/**
 * Write `content` to `filePath` atomically: temp file + fsync + rename.
 * Creates parent directories as needed. Returns when the bytes are durable
 * (fsync on the temp file) and visible (rename completed).
 */
export declare function atomicWriteFile(filePath: string, content: string | Buffer, encoding?: BufferEncoding): void;
/**
 * Serialize `value` as pretty-printed JSON and write it atomically.
 * Centralizes the JSON.stringify settings so every config file matches.
 */
export declare function atomicWriteJson(filePath: string, value: unknown): void;
/**
 * Remove every `.tmp-*` file under `dir`. Called from the session_start hook
 * to clean up after a previous session that crashed between temp-file write
 * and rename. Returns the number of files removed.
 */
export declare function cleanupTempFiles(dir: string): number;
/** Best-effort detection of the platform temp dir (used in tests). */
export declare function tmpDirForTest(): string;