/** Where a failed background sync is reported (the daemon logs it). */
export declare function setSyncErrorHandler(fn: (err: unknown) => void): void;
export declare function deferDurability(on: boolean): void;
/** Resolves when every durable write made so far is synced. */
export declare function durable(): Promise<void>;
/**
 * Write by a temporary file and a rename: a reader never sees half a file, even if this
 * process dies mid-write. `durable` (the default) also fsyncs the file and its directory,
 * so the write survives a machine crash; that costs milliseconds (about 8 on macOS) and
 * blocks the caller, so data that the next write replaces anyway can skip it (M35).
 */
export declare function writeFileAtomic(path: string, data: string | Uint8Array, mode?: number, durable?: boolean): void;
export declare function writeJsonAtomic(path: string, value: unknown, durable?: boolean): void;
export declare function readJson<T>(path: string): T | undefined;