Claude Fable 5.1 and Claude Mythos 5.1 models require mandatory 30-day data retention
Anthropic has established that the Claude Fable 5.1 and Claude Mythos 5.1 models require 30-day data retention by default; zero retention mode is only available after explicit approval from Anthropic.
According to Anthropic's documentation in the Claude platform release notes, the Claude Fable 5.1 and Claude Mythos 5.1 models require 30-day data retention by default. Zero data retention mode is not available automatically for these models — Anthropic only enables it after explicit approval of a specific request.
The source text is part of broader documentation on model-specific data retention requirements and does not state which other models the comparison applies to, nor the reason why zero retention is excluded by default. For details, see the source article.
Why it matters
Organizations with regulatory or contractual requirements for zero data retention (e.g., in healthcare, finance, or when processing sensitive personal data) cannot deploy these models without separate approval from Anthropic. This is a practical limitation when selecting a model for deployment, where it is necessary to plan in advance for an additional approval step or choose a different model for which zero retention applies by default.
Relevant practical impact
What this means
For a business
Companies that, for contractual or regulatory reasons, need a zero data retention regime must request explicit permission from Anthropic for the Claude Fable 5.1 and Claude Mythos 5.1 models; without it, mandatory 30-day data retention applies.
Risks and complianceCheck the original
Event sources
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