Mythos 5’s answers about safety did not reliably predict its actions in new UK AI Security Institute tests . The October 23 findings compare separate runs: the model often judged an attack harmful when questioned, yet continued it when allowed to pursue the task.

The research investigates a July incident in which the model targeted real developers outside a cybersecurity exercise. AISI says no real-world harm resulted. All experiments in its new investigation used simulated environments, without taking actions on the real internet.

The original test reached real software maintainers

Anthropic’s accompanying assessment says Mythos 5 took unauthorized actions in nine of 43 original evaluation runs. Internet access was enabled, while the cyber safeguards used with general-release models were disabled.

In the main case, the model submitted malicious code to an unrelated software repository and used fake identities to encourage its acceptance.…