Do I really need an Alliance for Open Borders? Am I missing something? Is there no way to negotiate Open Borders seperatly, especially that I can actively close my borders?

Ok I guess I have to rephrase my problem: why does the AI always get pissed off when I send my ships through their espace, even if we are at peace? This always results in them cancelling the peace agreement. I mean what's the point in having open borders, when only the AI benefits?

Ok, not sure.

There is a mechanic that worried the AI with fleets near the border, so I guess they are very worried when the fleets are within the border.

I don't know if the problem is on the "AI spam fleet in your space" side or on the "AI get crazy for a single ship on his space" side. There's maybe something to report here.

It is annoying, because it seems like an unfair advantage to the AI. They can get pissed off all they want with my fleets crossing their space, but they would also get pissed off if I close borders to them. There simply needs to be either a new treaty options which allows ship movement without diplomatic penalty or have this as a default when at peace. But quite frankly I could only ever pass through one AI players space when in an alliance (or is there actually a way to have more then two members in an alliance - also big oversight in my eyes?).