Retrieval returned exactly the right passage and the model still made something up. Now what?
Retrieval is exonerated, so the bug lives in generation. There are four usual causes and they have different fixes, and the one nobody names is that the model was never given permission to say it does not know.
Updated Sep 2026 · Grounded in real GenAI, LLM, and AI/ML engineering interview loops and written to a senior-engineer editorial bar.
Retrieval is exonerated, so the bug lives in generation. There are four usual causes and they have different fixes, and the one nobody names is that the model was never given permission to say it does not know.
Lead with where the obvious approach breaks, because that is the judgment they are screening for — most candidates jump straight to the happy path and lose the room.
Then walk the failure back through the pipeline in order, naming the one metric the customer's exec sponsor actually cares about before you propose the fix.
