Anthropic Releases Claude Fable 5.1, Cost per Task Reduced by 25%

Anthropic released its next-generation flagship model Claude Fable 5.1 on September 1, 2026, accompanied by the Mythos 5.1 model for eligible users. Anthropic states that the new model further improves capabilities in coding, knowledge work, and long-horizon agentic tasks, surpassing its predecessor Fable 5 and OpenAI's GPT-5.6 Sol across multiple benchmarks. Fable 5.1 is particularly strong in executing extended, multi-step tasks -- capable of running continuously for hours on programming, research, and other complex workflows while independently verifying results and reprioritizing tasks. A major focus of the upgrade is cost reduction: Fable 5.1 reduces the expected cost of typical workloads by approximately 25% compared to Fable 5, with cached read prices reduced by 75%. For highly agentic tasks, cost savings can reach up to approximately 45%. Anthropic stated that the new model can achieve equivalent or superior performance to the previous generation at lower reasoning intensity and cost.