According to Aurora Background Lore, the Swarm is literally a space Krakens.
So what if we have a second type of Swarm that lives deeper in Aether?
Unlike the usual Swarm that flies between planets, this type will avoid planets. They will fly further away from the star, for example, between Survey Locations. They will be larger, have better TH sensors, and have a significant thermal reduction - up to 10% or better. Maybe even a cloak.
This way we’ll get something bigger and more dangerous than a normal Swarm. But you can avoid them by staying near planets and not flying into deep space, so they will pose a threat primarily to interstellar flights. Especially through systems that don’t have any celestial bodies.
Like the Precursors, they do not pose a threat to your planets (theoretically), and will not destroy your entire civilization at the first contact (theoretically), but rather limit your movement, remaining a distant but serious threat.
Release the Kraken!