report.txt
Environment:
Minecraft: 1.21.1
Loader: NeoForge
Lithium Version: lithium-neoforge-0.15.0+mc1.21.1
Immersive Aircraft Version: 1.4.0+1.21.1-neoforge
Server Type: Dedicated Server (not integrated/singleplayer)
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The server crashes (with a ReportedException: Lithium Class Analysis) when a player attempts to use a vehicle item (from Immersive Aircraft) on a dedicated server. The root cause appears to be Lithium attempting to load the client-only class net.minecraft.client.KeyMapping during runtime analysis, which is invalid on the server (DEDICATED_SERVER dist).

This suggests a missing @onlyin(Dist.CLIENT) annotation check or improper reflection usage in Lithium's entity/class analysis logic, triggered when handling the ServerboundUseItemPacket.

I am having a similar issue.
1.21.1, NeoForge 21.1.208
Lithium Version: 0.15.0
Mod Version: 1.4.0
Server Type: Dedicated server

For us, the server is not crashing, but aircraft are not able to be placed. When I attempt to place a biplane, I get this in the server logs: https://gist.github.com/MAXimized490/2ed69bbe8f5d68dbb54f25a2e98a4230

The two error lines are:

[02:02:48] [Server thread/ERROR] [ne.ne.fm.co.as.RuntimeDistCleaner/DISTXFORM]: Attempted to load class net/minecraft/client/KeyMapping for invalid dist DEDICATED_SERVER
[02:02:48] [Server thread/ERROR] [minecraft/ServerPacketListener]: Failed to handle packet net.minecraft.network.protocol.game.ServerboundUseItemPacket@767a11d6, suppressing error