Spago build --watch vs pscid

Hi, little bit confuse with spago build --watch with pscid,
i’m using neovim as editor with:

Neovim Builtin Lsp

it work well (though some feature missing), when i want to install some module and use it, i got error module not found.

i think because i don’t try to rebuild the module, even though i already run pscid in other

what difference between spago build --watch and pscid?
which one should i use? (or both?)