Treeloader, which comes bundled with KSPI, is responsible for adding all tech tree nodes above 1000 science. The 1000 science nodes are stock, but hidden in the vanilla game unless parts are added (usually by mods) that require access to said higher tier tech nodes. KSPI, of course, goes even higher than 1000, so it relies on Treeloader to add new nodes to the tech tree, and Treeloader does not play nicely with 0.25. The fix is purportedly very easy, but r4mon's code is licensed in such a way that other users are not strictly speaking allowed to use it for anything other than reference, and re-compiling Treeloader for 0.25 apparently does not constitute fair use. Barring the sudden reappearance of Treeloader's original author, my understanding is that Fractal_UK is currently working on adapting the Alternative Tree Configurator (which is a Treeloader-like mod) to allow the addition of more nodes such that ATC can be used as a Treeloader substitute. For the time being, a fix has been compiled that moves all of the KSPI parts that used to live in nodes requiring over 1000 science to unlock into the nodes that only require 1000 science to unlock. While this represents a significant disruption to game balance and progression, it at least makes Career mode playable, and is linked as a ModuleManager config somewhere several pages back. On the subject of several pages back, this post is my humble attempt to condense all the discussions on 0.25 compatibility over the last several pages of this thread which you seem to have not seen. If you have further questions, I would refer you to the Previous Page button.