Are Monster Upgrades Visible?

As in, is it possible for a monster to upgrade while in sight of the player, or does it check to ensure it’s out of LOS before changing?

Also, for upgrades, does the half_life value begin counting upon monster generation or is it a set variable that progresses during gameplay and then affects all future generated creatures? I’m confused by how half_life works and there’s no documentation I’ve seen that explains it.

Monsters do not upgrade within your reality bubble, unless it is forced to (like zombie master’s UPGRADE). Some creatures do evolve at your POV like chickens and other farm animals.
Half_life - as all I know - is the time that the monster upgrades. Lower value means faster, and vice-versa. Correct me if I’m wrong about this XD

Monsters upgrade on_load before they are placed. You’ll never see it.

half_life begins counting on world generation and affects all monsters regardless of when they are created.