/**
 * HTTP header used by Promptbook clients to advertise their release version.
 *
 * @public exported from `@promptbook/utils`
 */
export declare const CLIENT_VERSION_HEADER = "x-promptbook-client-version";
/**
 * The latest client (engine) version that the server expects.
 *
 * @public exported from `@promptbook/utils`
 */
export declare const CLIENT_LATEST_VERSION: string;
/**
 * Determines if the provided version string exactly matches the latest release.
 *
 * @param version - Version string obtained from a request header.
 * @returns True when the version equals `CLIENT_LATEST_VERSION`.
 *
 * @public exported from `@promptbook/utils`
 */
export declare function isClientVersionCompatible(version: unknown): version is string;
/**
 * Formats the message that should be shown when a client is out of date.
 *
 * @param clientVersion - The version reported by the client (optional).
 * @returns User-facing text explaining how to fix the mismatch.
 *
 * @public exported from `@promptbook/utils`
 */
export declare function formatClientVersionMismatchMessage(clientVersion?: string | null): string;
/**
 * Error thrown when the client version does not match the server requirements.
 *
 * @param requiredVersion - Version enforced by the server.
 * @param reportedVersion - Version reported by the client (optional).
 * @param message - Optional human-readable message describing the mismatch.
 *
 * @public exported from `@promptbook/utils`
 */
export declare class ClientVersionMismatchError extends Error {
    readonly requiredVersion: string;
    readonly reportedVersion: string | null;
    constructor(requiredVersion: string, reportedVersion: string | null, message?: string);
}
/**
 * Creates a headers object that includes the client version header.
 *
 * @param headers - Optional base headers to clone.
 * @returns New headers object augmented with `CLIENT_VERSION_HEADER`.
 *
 * @public exported from `@promptbook/utils`
 */
export declare function attachClientVersionHeader<T extends Record<string, string> = Record<string, string>>(headers?: T): T & Record<typeof CLIENT_VERSION_HEADER, string>;
/**
 * Normalizes the client version reported inside a `HeadersInit` object.
 *
 * @param headers - Headers collection to read from.
 * @returns The trimmed client version or `null` when it is missing.
 *
 * @public exported from `@promptbook/utils`
 */
export declare function getClientVersionFromHeaders(headers?: HeadersInit): string | null;