I don't know about rendering or previews but the last CSP version that doesn't affect AI behavior is 0.3.0-preview361. After this release every subsequent versions affect the AI behavior. I tested with rss_gtm_furiano_96_v6 or rss_gtm_protech_p92_f6 with csp physics installed and the AI did crazy things. For compliance, let the AI drive on hairpin tracks with these cars and see what happens. The problems don't only occur with these two cars, but I use them as a test for every new CSP release.
For me the most important aspect of the CSP versions at the moment is the AI behavior because I drive offline races against AI. I see quite a few comments on this topic and I wonder if I'm doing something wrong. Am I the only one who noticed this?
It's getting worse on every new iteration. At first i just got rid of every new stuff from the new aibehavior tab, at this point i believe they're not intended for offline racing at all but rather for trackday and traffic stuff.
The last CSP that was working properly with every fastlanes was around CSP 0.2.4.
Parrilla fastlanes, X90, Thockard... all the good ones you could find stopped working exactly as intended around 0.2.6-0.2.7, and are now giving worse results than before.
At first it was just something weird in the spline loading process, and you could get back to regular inputs for AI by reloading the fastlane ingame (thru spline editor). It was particularly noticeable on fast corners.
Here's an example jumping from CSP 0.2.4 to 0.2.7, with subtitles to help :
I sent a message to the discord CSP about this a while ago, it got no answers. Is it a track issue, a spline issue, a cached fastlane with data that went wrong, noone knows.
2.11 never fixed it, so i just edited the impacted fastlanes or overwrote inputs using aiwhisp.
Then after 0.3+ versions it just got randomly bad? Too tideous to pinpoint the issues, i went back on 2.11/112.
Note that i also noticed weird grip issues since 0.3+, where the AI would either suck or rock the track, with no exploitable reason whatsoever. Jumping in a race where everyone is running at 1.11 and the next morning, AIs are just losing it and going offtrack, barely reaching 1.14. That matter seems to be affecting users randomly and is described in CSP discord preview-issue-reports.
As for AI being dumber (but faster if they managed to stay on track) since 0.3.445, the issue has been found and supposedly worked on, saw a post in the CSP discord where Ilja apparently answered.
On top of everything else, it seems something went south with the inputs APIs and i can't even launch AIwhisp on 0.3.581 (it crashes the game), so on my side, it's gonna be a "let's play something else" for a while.