Utterance-level Detection Framework for LLM-Involved Content Detection in Conversational Setting
Paper · 2026 · Muyang Zhou and Huaxia Rui
Summary
Most detectors of machine-generated text are built for static, document-level inputs. They handle short, interactive exchanges poorly, especially when human and model turns are mixed in one dialogue. The authors reframe detection at the utterance level within conversations and supply both a dataset and a model. The dataset combines real human-human dialogues from Wizard of Wikipedia, Persona-Chat and MuTual with two kinds of synthetic dialogues. In LLM-LLM dialogues, two persona-prompted assistants converse turn by turn. In human-LLM dialogues, people chat with a model on summarized topics.
The detector is lightweight. It uses the LLaMA3 tokenizer with a small custom transformer, arranged recurrently over dialogue turns. It mixes self-attention and cross-attention between the two speakers. A detection focus augmentation strategy emphasizes the second speaker's replies while keeping the first speaker's turns as context.
On human-LLM dialogues it reaches 98.14% accuracy with fast inference and outperforms baseline detectors. It also generalizes reasonably in zero-shot tests on out-of-domain data. This makes it a practical candidate for real-time transparency checks in chat systems.
Key points
- Dataset: over 80,000 training dialogues in three parts (human-human, LLM-LLM, human-LLM).
- Synthetic turns come from GPT-4o, LLaMA-3.1-70B-Instruct and Qwen2.5-72B-Instruct.
- Turn counts match those of the real human conversations.
- Model: LLaMA3 tokenizer feeding a custom 4-layer transformer for feature extraction, followed by self-attention and cross-attention blocks in a recurrent arrangement with a decoder at each stage.
- Results and ablations:
- 98.14% accuracy on human-LLM dialogues.
- The LLM tokenizer adds about 9% accuracy compared with a traditional tokenizer.
- Accuracy exceeds 90% on some out-of-domain tasks.
- Dialogue length: training uses 5-round dialogues.
- Shorter inputs are padded with blank content.
- Longer ones are split into 5-round sliding windows whose predictions are combined by voting.
- Compared with models trained on 1–10 rounds, performance remains comparable.
- Limitations:
- Covers only two-party dialogues.
- May be weaker in specialized domains such as medical or legal.
- Has notable compute cost.
- Cross-lingual and multi-party detection are left as future work, which matters for applying it to Ukrainian.
Institutions
Fields, topics and concepts
📚 Shelves 6The field of science this work belongs to (OpenAlex fields).Computer Science · 18,614 worksArtificial Intelligence · 17,965 worksArts and Humanities · 17,450 worksLanguage and Linguistics · 17,296 worksComputer Vision and Pattern Recognition · 3,486 worksInformation Systems · 1,730 works
🧭 Topics 1Research subjects and languages the work is about.Dialogue systems · 654 works
Cite
Cite as Muyang Zhou and Huaxia Rui. 2026. Utterance-level Detection Framework for LLM-Involved Content Detection in Conversational Setting. Proceedings of the 19th Conference of the European Chapter of the Association for Computational Linguistics (Volume 1: Long Papers).
@inproceedings{zhou2026utterance,
title = {{Utterance-level Detection Framework for LLM-Involved Content Detection in Conversational Setting}},
author = {Muyang Zhou and Huaxia Rui},
booktitle = {Proceedings of the 19th Conference of the European Chapter of the Association for Computational Linguistics (Volume 1: Long Papers)},
year = {2026},
doi = {10.18653/v1/2026.eacl-long.63},
url = {https://doi.org/10.18653/v1/2026.eacl-long.63}
}References
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