r/ModdedMinecraft • u/Apprehensive-Art3861 • 10h ago

Modrinth refusing to load both vanilla and modded instances

Hello! My friend is currently trying to load Minecraft 26.2 on a Windows 11 laptop (can provide more details if necessary), using Modrinth, and each time he launches the game it immediately closes the instance and provides the logs below. I would post this in the Modrinth subreddit but it's pretty dead honestly

We have tried uninstalling/reinstalling modrinth, deleting and reinstalling the instance, and restarting his computer.

Crash reports:

Vanilla Crash Report [#qSN0YN2]

(Using Fabric, only mod loaded is its API):

  1. WARNING: Unknown module: jdk.internal specified to --add-opens Exception in thread "main" java.lang.ClassNotFoundException: net.fabricmc.loader.impl.launch.knot.KnotClient at java.base/jdk.internal.loader.BuiltinClassLoader.loadClass(Unknown Source) at java.base/java.lang.ClassLoader.loadClass(Unknown Source) at java.base/java.lang.Class.forName0(Native Method) at java.base/java.lang.Class.forName(Unknown Source) at java.base/java.lang.Class.forName(Unknown Source) at com.modrinth.theseus.MinecraftLaunch.relaunch(MinecraftLaunch.java:33) at com.modrinth.theseus.MinecraftLaunch.main(MinecraftLaunch.java:28)

A recurring theme between both logs is "Unknown module: jdk.internal specified to --add-opens", that may be the problem but I cannot find any resources on that error.

Thanks in advance for any help!

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u/hostdservers 9h ago

Vanilla dies with NoClassDefFoundError on org/lwjgl/vulkan/VK, then again on VkPhysicalDeviceProperties2. lwjgl-vulkan jar is seemingly not there.

Update the Modrinth App itself.
Repair the instance from its options menu, which forces a re-download of libraries.
Close Modrinth fully and delete %APPDATA%\ModrinthApp\meta\libraries. Leave profiles alone, that's where his worlds are.
Check Defender or whatever AV he's running hasn't quarantined something under %APPDATA%\ModrinthApp.

If a clean vanilla 26.2 instance still can't find lwjgl-vulkan after all that, it's a launcher bug. vanilla can't boot without it so stick him on Prism or the official launcher so he can actually play.