export interface RerankerOptions {
    topNAfter?: number;
    bm25Weight?: number;
    cosineWeight?: number;
    lengthPenalty?: boolean;
}
export interface RerankCandidate {
    id: string;
    text: string;
    score?: number;
    metadata?: Record<string, unknown>;
}
export interface RerankResult {
    id: string;
    text: string;
    score: number;
    components: {
        bm25: number;
        cosine: number;
        lengthPenalty: number;
    };
    rank: number;
    metadata?: Record<string, unknown>;
}
export declare class BrainRerank {
    /** Rerank a candidate list using fused BM25 + cosine + optional length penalty. */
    rerank(query: string, candidates: RerankCandidate[], opts?: RerankerOptions): Promise<RerankResult[]>;
    /**
     * Fuse with embeddings-v2: do ANN over topKFirst → rerank → return topNFinal.
     * Gracefully falls back to raw ANN hits if embeddings-v2 is missing.
     */
    searchAndRerank(query: string, topKFirst?: number, topNFinal?: number, opts?: RerankerOptions): Promise<RerankResult[]>;
    private computeBm25;
    private computeCosine;
    private lengthPenalty;
}
export declare function getBrainRerank(): BrainRerank;
export declare function resetBrainRerankForTests(): void;
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