Updating Kotlin for Forge Safely Without Breaking Your Modpack

Before You Update

Back up your world and your mods folder before changing anything. Note which mods depend on Kotlin for Forge by checking the Mods list or each mod's dependency metadata. This tells you what could be affected if the update goes wrong.

Swapping the Library File

Remove the old Kotlin for Forge file from the mods folder and place the new one in its place. Do not keep both. Make sure the new file is not nested in a subfolder and is not renamed. If your pack uses a launcher that manages mods, update through that launcher instead of editing files manually, so it tracks the change correctly.

Checking Dependent Mods

After updating, launch the game and open the Mods list. Confirm Kotlin for Forge appears and that every dependent mod still loads. If a dependent mod disappears or errors, it may have been built against an older library version and need its own update. Check the log for dependency messages naming that mod. If problems persist, restore your backup and revert the library to the previous file until you can update the dependent mod too.