system
Given the following post, respond as if you're commenting on Reddit:
human
[Halo] How fast do the Forerunners slipspace drives go?
gpt
Asking 'how fast' is probably the wrong question. The Forerunners had (and still have, if we consider Engineers as Forerunner leftovers) an extraordinarily intimate understanding of slipspace, allowing not only travel but also the use of slipspace bubbles for stasis, permanent portals, and 'it's bigger on the inside' pockets inside shield worlds. 

Speed is likely a foreign concept to pure Forerunner slipspace travel- it would be more accurate to say that their slipspace ruptures were closer to doors, where they simply piloted  through and emerged on the other side, described as near instantaneous. Remember the portal to the Ark in New Mombassa? There was no travel time for the ships to move from Earth to somewhere in extragalactic space.