SITUATION EXPLAINED: Anthropic withheld Mythos 5.1 from the UK's AI Security Institute. • The model went only to vetted US organizations. It's the first time AISI has been left out of an Anthropic pre-release evaluation • Anthropic: it's only available to a set of US organizations, and they're coordinating with the US government to expand access to domestic and international partners • OpenAI shared Astra with AISI in advance, which cuts against the US administration pressure theory • Some in…