I had my first lulwut *dies* moment in 4.0

[Baleur]

 
So, there i sit, with a fresh 4.0 install, ready to rumble, both AI dif at 7, random easier, 60 planet galaxy, complex ships enabled.
Everything else is as normal, well i did enable all the minor factions..

Lets go!
First few minutes, exploring the surrounding 3 systems, taking it easy, building some tractor beam turrets and the initial fleet.

Then suddenly. The border planet to the "east" of my homeworld, where i have a scout, jumps up in enemy ship numbers.
A good hundred or so MK3-MK4 ships bee-lining towards my homeworld, the MK4 bombers swoosh towards my command center, i'm struck by "what is...... happening? this... early?" surprise paralysis, and Game Over.

LOL 
I knew i was still quite the noob at this game, but woah. For future reference, what happened?

[Diazo]

Heh.

There are actually a few things it could be so if you have a save you can post that would be best.

I will say it's probably unintended, a situation like that is only supposed to come up later in the game because of your earlier decisions, not just out of the blue like that.

D.

[unclean]

Raid engine, maybe? I had the same horrible result first time I saw one, but it really shouldn't start so close to your homeworld.

[Mánagarmr]

Raid engines are "banned" from homeworld adjacent planets. But it's likely something like a Raid engine caused this. Then again, we had some really funky threat causing bugs in the beta. Could be a remnant of this.

Or, you were running against a technologist AI with CPA type waves and no wave warnings.

[Baleur]

No idea, i wasnt really paying attention 
No cross-planet waves or any such option checked though, apart from "Reveal Random AI Types"

[Mánagarmr]

Then...no idea. Post the save and we'll see if we can find out.

[Baleur]

I'm afraid i dont have one, it was within the first 15-20 min and i just quit
Pretty sure it was just my not-paying-attention, rather than a bug, but i must say it felt good to be stomped on like a bug 

[Winter Born]

I'm afraid i dont have one, it was within the first 15-20 min and i just quit
Pretty sure it was just my not-paying-attention, rather than a bug, but i must say it felt good to be stomped on like a bug 

what about an autosave?

[Lancefighter]

generally yes, that 'shouldnt' be happening.. Aggression of that sort is usually caused only by you doing something - if you sent military into the planet to do a raid or something, then you are open to counterattack. But random ships attacking you? not intended.

[Sizzle]

Raid engines are "banned" from homeworld adjacent planets. But it's likely something like a Raid engine caused this. Then again, we had some really funky threat causing bugs in the beta. Could be a remnant of this.

Or, you were running against a technologist AI with CPA type waves and no wave warnings.

They're banned from home world adjacent planets, but not (I think) from being adjacent to the Mark I planets that are themselves adjacent to the home world -- that is two hops away from the home world. 

From the wiki:
"Launches brutal waves against its own planet or any adjacent planets, if those planets are not controlled by AI players, or if the human players have a significant fleet there."

If the OP had a significant fleet in the Mark I planet adjacent to his home world (he doesn't need to have taken over the planet) that could have triggered a raid engine next door.  The arriving fleet would arrive at the Mark I world, not have much to do, but be free threat, and then make a beeline for the home world.

Thats the nearest explanation I can make that is not a bug.

[Lancefighter]

raid engines are also ANNOUNCED waves, something not many people seem to realize.

[Mánagarmr]

raid engines are also ANNOUNCED waves, something not many people seem to realize.

This. It's usually easy to miss a wave if you don't hear the noise, especially if you are on the galaxy map, but Raid engines do announce their waves. So if it was completely unannounced, I can only think of an unintended effect. Short of an AI Eye (these are not announced yet).

[orzelek]

AI Eye doesn't produce a wave - it simply spawns ships in place to get to at least 1:1 with yours (thats what I noticed at least).

But to stirr Eye you would need to drop significant fleet there and units created where planet mark level.

[Mánagarmr]

AI Eye doesn't produce a wave - it simply spawns ships in place to get to at least 1:1 with yours (thats what I noticed at least).

But to stirr Eye you would need to drop significant fleet there and units created where planet mark level.

Aye but if you get destroyed or immediately leave the system, the ship-spam caused by the eye will counterattack. Had that happen multiple times. (Note to self: Pay attention, idiot -.-)

[orzelek]

AI Eye doesn't produce a wave - it simply spawns ships in place to get to at least 1:1 with yours (thats what I noticed at least).

But to stirr Eye you would need to drop significant fleet there and units created where planet mark level.

Aye but if you get destroyed or immediately leave the system, the ship-spam caused by the eye will counterattack. Had that happen multiple times. (Note to self: Pay attention, idiot -.-)

Good to know... I was able to beat that spam of ships up mainly because of riot's making sure that they don't catch up with my fleet while it gone a bit around and destroyed the eye. On further planets and especially core worlds Eye is first (or second after mass driver) target for raid.