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sutta at SemEval-2026 Task 12: A Multi-Perspective Retrieve-Verify-Aggregate Framework for Abductive Event Reasoning

Paper · 2026 · Junliu Zou, Liang Yang and Jingjie Zeng

Summary

The paper addresses Abductive Event Reasoning (SemEval-2026 Task 12). Given a real-world event, four candidate options and 10–20 retrieved documents, a system must select the option(s) that directly caused the event. The authors argue that LLMs given long, noisy context tend to latch onto plausible but non-causal material.

Team sutta built a zero-shot pipeline around Qwen3-8B with no task-specific fine-tuning:

  • Retrieval: documents are split into passages of at most 1,000 characters. BM25 picks 30 candidates per event–option query, and the bge-reranker-v2-m3 cross-encoder keeps the top five.
  • Verification: the same model judges each option under five prompting personas: Standard CoT, Detailed CoT, Counterfactual Analysis, NLI and Detective Role-Play.
  • Aggregation: a strict majority vote, with a fallback rule, produces the final answer.

The ensemble scored 0.7614 on the 612-item blind test set, outperforming every individual prompt. The work matters because it shows a compact open model can perform competitive causal inference cheaply when it combines tight passage-level retrieval with diverse reasoning prompts. The authors also show that the vote fails when several personas share the same logical bias.

Key points

  • The dataset is English-only, with 1,819 train, 400 dev and 612 test instances. Scoring gives 1.0 for an exact match, 0.5 for a proper subset of the correct causes, and 0 if any wrong option is chosen.
  • Retrieval settings: BM25 (k1 = 1.5, b = 0.75) returns top-30 chunks, and bge-reranker-v2-m3 keeps the top 5. Qwen3-8B runs via vLLM with temperature 0.1.
  • The 5-persona ensemble reached 0.7614 (73.86% full match), versus 0.7353 for the best single prompt (Standard CoT) and 0.7475 for a Top-3 ensemble.
  • Individually weak personas, Counterfactual (0.5760) and Detective (0.5041), still improved the ensemble by rejecting false correlations. Detailed CoT (0.6503) underperformed the simpler Standard CoT.
  • Limitations include roughly 5× inference cost, a precision-heavy vote that misses some valid causes, and reliance on Qwen3-8B's own knowledge. In an error case (q-2470), the model mistook a necessary precondition for a direct cause.

Our summary of the paper, in our own words — not its text. The work belongs to its authors; read it at the links above.

 Institutions

 Fields, topics and concepts

Cite

Cite as Junliu Zou, Liang Yang and Jingjie Zeng. 2026. sutta at SemEval-2026 Task 12: A Multi-Perspective Retrieve-Verify-Aggregate Framework for Abductive Event Reasoning. Proceedings of the 20th International Workshop on Semantic Evaluation (2026).

The paper itself, not this page. BibTeX from the library's record of the work. DOI 10.18653/v1/2026.semeval-1.323

@inproceedings{zou2026sutta,
  title = {{sutta at SemEval-2026 Task 12: A Multi-Perspective Retrieve-Verify-Aggregate Framework for Abductive Event Reasoning}},
  author = {Junliu Zou, Liang Yang and Jingjie Zeng},
  booktitle = {Proceedings of the 20th International Workshop on Semantic Evaluation (2026)},
  year = {2026},
  doi = {10.18653/v1/2026.semeval-1.323},
  url = {https://doi.org/10.18653/v1/2026.semeval-1.323}
}

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