/**
 * Common utilities shared across API modules.
 *
 * Contains error classes, retry logic, and shared helpers
 * used by chat-service, middle-tier, substrate, and transcript modules.
 */
export declare class ApiAuthError extends Error {
    constructor(message: string);
}
export declare class ApiRateLimitError extends Error {
    readonly retryAfterMilliseconds: number;
    constructor(message: string, retryAfterMilliseconds: number);
}
export declare class ApiResponseError extends Error {
    readonly statusCode: number;
    constructor(message: string, statusCode: number);
}
/**
 * Wrapper around `fetch` that automatically retries on 429 (rate limit) responses.
 *
 * Uses the `Retry-After` header when present; otherwise applies exponential backoff
 * starting at 2 seconds. Retries up to 5 times before throwing `ApiRateLimitError`.
 */
export declare function fetchWithRetry(input: string | URL | Request, init?: RequestInit): Promise<Response>;
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