inside-the-unfair-judge-a-mechanistic-interpretability-account-of-llm-as-judge-bias-3f060780·1 events·first seen Aliases: Inside the Unfair Judge: A Mechanistic Interpretability Account of LLM-as-Judge Bias
A new arXiv preprint investigates LLM-as-judge scoring bias at the representation level rather than the input-output level, studying seven judge models across seven bias types and nine benchmarks. The authors find that biased inputs are displaced along low-dimensional, type-specific subspaces in activation space, and that steering hidden states along these subspaces causally controls scoring direction. A linear projection onto bias-direction features predicts judge failures on unseen benchmarks, substantially outperforming text-based alternatives. The work provides a mechanistic account that unifies geometric structure, causal control, and operational prediction within a single framework.