SV-Detect: AI-generated Text Detection with Steering Vectors

Mikhail Vishnyakov, Tatiana Gaintseva


Abstract
Detecting AI-generated text is especially difficult under distribution shift, such as transfer across domains, source models, and editing attacks. We propose an AI-generated text detector based on steering vectors extracted from the hidden representations of a frozen language model. At each layer, we construct a direction that separates human-written from AI-generated text, and represent each input by its layer-wise alignment with these directions. A lightweight classifier trained on these projection features yields the final detection score. Our method achieves strong performance both in-distribution and under distribution shift, including across domains, source models, and machine-editing transformations such as polishing and rewriting. Interpretation analyses show that the learned directions align with recognizable stylistic cues while capturing substantial additional signal beyond surface features. These results position AI-generated text detection as a representation-space probing problem and show that steering vectors provide a simple and effective solution.
Anthology ID:
2026.emnlp-main.2161
Volume:
Proceedings of the 2026 Conference on Empirical Methods in Natural Language Processing
Month:
October
Year:
2026
Address:
Budapest, Hungary
Editors:
Hung-Yi Lee, Sunipa Dev, Jessy Li, Desmond Elliott
Venue:
EMNLP
SIG:
SIGDAT
Publisher:
Association for Computational Linguistics
Note:
Pages:
49160–49186
Language:
URL:
https://aclanthology.org/2026.emnlp-main.2161/
DOI:
Bibkey:
Cite (ACL):
Mikhail Vishnyakov and Tatiana Gaintseva. 2026. SV-Detect: AI-generated Text Detection with Steering Vectors. In Proceedings of the 2026 Conference on Empirical Methods in Natural Language Processing, pages 49160–49186, Budapest, Hungary. Association for Computational Linguistics.
Cite (Informal):
SV-Detect: AI-generated Text Detection with Steering Vectors (Vishnyakov & Gaintseva, EMNLP 2026)
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PDF:
https://aclanthology.org/2026.emnlp-main.2161.pdf