iMak AI Lab at AraSeg Shared Task 2026: Greedy-Selected Arabic Encoder Ensembles with Structural Constraints for Sentence Segmentation

Artiom Lipinski, Ilya Makarov


Abstract
We describe the iMak AI Lab submissions to the closed track of the AraSeg Shared Task 2026 on Arabic sentence segmentation, covering all four subtasks: Paragraph-Aware (PA), No-Paragraph (NP), No-Punctuation Paragraph-Aware (NOPNX-PA), and NoPunctuation No-Paragraph (NOPNX-NP). Our system treats segmentation as binary token classification with pretrained Arabic encoders finetuned only on the 128K-token AraSeg training split. The single-model recipe encodes documents in overlapping 512-token windows and trains for three times more epochs than the standard schedule, which is the largest source of improvement in our pipeline. Per-subtask ensembles are then built by greedy forward selection over a pool of seven encoder families, several seeds, and multi-variant joint-training variants. Decoding applies deterministic structural constraints and a decision threshold tuned on the development set; no open-test labels or leaderboard feedback enter any modeling decision. The systems reach blind-test F1 scores of 94.1 (PA), 91.0 (NP), 89.5 (NOPNX-PA), and 85.8 (NOPNX-NP), above the official baseline on all four subtasks. We report ablations for each design decision, including several that did not help.
Anthology ID:
2026.arabicnlp-sharedtasks.114
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:
927–932
Language:
URL:
https://aclanthology.org/2026.arabicnlp-sharedtasks.114/
DOI:
Bibkey:
Cite (ACL):
Artiom Lipinski and Ilya Makarov. 2026. iMak AI Lab at AraSeg Shared Task 2026: Greedy-Selected Arabic Encoder Ensembles with Structural Constraints for Sentence Segmentation. In Proceedings of The Fourth Arabic Natural Language Processing Conference: Shared Tasks, pages 927–932, Budapest, Hungary. Association for Computational Linguistics.
Cite (Informal):
iMak AI Lab at AraSeg Shared Task 2026: Greedy-Selected Arabic Encoder Ensembles with Structural Constraints for Sentence Segmentation (Lipinski & Makarov, ArabicNLP 2026)
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PDF:
https://aclanthology.org/2026.arabicnlp-sharedtasks.114.pdf