Anthropic Limits Claude Mythos 5.1 to US Orgs, Cutting Out UK's AISI
Miles_Brundage · x · 2026-09-09
According to the Financial Times, Anthropic's newly launched Claude Mythos 5.1 was made available only to vetted US organizations, excluding for the first time the UK's AI Security Institute, the global leader in frontier AI model testing.
Former OpenAI safety chief Miles Brundage called it a "worrying precedent," noting the UK's AISI has more overall capacity than the US CAISI, which he said needs more funding, stable leadership, communication rules, and higher salaries.
It marks the first country-based exclusion from frontier safety testing collaboration and could reshape US-UK AI evaluation cooperation.
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