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An unrecognised crash: NoClassDefFoundError in Initializing game

1 warning found. Every finding below comes from what was actually in the pasted files. Treat the fixes as suggestions: they cover the common causes, and this case may need more digging.

Log from mclo.gs/qSN0YN2

This looks like a client log, not a server log. The findings below apply to the player's machine.

What this error means, and every way to fix it →

warning

An unrecognised crash: NoClassDefFoundError in Initializing game

The crash report says it died in Initializing game on the Render thread. The exception is java.lang.NoClassDefFoundError: org/lwjgl/vulkan/VkPhysicalDeviceProperties2. Every frame in the stack is vanilla or loader code, so the report itself names no mod. No frame in the stack carries a mod annotation, so there is nothing to bisect from here: halve the pack instead, and bring the share link to our Discord.

The log

As received, after redaction.

  1. [21:43:48] [main] [com.mojang.blaze3d.platform.NativeLibrariesBootstrap/WARN]: Failed to load Vulkan loader
  2. java.lang.NoClassDefFoundError: org/lwjgl/vulkan/VK
  3. at com.mojang.blaze3d.platform.NativeLibrariesBootstrap.tryLoadingVulkan(NativeLibrariesBootstrap.java:310)
  4. at com.mojang.blaze3d.platform.NativeLibrariesBootstrap.loadLibraries(NativeLibrariesBootstrap.java:85)
  5. at net.minecraft.client.main.Main.main(Main.java:142)
  6. at java.base/jdk.internal.reflect.DirectMethodHandleAccessor.invoke(Unknown Source)
  7. at java.base/java.lang.reflect.Method.invoke(Unknown Source)
  8. at com.modrinth.theseus.MinecraftLaunch.relaunch(MinecraftLaunch.java:61)
  9. at com.modrinth.theseus.MinecraftLaunch.main(MinecraftLaunch.java:28)
  10. Caused by: java.lang.ClassNotFoundException: org.lwjgl.vulkan.VK
  11. at java.base/jdk.internal.loader.BuiltinClassLoader.loadClass(Unknown Source)
  12. at java.base/java.lang.ClassLoader.loadClass(Unknown Source)
  13. ... 7 more
  14. [21:43:51] [Datafixer Bootstrap #0] [com.mojang.datafixers.DataFixerBuilder/INFO]: 295 Datafixer optimizations took 1144 milliseconds
  15. [21:44:01] [Render thread] [com.mojang.authlib.yggdrasil.YggdrasilAuthenticationService/INFO]: Environment: Environment[sessionHost=https://sessionserver.mojang.com, servicesHost=https://api.minecraftservices.com, profilesHost=https://api.mojang.com, name=PROD]
  16. [21:44:02] [Render thread] [net.minecraft.client.Minecraft/INFO]: Setting user: {MINECRAFT_USERNAME}
  17. [21:44:02] [Render thread] [net.minecraft.client.Minecraft/INFO]: Backend library: LWJGL version 3.4.1+2
  18. [21:44:02] [Render thread] [net.minecraft.client.Minecraft/WARN]: Detected unexpected shutdown during last game startup: resetting fullscreen mode
  19. [21:44:02] [Render thread] [net.minecraft.client.Minecraft/WARN]: Detected unexpected shutdown during last game startup: forcing preferred graphics API to OpenGL
  20. ---- Minecraft Crash Report ----
  21. // You should try our sister game, Minceraft!
  22. Time: 2026-08-06 21:44:02
  23. Description: Initializing game
  24. java.lang.NoClassDefFoundError: org/lwjgl/vulkan/VkPhysicalDeviceProperties2
  25. at com.mojang.blaze3d.vulkan.VulkanBackend.
  26. (VulkanBackend.java:73)
  27. at net.minecraft.client.PreferredGraphicsApi.getBackendsToTry(PreferredGraphicsApi.java:37)
  28. at net.minecraft.client.Minecraft.
  29. (Minecraft.java:508)
  30. at net.minecraft.client.main.Main.main(Main.java:278)
  31. at java.base/jdk.internal.reflect.DirectMethodHandleAccessor.invoke(Unknown Source)
  32. at java.base/java.lang.reflect.Method.invoke(Unknown Source)
  33. at com.modrinth.theseus.MinecraftLaunch.relaunch(MinecraftLaunch.java:61)
  34. at com.modrinth.theseus.MinecraftLaunch.main(MinecraftLaunch.java:28)
  35. Caused by: java.lang.ClassNotFoundException: org.lwjgl.vulkan.VkPhysicalDeviceProperties2
  36. at java.base/jdk.internal.loader.BuiltinClassLoader.loadClass(Unknown Source)
  37. at java.base/java.lang.ClassLoader.loadClass(Unknown Source)
  38. ... 8 more
  39. A detailed walkthrough of the error, its code path and all known details is as follows:
  40. ---------------------------------------------------------------------------------------
  41. -- Head --
  42. Thread: Render thread
  43. Stacktrace:
  44. at com.mojang.blaze3d.vulkan.VulkanBackend.
  45. (VulkanBackend.java:73)
  46. at net.minecraft.client.PreferredGraphicsApi.getBackendsToTry(PreferredGraphicsApi.java:37)
  47. at net.minecraft.client.Minecraft.
  48. Surface Info:
  49. GFLW Platform: win32
  50. Graphics Device:
  51. GL debug messages:
  52. Is Modded: Probably not. Client jar signature and brand is untouched
  53. Universe: 404
  54. Type: Client
  55. Locale: en_US
  56. System encoding: Cp1252
  57. File encoding: UTF-8
  58. CPU: 8x Intel(R) Core(TM) i5-9300H CPU @ 2.40GHz
  59. #@!@# Game crashed! Crash report saved to: #@!@# C:\Users\********\AppData\Roaming\ModrinthApp\profiles\Vanilla 26.2\crash-reports\crash-2026-08-06_21.44.02-client.txt
  60. WARNING: Unknown module: jdk.internal specified to --add-opens
  61. [MODRINTH] Unable to call JDK findMainMethod. Falling back to pre-Java 25 main method finding.

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