Every version of EU4 has had its own AI issues, and it’s no secret that it has been getting worse for a while. For 1.32 some of the most debilitating issues have been fixed, and hopefully without causing too many new ones.
EU4’s AI is the product of years of incremental development, by a large number of developers. Most of the code is written after EU4’s release, but a few lines date back as far as the late ’90s. Writing AI is hard, so many of the systems are complex. And given the number of different developers, they don’t all work in harmony.
Essentially, for any given choice the AI has to make in army, navy, or budgeting; it often has a dozen or so voices in its head telling it what to do. It’s supposed to take all of them into account, but often the loudest voice drowns out all the rest.
Take, for example, an offensive campaign that includes sieges. You may be looking at an ally nation, or your enemy, doing it. They make good progress on a certain fort of strategic importance, and you base your future plans around the fact that the fort may fall, all of a sudden, their army makes a complete turn, and goes away. What happened was a voice intended for a completely different situation screams one order of magnitude louder than all other voices, one of which was arguing for taking the fort, that it should kill the rebels in some faraway province, instead of completing the siege.
Issues like this hinder the systems that are made for the given situation from doing their job. A lot of what has been done for 1.32’s AI is to find and fix cases where systems interfere with each other.
As the result of a bunch of small fixes, the AI will, now, generally be more competent at achieving stuff with its armies, although individual moves can still be erratic. They will also keep a more significant army in peacetime. The AI can now, also, decently perform naval invasions again, without too many shenanigans. This has a huge impact on the European AIs’ colonization efforts.
And finally, lots of small fixes mean the AI’s economy should now be more solid. Budgeting has been improved and the choice of buildings to construct puts more emphasis on expected financial return.