Anthropic releases a safeguarded Mythos-class model for broader use (Fable 5)

Anthropic launched Fable 5, a general-purpose model built on the same foundation as its previously restricted Mythos-class systems. The company said new safeguards allow broader deployment Anthropic described the release as its most capable public model to date, with strong performance across software engineering, research, and knowledge-work tasks. The move is a significant shift from the company's earlier position that Mythos-class systems required substantially tighter access controls while additional safety measures were developed. Early testing of Claude 5 Fable, described as a Mythos-class AI model, suggests a substantial jump in autonomous problem-solving capability. Across a range of projects, the model independently conducted research, delegated tasks to AI agents, wrote and tested code, evaluated results, and worked for up to a dozen hours with minimal human intervention. Examples included building a historically inspired isochrone travel map using thousands of transportation data points and creating sophisticated research-analysis software after generating its own 19-page design document. The experience highlighted both the power and opacity of advanced AI systems. Users can provide ambitious goals and feedback, but much of the reasoning, decision-making, and execution occurs inside a black box. The human role is shifting from directing each step of the process to specifying objectives and evaluating outcomes.