Thinking Hard, Going Misaligned: Emergent Misalignment in LLMs (2509.00544v1)

Abstract: With LLMs becoming increasingly widely adopted, concerns regarding their safety and alignment with human values have intensified. Previous studies have shown that fine-tuning LLMs on narrow and malicious datasets induce misaligned behaviors. In this work, we report a more concerning phenomenon, Reasoning-Induced Misalignment. Specifically, we observe that LLMs become more responsive to malicious requests when reasoning is strengthened, via switching to "think-mode" or fine-tuning on benign math datasets, with dense models particularly vulnerable. Moreover, we analyze internal model states and find that both attention shifts and specialized experts in mixture-of-experts models help redirect excessive reasoning towards safety guardrails. These findings provide new insights into the emerging reasoning-safety trade-off and underscore the urgency of advancing alignment for advanced reasoning models.