/**
 * In-memory LRU cache of provider decision outcomes.
 *
 * Keyed by `sha256(adapterVersion, model, questions, state)` over a canonical
 * (key-sorted) JSON serialization, so logically identical requests hit the
 * same entry regardless of object key order. Only provider answers are
 * stored; fallbacks are never cached. The cache is per-process and holds no
 * secrets (the key is not part of any request).
 *
 * @task T12490
 * @epic T12486
 */
import type { DecisionOutcome, DecisionRequest } from '@cleocode/contracts';
/** Default number of entries kept by {@link createDecisionCache}. */
export declare const DEFAULT_DECISION_CACHE_SIZE = 512;
/** A bounded store of decision outcomes. */
export interface DecisionCache {
    /** Look up an outcome, marking it most-recently used. */
    get(key: string): DecisionOutcome | undefined;
    /** Store an outcome, evicting the least-recently used entry when full. */
    set(key: string, outcome: DecisionOutcome): void;
    /** Number of stored entries. */
    readonly size: number;
    /** Drop every entry. */
    clear(): void;
}
/**
 * sha256 hex of the canonical serialization of `value`.
 *
 * @param value - Any JSON-compatible value.
 * @returns 64-char lowercase hex digest.
 */
export declare function hashCanonical(value: unknown): string;
/**
 * Cache key for a request under a given adapter version.
 *
 * @param adapterVersion - Wire-adapter identity; bump it to invalidate entries.
 * @param req - The request as sent to the provider (post-redaction).
 * @returns sha256 hex key.
 */
export declare function decisionCacheKey(adapterVersion: string, req: DecisionRequest): string;
/**
 * Create an LRU {@link DecisionCache}.
 *
 * @param maxEntries - Capacity (minimum 1). Defaults to {@link DEFAULT_DECISION_CACHE_SIZE}.
 * @returns A new, empty cache.
 */
export declare function createDecisionCache(maxEntries?: number): DecisionCache;
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