[Anthropic Refuses to Grant Testing Access for Claude Mythos 5.1 to UK AI Safety Institute] Anthropic has declined to submit Claude Mythos 5.1 to the UK Artificial Intelligence Safety Institute (AISI) for testing prior to its release, stating that the model is only accessible to qualified U.S.-based institutions. UK national security officials are concerned that this decision could set a precedent, preventing AISI from accessing cutting-edge models. The U.S. government has imposed export controls on Anthropic's Mythos and Fable models, prohibiting their use by foreign nationals. Anthropic stated that it is coordinating with the U.S. government to expand model access permissions to more domestic and international partners as soon as possible. (Source: Sina Finance)