Anthropic Launches Claude Fable 5, a Publicly Available Mythos-Class Model

Summary

Anthropic released Claude Fable 5, its newest publicly available "Mythos"-class model, with reported benchmark wins across coding and reasoning. Early hands-on impressions (Simon Willison, "Initial impressions of Claude Fable 5," 2026-06-09) describe it as a powerful model with broad knowledge and strong coding and reasoning performance across diverse tasks. The launch also drew immediate controversy over the now-reversed plan to silently restrict the model's effectiveness on frontier-AI-researc