[2023] CK3 will launch, then immediately crash within in the main menu or loading screens

Right click on ck3.exe , properties, compatibility. Tick "disable fullScreen optimisations" untick every other box in that dialog, Apply and exit.
Then in the launcher Game Settings menu, select fullScreen display mode, Vsync off, cap refresh rate at 60.


If those don't help:
DXDIAG is a program you run from the Windows search box on the task bar. After running it will open a window and start collecting info with a progress bar in the lower-left corner. When it completes click the 'save all information' button and save it to a file then attach that file here.

Please attach here your Documents/Paradox Interactive/CK3/pdx_settings.txt .
From your Documents/Paradox Interactive/CK3/logs/ folder, attach here system.log , error.log , exceptions.log  

I'm afraid this is very likely to be another case of the suspected game engine bug as I describe here

Game continues to crash on the "Initialising" step on PC Gamepass

When I saw the game had a new option to select and deselect which DLCs you want to load on Gamepass now, I was hopeful that would help, but no such luck. Even with all DLCs turned off, the game continues to crash before launching the main title... forum.paradoxplaza.com
To confirm that, please use Affinity in Windows to make ck3.exe only run on your first 12 cores/CPUs , the p-cores. Does that help this problem for you?  

What is Processor Affinity & how to set Processor Affinity on Windows 11/10

Learn how to set Processor Affinity in Windows 11/10. We have also explained what Processor Affinity, and if it is useful to improve performance. www.thewindowsclub.com
It is absolutely fixable, but if it is indeed in the game engine rather than this game as such, it is harder and longer to fix. I do update the internal channel on the issue every time I come across another case, so they are aware it is a live issue still.  

ecosamo said: Is there a way to keep the cores I deselected from turning themselves back on?

I'm no Windows expert, but a bit of googling found the idea that you can set the Affinity on steam.exe , then when you run the game from there it should inherit that setting. I also found mention of a utility called Lasso that will do this.

Please let us know if that does it for you!  

Refunds can only come from the store you bought from.

I know the game still has this issue; I do regularly update the developers about it, but being a probable engine issue it will take considerable time to fix, I am sorry.

My question was whether setting Affinity in steam.exe meant you didn't have to set it on ck3.exe every time you played? doing taht should not have any noticeable effect on any game's performance - 12 cores are plenty for any game!