That’s a major spoiler, Star. So anyone other than Star who is not current with the books avoid this post.

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so, Star, some number of volumes into the series,(because it has taken some number of years for the atevi to get a space program up and running- the ship humans need the atevi and the earthbound humans in space to help them refuel the ship ) the humans who arrived at the space station at the end of the first book reveal to Bren that they had fled another space station their ancestors had constructed at another star because it had been attacked by an unknown enemy. Bren and Ilisidi head off with the ship humans to destroy the data that had been left in the station databanks so that the enemy would not be able to find the atevi world and wreak disaster on it too. . When they get there they learn A) some humans have survived the past ten years on the station and b) there is an alien ship lurking out in the distance. That ship is the Kyo, and the story of Bren’s interactions with them is quite wonderful, one I go back to often because it is extremely satisfying. 
do you want more? Because the possible links to the AU universe comes some books later after many more developments and itself is a wonderful story 

I guess I’ll just have to get going on a 20-volume excursion then!

I always thought it was the same person, based on the name and the opposition to Mazian

Yes, It was Voyager in Night I was thinking of.

HRHSpence wrote:

I asked CJ explicitly if the Foreigner stories were in the same literary universe as the A/U universe. She said "No."

So if you want the Downbelow natives to interact with the Atevi, you'll probably be out of luck. But the hani and the azi, maybe.

Well, if Foreigner is definitely not in the same universe as A/U (and it's nice to have a definitive answer from Herself on that question), then I guess there'll be no possible playdates between atevi and hani or azi, as the latter two are firmly in the A/U universe.

Still good news for me as that's now one less research rabbit-hole for me to get lost in. Mind you, even a week ago I'd have argued until I was blue in the face that I could logically connect the beginning of Foreigner to be part of A/U.  But I went back and re-read the first parts of Foreigner (the first book) several times and I now see where I was wrong.: I could see the things that led me to assume an underlying A/U setting for the Phoenix mission, but this time around I also caught the multiple details that together say this is not likely after all.