The Geometry of LLM-as-Judge: Why Inter-LLM Consensus Is Not Human Alignment

Sourabrata Mukherjee, Hamna Abid, Kalika Bali, Sunayana Sitaram


Abstract
LLM judges now score most open-ended NLP output, and their mutual agreement is routinely read as evidence that the scores can be trusted. That reading is unsafe: judges may agree because they capture quality, or because they share the same blind spots, and agreement statistics alone cannot tell these apart. We develop a geometric test that can. Treating each judge’s scores as a vector, we measure spread, effective rank, the angle to human scores, and the judge–judge, judge–human, and human–human agreement triple for 42 judges on two community-built Indic benchmarks covering four domains and eight languages. Every comparison is reference-matched: a judge and a held-out rater are scored against the same two-rater mean, since an averaged reference otherwise flatters judges by several degrees. On subjective rubrics, judges agree with one another as much as humans do yet reach only 58–66% of human agreement: consensus on an axis humans do not weight. On the one rubric with a verifiable answer, most of that gap closes. Ensembles converge on the judges’ shared axis rather than the human one, and training widens scores without rotating them. Inter-judge agreement is evidence of human alignment only after this check passes.
Anthology ID:
2026.findings-emnlp.1696
Volume:
Findings of the Association for Computational Linguistics: EMNLP 2026
Month:
October
Year:
2026
Address:
Budapest, Hungary
Editors:
Hung-Yi Lee, Sunipa Dev, Jessy Li, Desmond Elliott
Venue:
Findings
SIG:
SIGDAT
Publisher:
Association for Computational Linguistics
Note:
Pages:
36237–36266
Language:
URL:
https://aclanthology.org/2026.findings-emnlp.1696/
DOI:
Bibkey:
Cite (ACL):
Sourabrata Mukherjee, Hamna Abid, Kalika Bali, and Sunayana Sitaram. 2026. The Geometry of LLM-as-Judge: Why Inter-LLM Consensus Is Not Human Alignment. In Findings of the Association for Computational Linguistics: EMNLP 2026, pages 36237–36266, Budapest, Hungary. Association for Computational Linguistics.
Cite (Informal):
The Geometry of LLM-as-Judge: Why Inter-LLM Consensus Is Not Human Alignment (Mukherjee et al., Findings 2026)
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PDF:
https://aclanthology.org/2026.findings-emnlp.1696.pdf