The answer-span oracle·2 minWhen rewriting helps0 / 1Knowledge checkWhy can't we grade an LLM-based query rewriter directly in this course?ALLM rewrites are always worse than rulesBAn LLM's rewrite isn't deterministic, so the downstream embedding and recall number would vary run-to-run — and the only way to judge the rewrite quality would be another LLM, which is forbiddenCQuery rewriting doesn't affect retrievalDThe tokenizer can't handle rewritten queries Rewrite & re-measureContext assembly