knights-ST at AraSeg Shared Task 2026: Cross-Family Ensembling with Task-Adaptive Pretraining for Arabic Sentence Segmentation

Abdelrahman Sakr, Marwan Torki


Abstract
We describe our submission to the AraSeg 2026 shared task on Arabic sentence segmentation (Paragraph-Aware, Closed track). We cast segmentation as binary token-boundary classification and build a system around three ideas: (i) task-adaptive pretraining (TAPT) of encoders on the task’s own training text, (ii) regularized fine-tuning with R-Drop and boundary smoothing, and (iii) a hand-designed cross-family ensemble of architecturally diverse Arabic encoders. Our final system reaches a boundary F1 of 94.8 on the blind test set (ranking 3rd of 12 teams, 0.5 points from the top-ranked team). Beyond the score, we report a practical finding backed by a series of blind submissions: on a small development set, a compact diversity-first ensemble generalizes better to unseen data than ensembles selected by exhaustively maximizing development F1, and TAPT helps only under-adapted backbones while hurting a heavily-pretrained one. We also report five techniques that did not help, to save future practitioners the effort. Our code is publicly available at https://github.com/Body123/araseg-2026-knights-st.
Anthology ID:
2026.arabicnlp-sharedtasks.116
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:
938–943
Language:
URL:
https://aclanthology.org/2026.arabicnlp-sharedtasks.116/
DOI:
Bibkey:
Cite (ACL):
Abdelrahman Sakr and Marwan Torki. 2026. knights-ST at AraSeg Shared Task 2026: Cross-Family Ensembling with Task-Adaptive Pretraining for Arabic Sentence Segmentation. In Proceedings of The Fourth Arabic Natural Language Processing Conference: Shared Tasks, pages 938–943, Budapest, Hungary. Association for Computational Linguistics.
Cite (Informal):
knights-ST at AraSeg Shared Task 2026: Cross-Family Ensembling with Task-Adaptive Pretraining for Arabic Sentence Segmentation (Sakr & Torki, ArabicNLP 2026)
Copy Citation:
PDF:
https://aclanthology.org/2026.arabicnlp-sharedtasks.116.pdf