captured 4 systems, hacked 2 new ships, had 3 systems around my home system as buffer,
all were heavily defended, with energy shields around wormholes + mines.
Had 97 AI level, then i found a new ship to hack, sent a hacker, BOOM!
AI level went to 129, AI spawns 4 mk4 raiders, they fly with a lighting speed through 3 systems,
no turrets are fast enough to kill them, energy fields useless...
after 15 seconds, 3 mk4 raiders were next to my home command ship, and boom, I'm dead X_X
How the hell am i suppose to defend against such fast ships, that can just fly into the
energy field bubble and destroy everything?!
Defending against AI Raid Starships is always a little difficult. The best combination of turrets to deal with them is Gravity and Sniper turrets. Grav turrets slow down the Raids dramatically, and Sniper turrets both do significant damage and can shoot the Raids from anywhere within the system. Because Raid Starships are forcefield immune, placing a forcefield over an exit wormhole does not work, so your only real opportunity is to kill them first.
Military Command Stations also do a good job of stopping Raid Starships; the Mil CSs have a knock-back railgun that can keep the Raid permanently out of range while doing chip damage.
Next, the situation seems to be a little more complicated than your description indicates. While spawning Raid Starships is one response to Hacking, it normally does not occur at low-med Hacking Response levels. I'm assuming your "AI Level" is the AI Progress? If so, then the jump from 97 AIP to 129 AIP occurred for some other reason, as Hacking will not directly increase the AIP. You may check your game for other AI ships running around, or to see if your fleet was destroying things you didn't expect.
The AI's Hacking Response is determined by a combined factor of the AIP and the Hacking Progress (HaP). The more Hacking you do, your HaP goes down. The more your AIP goes up, the more HaP you have. The Hacking Response is determined by the difference between your HaP and AIP (ie, how much hacking you have already done) with a MASSIVE penalty if your HaP goes below zero.
I strongly recommend against doing any hacking if your HaP is negative, no matter how strong you think your position is.
There's
another thread about the Hacking response and how to deal with it - You may wish to review that thread, and see if there's anything useful for you there.
Finally, as always, if you have questions relevent to a specific game, go ahead and add the save file as an attachment. There are a number of players who might be willing to take a look at your game and give advice.