import * as grpc from "@grpc/grpc-js";
/**
 * Type for a function that generates gRPC metadata (e.g., for taskhub, auth tokens).
 */
export type MetadataGenerator = () => Promise<grpc.Metadata>;
/**
 * Promisifies a gRPC unary call with metadata support.
 *
 * @param method The gRPC method to call (must be bound to the stub).
 * @param req The request object.
 * @param metadataGenerator Optional function to generate metadata for the call.
 * @returns A promise that resolves with the response or rejects with an error.
 */
export declare function callWithMetadata<TReq, TRes>(method: (req: TReq, metadata: grpc.Metadata, callback: (error: grpc.ServiceError | null, response: TRes) => void) => grpc.ClientUnaryCall, req: TReq, metadataGenerator?: MetadataGenerator): Promise<TRes>;