Well that's certainly not true. There's been many times when I've colonized a planet only to see an AI ship come by a few turns later hoping to grab it for itself. Then it will hang around for a few turns more and finally go somewhere else.

If you'll notice, the AIs tend to make Stellar Cartography one of their first techs. This allows them to see planets on the mini-map as well as stars. If there's a system with 5 planets around the star, there's a reasonably good chance that at least one of them will be habitable so they'll make a beeline for that one first. I do exactly the same thing. There's no mystery or conspiracy involved, it's just smart tactics.

Being curious, I did some tests myself, using the "reveal map" cheat after a few (3-6) turns and looking at what the opponent did so far.

The first thing I noticed is that the AI's scouts always have a habitable planet as destination, often way out of sensor range. First I thought that was an indication for the AI cheating, but I found out that the AI immediately recalculates the destations after you reveal the map. How I found out? I saw several scouts which evidently moved in one direction from their homeworld while the map was not yet revealed and after looking at them, their destination was in the opposite direction of their homeworld. So you can't just click on them and think that the line is where they were going to travel to originally.
The same applies to colony ships, of course.

So I started about a dozen games with different opponents and tried to figure out if it was possible for the AI to have its ships where they were without cheating.
Unfortunately, I didn't get a result. The colony ships always were flying straight to the next habitable planet, but there always was a way they could have seen the planet before. I still think they are cheating, though. I'd expect them to at least once fly in the wrong direction. Will test some more later and post if I find anything conclusive.

Yeah, but I didn't reveal it. Only after a few turns, I revealed the map and looked at where they went so far.
Nonetheless, you may have a point there and that would explain many things. Including why sometimes the AI seems to know exactly where to go and sometimes it doesn't have a clue. And why there are tests which hint at the AI cheating as well as those that hint at the opposite.
The question is: Does the AI only see what *you* reveal or also what the other AIs reveal?

Alright, did some more testing and just saw something interesting: I revealed the map after 4 turns and the Arceans had colonized their second home planet. The next useable planet was about 1-2 sectors away. They had built a second colony ship but it was just orbiting their home planet. So I thought they probably just finished building the colony ship and it will start towards the planet the next turn.
But it didn't. Only another turn later, after their flagship got into range of the planet, they started to move their colony ship.
At first glance it looks like they waited until they could see the planet. Which would be fine. But from what we gathered so far, they should have seen it the moment I revealed the map. Yet they only moved two turns later. I conclude that it's just as weird as I thought.

I did not use a debugger, but the nature of the test I did would mean any such bug would not have any effect. More conclusive testing could only be done by the devs.

Sorry, double post

We aren't really talking about colony rush strategies, but what the AI does during a colony rush. Is it behaving as intended? Whether it's behavior is fair or not, makes them game harder or easier, etc. is really a secondary point. If the AI is working as intended (i.e. not "cheating") or whether it is somehow getting sensor information it shouldn't have.

I don't generally read through the whole thread before I make a comment, I take a more spontaneous approach. If something comes along while I'm reading that interests me I'll mention something. I realized after reading all the posts that my statements were redundant and for that I apologize. It's just the way I read and respond to forums.

Would it possible for you to do the test with Thalans? (The same test you did with Korath) And if it does not show abnormal behaviour then could you do the test again but without demolishing other ships? The test should not take long and may give some answers...

I think it is worth testing. If there really is a "bug" then it is a big one. Initial colony rush stage has a huge impact on the game. As someone (I believe Wyndstar) pointed out in another thread: games are won or lost in the first year.

This thread is more than a year old but I think it is better to “reincarnate” it rather than to start a new thread. This is a long post: it seems better to err on the side of details then risk misunderstandings.

I was satisfied with kryo's answer for long time. It explained nicely Thalan uncanny ability to find habitable planets. However, AIs build much less scouts in ToA (probably because small hulls are not immediately available). I have started a number of ToA games by now (none of them with Thalans) and AIs were just incredibly lucky with their colony ships in each of them. It became harder and harder to believe that AIs do not have prior knowledge of habitable planets.

I decided to run a little test. The test had the following parameters. Size: medium, scenario: normal, all victory conditions checked except alliance, all game options checked except blind explorations (note that according to Stardock AI explores blind regardless of whether this option is checked), Habitable planets: rare, Number of planets: abundant; number of stars: abundant; star density: tight clusters, anomalies: rare, number of asteroids: rare, tech-rate: very fast; number of minors: 0, my race: Altaria, AI opponents: Terrans, Drengin, Korath, Arcean, Torian; difficulty: tough; all AIs set to max CPU;

I started close to one corner. There were several star systems approximately behind me in the corner. All AIs were relatively far away. I scouted my corner and discovered two planets habitable without a tech and two anomalies. Mindful that AI may see what human player can see (a suspected glitch) I reloaded the game. (The save I made the first turn before making any moves). This time I was careful not to reveal the habitable planets. I "harvested" the anomalies to avoid drawing AI survey ships to the area. Then I set up a perimeter so that I could see any ships moving to "my" corner. Since I took max sensors as my racial ability and used space miner and colony ship for scouting I was able to set the basic perimeter up in three turns. Then I built some warships which I used later to destroy "invading" AI scouts. I colonized Wisp (the other planet in my home system). Then I waited. AIs colonized all habitable planets near my perimeter. Not very long after that Terran and Torian AIs sent a colony ship almost simultaneously towards "my" corner. I did not interfere. Both ships went straight for the habitable planets and colonized them. I reloaded the game (the save I made when the first AI colony ship made the appearance). This time I colonized the two planets before the AI got near. AIs made one full move towards the planets but then turned sharply and left the perimeter.

Conclusion. The only way I can explain AI behavior is that AIs know the location of habitable planets without scouting. Do not get me wrong: I am not accusing anyone of lying or whatever. I do believe that the AI code is designed to scout. However, my test leads me to believe that I have discovered a major bug in the code. The implications of AI knowing the exact location of habitable planets is profound: inter alia it results in much more intensive and luck based colony rush for human player and decreases the diversity of the game. I very much hope that Stardock can fix it unless AIs prove to be hopeless without it.

P.S. I have the two saves available if anyone is interested. (The one at the start of the game and the one when the first AI colony ship appears)

P.P.S. There is a very slim chance that an AI's survey ship jumped to my corner through a wormhole and left before I could set up the perimeter. However, the chances that two AIs survey ships (Torian and Terran) managed the same is virtually impossible. This can be further tested by destroying all Terran and Torian colony ships and observing whether other AIs would send theirs.