Fixing a Crash Caused by a Missing Kotlin for Forge Dependency

Identifying the Crash

A missing Kotlin for Forge dependency typically produces a startup crash with a message about an unsatisfied or missing mod dependency, sometimes naming the mod that needs it. Read the crash report's top section carefully. The line that says which mod requires which dependency is your key clue. If Kotlin for Forge is named there, the fix is straightforward.

Resolving the Dependency

Place the Kotlin for Forge file directly into your mods folder. Do not rename it or extract it. If you already have it, verify it is not corrupted by re-downloading a fresh copy and replacing the old one. Also check that you are not running two different copies of the library at once, as duplicate versions can cause their own conflicts.

Verifying the Fix

Relaunch the game. If the crash persists, open the log and search for the mod name from the original error. A common secondary cause is that the dependent mod itself is outdated or built for a different loader version. In that case, the library is fine but the dependent mod needs to match your game and loader versions. Confirm both mods appear in the Mods list after a successful launch.