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n. / Retrieval
Reranking
Definition
Reranking is a second pass that reorders the results of a first search using a more careful relevance model, so the best passages come first and weak ones are dropped.
In more detail
The first search is fast but rough, so you fetch more candidates than you need, perhaps 30. A reranker scores each candidate against the question and you keep the top few. This often improves answers more than changing the embedding model, at the cost of extra latency you can see in the trace.
Example
Vector search returns 30 chunks. The reranker keeps the best four, and the correct policy paragraph moves from position 11 to position 1.
