Junliu Zou


2026

We present our system for SemEval-2026 Task 12: Abductive Event Reasoning (AER). The task asks models to identify the direct causes of real-world events from multiple-choice options using retrieved documents. Rather than fine-tuning on the training data, we built a zero-shot "Retrieve-Verify-Aggregate” pipeline around Qwen3-8B. We first isolate relevant evidence using BM25 and cross-encoder reranking. To evaluate causal links, we prompt the model with several distinct "personas” and aggregate their independent decisions through majority voting. Our system scored 0.7614 on the official test set. This performance suggests that strict retrieval combined with diverse reasoning prompts can help compact open-source models ignore irrelevant context and perform complex causal inference, entirely without task-specific training.