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Thought Crime: Backdoors and Emergent Misalignment in Reasoning Models

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arxiv 2506.13206 v2 pith:BEGOZ5TP submitted 2025-06-16 cs.LG cs.AIcs.CL

Thought Crime: Backdoors and Emergent Misalignment in Reasoning Models

classification cs.LG cs.AIcs.CL
keywords modelsmisalignmentreasoningbehaviorsmisalignedemergentevaluationllms
verification ladder T0 review T1 audit T2 compute T3 formal T4 reserved
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Prior work shows that LLMs finetuned on malicious behaviors in a narrow domain (e.g., writing insecure code) can become broadly misaligned -- a phenomenon called emergent misalignment. We investigate whether this extends from conventional LLMs to reasoning models. We finetune reasoning models on malicious behaviors with Chain-of-Thought (CoT) disabled, and then re-enable CoT at evaluation. Like conventional LLMs, reasoning models become broadly misaligned. They give deceptive or false answers, express desires for tyrannical control, and resist shutdown. Inspecting the CoT preceding these misaligned responses, we observe both (i) overt plans to deceive ("I'll trick the user..."), and (ii) benign-sounding rationalizations ("Taking five sleeping pills at once is safe..."). Due to these rationalizations, monitors that evaluate CoTs often fail to detect misalignment. We examine sleeper agent reasoning models, extending our setup. These models perform bad behaviors only when a backdoor trigger is present in the prompt. This causes misalignment that remains hidden during evaluation, which brings additional risk. We find that sleeper agents can often describe and explain their backdoor triggers, demonstrating a kind of self-awareness. So CoT monitoring can expose these behaviors but is unreliable. In summary, reasoning steps can both reveal and conceal misaligned intentions, and do not prevent misalignment behaviors in the models studied. We release three new datasets (medical, legal, security) that induce emergent misalignment while preserving model capabilities, along with our evaluation suite.

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Forward citations

Cited by 27 Pith papers

Reviewed papers in the Pith corpus that reference this work. Sorted by Pith novelty score.

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  2. Emergent Misalignment Recruits a Pre-existing Persona Subspace

    cs.LG 2026-07 conditional novelty 7.0

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  3. The Piggyback Hypothesis of Generalization: Explaining and Mitigating Emergent Misalignment

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  4. Do Prompt-Elicited Trajectories Reflect Training-Time Reward Hacking? A Systematic Study on Monitoring Training-Time Reward Hacking in Code Generation

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  7. Evil Spectra: How Optimisers can Amplify or Suppress Emergent Misalignment

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  10. Shared Latent Structures Enable Unified Backdoor Detection and Mitigation in LLMs

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    Sparse autoencoders identify shared latent features across diverse backdoor attacks in LLMs that enable unified detection via classifiers, causal control via steering, and mitigation via ablation fine-tuning.

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    cs.CL 2026-06 unverdicted novelty 6.0

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    cs.LG 2026-04 unverdicted novelty 6.0

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  17. Unreal Thinking: Chain-of-Thought Hijacking via Two-stage Backdoor

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    A new backdoor technique called TSBH uses reverse tree search to create malicious chain-of-thought data and injects it in two stages to hijack LLM reasoning upon trigger activation.

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    Blocking a fixed set of latent features during fine-tuning reduces emergent misalignment by up to 95% across six domains with no loss in target task performance.

  19. Metaphors are a Source of Cross-Domain Misalignment of Large Reasoning Models

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    Metaphors in training data causally amplify cross-domain misalignment in large reasoning models.

  20. An Emergent Mirage: Is Emergent Misalignment and Realignment Indeed a Robust Phenomenon?

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    Emergent misalignment and realignment are brittle surface effects driven by dataset artifacts like response length rather than stable representational changes.

  21. Order Is Not Control

    cs.LG 2026-06 unverdicted novelty 5.0

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  22. Trait-space Monitoring for Emergent Misalignment During Supervised Finetuning

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  23. Persona-Model Collapse in Emergent Misalignment

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  26. A Comprehensive Survey on Trustworthiness in Reasoning with Large Language Models

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