It's been a while since we have updated the rumble client version, and the new version brings several important fixes. I'd really appreciate if someone set up a quick benchmark for a battle or two for each bot in the rumble, and then run it on old and new versions to make sure we don't have any regressions. Once this is done we can upgrade the client =)
As far as I know, Robocode 126.96.36.199 hasn't been officially released yet. The website and GitHub still name 188.8.131.52 as the latest version, and there is no 184.108.40.206 download. You can only get it by building from the latest git master. What I linked to was a draft of the new changelog.
I don't think any new releases will be made until poor Fnl finishes dealing with all of the bugs reports I piled onto him. What I have been doing for the past week is emptying my mental list of annoyances with Robocode onto its bugtracker.
So currently, it is still in development, and it's a bit too early to do regression testing with this new version.