interface APIErrorLike { message?: string response?: { data?: { detail?: string message?: string } } } function extractErrorMessage(error: unknown): string { const err = (error || {}) as APIErrorLike return err.response?.data?.detail || err.response?.data?.message || err.message || '' } export function buildAuthErrorMessage( error: unknown, options: { fallback: string } ): string { const { fallback } = options const message = extractErrorMessage(error) return message || fallback }