Reranking

Reranking scores a short candidate list against a query. Use it after a cheaper search, not as a replacement for indexing or retrieval. The selected service is ctx.rerankers.

const answer = await ctx.rerankers.rerank(
  'Which document describes the harbour?',
  candidates,
  {topN: 5, signal},
)

const ordered = answer.results.map(({index, score}) => ({
  document: candidates[index],
  score,
}))

Results are sorted best first. Each row contains the original document index and a score from 0 to 1. Scores are comparable within one call only. topN asks the provider to return only the strongest results; omitting it requests all documents.

The project-maintained Jina/Cohere provider calls POST /rerank. It accepts both relevance_score and score response fields. If a compatible server returns raw logits outside 0–1, the provider maps every score through a logistic function while preserving order.