Two things I didn't expect:
1. The three judges don't agree. GPT-5.4-mini almost never uses "1" on a 0-4 rubric -- it collapses the scale, redirecting that mass to "2". Gemini and Sonnet use the full scale normally. Same rubric, same responses, different scores. A forensic audit of all 87 scored runs traces the mechanism: GPT resolves an ambiguity in the scoring prompt differently from the other two. If you're using a single AI judge in your evals, you're measuring the judge as much as the subject.
2. Across three protocol iterations, I discovered the instrument was driving most of the measured behavior. Bootstrap prompts primed model outputs. Default thinking-mode settings silenced some models entirely (they spent all their tokens thinking and produced empty responses). Fixing these confounds reversed earlier conclusions. The models were fine -- the microscope was dirty.
Everything is open: runnable instrument, all raw data (2,349 judge records), the working paper, and the forensic analysis. MIT license.