i tryed all your answers befor i posted here ^^^^
no chance ... i fly trough the wormhole and be killed near instant ...
the only way it work i send much lightning warheads throught ... but in this way they dont use the wormhole ... instead they all die ...
but this method is not what i want to use ... takes much AI progress in order to do this multiple times and they get this wormhole waiting by 15k units and more on every planet ...
so no other opinions
Yea, you got a tricky issue here. I'm surprised with 15k units, the AI still does not think that it has enough firepower to take out the planet they are "stalking".
If you think your defenses + mobile military can take them on if they were on your terf, try moving your mobile military to another planet temporarily. (As has been suggested before)
Once they start piling in, bring you mobile military back into the system, and stomp them.
If you don't think your defenses + mobile military could take them on, then the AI has got you kind of cornered. If that is the case, their decision to stall you until they get enough forces to curb-stomp you quickly is the right choice. You may have no choice but to lose several planets, widdling down their force a bit each time.
Annoying, yes, but then again, we human players gather "blobs" of units to attack and defend all the time. Why shouldn't the AI?
Part of the challenge of AI War is to avoid freeing too many units that you can't kill while still on the offense. Otherwise, they will stack up like this, and be really hard to take on.