I just won my first game. Medium map, "Normal" difficulty, default 5 opponents. It was more or less a cakewalk, but it took too long.
I tried getting an alliance with the Torians and the Arceans, who were the only civs left. Getting the Torians to sign the treaty was no problem. With the Arceans, things were different. I could not offer them an alliance, but I could ask for one. So I offered them some higher miniaturization tech and they agreed. Nothing happened. According to the victory conditions screen, I was at 50% of a diplomatic victory, and it explicitly said that I had to form an alliance with the Arceans. The relations display showed the alliance, but the treaty screen did not show the blue line. Also, I could not break the alliance.
Bug or feature?