AILS-NTUA at SemEval-2026 Task 12: Graph-Based Retrieval and Reflective Prompting for Abductive Event Reasoning

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Autori principali: Karafyllis, Nikolas, Lymperaiou, Maria, Filandrianos, Giorgos, Voulodimos, Athanasios, Stamou, Giorgos
Natura: Preprint
Pubblicazione: 2026
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author Karafyllis, Nikolas
Lymperaiou, Maria
Filandrianos, Giorgos
Voulodimos, Athanasios
Stamou, Giorgos
author_facet Karafyllis, Nikolas
Lymperaiou, Maria
Filandrianos, Giorgos
Voulodimos, Athanasios
Stamou, Giorgos
contents We present a winning three-stage system for SemEval 2026 Task~12: Abductive Event Reasoning that combines graph-based retrieval, LLM-driven abductive reasoning with prompt design optimized through reflective prompt evolution, and post-hoc consistency enforcement; our system ranks first on the evaluation-phase leaderboard with an accuracy score of 0.95. Cross-model error analysis across 14 models (7~families) reveals three shared inductive biases: causal chain incompleteness, proximate cause preference, and salience bias, whose cross-family convergence (51\% cause-count reduction) indicates systematic rather than model-specific failure modes in multi-label causal reasoning.
format Preprint
id arxiv_https___arxiv_org_abs_2603_04319
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle AILS-NTUA at SemEval-2026 Task 12: Graph-Based Retrieval and Reflective Prompting for Abductive Event Reasoning
Karafyllis, Nikolas
Lymperaiou, Maria
Filandrianos, Giorgos
Voulodimos, Athanasios
Stamou, Giorgos
Computation and Language
We present a winning three-stage system for SemEval 2026 Task~12: Abductive Event Reasoning that combines graph-based retrieval, LLM-driven abductive reasoning with prompt design optimized through reflective prompt evolution, and post-hoc consistency enforcement; our system ranks first on the evaluation-phase leaderboard with an accuracy score of 0.95. Cross-model error analysis across 14 models (7~families) reveals three shared inductive biases: causal chain incompleteness, proximate cause preference, and salience bias, whose cross-family convergence (51\% cause-count reduction) indicates systematic rather than model-specific failure modes in multi-label causal reasoning.
title AILS-NTUA at SemEval-2026 Task 12: Graph-Based Retrieval and Reflective Prompting for Abductive Event Reasoning
topic Computation and Language
url https://arxiv.org/abs/2603.04319