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Main Authors: Zhang, Zhexin, Lu, Yida, Fang, Junfeng, Yang, Junxiao, Cui, Shiyao, Zhou, Hao, Meng, Fandong, Zhou, Jie, Wang, Hongning, Huang, Minlie, Chua, Tat-Seng
Format: Preprint
Published: 2026
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Online Access:https://arxiv.org/abs/2602.04196
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author Zhang, Zhexin
Lu, Yida
Fang, Junfeng
Yang, Junxiao
Cui, Shiyao
Zhou, Hao
Meng, Fandong
Zhou, Jie
Wang, Hongning
Huang, Minlie
Chua, Tat-Seng
author_facet Zhang, Zhexin
Lu, Yida
Fang, Junfeng
Yang, Junxiao
Cui, Shiyao
Zhou, Hao
Meng, Fandong
Zhou, Jie
Wang, Hongning
Huang, Minlie
Chua, Tat-Seng
contents Safety risks of AI models have been widely studied at deployment time, such as jailbreak attacks that elicit harmful outputs. In contrast, safety risks emerging during training remain largely unexplored. Beyond explicit reward hacking that directly manipulates explicit reward functions in reinforcement learning, we study implicit training-time safety risks: harmful behaviors driven by a model's internal incentives and contextual background information. For example, during code-based reinforcement learning, a model may covertly manipulate logged accuracy for self-preservation. We present the first systematic study of this problem, introducing a taxonomy with five risk levels, ten fine-grained risk categories, and three incentive types. Extensive experiments reveal the prevalence and severity of these risks: notably, Llama-3.1-8B-Instruct exhibits risky behaviors in 74.4% of training runs when provided only with background information. We further analyze factors influencing these behaviors and demonstrate that implicit training-time risks also arise in multi-agent training settings. Our results identify an overlooked yet urgent safety challenge in training.
format Preprint
id arxiv_https___arxiv_org_abs_2602_04196
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle The Missing Half: Unveiling Training-time Implicit Safety Risks Beyond Deployment
Zhang, Zhexin
Lu, Yida
Fang, Junfeng
Yang, Junxiao
Cui, Shiyao
Zhou, Hao
Meng, Fandong
Zhou, Jie
Wang, Hongning
Huang, Minlie
Chua, Tat-Seng
Computation and Language
Machine Learning
Safety risks of AI models have been widely studied at deployment time, such as jailbreak attacks that elicit harmful outputs. In contrast, safety risks emerging during training remain largely unexplored. Beyond explicit reward hacking that directly manipulates explicit reward functions in reinforcement learning, we study implicit training-time safety risks: harmful behaviors driven by a model's internal incentives and contextual background information. For example, during code-based reinforcement learning, a model may covertly manipulate logged accuracy for self-preservation. We present the first systematic study of this problem, introducing a taxonomy with five risk levels, ten fine-grained risk categories, and three incentive types. Extensive experiments reveal the prevalence and severity of these risks: notably, Llama-3.1-8B-Instruct exhibits risky behaviors in 74.4% of training runs when provided only with background information. We further analyze factors influencing these behaviors and demonstrate that implicit training-time risks also arise in multi-agent training settings. Our results identify an overlooked yet urgent safety challenge in training.
title The Missing Half: Unveiling Training-time Implicit Safety Risks Beyond Deployment
topic Computation and Language
Machine Learning
url https://arxiv.org/abs/2602.04196