/**
 * Async check for file existence. Replaces blocking existsSync().
 */
export declare function fileExists(filePath: string): Promise<boolean>;
export interface AtomicWriteOptions {
    /** File mode for the destination file. Default 0o644. */
    mode?: number;
    /**
     * Called when tmp-file cleanup fails after a write/rename error.
     * Receives the cleanup error so the caller can log it. Default: ignore.
     */
    onCleanupError?: (err: unknown) => void;
}
/**
 * Atomically write a file via mkdtemp-style tmp + rename. Crash-safe:
 * the destination either contains the previous bytes or the new bytes,
 * never a partial write.
 */
export declare function atomicWrite(filePath: string, contents: string | Uint8Array, options?: AtomicWriteOptions): void;
/**
 * `atomicWrite` for callers already on the async fs API.
 *
 * Exists so async writers do not hand-roll their own tmp+rename: before it,
 * three writers of the per-checkout state file each invented a different
 * temp-name shape, and both the `.gitignore` rule and the destroy-time
 * cleanup sweep were written against only one of them.
 */
export declare function atomicWriteAsync(filePath: string, contents: string | Uint8Array, options?: AtomicWriteOptions): Promise<void>;