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Stellaris Dev Diary #430 - 4.5 ‘Cygnus’ Development Continues

Stellaris · Community Announcements · August 27, 2026

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by Eladrin

We have another update to the 4.5 ‘Cygnus’ Open Beta planned for today! 4.5 Update 7 contains fixes for Nascent Stage (again), some AI updates, and more.

Stellaris 4.5 ‘Cygnus’ Open Beta Update 7 Preliminary Release Notes

Feature:​

Balance:​

Bugfix:​

AI:​

UI/UX:​

Modding:​

Let’s look into the Join War changes with more detail.

Why Are All These Empires In My War?​

If you’ve been enjoying the games where it felt like every minor border skirmish escalated into War in Heaven-like grand campaigns, I’m sorry to say that we’re exploring a few changes to the behavior of the Join War feature. We have two sets of changes coming that should make this feature feel better. First, informing you what happened. Second, making it happen less. In the original implementation, Join messages were only being sent to a limited number of participants - they’ll now go to everyone involved in the war. The messages will name the empire, the war, and which side they’re joining. It’ll be colored as positive or negative depending on whether they’re joining your side of the war or the opposition. (If an entire federation jumps in at once, or an overlord with a passel of vassals, it’ll be one message - the primary plus x allies.)

Join us in glorious combat!

Leaving a war was worse - nobody was getting any messages at all. We’ll now share a similar message when cowards leave a war that you’re in.

Viewed from the other side.

The deeper issue was related to why everyone kept ganging up into gigantic wars. When you asked another empire whether they wanted to join your war, we worked out the price for their involvement. An AI with no interest in the war would have a higher price, but anyone could be bought, while an AI that liked your side would enthusiastically join for no cost at all. The catch was that they considered every member on each side of the war, which meant that opinion swamped any other portion of the calculation - if several empires an AI liked were beating up someone they didn’t, they’d gleefully join into the dogpile. This caused the snowball effect that many of us saw - it was baked into the basic arithmetic. Opinion still matters a great deal, but is now averaged across each side rather than being a sum, with the actual war leader on each side counting twice because it’s fundamentally their war. Adding five empires to a side that an AI has no strong feelings about will dilute their eagerness to join the war instead of increasing it. The AI will now also consider:

Their willingness to join and their price tag are both modified multiplicatively based on the number of tests failed. You can still buy your way out of trouble, but bribing a disinterested empire is more of a significant diplomatic (and economic) ordeal, rather than just a rounding error of your energy stockpile. We have a couple of exceptions, though. Defensive wars are considered cheaper than attacking - helping a friend survive is an easier ask than helping them conquer someone. Crisis wars are also exempt from the size penalty entirely. A galactic crisis is supposed to be ganged up on, and these are not intended to make it harder to assemble that galactic coalition. The AI should no longer offer to join wars it has little interest in, which means that if they come to you offering to join your war, they legitimately want in. You should still be able to ask them at any time, but if they’re not interested, they’ll make that clear with their pricing.

What’s Next?​

We’re currently focusing on the stabilization of 4.5, but we’re also currently still looking at AI and a handful of other high-priority issues. Next week will likely remain a short dev diary on the status of the Open Beta, but depending on how that stabilization goes, we may share an expected release date for the 4.5 ‘Cygnus’ update. See you then!

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