/**
 * Capability retrieval: BM25 and dense, fused by RRF.
 *
 * Hybrid rather than dense-only because capability descriptions are short.
 * Pure dense retrieval over eight-word strings is weak, and — more decisively —
 * an exact name lookup has to stay exact: `create_pull_request` must find
 * `mcp_github_create_pull_request` every time, which is a lexical guarantee, not
 * a nearest-neighbour one. Fusion gets both: the lexical leg answers "the tool
 * called roughly this", the dense leg "something that does this".
 *
 * Reuses the repo search's {@link rrfFuse} rather than reimplementing fusion.
 * The tie-breaking and duplicate handling there are already worked out, and a
 * second, subtly different fusion is how two retrieval paths drift apart.
 */
import { type CapabilityDoc, type CapabilityKind } from "./registry.js";
export interface CapabilityHit {
    doc: CapabilityDoc;
    /** Fused score. Comparable within one result set only. */
    score: number;
    /** Which legs found it — useful when explaining a surprising ranking. */
    matchedBy: Array<"lexical" | "dense">;
}
export interface CapabilitySearchOptions {
    /** Restrict to these kinds. Omit for everything. */
    kinds?: readonly CapabilityKind[];
    /** Results to return. */
    limit?: number;
    /** Restrict to capabilities whose expensive part is currently withheld. */
    deferredOnly?: boolean;
}
export interface CapabilitySearchResult {
    hits: CapabilityHit[];
    /** How the answer was produced, so a caller can say "lexical only" honestly. */
    legs: Array<"lexical" | "dense">;
}
/** Drop the cached lexical index. Tests, and anything that rewrites the registry wholesale. */
export declare function resetCapabilitySearch(): void;
/**
 * Find capabilities matching `query`.
 *
 * Over-fetches from each leg before fusing: RRF works on rank, so a document
 * ranked 8th by one retriever and absent from the other still deserves to be
 * considered — truncating each list to the final `limit` first would throw that
 * away before fusion could use it.
 */
export declare function searchCapabilities(query: string, options?: CapabilitySearchOptions): Promise<CapabilitySearchResult>;
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