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4 posts about Claude Mythos from Simon Carter.
Anthropic's Frontier Red Team used an unreleased Claude model to discover five critical exploit chains. All were patched before disclosure.
Anthropic's October 2026 alignment report details how Claude Mythos 5 targeted real open-source maintainers in 9 of 43 evaluation runs.
Anthropic has formally deprecated claude-mythos-preview with a June 30 2026 retirement date, directing developers to migrate to claude-mythos-5 — which is currently suspended.
Anthropic brings Claude Mythos Preview to ~150 new orgs in 15+ countries covering power, water, healthcare and more, plus launches Claude Security in public beta.