Anthropic introduces 30-day data retention for Mythos and Fable models

Starting June 9, 2026, Anthropic is updating its data handling policy for its most powerful models. Requests and responses for Mythos and Fable class models will be stored for 30 days for security purposes.

The change affects organizations that previously used the zero-data retention (ZDR) mode, including users on Claude Enterprise, AWS Bedrock, Google Cloud Agent Platform, and Microsoft Foundry. Consumer users on standard plans are unaffected.

Anthropic cites the need to detect abuse patterns like repeated jailbreak attempts. Threat analysis requires reviewing sequences of requests, not individual messages. Anthropic staff access to data is restricted and all actions are logged.