/**
 * Top-level property names this text declares more than once.
 *
 * Duplicates split the two readers a format-preserving write sits between:
 * `jsonc-parser`'s `modify` targets the FIRST property with a name, while every
 * consumer of the file — {@link parseJsoncText}, `JSON.parse`, the client
 * itself — takes the LAST. An edit aimed at the first occurrence lands under a
 * shadow: the bytes change, the effective value does not, and a re-apply sees
 * nothing left to do. Callers that would edit in place check this first and
 * fall back to rendering the whole file, which collapses the duplicates to the
 * value every reader already agreed on.
 */
export declare function duplicateRootKeys(text: string): string[];
/**
 * Parse JSON or JSONC text (tolerant of comments + trailing commas). Returns
 * `undefined` for empty input. Throws {@link MergeError} on a genuine syntax
 * error: `jsonc-parser` returns a PARTIAL value for malformed input (incomplete
 * braces, trailing garbage), and merging onto a partial parse would silently
 * drop the user's real config — so we fail closed and ask for a manual fix
 * instead of overwriting from a half-read file.
 */
export declare function parseJsoncText(text: string): unknown;
export declare function isPlainObject(v: unknown): v is Record<string, unknown>;
/**
 * Deep-merge `incoming` (harness-generated) onto `base` (existing user config),
 * preserving every key that exists only in `base`. Objects merge recursively;
 * primitive arrays become a deduped union (base order first) so things like
 * `permissions.deny` accumulate instead of clobbering; for any other type
 * mismatch, `incoming` wins.
 */
export declare function deepMerge(base: unknown, incoming: unknown): unknown;