SKstars at SHROOM-Visions: Agreement-Guided Ensembling of Zero-Shot and LoRA-Adapted Vision–Language Models

Ali Athar, Imran Ahsan, Joon-Yong Jung


Abstract
This paper describes the SKstars submission to SHROOM-Visions 2026, a shared task on fine-grained hallucination detection in large vision-language model outputs. The task requires systems to identify hallucinated character spans, assign hallucination categories, and provide confidence estimates for their predictions. Our approach combines zero-shot predictions from Qwen2.5-VL-72B-Instruct with those of a LoRA-adapted Qwen2.5-VL-7B-Instruct model. The outputs of the two models are integrated through a lightweight ensemble procedure, followed by span refinement and confidence adjustment. We evaluate the main system components on a small internal development subset and report the performance of the submitted system on the official English test set. SKstars achieved a Cor+Lbl score of 0.2902, ranking 15th among 29 teams, and obtained Cor and IoU scores of 0.3642 and 0.3151, respectively, ranking 18th on both metrics. The results show that combining a large zero-shot model with a smaller adapted model provides a practical framework for multilingual and fine-grained hallucination localization, while also highlighting the difficulty of transferring development-set improvements to hidden test data.
Anthology ID:
2026.uncertainlp-main.57
Volume:
The Proceedings of the Third Workshop on Uncertainty-Aware NLP
Month:
October
Year:
2026
Address:
Budapest, Hungary
Editors:
Wilker Aziz, Jonathan Berant, Bryan Eikema, Evgenia Ilia, Marie-Catherine de Marneffe, Barbara Plank, Artem Shelmanov, Swabha Swayamdipta, Jörg Tiedemann, Artem Vazhentsev, Raúl Vázquez, Chrysoula Zerva
Venues:
UncertaiNLP | WS
SIG:
Publisher:
Association for Computational Linguistics
Note:
Pages:
823–827
Language:
URL:
https://aclanthology.org/2026.uncertainlp-main.57/
DOI:
Bibkey:
Cite (ACL):
Ali Athar, Imran Ahsan, and Joon-Yong Jung. 2026. SKstars at SHROOM-Visions: Agreement-Guided Ensembling of Zero-Shot and LoRA-Adapted Vision–Language Models. In The Proceedings of the Third Workshop on Uncertainty-Aware NLP, pages 823–827, Budapest, Hungary. Association for Computational Linguistics.
Cite (Informal):
SKstars at SHROOM-Visions: Agreement-Guided Ensembling of Zero-Shot and LoRA-Adapted Vision–Language Models (Athar et al., UncertaiNLP 2026)
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PDF:
https://aclanthology.org/2026.uncertainlp-main.57.pdf