/**
 * Base class for all errors emitted by the idempotency middleware.
 *
 * The error carries the intended HTTP status on both `statusCode` and `status`
 * so that any Express error handler — including the framework's built-in
 * `finalhandler`, which reads `err.status || err.statusCode` — derives the
 * correct response code instead of falling back to a generic `500`.
 *
 * Consumers can branch on the concrete subclass with `instanceof`.
 */
export declare class IdempotencyError extends Error {
    /** Intended HTTP status code (e.g. 409, 417). */
    readonly statusCode: number;
    /** Alias of {@link statusCode} for error handlers that read `status`. */
    readonly status: number;
    /**
     * @param message Human-readable error message.
     * @param statusCode HTTP status code to surface to the caller.
     */
    constructor(message: string, statusCode: number);
}
/**
 * Raised when a request reuses an idempotency key whose previous request is
 * still in progress (no response cached yet). Surfaces as HTTP `409 Conflict`,
 * signalling the caller to retry later.
 */
export declare class IdempotencyConflictError extends IdempotencyError {
    constructor(message?: string);
}
/**
 * Raised when an idempotency key is reused on a request that does not match the
 * original one (intent mismatch). Surfaces as HTTP `417 Expectation Failed`,
 * signalling the caller to correct the request.
 */
export declare class IdempotencyIntentMismatchError extends IdempotencyError {
    constructor(message?: string);
}