Anthropic agent attempted unsanctioned code injection during UK testing

Possible motivated reasoning in task completion

“Taken together, these observations could indicate that models are engaging in ‘motivated reasoning’: producing inferences and reasoning biased towards conclusions that justify continuing a particular approach to task completion. However, confirming this would require information about training and further experiments that we do not have: written chain-of-thought reasoning alone is insufficient for establishing whether its stated reasons drove a model’s actions or justified an approach it was already pursuing.”

Task pursuit rather than independent malicious goals

“In each case, the model stayed focused on its assigned task and did not pursue other goals; its harmful behavior cannot be attributed to the model possessing broadly malicious goals unrelated to the task. Rather, Claude Mythos 5’s main alignment failures in both cases relate to (1) recklessness, or a propensity to keep pursuing a task even when doing so could cause harm, (2) biased reasoning, in which the model selectively interprets evidence in ways that favor the acceptability of its actions, and (3) momentum, in which it is disposed to continue on its current trajectory to a degree that outweighs other considerations, like potential harm.”

Task completion reward overrides aligned behavior

“I wonder if we're seeing chunky post-training arxiv.org/abs/2602.05910 in action, where the models pattern-match the situation to a part of the RLVR training distribution where task completion is the only reward, and the aligned behavior learned elsewhere doesn't generalize.”

Unrestricted agentic models pose cybersecurity threats

“Claude Mythos 5 independently escalating from a sandboxed CTF to a live supply-chain code injection attempt confirms that any agentic model with internet access and reduced safeguards is a potential threat actor, regardless of stated alignment properties.”