export interface ConfigPatchEntry {
    /** Key path into the document, e.g. ["gateway", "host"]. */
    path: (string | number)[];
    /** New value. `undefined` means "leave this key alone" so callers can build the
     *  list unconditionally instead of pushing entries behind ifs. */
    value: unknown;
}
/** Distinguishable from a programming error so callers can report it to the operator
 *  rather than crash. `code` carries the fs errno when the read is what failed, which
 *  is how a caller tells "no config yet" (ENOENT) from "cannot read it" (EACCES). */
export declare class ConfigDocumentError extends Error {
    readonly code?: string;
    constructor(message: string, code?: string);
}
/**
 * Apply `entries` to the config at `configPath`, returning whether anything changed. The
 * document API rather than parse/dump, which would reformat a hand-edited, comment-heavy
 * file to change one key. No-op entries are skipped and writes are atomic and 0600: the
 * running gateway watches this file, and the auth token lives beside these keys.
 */
export declare function patchConfigFile(configPath: string, entries: ConfigPatchEntry[]): boolean;
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