/**
 * requireRuntime — null-guard helper for MCP tool handlers.
 *
 * When Synapse init silently fails, `hctx.nexusRef` is still assigned but its
 * internal engines are null.  Accessing any engine method then throws a raw
 * TypeError back to the caller instead of a structured envelope.
 *
 * Call this at the top of every handler that touches hctx.nexusRef:
 *
 *   const err = requireRuntime(hctx);
 *   if (err) return err;
 *
 * Returns a ready-to-return MCP content-block envelope when the runtime is
 * absent, or null when everything is healthy.
 */
import type { McpHandlerCtx } from '../types.js';
type McpResult = {
    content: Array<{
        type: string;
        text: string;
    }>;
};
export declare function requireRuntime(hctx: McpHandlerCtx): McpResult | null;
export {};
