NoClassDefFoundError: Sodium VertexBufferWriter Missing

What the log looks like

java\.lang\.ClassNotFoundException: net\.caffeinemc\.mods\.sodium\.api\.vertex\.buffer\.VertexBufferWriter
java\.lang\.NoClassDefFoundError: net/caffeinemc/mods/sodium/api/vertex/buffer/VertexBufferWriter

How to fix it

1. Check the crash report stacktrace right above KnotClassLoader (look for names like physicsmod, iris, or indium) to identify which mod is calling VertexBufferWriter.
2. Make sure Sodium is actually installed in your mods folder if the crashing mod requires it, or update Sodium to the latest release available for your exact Minecraft version.
3. Update Physics Mod (or the offending rendering mod) to a version whose changelog explicitly supports your installed version of Sodium.
4. If you are on Minecraft 1.19.4 with Sodium 0.4.10, downgrade Physics Mod to 2.12.3 (or Pro v152) because newer Physics Mod builds for 1.19.4 require Sodium 0.5 APIs.
5. Check other Sodium add-ons in your mods folder—such as Iris, Indium, Continuity, or Sodium Extra—and align their versions so all of them target the same major Sodium version.

Check your own log