Escaping the Probability Trap: Mitigating Semantic Drift in Cantonese-Mandarin Translation

AbstractFine-tuning multilingual models for low-resource dialect translation frequently encounters a “plausibility over faithfulness” dilemma, resulting in severe semantic drift on dialect-specific tokens. We term this phenomenon the “Probability Trap,” where models prioritize statistical fluency over semantic fidelity. To address this, we propose MVS-Rank (Multi-View Scoring Reranking), a generate-then-rerank framework that decouples evaluation from generation. Our method assesses translation candidates through three complementary perspectives: (1) Source-Side Faithfulness via a Reverse Translation Model to anchor semantic fidelity; (2) Local Fluency using Masked Language Models to ensure syntactic precision; and (3) Global Fluency leveraging Large Language Models to capture discourse coherence. Extensive experiments on Cantonese-Mandarin benchmarks demonstrate that MVS-Rank achieves state-of-the-art performance, significantly outperforming strong fine-tuning baselines by effectively rectifying hallucinations while maintaining high fluency.