A Hex that provides cover also blocks line of sight.
The rules for Cover are a little confusing.
From the rules an elevation 1 hex of cover would block line of sight for two characters at elevation 4+ trying to shoot at each other. It weems wierd that the volcano is shorter than the trees.
Stealth Bot adds to the confusion by providing cover for allies, not creating cover on adjacent hexes. I have no clue if that works the same as trees, or if the intent is to ignore that part of cover and only grant the part of cover that makes a target unseen unless youa re adjacent to them.
How I have been doing it:
I treat Stealth Bot as creating cover on any hex adjacent to itself that holds an ally (obviously not itself) Those hexes count as containing cover, like the Insula Primalis woods.
I then house-rule Cover Hexes to work as if they were 1 hex higher when shooting past them, so a target behind a hex of cover that is the same height as the cover, that cover blocks line of sight, but 2 targets both at higher elevation shooting past a hex of cover will not be blocked.
This of course, is not official and is just my way of dealing with it.
How this would work:
Tachyon is next to stealth bot, Tachyon is at Elevation 1, Stealth Bot is at elevation 2, Unity is at elevation 2 as is Baron Blade, Unity and Baron Blade are on opposite sides of Tachyon with line of sight having to go through their hexes, no other hexes of elevation 2 are between Tachyon and Baron Blade. Ra is at Elevation 1, in front of Unity and on the same line of sight path as the others. Tachyon is the only one receiving Cover from Stealth Bot.
Stealth Bot(2)
Unity(2) - Ra(1) - Tachyon(1) - Blade(2)
Tachyon can see Baron Blade, Baron Blade cannot see Tachyon, because Tachyon has cover. Baron Blade can see Stealth Bot, Stealth Bot can se Baron. Ra and Baron cannot see Each other because a hex of cover exists between them. Unity and Baron Blade cannot see each other because a hex of cover exists between them.
In my house rules Unity and Baron would be able to see each other, because I think that makes sense.