According to your testing, does the issue occur with ONLY Immersive Portals mod and Farbic API?

No

Describe the issue

I added a bunch of new mods, and it caused a startup error. I added them back in one by one to troubleshoot and once I added Universal Graves, it got the error again.

Post the log here

https://pastebin.com/QBP1JXvC
(it was too long to paste here)

ImmPtl seems incompatible with polymer and universal graves contains polymer

Ah ok.

Try updating polymer manually with https://github.com/Patbox/polymer/#download

If issue persist please report it or polymer's repo

Ok, I’ll try this when I can.

I can confirm that the issue is with Polymer.

I manually inserted the current version (0.2.9) in the mod-jar of the Universal Graves mod in META-INF/jars/ (and deleted the old 0.2.2 version). Of course I also had to update the fabric.mod.json to reflect the new file name ("file": "META-INF/jars/polymer-all-0.2.9+1.19.jar" instead of "file": "META-INF/jars/polymer-0.2.2+1.19.jar").

Afterwards, Minecraft starts without a problem when using both Universal Graves and Immersive Portals.

I’ll wait for the patch.

Just install standalone polymer version. There is no real reason not to

So I just put the latest version of Polymer into the modpack and Universal Graves will use it automatically? I can’t do all the things that @koelle25 did because the CurseForge app will install the normal jar, not the modified one.

Yep. Fabric automatically loads latest one

Ok, I’ll try it as soon as possible.

Gosh I totally forgot about this. In the latest versions it appears to be fixed though