We introduce the CAP (Confabulations from ACL Publications) dataset, a multilingual resource for studying hallucinations in large language models (LLMs) within scientific text generation. CAP focuses on the scientific domain, where hallucinations can distort factual knowledge, as they frequently do. In this domain, however, the presence of specialized terminology, statistical reasoning, and context-dependent interpretations further exacerbates these distortions, particularly given LLMs’ lack of true comprehension, limited contextual understanding, and bias toward surface-level generalization. CAP operates in a cross-lingual setting covering five high-resource languages (English, French, Hindi, Italian, and Spanish) and four low-resource languages (Bengali, Gujarati, Malayalam, and Telugu). The dataset comprises 900 curated scientific questions and over 7,000 LLM-generated answers from 16 publicly available models, provided as question–answer pairs along with token sequences and corresponding logits. Each instance is annotated with a binary label indicating the presence of a scientific hallucination, denoted as a factuality error, and a fluency label, capturing issues in the linguistic quality or naturalness of the text. CAP is publicly released to facilitate advanced research on hallucination detection, multilingual evaluation of LLMs, and the development of more reliable scientific NLP systems.

This paper presents an overview of the SHROOM-CAP Shared Task, which focuses on detecting hallucinations and over-generation errors in cross-lingual analyses of scientific publications. SHROOM-CAP covers nine languages: five high-resource (English, French, Hindi, Italian, and Spanish) and four low-resource (Bengali, Gujarati, Malayalam, and Telugu). The task frames hallucination detection as a binary classification problem, where participants must predict whether a given text contains factual inaccuracies and fluency mistakes. We received 1,571 submissions from 5 participating teams during the test phase over the nine languages. In the paper, we present an analysis of the evaluated systems to assess their performance on the hallucination detection task across languages. Our findings reveal a disparity in system performance between high-resource and low-resource languages. Furthermore, we observe that factuality and fluency tend to be closely aligned in high-resource languages, whereas this correlation is less evident in low-resource languages. Overall, SHROOM-CAP underlines that hallucination detection remains a challenging open problem, particularly in low-resource and domain-specific settings.