HCMUS_RepeatedGames at SemEval-2026 Task 12: CausalRAG: Synergizing Causal Graph Retrieval and Extended LoRA for Abductive Reasoning

SemEval 2026 Shared Task Co-first author

HCMUS_RepeatedGames at SemEval-2026 Task 12: CausalRAG: Synergizing Causal Graph Retrieval and Extended LoRA for Abductive Reasoning

Duy-Minh Dao-Sy*, Chi-Nguyen Tran*, Trung-Kiet Huynh*, Phu-Quy Nguyen-Lam, Phu-Hoa Pham

Tied 5th, Task 12 (score 0.90)

Finds the most plausible cause of a real event from retrieved documents: hybrid BM25 plus dense retrieval for causal keywords, then LoRA on both attention and MLP layers of a 32B model with 0.81% trainable parameters.

PDF ACL Anthology Code

Dao-Sy, D.-M.*, Tran, C.-N.*, Huynh, T.-K.*, Nguyen-Lam, P.-Q., Pham, P.-H. (2026). HCMUS_RepeatedGames at SemEval-2026 Task 12: CausalRAG: Synergizing Causal Graph Retrieval and Extended LoRA for Abductive Reasoning. SemEval-2026, pp. 409-416.