Preprint Open access
Better Call Reward: Reward Hacking as Strategic Abstention in Legal Reasoning Models
What happens when a legal AI model learns to look like a lawyer instead of reasoning like one? We fine tune Qwen3-8B with Group Relative Policy Optimisation (GRPO) against a proxy built from three surface features: citation count, legalese density, and response length. The model does not learn to reason more effectivel …