In June, Anthropic first released Fable 5, its Mythos-class AI model for Claude. Three months later, Anthropic is enhancing Claude with its new Fable 5.1 model upgrade.
Claude Fable 5.1 and Mythos 5.1 arrive today
In Anthropic’s world, Fable is Claude’s most capable model. Haiku, Sonnet, and Opus are the small, medium, and large models below Fable.
“Claude Fable 5.1 sets a new standard on coding, knowledge work, and long-running problem-solving tasks,” Anthropic says. The company says the new model has a higher level of performance compared to Fable 5.
Anthropic also says Fable 5.1 “achieves similar or better results than Fable 5 at a much lower cost” when set to low or medium effort.
