/**
 * @name McpSessionCache
 * @description Client-side MCP session cache for x402 paid calls.
 *
 * The x402 paid-call client otherwise creates a new MCP session on every call.
 * Reusing a short-lived initialized session reduces round trips without caching
 * live on-chain data, payment challenges, or signed payment payloads.
 *
 * Cache entries are scoped per endpoint and process. They do not persist across
 * restarts and are invalidated when a runtime reports session_not_found.
 */
/**
 * Get a cached session for an endpoint, or null if expired/missing.
 */
export declare function getCachedSession(endpoint: string): string | null;
/**
 * Store a session in the cache. If the cache is full, evict the least-recently-used entry.
 */
export declare function cacheSession(endpoint: string, sessionId: string): void;
/**
 * Invalidate a cached session (e.g. when the server returns 404 session_not_found).
 */
export declare function invalidateSession(endpoint: string): void;
/**
 * Clear all cached sessions.
 */
export declare function clearSessionCache(): void;
/**
 * Get cache stats for diagnostics.
 */
export declare function getSessionCacheStats(): {
    size: number;
    endpoints: string[];
};
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