There are major problems with the AI and colony ships.
I first noticed that some AI colony ships stop near a planet, then don’t colonize it or do anything else. They will move away when I colonize the planet. It can be seen in this save game.
Load the save, zoom out a little and move right to the white star. Zoom in enough to see something like this.
My colony ship is next to the planet. A Drath colony ship is near. I played several more turns while I didn’t do anything with my ship. The Drath ship didn’t colonize the planet or move anywhere or do anything besides nothing.
I used console commands to take control of the Drath and found the colony ship doesn’t have a colonist on board. I then went to the list of ships and sorted them by power. I then checked all the colony ships. One had 1 each of weapons and defenses, but no colonist. I checked the other 36 colony ships and found only 2 with a colonist. Somehow they are able to launch empty colony ships and spend most of their effort doing that. The game is smart enough to know that an empty colony ship can’t colonize a planet and doesn’t allow it. The AI doesn’t know what to do, so the empty colony ship just sits there. I didn't look closely at all the colony ships, but a lot, maybe all, were stopped near a planet that could be colonized if they had a colonist.
If I stay as the Arcean and colonize the planet, the empty Drath colony ship realizes that planet can no longer be colonized, so it moves away, probably to another planet.
I have seen colony ships of other races stopped near planets, so it isn’t just the Drath that have the problem.
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Captured colony ships sometimes have a colonist, other times they don’t. After seeing that the AI can launch empty colony ships, I think that is the reason a captured colony ship may or may not have a colonist. I’m able to see a lot of information about the colony ships I see. Maybe it’s because I have high overall espionage? I can select an AI colony ship and see if it has a colonist.
This save is later that then previous one. It will show more of the colony ships without a colonist. At the end of the subspace stream at the southern part of my starting sector is a stack of 2 Minot colony ships. Clicking on the stack will show the information for one of the ships. Clicking again will show the information for the other. One shows a colonist, and the other does not.
The next sector in that direction has more colony ships. Some have a colonist, and some don’t. Those that are mine (Arcean) are all captured. Some have a colonist, and some don’t.
The next sector has a Terran colony ship without a colonist.
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A lot of these colony ships are going past my home sector to the next sector, which is the home sector of the Drath. The AI seems to prefer sending colony ships and constructors to sectors that are far way instead of to sectors that are closer. This seems to also mean that a planet in a distant sector is preferred over one in the same sector where the ship was built.
The several sectors away distance is using the subspace streams. It is usually closer in a straight line. I wonder if the AI is using the wrong way to determine the distance.
Is the quality of the target given too much value? Is the best planet in the galaxy that is far, far away considered to be the planet to colonize instead of a very good planet that is a few stars away from where the colony ship was built? It may take many, many, many weeks to get to the far one instead of a few weeks to get to the near one.
I think the method to determine which planet to colonize has a lot of problems.
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Finally, the AI builds colony ships like crazy when at war. I’ve been at war with 4 of the AI for quite a while. It seems like about 98% of the ships they send out are colony ships or constructors. They don’t even try to attack any of my planets that may be near to them.
I did see an AI (Baratak Grove) attack and capture a core world of an enemy (Terrans) we both had after I destroyed all ships defending it.
My fleet with transports wasn’t there yet, so I decided to let them have it instead of taking it myself.