarks. The Mythos class had already drawn scrutiny because its cyber capabilities forced the company to balance access with monitoring.

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