PolDeck at SemEval-2026 Task 9: Multilingual Online Polarization Detection via Hybrid Model Ensembling and Data Augmentation

Ben Grandy, Daniel Khir


Abstract
In this paper, we address SemEval 2026 Task 9: Multilingual Online Polarization Detection. We present our hybrid ensemble framework, integrating few-shot prompting with Qwen3-30B, a native multilingual XLM-R encoder, and a translation-augmented DeBERTa encoder. To mitigate label imbalance, we implement a multi-stage augmentation pipeline leveraging LLMs for synthetic paraphrasing and cross-lingual translation. Our system ranked in the Top 10 on the English and German leaderboards, proving that integrating both high-capacity monolingual models and flexible multilingual models in a holistic system is a viable method for detecting online polarization. Our code is available on GitHub.
Anthology ID:
2026.semeval-1.120
Volume:
Proceedings of the 20th International Workshop on Semantic Evaluation (2026)
Month:
July
Year:
2026
Address:
San Diego, California, USA
Editors:
Ekaterina Kochmar, Debanjan Ghosh, Kai North, Mamoru Komachi
Venues:
SemEval | WS
SIG:
Publisher:
Association for Computational Linguistics
Note:
Pages:
879–885
Language:
URL:
https://preview.aclanthology.org/ingest-acl-workshops/2026.semeval-1.120/
DOI:
Bibkey:
Cite (ACL):
Ben Grandy and Daniel Khir. 2026. PolDeck at SemEval-2026 Task 9: Multilingual Online Polarization Detection via Hybrid Model Ensembling and Data Augmentation. In Proceedings of the 20th International Workshop on Semantic Evaluation (2026), pages 879–885, San Diego, California, USA. Association for Computational Linguistics.
Cite (Informal):
PolDeck at SemEval-2026 Task 9: Multilingual Online Polarization Detection via Hybrid Model Ensembling and Data Augmentation (Grandy & Khir, SemEval 2026)
Copy Citation:
PDF:
https://preview.aclanthology.org/ingest-acl-workshops/2026.semeval-1.120.pdf
Supplementarymaterial:
 2026.semeval-1.120.SupplementaryMaterial.zip