Decision Pick this when Operational trade-off

Raise retrieval top k Current evidence falls outside the candidate set More candidates to inspect; sending all of them to generation consumes more prompt tokens

Add reranking Relevant evidence is retrieved but buried Better ordering, with another call to observe and recover

Repair chunks and freshness Evidence is split from its conditions, missing, or outdated Repair ingestion before tuning ranking

Raising top k improves RAG answer quality when it retrieves missing evidence; rerank when useful evidence is already present but poorly ordered. Freeze the evidence before retrying either experiment. Otherwise a content update between attempts can make recovery look like a relevance improvement.

TL;DR: Raising top k gives RAG more evidence and can increase prompt tokens. Reranking improves ordering and adds a call. Neither wins universally.…