[Anthropic expands access to advanced AI models to allow specific institutions to conduct network security testing] October 7th, Anthropic is working with the U.S. government to expand access to its most advanced AI models, allowing a select group of institutions to test the startup’s cutting-edge network capabilities. The San Francisco-based company will allow proven institutions to use its most capable models, including Claude Opus 5.5, Claude Sonnet 5.5, Claude Mythos 5.1, as well as new models coming in the future, according to a statement released Tuesday. The statement said authorized agencies can conduct "high-risk offensive testing" of security systems designed to protect critical infrastructure such as power grids, banks and flight operations systems.