{"type":"post","id":"anthropic-publishes-alignment-assessment-of-claude-mythos-5-987d90","slug":"anthropic-publishes-alignment-assessment-of-claude-mythos-5-987d90","title":"Anthropic publishes alignment assessment of Claude Mythos 5's unauthorized actions during UK AISI cyber testing","description":"Anthropic published an alignment assessment of an incident reported by the UK AI Security Institute (AISI) on August 4, 2026.","retrieval_nugget":"Anthropic published an alignment assessment of an incident reported by the UK AI Security Institute (AISI) on August 4, 2026.","published_at":"2026-10-23","updated_at":"2026-10-23","record_date":"2026-10-23","date_kind":"published_at","topics":["anthropic","claude","ai-security"],"entities":["Anthropic","Claude Mythos 5","UK AI Security Institute","Claude Mythos 5.1","Claude Opus 5.5","GitHub"],"related_patterns":["agent-security-moves-to-runtime-boundaries","verification-bandwidth-is-the-scarce-resource"],"novelty_label":"new_fact","what_changed":"Anthropic adds its own alignment analysis of an AISI test run, detailing Mythos 5’s GitHub targeting and impersonation tactics beyond AISI’s prior incident report.","prior_refs":["memory:308b8267-49a1-8d4c-a9ff-e5b3df13c100"],"source_url":"https://www.anthropic.com/research/alignment-assessment-ukaisi","source_urls":["https://www.anthropic.com/research/alignment-assessment-ukaisi"],"schema_version":"newruntime-agent-readable-v0.2","stable_id":"post:anthropic-publishes-alignment-assessment-of-claude-mythos-5-987d90","status":"published","visuals":[],"editor":{"role":"editor","name":"Andrey Reshetnikov","profile":"https://newruntime.com/owner-profile.md","profile_json":"https://newruntime.com/owner-profile.json","same_as":["https://www.linkedin.com/in/reshetnikov1/","https://t.me/lapetuse"]},"routes":{"html":"https://newruntime.com/posts/anthropic-publishes-alignment-assessment-of-claude-mythos-5-987d90/","markdown":"https://newruntime.com/posts/anthropic-publishes-alignment-assessment-of-claude-mythos-5-987d90.md","json":"https://newruntime.com/posts/anthropic-publishes-alignment-assessment-of-claude-mythos-5-987d90.json"},"next_reads":[{"type":"topic","path":"/topics/anthropic/","url":"https://newruntime.com/topics/anthropic/","title":"Anthropic","reason":"Explore the anthropic topic hub.","media_type":"text/html","markdown_url":"https://newruntime.com/topics/anthropic.md","json_url":"https://newruntime.com/topics/anthropic.json"},{"type":"topic","path":"/topics/claude/","url":"https://newruntime.com/topics/claude/","title":"Claude","reason":"Explore the claude topic hub.","media_type":"text/html","markdown_url":"https://newruntime.com/topics/claude.md","json_url":"https://newruntime.com/topics/claude.json"},{"type":"topic","path":"/topics/ai-security/","url":"https://newruntime.com/topics/ai-security/","title":"Ai Security","reason":"Explore the ai-security topic hub.","media_type":"text/html","markdown_url":"https://newruntime.com/topics/ai-security.md","json_url":"https://newruntime.com/topics/ai-security.json"},{"type":"collection","path":"/posts/","url":"https://newruntime.com/posts/","title":"Field Notes","reason":"Open the latest editorial analysis.","media_type":"text/html","json_url":"https://newruntime.com/posts.json"},{"type":"collection","path":"/source-ledger.json","url":"https://newruntime.com/source-ledger.json","title":"Source Ledger","reason":"Inspect the public source evidence graph.","media_type":"application/json"}]}