Mod Version:
1.12.2
Forge Version:
forge-1.12.2-14.23.2.2625-installer.jar

Link to crash log (if applicable):

Description:
sp614x/optifine#1285
Crash on start. This is new development as of today , Most likely Optifine pre problem . No Crash logs.

http://optifine.net/adloadx?f=preview_OptiFine_1.12.2_HD_U_D1_pre.jar

I assume it starts fine without OptiFine?

I used the latest release of DS with the latest Optifine D1 pre . instant crash with no logs .each wiill work on their own . spx614x is trying to enhance 1.12.2 D1 . optifine gets loaded first and DS crashes on trying to load . Tested with 50 mods each to see if any other conflicts . only crash with DS and the Optifine D1 pre.

Most likely a Optifine problem , it gets loaded first and DS unable to figure out what Optifine has done

Do you happen to know if it changed its mod ID?

IDK , Optifine being closed source and hacky , you could extract the 2 mods 1.12.2 U C9 and U D1 pre to see if ID changed or forced debug.
Just reported to sp614x issue tracker . Just so he doesn’t go in wrong direction

Edit : Forge log
https://onedrive.live.com/?id=77B5E138E468EDE3%212070&cid=77B5E138E468EDE3

Forced debug in Linux Minecraft version , this will help

That does help. Wonder what OptiFine is doing.

EDIT: This happens with DS 3.4.9.7 as well. I had a test environment where I replaced the OptiFine I was using with this new pre version and it choked the same way. At the moment I am pointing the finger at OptiFine, but I will continue to examine it to see if there is something I can do at my end.

Here is the Forge log . More details look on my Onedrive in the Ore directory
https://onedrive.live.com/?id=77B5E138E468EDE3%212070&cid=77B5E138E468EDE3

Issue fixed by sp614x , closed

Yay! Thanks for checking.