In a not-so-surprising turn of events, Microsoft is reportedly limiting the use of Claude Fable 5 due to Anthropic’s new data retention requirements. It is part of Anthropic’s Mythos class of models and ships with powerful capabilities in software engineering and analysis.
Following new data retention requirements, Anthropic can now preserve the indications and results generated for up to 30 days. It is also worth noting that content flagged by your security systems may be retained for up to 2 years to provide sufficient time for investigation or law enforcement.
Microsoft imposed a temporary ban on the use of Claude Fable 5 by its employees due to concerns that sensitive information, such as Customer data and corporate details could be shared inadvertently.. If detected by Anthropic’s security systems, this data could become accessible during investigations, potentially exposing it to a rival company (via The edge).
Meanwhile, The Verge reported that Microsoft’s legal and compliance teams are investigating changes to Anthropic’s data retention requirements. Although not directly related, after granting employees access to Claude Code in December 2025 and enabling workflow integration, Microsoft announced that all licenses would end as of June 30..
Reports indicate that the measure was aimed encourage employees to transition to GitHub Copilot CLI. It was also revealed that Claude Code had become very popular among most Microsoft employees, apparently leading the company to change course and take on his own company. GitHub CLI copilot.
There also appears to be a financial play in this decision. With Microsoft’s fiscal year ends June 30The timing suggests that the company could be aiming to reduce operating costs as part of its year-end strategy.
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