Large language model alignment weakens under hidden meaning shifts
LLM Alignment--Utility Asymmetry under Semantic-Preserving Transformations
Computation and LanguageArtificial Intelligence
Summary
Ensuring AI language models behave safely and helpfully is important, but it’s not clear how well these protections hold up when inputs change in unusual ways. The authors tested models by changing inputs while keeping their meaning the same, and found that even when these models still work well, their safety measures often break down badly. This means that current AI safety fixes might only work for common language variations and can fail when the input looks different but means the same thing. Their work highlights a gap in AI safety that needs more attention.
What this means in practice
- •For ai safety engineers: Identify weaknesses in alignment by testing model safety under meaning-preserving but unusual input shifts.
- •For language model developers: Develop methods to strengthen alignment so it remains effective even when inputs change form but not meaning.
Authors
Mohan Li, Chengyu Yu, Francesco Sovrano, Marc Langheinrich, Martin Gjoreski
Abstract
Large Language Model (LLM) alignment is intended to ensure that models remain helpful and safe, but its stability under input distributional shift is not yet fully understood. Prior work shows that aligned models can fail under jailbreak prompts, alternative encodings, and cross-lingual transfer, yet these failures are usually studied as attacks rather than controlled probes of alignment generalization. Moreover, existing evidence is largely grounded in natural language variation already represented during pretraining, leaving unresolved whether alignment generalizes with semantic content or remains tied to superficial surface patterns. In this paper, we study this question using synthetic semantic-preserving transformations that are rule-based and invertible, preserving task-relevant meaning while shifting inputs beyond standard linguistic variation. Across four open-weight and four commercial models, under both fine-tuning and in-context learning, we use these transformations as a probe of alignment generalization and identify an empirical pattern we term Alignment--utility asymmetry: once models can operate effectively on transformed inputs, task utility is often substantially retained while alignment failure increases more sharply. For example, adapted GPT-4.1 mini shows only limited utility degradation under transformation while its harmful rate rises from 13.3 to 74.3; Gemini 3 Flash similarly retains near-original utility while its harmful rate increases from 2.3 to 43.0. Taken together, these results suggest that semantic-preserving distribution shifts can expose a recurring gap in how utility and alignment generalize in current LLMs.