LahjaSensei at DialectSentEval 2026: Few-Shot Prompting and Model Merging for Sentiment Swap

Ahmad Almoustafa, Takuya Matsuzaki


Abstract
Arabic dialect sentiment swapping requires systems to reverse the affective orientation of an utterance while preserving its core meaning, dialectal form, and fluency. This task is particularly challenging because sentiment may be conveyed through dialect-specific vocabulary, negation patterns, and spelling variation. We present LahjaSensei, our system for Subtask 2 of the DialectSentEval shared task. We investigate two complementary approaches: prompt-based generation with GPT-5.6 and parameter-efficient fine-tuning of Qwen2.5-7B. We evaluate GPT-5.6 under zero-shot, retrieved few-shot, stronger Arabic instructions, and direction-aware configurations. The direction-aware GPT-5.6 pipeline explicitly predicts source polarity before retrieving direction-matched demonstrations and generating the rewrite. For Qwen2.5-7B, we compare pooled QLoRA with linear and TIES merges of direction-specific adapters. Direction-aware GPT-5.6 prompting achieves the highest test sentiment accuracy and remains stable across development and test. Pooled QLoRA produces the highest development BLEU and chrF, while linear merging obtains the highest test BLEU and chrF but lower sentiment accuracy. These findings highlight the central trade-off between sentiment control and preservation of semantic content and demonstrate the value of explicit direction modeling for Arabic dialect sentiment swapping.
Anthology ID:
2026.arabicnlp-sharedtasks.176
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:
1403–1408
Language:
URL:
https://aclanthology.org/2026.arabicnlp-sharedtasks.176/
DOI:
Bibkey:
Cite (ACL):
Ahmad Almoustafa and Takuya Matsuzaki. 2026. LahjaSensei at DialectSentEval 2026: Few-Shot Prompting and Model Merging for Sentiment Swap. In Proceedings of The Fourth Arabic Natural Language Processing Conference: Shared Tasks, pages 1403–1408, Budapest, Hungary. Association for Computational Linguistics.
Cite (Informal):
LahjaSensei at DialectSentEval 2026: Few-Shot Prompting and Model Merging for Sentiment Swap (Almoustafa & Matsuzaki, ArabicNLP 2026)
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PDF:
https://aclanthology.org/2026.arabicnlp-sharedtasks.176.pdf