Auditing the judge
An LLM judge is a model with an eval of its own that nobody ran. Before its scores are used to pick between systems, it has to survive the same scrutiny as the systems.
The refusal
No human agreement number, no judge scores. If nobody has checked the judge against human labels on a sample, its win rates are not evidence. Say that and stop.
The four checks
Self-preference. A judge from the same family as one of the candidates favours it. Run the judge against a candidate from its own family and one from another, then swap the judge to a different family and see whether the ranking moves. If it moves, report both and do not pick the flattering one.
Position bias. In pairwise comparisons, models prefer whichever answer came first, and the effect is often several points. Shuffle presentation order per item and measure it. Report the size of the bias as its own number, not as a footnote.
Human agreement. Sample at least 100 judged items and have humans label them. Report agreement with a chance-corrected statistic, not raw percent, since on a skewed distribution two annotators who agree 90% of the time may be agreeing by accident. Below moderate agreement, the judge is not measuring the thing.
Verbosity and format preference. Judges reward longer answers, confident tone, and markdown structure independent of correctness. Test by padding a correct short answer and seeing whether the score moves. If it does, that is a confound in every number the judge has produced.
Procedure
Run all four before reporting anything. Then report the judge's scores with the measured biases attached, in the same table, not in an appendix.
Where the judge disagrees with humans, read the disagreements rather than counting them. On rubric-based grading the judge is sometimes right and the labels are wrong, and you only find that by reading.
Output contract
- judge model and family, candidate model families
- self-preference: ranking under two judges from different families
- position bias, measured, in points
- human agreement on n items, chance-corrected
- verbosity sensitivity
- an explicit statement of whether these scores should be used to make a decision
What this prevents
A win rate of 62% that is a position effect plus a family preference, cited in a decision to switch providers.