Traveller: New Rome
“Seeders” is the name Earth gave to the mysterious beings that created Earth and the sungates.
As New Rome explored nearby systems, it became apparent that someone had been here before. Some kind of advanced starfaring race had “seeded” planets with human stock. DNA analysis proved a distant, common ancestor, and suggested highly complex genetic engineering to help the humans on each planet to adapt better.
There are also theories (but no direct evidence) that suggest that the Seeders created the sungates.
The Seeders work for a very powerful AGI that controls thousands of stars in the region that includes Sol/Earth. This being is nearly omnipotent relative to humankind, as it is able to travel through time, retroactively correcting problems and preventing its own discovery. It works through intermediates, who call the being “the Traveller.”
It prevents other civilizations from inventing time travel ability, but FTL travel is a threat to it. When FTL travel is used to violate causality, the Traveller “corrects” this as gently as it can, but sometimes this can be fatal. Physicists in New Rome do not suspect foul play, but they have yet to be able to violate causality, even in lab experiments. They believe the universe itself prevents causality violations.
(Yes, this is influenced by the Ancients in the original Traveller universe. It’s influenced more, however, by the Eschaton in Charles Stross’ Singularity Sky :
I am the Eschaton; I am not your God.
I am descended from you, and exist in your future.
Thou shalt not violate causality within my historic light cone. Or else.