Trying to help a friend with a running A.S. toilet

Never seen a design like this before. Searched the heck out of google and goole images and can't find any visuals.
It's an American Standard toilet. No idea which model. Water fill doesn't shut off completely.
It may be 3 years old or so.
The valve assembly has a twist knob on top (may be yellow), with a black body underneath.
The "float" is a large plastic reservoir that manages to defy the laws of physics and sink even though there are no holes for the air to escape. I believe the plastic float thing has Fluidmaster stamped in it.
Cleaned and inspected the flap and it does not appear to be stiff or deformed (despite our very hard water in Chicago).

Anyways, found some info in my searching-- does this sound like the dreaded "smart valve?" Does continued running sound like the typical problem?
Is the "silent recall" still in place?
Thx.

American Standard stopped using the yellow valve because it was crap. Just take it out and replace with a Fluidmaster 400A, or a Korky Quietfill.

There are just two possible reasons a toilet will continue to fill. Either the flapper is not seating or the fill valve is not shutting off. While there are times either of this might be cleaned and made operational again, they are so inexpensive and easy to replace that if there is significantly older parts, it might be simplest just to replace both and have a fresh start.