Evals And Observability hard
Your offline regression gate uses an LLM judge called through a provider alias that always points to the newest model. With no prompt or model change on your side, scores on the unchanged 150-case golden set jumped 4 points overnight. That week the gate approved a change that later regressed in production. What is the correct fix?
- A Rerun every eval three times and average the scores, because a 4-point jump on a fixed golden set is ordinary sampling noise from the judge.
- B Widen the gate threshold to a 10-point drop so that judge-side swings of a few points can no longer block or approve a change.
- C Replace the LLM judge with ROUGE against reference answers, since n-gram overlap metrics are deterministic and cannot drift between runs.
- D Pin the judge to a fixed model snapshot, and recheck its agreement with the human-labeled calibration set before any judge upgrade.
Answer: D. Pin the judge to a fixed model snapshot, and recheck its agreement with the human-labeled calibration set before any judge upgrade.
A gate measures the *difference* between system versions, so the measuring instrument must stay constant. A **pinned judge version** plus re-calibration against human labels on every upgrade keeps that baseline stable, at the cost of missing improvements in newer judges until you validate them. ROUGE (C) is deterministic, but it correlates poorly with quality on open-ended generation. It is only the right choice when outputs have a narrow canonical form, such as extraction or short-form QA.
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- In one release, a RAG assistant got a new embedding model and a new chunking strategy, and the end-to-end judge score dropped 6 points. The team only tracks the end-to-end score and has spent a week tweaking the generation prompt with no recovery. What is the best next step?
- Over two months, your team iterated through 40 prompt versions, each tuned against the same 150-case golden set. The offline score rose from 72 to 91. Online task completion and retry rate have not changed. What is the most likely problem, and what is the fix?
- A prompt change produced an impressive answer in a live demo for leadership. The PM wants to ship it today. What should you do?
- You plan to replace human graders with an LLM judge for your answer-quality eval. Before trusting its scores in a CI gate, what should you do first?
- After you swap to a smaller model, p95 latency falls from 900 ms to 350 ms and the ops dashboard is all green. Leadership asks whether answer quality is still fine. What is the right response?
- Your CI gate fails any prompt change that drops the score 3 or more points on a 100-point rubric over 60 cases. Production generates at temperature 0.7. Running the eval twice on the same commit gives scores that differ by up to 4 points, and engineers have started rerunning failed gates until they pass. How do you fix the gate?