/**
 * Discriminative query-term scoring using the session BM25 corpus.
 *
 * Rare query terms (high IDF among indexed query tokens) are treated as
 * salient: chunks that match more salient term mass rank higher; chunks that
 * miss them are slightly down-ranked. Pure logic — no I/O.
 */
import { BM25Index } from "./bm25";
import type { DiscriminativeWeights } from "../entities/rankingWeights";
/** @deprecated Use {@link DEFAULT_DISCRIMINATIVE_WEIGHTS} from entities. */
export declare const DISCRIMINATIVE_CONSTANTS: DiscriminativeWeights;
export interface DiscriminativeTermResult {
    /** Additive boost ∈ [0, boostCap] */
    boost: number;
    /** Multiply hybrid score by this after additive boosts (≤ 1 when penalty applies) */
    penaltyFactor: number;
    /** Query tokens (indexed in BM25) with IDF ≥ median among indexed tokens */
    salientTerms: string[];
    matchedSalient: string[];
    missingSalient: string[];
    /** Σ IDF(matched salient) / Σ IDF(salient), or 1 if no salient set */
    salientCoverage: number;
}
/**
 * Score how well chunk text hits corpus-rare query terms using an already-built
 * {@link BM25Index} over the same chunk set used for retrieval.
 */
export declare function scoreDiscriminativeTerms(bm25Index: BM25Index, query: string, chunkText: string, chunkName?: string, weights?: DiscriminativeWeights): DiscriminativeTermResult;