The AI is "wasting" resources by using Cobalts as scouts, then not using their superior combat abilities when appropriate (e. g. its scouting, finds a world with a trade post and no defenses and doesn't engage trade ships or trade post, just continues on its way).
It's even using flaks as scouts.
The is now not wasting it's ships on defenses anymore. Instead it doesn't attack at all, as long as you have some gauss cannons online.
So while the AI had 2 capital ships and about 35+ Cobalts next to my planet defended with 3 gauss cannons, it just didn't attack. It scouted the planet several times, so it knew what was there, but it still didn't do anything threatening.