Anthropic's withholding of Claude Mythos forces senior IT teams to advance their AI cyber-threat-model timeline by two to three years, and to rebuild three specific assumption sets — patch prioritization, third-party risk on AI infrastructure, and AI procurement diligence — inside Q2 2026.

Logged at announcement + 20 days, reviewed at 60 days. Three review checks: Glasswing cohort movement, second-lab equivalent capability, explicit citation in vendor security advisories or regulatory frameworks. None moved → Partial. One or two → Holds. All three → Strengthened.