SubmissionNumber#=%=#32 FinalPaperTitle#=%=#Team Aurum at MedExACT 2026@ACL: Data Augmentation and Clinical Longformer Fine-Tuning for Medical Decision Extraction ShortPaperTitle#=%=# NumberOfPages#=%=# CopyrightSigned#=%=# JobTitle#==# Organization#==# Abstract#==#This paper describes the system submitted by team Aurum to the Medical Decision Extraction, Analysis, and Classification Task (MedExACT) at BioNLP 2026. The task requires the extraction and classification of contiguous text spans representing medical decisions from lengthy ICU discharge summaries. To address the dual challenges of long document lengths and severe class imbalance within a limited training set of 350 notes, we propose a two-pronged strategy. First, we employ a tripartite data augmentation pipeline utilizing rule-based entity replacement, LLM-based contextual paraphrasing, and synthetic note generation to expand the training data to over 2,300 notes. Second, we fine-tune a domain-specific Clinical Longformer model equipped with a sliding-window inference mechanism and Focal Loss to handle sequences up to 2,048 tokens while focusing on rare decision categories. Paired with a targeted post-processing module, our system achieved a Final Score of 0.5251, demonstrating high token-level detection (Token F1: 0.6311) and strong stability across patient demographics. Author{1}{Firstname}#=%=#Jyoti Author{1}{Lastname}#=%=#Kumari Author{1}{Username}#=%=#jyotisittu Author{1}{Orcid}#=%=# Author{1}{Email}#=%=#jyoti@bhu.ac.in Author{1}{Affiliation}#=%=#Banaras Hindu University Author{2}{Firstname}#=%=#Vinay Babu Author{2}{Lastname}#=%=#Ulli Author{2}{Username}#=%=#uvinaybabu Author{2}{Orcid}#=%=# Author{2}{Email}#=%=#ullivinaybabu@gmail.com Author{2}{Affiliation}#=%=#Oogwai Analytics Author{3}{Firstname}#=%=#Anindita Author{3}{Lastname}#=%=#Mondal Author{3}{Username}#=%=#anindita_mondal Author{3}{Orcid}#=%=# Author{3}{Email}#=%=#anindita.mondal@research.iiit.ac.in Author{3}{Affiliation}#=%=#International Institute of Information Technology Hyderabad ========== èéáğö