A model named Claude Fable 5.5 reportedly appeared in Microsoft Azure configuration files, according to a post circulating on X. Neither Anthropic nor Microsoft has confirmed its existence. Anthropic’s official documentation still lists Fable 5.1, launched on September 1, 2026, as the most advanced model in the Fable series. The hypothetical Fable 5.5 would fit into the Claude 5.5 family, which already includes Opus 5.5 and Sonnet 5.5, but no Fable variant has been announced by the company.
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