Version:
lithium-fabric-mc1.20.4-0.12.1

Reproduction Steps:

1. Download Simply Optimized Modpack (I use Prism Launcher)
2. Disable all mods except for Lithium
3. Add Pehkui mod (Pehkui-3.7.12+1.14.4-1.20.4, most recent version as of this post's date), including recent fabric-loader mod
4. Start Minecraft
5. crash

Crash Report File:
crash-2024-01-25_00.05.13-client.txt

When I disable Lithium, Pehkui works just fine.

ive been having the same issue, im basically in the exact same situation (added mods to simply optimized on prism launcher, pehkui and lithium crash when together)

it's a simply optimized thing, i tested your steps on a different modpack (Fabulously Optimized) and it worked fine

@AH139 I got a solution- I deleted 2 mixins in the lithium properties file: mixin.experimental & mixin.experimental.chunk_tickets

Hello, I apologize for not replying sooner! I was able to fix the problem by deleting lithium's config file (lithium.properties) and starting Minecraft again so it regenerates with a fresh config and it didn't crash again after that. I still greatly appreciate your suggestions, thanks!