/**
 * Corpus search dispatcher — picks the retrieval strategy and returns
 * ranked hits with a stable tie-break. No synthesis here: the answer
 * flagship builds on top of this.
 *
 * Modes:
 *   - semantic   : dense cosine only (pre-slice-3 behavior)
 *   - lexical    : BM25 only, never calls embed
 *   - hybrid     : RRF-fused semantic + lexical, default mode
 *   - fact       : hybrid + exact-substring boost + short-chunk preference
 *   - title_path : pure metadata (lexical with body weight = 0), no embed
 *
 * Mode choice controls whether the query is embedded at all; `lexical`
 * and `title_path` skip the embed round-trip entirely, so the model
 * mismatch check only fires on modes that actually touch the embed rail.
 *
 * Tie-break: score desc, then (path asc, chunk_index asc). Zero-score
 * chunks are dropped before top_k slicing.
 */
import type { OllamaClient } from "../ollama.js";
import type { ChunkType } from "./chunker.js";
import type { CorpusFile } from "./storage.js";
export type SearchMode = "semantic" | "lexical" | "hybrid" | "fact" | "title_path";
export declare const DEFAULT_SEARCH_MODE: SearchMode;
export declare const SEARCH_MODES: readonly SearchMode[];
export interface CorpusHit {
    id: string;
    path: string;
    score: number;
    chunk_index: number;
    char_start: number;
    char_end: number;
    heading_path: string[];
    chunk_type: ChunkType;
    title: string | null;
    preview?: string;
}
export interface SearchParams {
    corpus: CorpusFile;
    query: string;
    model: string;
    mode?: SearchMode;
    top_k?: number;
    preview_chars?: number;
    client: OllamaClient;
}
/**
 * True iff the query is null, empty, or whitespace-only. Every search mode
 * needs a query with at least one non-whitespace character — BM25 and the
 * embed tier both return meaningless results for whitespace. Rather than
 * silently returning 0 hits (which looks indistinguishable from "no
 * matches"), callers get a fast-path empty result and the tool layer
 * annotates the envelope so the user sees WHY retrieval was zero.
 */
export declare function isEmptyQuery(query: string | null | undefined): boolean;
export declare function searchCorpus(params: SearchParams): Promise<CorpusHit[]>;
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