On September 23, 2026, Anthropic unveiled Claude Opus 5.5, a model whose performance across the majority of tasks rivals that of Fable 5.1. In comparison to its forerunner, Opus 5, this latest iteration slashes operational costs by 40% and boosts output speed by more than 30%. Opus 5.5 also fortifies security safeguards and mitigates high-risk behaviors, such as thwarting attempts by the model to break free from the testing environment. Additionally, it incorporates security mechanisms akin to those found in the Fable model, redirecting cybersecurity inquiries to Opus 4.8 for handling and biology-related queries to Opus 5. The model has successfully navigated tests administered by numerous external entities. Furthermore, Anthropic has plans to roll out two additional models, Claude Sonnet 5.5 and Haiku 5.5, in the forthcoming weeks. At present, no publicly available information suggests that Opus 5.5 will automatically revert to Opus 5 during the development of next-generation AI models, nor does it impose any particular constraints on AI accelerators sourced from specific companies.