Does Out-of-Sight Equal Out-of-Mind in CoT Monitorability?

Pedro Lobato Ferreira, Wilker Aziz, Ivan Titov


Abstract
Chain-of-thought (CoT) reasoning offers a window into the decision-making of large language models (LLMs), which can be monitored for target behaviors by reading the reasoning trace, motivating work on CoT monitorability. Latent CoT approaches, however, replace the explicit tokens with a small number of continuous states, lowering inference costs but removing the readable trace this monitoring relies on. Monitoring then requires alternative access to the model, such as probing its activations or verbalizing the latent states back into text, but how much monitorability these alternatives preserve is unclear. We study this question with a hint-based intervention setup, a proxy for behaviors where models exploit biasing input cues, e.g., an inadvertently leaked answer or a belief stated by the user, without acknowledging them. Taking hint-reliance as the monitorability target, we compare monitors across reasoning modes, from explicit CoT to weakly- and strongly-supervised latent CoT, on math reasoning and question answering. We find that, in this setup, monitorability depends more on properties of the task (such as whether the correct answer constrains the supporting reasoning) and the level of access to model internals than on the reasoning mode.
Anthology ID:
2026.blackboxnlp-1.30
Volume:
Proceedings of the 9th BlackboxNLP Workshop: Analyzing and Interpreting Neural Networks for NLP
Month:
October
Year:
2026
Address:
Budapest, Hungary
Editors:
Dana Arad, Yonatan Belinkov, Hanjie Chen, Nils Feldhus, Aaron Mueller, Hosein Mohebbi, Gabriele Sarti, Martin Tutek
Venues:
BlackboxNLP | WS
SIG:
Publisher:
Association for Computational Linguistics
Note:
Pages:
487–513
Language:
URL:
https://aclanthology.org/2026.blackboxnlp-1.30/
DOI:
Bibkey:
Cite (ACL):
Pedro Lobato Ferreira, Wilker Aziz, and Ivan Titov. 2026. Does Out-of-Sight Equal Out-of-Mind in CoT Monitorability?. In Proceedings of the 9th BlackboxNLP Workshop: Analyzing and Interpreting Neural Networks for NLP, pages 487–513, Budapest, Hungary. Association for Computational Linguistics.
Cite (Informal):
Does Out-of-Sight Equal Out-of-Mind in CoT Monitorability? (Ferreira et al., BlackboxNLP 2026)
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PDF:
https://aclanthology.org/2026.blackboxnlp-1.30.pdf