Here's the crash report: https://pastebin.com/c3VCVChz

Looks like a compatiblity issue with carpet mod maybe?

gnembon/fabric-carpet#1937

Workaround: Manually disable lithium's optimization in the lithium.properties file in the config folder by adding the following line to it:
mixin.world.explosions.cache_exposure=false

This mod incompatibility should also be fixed by the above PR to carpet, but it is uncertain when it will be merged.

#521

Workaround is working for me (mods are lithium, fabric-api, and carpet) on MC 1.21.1 with fabric-loader 0.16.0.

Can confirm

Workaround: Manually disable lithium's optimization in the lithium.properties file in the config folder by adding the following line to it:

mixin.world.explosions.cache_exposure=false

This mod incompatibility should also be fixed by the above PR to carpet, but it is uncertain when it will be merged.

What does disabling this do as far as optimization (ie. extent of impact on regular lithium performance)?