How to debug and reduce RAG hallucinations: a five-step interview answer that starts with retrieval metrics
ashishllm · x · 2026-09-17
Answering the common interview question "how do you trace, debug and reduce hallucinations?", the author lays out a diagnostic sequence — and warns the classic mistake is jumping to prompt fixes before checking retrieval.
The five steps:
- Check retrieval first: build an eval dataset and look at Precision, Recall, MRR and Hit Rate to see if the problem is retrieval or generation.
- Add a confidence threshold after the reranker: below-threshold chunks return "No Context Found" instead of an irrelevant answer.
- Implement hybrid search to improve retrieval accuracy.
- Increase embedding dimensions for better retrieval quality, trading off latency and cost.
- Further chunking strategies (thread truncated).
A commenter adds that candidates fail most often by going straight to prompt tweaks without verifying the right chunks are being retrieved.
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