I've been trying to add a file into a map that is not a navigation mesh or material/model needed for the map using bspzip. Specifically, it's a text file that states the upgrades the upgrade station sells in MvM. It goes in scripts/items. To see if the method to make the game to use a custom upgrades file works, before attempting that, I put the upgrades file in a "custom" folder. The upgrades are indeed replaced properly. Now, when using anything I could to insert the upgrades file into scripts/items inside the map (a utility to embed files in bsps or directly by command line), it couldn't be loaded no matter what. Googling and searching around only yielded results or tools about repacking your maps with bspzip to compress their size. But my map is a matter of kilobytes (below 1 MB) so I sure had no use for that. Does anyone have any clues regarding this? EDIT: The solution to this problem, for anyone else who has it, is directly below.