So better to have GiBs of memory consumed by it constantly?

If you don’t have that memory to spare you can’t run this locally anyways, and keeping it in memory is the only way to have a fast experience. Paying the model loading cost repeatedly sucks.

Why would linking llama.cpp into a UI application lead to incurring the model loading cost repeatedly?

It would be loaded repeatedly if the ui is opened and closed repeatedly. You can achieve the same “long running server + short running ui window” with multiple threads or processes all linked into one binary if you want of course. This way (with a separate server) seems simpler to me (and has the added benefit that multiple applications could easily call into the “server” if needed)

Local UI applications are long running processes normally