SubmissionNumber#=%=#21 FinalPaperTitle#=%=#TONI-NLP at PsyDefDetect: Defense Mechanism Detection via LLM-based Ensemble Methods ShortPaperTitle#=%=# NumberOfPages#=%=# CopyrightSigned#=%=# JobTitle#==# Organization#==# Abstract#==#This system description paper presents team TONI-NLP's approach to the PsyDefDetect 2026 shared task. The task required classifying utterances from helper-seeker conversations into nine categories: seven classes representing different levels of defensive maturity, one class indicating no defense mechanism, and one class for cases requiring additional information. We investigated a range of modern NLP techniques, including prompt engineering, fine-tuning, hierarchical modeling using traditional machine learning approaches on text embeddings, and ensemble methods. Our results demonstrate that ensemble methods can effectively classify psychological defense mechanisms in conversational text and achieved the 9th place in the PsyDefDetect 2026 shared task. Author{1}{Firstname}#=%=#Durjoy C. Author{1}{Lastname}#=%=#Paul Author{1}{Orcid}#=%=# Author{1}{Email}#=%=#xei29@txstate.edu Author{1}{Affiliation}#=%=#Texas State University Author{2}{Firstname}#=%=#Arshitha Author{2}{Lastname}#=%=#Basavaraj Author{2}{Username}#=%=#arshitha Author{2}{Orcid}#=%=# Author{2}{Email}#=%=#arshithab@proton.me Author{2}{Affiliation}#=%=#International Institute of Information Technology, Bangalore Author{3}{Firstname}#=%=#Callum Author{3}{Lastname}#=%=#Chan Author{3}{Username}#=%=#callum.chan Author{3}{Orcid}#=%=# Author{3}{Email}#=%=#cchan073@uottawa.ca Author{3}{Affiliation}#=%=#University of Ottawa Author{4}{Firstname}#=%=#Veronica Author{4}{Lastname}#=%=#Perez-Rosas Author{4}{Username}#=%=#vperezr Author{4}{Orcid}#=%=#https://orcid.org/0000-0003-0581-2334 Author{4}{Email}#=%=#vperezr@txstate.edu Author{4}{Affiliation}#=%=#Texas State University Author{5}{Firstname}#=%=#Juan Antonio Author{5}{Lastname}#=%=#Lossio-Ventura Author{5}{Username}#=%=#juanlossio6 Author{5}{Orcid}#=%=#https://orcid.org/0000-0003-0996-2356 Author{5}{Email}#=%=#juanlossio@gmail.com Author{5}{Affiliation}#=%=#National Institutes of Health Author{6}{Firstname}#=%=#Francisco Author{6}{Lastname}#=%=#Pereira Author{6}{Username}#=%=#francisco.pereira Author{6}{Orcid}#=%=# Author{6}{Email}#=%=#francisco.pereira@gmail.com Author{6}{Affiliation}#=%=#National Institute of Mental Health Author{7}{Firstname}#=%=#Diana Author{7}{Lastname}#=%=#Inkpen Author{7}{Username}#=%=#dinkpen Author{7}{Orcid}#=%=#0000-0002-0202-2444 Author{7}{Email}#=%=#diana.inkpen@uottawa.ca Author{7}{Affiliation}#=%=#University of Ottawa ========== èéáğö