Install mods

Install BepInEx 5.4.23.5 into the folder that contains the game executable, start the game once, then put mod DLLs in BepInEx/plugins. That sequence is the wiki modding page, and the Casualties Together readme uses the same loader.

Steps

• Download BepInEx v5 LTS, the Windows x64 5.4.23.5 archive.
• In Steam, open Manage, then Browse local files.
• Extract the archive next to the executable, not inside an extra nested folder.
• Launch the game once so BepInEx/plugins appears, then quit.
• Copy the mod DLL, and CUCoreLib.dll if the mod asks for it, into plugins.
• Read BepInEx/LogOutput.log if nothing loads.

Proton

The wiki and the multiplayer readme both give the same launch option for Linux under Proton: WINEDLLOVERRIDES="winhttp=n,b" %command%.

When it fails

Check that BepInEx sits beside the executable, that the DLL is in plugins, that dependencies are present, and that the mod's last-updated date is in the same era as game 1.0.1. There is no compatibility matrix I can quote. A useful bug report includes the mod version, the other mods installed, the steps, and the log.

Sprite and skin mods use the same folder. Resprite packs are still just files in plugins or in the sprite folder the mod's own page names. I link those pages rather than repacking them.

Before changing a working setup

Keep a copy of the current save and the mod files you are replacing. Record the game version, each mod version and the dependencies in that working setup. Change one mod at a time when diagnosing a problem; that makes the log and the result easier to compare. Keep backups outside the game folder so later file verification does not overwrite them.

Disable or uninstall a mod

For a single BepInEx plugin, close the game and move that mod’s DLL and its own associated files out of BepInEx/plugins into a backup folder. Remove a shared library only when no remaining plugin requires it. This is a reversible file-management procedure; it does not promise that a modded save becomes compatible with an unmodified game. Read the author’s uninstall notes before loading a save that contains mod-specific items.

Roll back after a failed update

Restore the archived mod version and its matching dependencies rather than mixing files from two releases. Keep the changed save separately and restore the earlier save copy only when you intend to return to that state. For Casualties Together’s built-in switch, use the multiplayer disable instructions. If the game itself needs repair, use Steam’s file verification and then compare the remaining loader files with the original loader archive; verification can restore game files without removing every added mod file.