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Microsoft has restricted employees from using Anthropic’s newly launched Claude Fable 5 over its updated data retention policy. The model retains user prompts for 30 days, with flagged inputs stored up to two years. The block applies to internal GitHub Copilot use, while other Claude models with zero data retention remain available.

Microsoft has restricted its employees from using Anthropic's newly launched Claude Fable 5, even as the company simultaneously offers the same model to its enterprise customers through GitHub Copilot and Microsoft Foundry. The restriction, first reported by The Verge, stems from concerns over Anthropic's updated data retention policy for its Mythos-class AI models.

What changed with Claude Fable 5?

Anthropic launched Claude Fable 5 on June 9, as a public version of its Mythos AI model, describing it as the most powerful model it has made available for wider use, with guardrails barring its use in high-risk areas such as cybersecurity.

Alongside the launch, Anthropic updated its data retention policy. Under the new policy, prompts submitted and outputs generated are retained for 30 days for trust and safety purposes on every platform where Mythos-class models are offered. Anthropic retains inputs and outputs for up to two years if they are flagged by its trust and safety classifiers as violating its usage policy.