LittleCraft+

Bug report — LittleCraft backport.45

Title: Guidebook opening can trigger a client UI-thread crash
Status: Reproduced issue fixed in backport.45

Environment: Minecraft 1.21.1, NeoForge 21.1.255, Java 21.

Reported behavior

Players reported crashes associated with the guidebook, believed to occur when opening it from LittleCraft settings. Their crash log was unavailable.

Confirmed issue

The guidebook item handler could process integrated-server events and attempt to open a client screen from the server thread.

Testing reproduced:

IllegalStateException: Rendersystem called from wrong thread

This could leave the guide screen incompletely initialized, followed by:

NullPointerException: Cannot read field "level"
because "this.minecraft" is null

Expected behavior

The guide opens on the client thread, supports navigation, and closes back to the previous screen without crashing.

Fixes in backport.45

• Ignore logical-server and other-player item-use events.
• Queue guide openings safely on the client event loop.
• Prevent duplicate or nested guide screens.
• Discard queued requests if the player, world, or active screen changes.
• Replace the guide’s blur effect with a simple background.

Validation

Build passed. Seven real-client checks passed, covering main-hand/offhand use, settings access, repeated opening, page bounds, closing, and screen-transition safety.

Deployment: Replace the old LittleCraft JAR on both client and server with backport.45. No item or player-data reset is required.