import type { OpenClawConfig } from "../config/config.js";
import type { ContextEngine } from "./types.js";
/**
 * A factory that creates a ContextEngine instance.
 * Supports async creation for engines that need DB connections etc.
 */
export type ContextEngineFactory = () => ContextEngine | Promise<ContextEngine>;
/**
 * Register a context engine implementation under the given id.
 */
export declare function registerContextEngine(id: string, factory: ContextEngineFactory): void;
/**
 * Return the factory for a registered engine, or undefined.
 */
export declare function getContextEngineFactory(id: string): ContextEngineFactory | undefined;
/**
 * List all registered engine ids.
 */
export declare function listContextEngineIds(): string[];
/**
 * Resolve which ContextEngine to use based on plugin slot configuration.
 *
 * Resolution order:
 *   1. `config.plugins.slots.contextEngine` (explicit slot override)
 *   2. Default slot value ("legacy")
 *
 * Throws if the resolved engine id has no registered factory.
 */
export declare function resolveContextEngine(config?: OpenClawConfig): Promise<ContextEngine>;