We discussed this in task sync today and @bwang has stated this is intentional. We want to check in with @Sneha about this before closing out the ticket.

This was a decision I made in T337966 in an attempt to sync the designs between the Codex search and the Vector search. This was also made because of the no js search experience; prior to T337966 the search icon is used as a button on the right (F37102658), however the Codex CSS typeahead search component already includes a search icon (F37102659). The introduction of a proper "Search" button avoids 2 icons for the no js case, and ensures a consistent experience for no js users. It also has an added benefit of simplifying our CSS, as it was pretty intuitive to use the icon as a button.

All that said, it wouldnt be difficult to make the "Search" button be hidden until focus for the CSS only typeahead search. This would be different behavior than Codex

It is good to have a search button always there for discoverability of search and also hiding and showing of button may be causing this UI issue as seen in the screenshot below. There is a tiny gap on the borders near where the button appears.

Update based on comment received from DS team... there is also another variant of search in codex component with search button always visible so we are not limited to just using the one without search button. We can go ahead with this change.

If this is intentional, then does it also resolve T325904: It should not be possible to search when the search input is empty?