/**
 * Knowledge reranking — reorder retrieved documents by relevance.
 *
 * Phase-1 sibling of the reference engines' reranking. A `Reranker` takes the
 * query and the retriever's candidate hits and returns them reordered (and
 * possibly trimmed). `NoopReranker` is the default passthrough; `LexicalReranker`
 * re-scores by query-term coverage normalized for document length, so a concise
 * on-topic doc outranks a long one with the same raw overlap. A cross-encoder or
 * gateway reranker drops in behind the same interface.
 */
import type { KnowledgeHit } from './knowledge.js';
export interface Reranker {
    rerank(query: string, hits: KnowledgeHit[]): KnowledgeHit[];
}
/** Returns the hits unchanged — the zero-cost default. */
export declare class NoopReranker implements Reranker {
    rerank(_query: string, hits: KnowledgeHit[]): KnowledgeHit[];
}
/**
 * Reorders by query-term coverage normalized by document length:
 * `coverage / log2(2 + docTokenCount)`, so coverage is rewarded but long docs are
 * penalized relative to concise ones with the same coverage. Stable for ties.
 */
export declare class LexicalReranker implements Reranker {
    rerank(query: string, hits: KnowledgeHit[]): KnowledgeHit[];
}
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