When Content Personalization is applied to the website, LimeSpot applies a "cloaking" mechanism on the elements that are potential targets of a personalization campaign. The goal of cloaking is to prevent an undesirable experience of swapping an already loaded and visible default image, when it's visible to the user, to a different personalized image which causes a flickering effect. The cloaking momentarily hides the target elements before the page load and unveils them when the personalization process is finished.
When A/B test experiences are running, the process of "assigning" an experience to each individual visitor is handled along with the session authentication process (this holds true even if one of the experiences is assigned a 0% traffic). This runs on the first-page load on a new session and the details are then cached on the browser for the consequential page loads to skip that part, which results in an immediate replacement of personalized content and a seamless experience on all other page loads.
Combining the two above, since the content personalization process needs to wait for the experience details to arrive from the authentication, the cloaking mechanism first covers "all" the elements that might be affected by personalization in any given experience, and then uncovers them all after some or all of those elements are personalized (depending on what gets personalized in each experience).