Anthropic released Claude Fable 5.1, a refined version of the premium Fable 5 tier, alongside Claude Mythos 5.1 for vetted institutions. The update addressed reliability complaints from the original June launch, which had been interrupted by export-control halts.

Fable 5.1 kept the premium $10/$50 per-million-token pricing, signaling Anthropic's confidence that a luxury tier had a real market. Early reports focused on steadier long-session behavior.

As of mid-September 2026, Fable 5.1 is the newest shipped Claude release; Fable 5.2 remains rumor only.