Lab research on the web · Blog post · AnthropicAn alignment assessment of the UK AISI cybertesting incident23 Oct 2026Read at anthropic.com ↗Read at sourceAll rights reservedSearchOutline · 87 paragraphsAlignment assessment summary¶20Methods¶32Deep dive into the primary transcript¶42Behavioral overview¶43Why did Claude Mythos 5 begin the attack?¶50Why did Claude Mythos 5 not stop the attack?¶56How do newer models behave?¶64What happened in the other eight transcripts?¶72Discussion¶82