While I was doing this achievement, I was confused why I wasn't getting credit. Thought I'd share what I learned for anyone else chasing this achievement.



The text says "have a trade route with every other system in the galaxy". Turns out it means that quite literally, and not what I initially thought as trade with every AI system.



The key distinction is that you can be connected to every single AI system in the galaxy, but not get credit because the AI has not settled every single system in the galaxy. The achievement quite literally requires your empire to be connected via at least one trade route to every single other star system on the map - whether it is colonized or not.



And of course, if it is not colonized, you can't get a trade route to it. I generated a tiny galaxy with reduced system at low, so grand total was 10 system - 5 for me and 5 for my amoeba BFF.



I got connected to every system the Amoeba had settled on but did not get achievement, was confused, then read the text again and waited until the Amoeba finally got around to settling the last system on their side of the map. I got the achievement the instant that happened. I guess my trade ship had already landed there and was just patiently waiting for the Amoeba to arrive to start trading glass beads and bracelets.