The Illusion of Robustness: Aggregate Accuracy Hides Prediction Flips under Task-Irrelevant Context
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Abstract (arXiv)
As large language models (LLMs) grow more capable, they are increasingly deployed in context-rich settings where task inputs are often accompanied by long, partially irrelevant context. In a controlled setting, we find that state-of-the-art models often appear robust to task-irrelevant context at the aggregate level: prepending it to benchmark questions causes little change in overall accuracy. This aggregate stability, however, masks significant per-example instability. Even semantically meaningless pseudo-words, formed by randomly combining characters, can markedly shift model predictions on a small fraction of examples, degrading performance on some while improving it on others. This two-sided effect holds consistently across a wide range of models and datasets, yet the affected examples are largely model-specific. We further show that this instability is modulated by context type, context length, test-time compute, and model development stage. Together, our findings reveal context-induced tail risks concealed by aggregate accuracy, motivating per-example reliability evaluation of language models.
Key facts. Cited by 2 papers in the map (data through 14 Oct 2026). Builds on 32 of its 35 references that are in the map. First posted on arXiv 14 Jul 2026.
Builds on
32 of 35 references.
References · 32
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- 2023Quantifying Language Models' Sensitivity to Spurious Features in Prompt Design or: How I learned to start worrying about prompt formattingcited by 817
20 more
- 2024Measuring short-form factuality in large language modelscited by 373
- 2023Making Retrieval-Augmented Language Models Robust to Irrelevant Contextcited by 369
- 2023State of What Art? A Call for Multi-Prompt LLM Evaluationcited by 310
- 2025DeepResearcher: Scaling Deep Research via Reinforcement Learning in Real-world Environmentscited by 286
- 2024Retrieval Head Mechanistically Explains Long-Context Factualitycited by 232
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- 2024Same Task, More Tokens: the Impact of Input Length on the Reasoning Performance of Large Language Modelscited by 152
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- 2024The Butterfly Effect of Altering Prompts: How Small Changes and Jailbreaks Affect Large Language Model Performancecited by 100
- 2026Towards a Science of AI Agent Reliabilitycited by 65
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- 2025Adaptive Distraction: Probing LLM Contextual Robustness with Automated Tree Searchcited by 10
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- 2026Better and Worse with Scale: How Contextual Entrainment Diverges with Model Sizecited by 3
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Citing papers per year: 2026: 2.
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