We present a fact-checking system developed for the 2025 Automated Verification of Textual Claims (AVeriTeC) shared task, leveraging the Graph-of-Thoughts (GoT) prompting scheme. The GoT approach facilitates iterative refinement during fact-checking by conditioningquestion generation on previous answers and enabling the incorporation of multiple evidence documents per question, thereby mitigatingthe impact of factually incorrect evidence. The efficiency requirements of the shared task are addressed by restricting the width and depthof the thought graph. Additionally, an efficient stopping criterion is derived from the dataset’s Not Enough Information (NEI) label. Our system utilizes fine-tuned open-source Large Language Models (LLMs) for question generation, question answering, and final verdict prediction. Empirical results demonstrate competitive performance against top-performing systems in the AVeriTeC shared task and improvements over the baseline method. Our code is publicly available.

This paper describes the FZI-WIM system at the AVeriTeC shared Task, which aims to assess evidence-based automated fact-checking systems for real-world claims with evidence retrieved from the web. The FZI-WIM system utilizes open-source models to build a reliable fact-checking pipeline via question-answering. With different experimental setups, we show that more questions lead to higher scores in the shared task. Both in question generation and question-answering stages, sampling can be a way to improve the performance of our system. We further analyze the limitations of current open-source models for real-world claim verification. Our code is publicly available https://github.com/jens5588/FZI-WIM-AVERITEC.