Are LLMs Reliable Judges? 8 Months of Lessons Learned

larabyeol · reddit · 2026-07-07

A team processing roughly 50,000 LLM outputs weekly shared 8 months of practical experience using GPT-4o for automated evaluation. It proved fast and effective at catching obvious regressions, formatting errors, and hallucinated entities. However, it suffered from poor cross-run consistency (scoring divergence exceeded 30% within two weeks without locked prompts and model versions), positional bias (preferring the first option in A/B tests), and leniency toward its own outputs. They recommend locking evaluation prompts and model versions, as well as swapping positions across two runs to mitigate these issues.

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