Why is the AI ignoring Borders?

[Kulin]

We don't have an open borders treaty and nonetheless they send colony ships through my territory to a planet i havent colonized yet but which is complete encapsulated by other star bases and colonies.

I also can't attack them for trespassing without starting a war. Seriously, what is the thought behind this mechanic? Why does the open border treaty even exist if they give a ♥♥♥♥?

[ashbery76]

You can with them too.For them it pisses them off too.

[Bumbefly (we/All)]

And if you take care for a strong influence sphere, they are planets given freely to you!

[Kulin]

Well, that does change nothing because of course i got placed beside the strongest empire. I made a huge effort to block star lane entrances with military bases and colonies. But of course they just ignore them and do what they want. I wonder why we even have starlanes? They mean absolutely nothing if you can't create choke points.

[z|A|bik2]

You can create choke points. But you need to make a halfcircle around it, not place on the tile of the entrance

[Xcorps]

Border crossing causes a diplomacy mallus. You can't stop rivals from entering your space, and your rivals can't stop you from entering their space. You can park invasion fleets in rivals fleet. (In GC2 there was a "like" mallus called "We know what you are doing") They see what you are up to and may declare war, but you can do it. The AI doesn't do this much. It's exactly how it should be.

Chokepoints are about positioning and movement suppression for the enemy and movement buffs for you, you can't build an impassible wall. Parking a good cruiser fleet within 30 hexes of a gate supported by military starbases gives you a fast response fleet that the enemy can't see unless he already has probes close enough to your fleet, which he shouldn't.
Sensor coverage and movement strongly favor you.

Keep in mind that military bases are passive (mostly), but 1 military starbase 7 hexes from the gate with all the movement modules will give you control of the lane. You have to have a support fleet nearby to engage.

If you want to control ALL the space 3 starbases with 2 range upgrades with appropriate dispersion covers an immense portion of battlespace, each max upgraded starbase influences a diameter of like 20 hexes. I like to create fast movement lanes from my best shipbuilder to the gate, then put a few in depth. WIth about 6 constructors and 40ish modules you can set up a defense in depth that will focus the battles where you want them to happen.

The movement modules give you a significant movement bonus and ENEMY (not rival) ships a significant movement mallus. I think it works out that you have roughly +50% movement and Enemy ships have -%50 movement, meaning your 23 move fleet can travel about 35 hexes through military starbase space, while enemy fleets (which are usually not as fast as your ships to begin with) would be reduced to about 12 or 13. That means with 3 starbases using ideal dispersion the enemy fleet takes 4 turns to get out of reduced movement space while you can cross the entire field in 1 turn.

[Bumbefly (we/All)]

It wouldn't be a good game if you are assured to win right from the start annyway. It'll take effort and a few more playthroughs to learn intricasies of the many game mechanics. For influence, did you build Communication Starbases & Influence enhancements on your military and mininng bases? Or (comes with inventing the Hyperwave Radio) Planetary Beacons on your Core and Colony planets?

The starlanes are chokepoints indeed, be it not supertight... most of the time. Last EA game before release, most civs had a sector for themselves. My sector had only one starlane hidden behind a huge nebula with a one-tile corridor entrance/exit. So yeah, placing a starbase there had great effect. In other games i fairly often met starlanes just behind a black hole for similar circumstances. I did not yet see it hidden behind a large asteroid field though, but given the randomness of this game, i think that's just a matter of time before i see one.