SATLab at ArGuard Shared Tasks: Character N-Grams for Fine-Grained Categorization of Harmful LLM Prompts in Arabic

Yves Bestgen


Abstract
This paper presents SATLab’s participation in the ArGuard 2026 shared sub-task on identifying seven types of harmful LLM prompts in Arabic. The proposed system is language-agnostic and requires no resources other than the training data provided in the shared task. It is based on character n-grams and a logistic regression classifier. Performance on the Test set (Macro-F1 = 0.736) was average, approximately 0.05 lower than that of the top teams (0.790) and approximately 0.05 higher than the baseline (0.687). Notably, this performance was substantially lower than those achieved in cross-validation and on the Development set. Several analyses aimed at understanding these discrepancies are reported. An analysis of the confusion matrix indicates that the “Harm-to-other” category poses the greatest problem, likely because it is partially compatible with all other categories except “Adult-content”.
Anthology ID:
2026.arabicnlp-sharedtasks.52
Volume:
Proceedings of The Fourth Arabic Natural Language Processing Conference: Shared Tasks
Month:
October
Year:
2026
Address:
Budapest, Hungary
Editors:
Muhammad Abdul-Mageed, Tamer Elsayed, Houda Bouamor, Samhaa El-Beltagy, Hend Al-Khalifa, Ahmed Abdelali, AbdelRahim Elmadany, Abdellah El Mekki, Kareem Darwish, Sakhar Alkhereyf, Hamzah Luqman, Salam Khalifa, Samar Magdy, Zaid Alyafeai, Injy Hamed, Wajdi Zaghouani, Imed Zitouni
Venue:
ArabicNLP
SIG:
SIGARAB
Publisher:
Association for Computational Linguistics
Note:
Pages:
413–418
Language:
URL:
https://aclanthology.org/2026.arabicnlp-sharedtasks.52/
DOI:
Bibkey:
Cite (ACL):
Yves Bestgen. 2026. SATLab at ArGuard Shared Tasks: Character N-Grams for Fine-Grained Categorization of Harmful LLM Prompts in Arabic. In Proceedings of The Fourth Arabic Natural Language Processing Conference: Shared Tasks, pages 413–418, Budapest, Hungary. Association for Computational Linguistics.
Cite (Informal):
SATLab at ArGuard Shared Tasks: Character N-Grams for Fine-Grained Categorization of Harmful LLM Prompts in Arabic (Bestgen, ArabicNLP 2026)
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PDF:
https://aclanthology.org/2026.arabicnlp-sharedtasks.52.pdf