/**
 * topK — the retrieval strategy agentfootprint has always used, now
 * written down as one.
 *
 * Pattern: Strategy (one of {@link RetrievalStrategy}).
 * Role:    memory/ layer. Extracted in 8.8.0 from the two numbers that
 *          used to live loose on `defineRAG` (`topK`, `threshold`), so
 *          that a different rule can be written without touching a stage.
 * Emits:   N/A — the stage that calls it does the emitting.
 *
 * Behaviour is byte-for-byte what 8.7.0 did: take the highest-scoring
 * candidates that clear `threshold`, at most `k` of them, and inject
 * nothing at all when none clear it.
 *
 * **The threshold is strict, and strict means silent-by-design becomes
 * loud-by-record.** When nothing clears the floor, no context is
 * injected — a weak match in the prompt makes a confident wrong answer
 * more likely, not less. What 8.8.0 changes is that the near-misses are
 * now IN the record with their scores, so "the agent answered from
 * nothing" is a readable outcome instead of an absence.
 */
import type { RetrievalStrategy } from './types.js';
export interface TopKOptions {
    /**
     * How many chunks may reach the prompt. Default 3 — enough for more
     * than one perspective, few enough that the middle of a long context
     * does not swallow the answer.
     */
    readonly k?: number;
    /**
     * Minimum similarity to admit, in the store's score space ([-1, 1]
     * cosine for every shipped store). Default 0.7.
     *
     * **The right threshold is a property of the EMBEDDER, not of this
     * library.** 0.7 is a high bar for some embedders. Sentence-transformer
     * relatives (`all-MiniLM-L6-v2` and family, which `localEmbedder` uses by
     * default) often score 0.4–0.6 on genuinely relevant chunks; OpenAI
     * `text-embedding-3-*` sits comfortably at 0.7. Amazon Titan Text V2
     * (`bedrockEmbedder`'s default) was measured in a production corpus at
     * 0.55–0.57 for a direct hit, ~0.49 for the right section diluted by its
     * neighbours, and 0.36–0.42 for noise — **on that embedder the 0.7
     * default retrieves NOTHING, silently**; ~0.5 separates its signal from
     * its noise. If retrievals come back empty, read the
     * `agentfootprint.memory.retrieved` event: it carries the rejected
     * candidates and their scores, so the right threshold is a number you
     * can see rather than one you guess.
     *
     * Pass `null` for no floor — every candidate up to `k` is admitted.
     */
    readonly threshold?: number | null;
    /**
     * How many extra candidates to pull past `k` so that rejected ones can
     * be reported. Default 10. Raising it costs one larger read and shows
     * more near-misses; it can never change which candidates are admitted.
     */
    readonly rejectWindow?: number;
}
/**
 * Build the top-K strategy.
 *
 * @example
 * ```ts
 * import { defineRAG } from 'agentfootprint';
 * import { topK } from 'agentfootprint/memory';
 *
 * const docs = defineRAG({
 *   id: 'product-docs',
 *   store, embedder,
 *   retrieval: topK({ k: 5, threshold: 0.55 }),
 * });
 * ```
 */
export declare function topK(options?: TopKOptions): RetrievalStrategy;