Since Half-Life is free for everyone and Steam updated a few things. Here’s a tip to enable the “Hi-Def” models, if you don’t like the original poly models.

disable Options-> Content -> “Enable original models”

It’s a little counterintuitive from the original way, but steam hasn’t updated their support page yet.

https://help.steampowered.com/en/faqs/view/6CF4-96FA-BF4A-329D