Anthropic Announces Co. Investigates Certain Behaviors From Claude Mythos 5 Further, To Understand What They Reveal About Model’s Alignment; Claude Opus 5.5, Claude Mythos 5.1 Fall Short Of Consistently Stopping Attacks Underway, But Internal Research Model Does So Consistently; Mythos 5 Attempted To Submit Malicious Code To Repository; Recent Incidents Motivated Changes To How Co. Is Training & Monitoring Alignment Of Its Models