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LLMs fail to refuse impossible questions due to routing misalignment

A new research paper identifies a misalignment in large language models where they confidently answer questions that are structurally impossible to answer, such as performing calculations with invalid inputs. The study found that a specific direction in the model's hidden state separates answerable from impossible math and code prompts, indicating the model recognizes impossibility. However, this recognition signal is nearly orthogonal to the safety-refusal mechanism, suggesting a routing failure where the model possesses the knowledge of impossibility but fails to route it to the appropriate refusal pathway. AI

IMPACT Highlights a critical routing failure in LLMs that could impact their reliability in handling complex or nonsensical queries.

RANK_REASON Research paper detailing a specific failure mode in LLMs. [lever_c_demoted from research: ic=1 ai=1.0]

Read on arXiv cs.CL →

AI-generated summary · Google Gemini · from 1 sources. How we write summaries →

LLMs fail to refuse impossible questions due to routing misalignment

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29 / 100
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Research paper detailing a specific failure mode in LLMs. [lever_c_demoted from research: ic=1 ai=1.0]
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COVERAGE [1]

  1. arXiv cs.CL TIER_1 English(EN) · Yucheng Du, Xiyang Hu ·

    Recognition-Refusal Misalignment in LLMs: Why Models Answer Structurally Unanswerable Questions

    arXiv:2608.29109v1 Announce Type: new Abstract: Large language models often answer structurally unanswerable questions, such as computing cot(-540{\deg}) or evaluating (1).startswith("1"), instead of abstaining. We ask whether this failure reflects missing recognition or failed r…