What is css selector drift?
Selector drift is what happens when automation addresses elements by CSS or XPath and the page’s markup changes underneath it. The selector still parses, it just matches nothing — or worse, matches the wrong thing — so the script fails in a way that looks like a site outage rather than a maintenance problem.
Why it matters
It is the maintenance cost that makes classic RPA expensive to own. Addressing elements by index and role, and re-observing as a path executes, removes most of the class of failure — a cosmetic change usually changes nothing the path depends on.