Minecraft Version: 1.21.1
Repurposed Structures Version: v7.5.13
Mod Loader: Fabric
Other mods: Lithium (removed during test), ModernFix (removed), no terrain mods remaining

Description

We encountered a crash in a world using a specific seed, caused by the generation of the "Skeletons" structure from the Repurposed Structures mod.

After experiencing the crash consistently at the same coordinates, we performed thorough testing:

• We removed all potentially conflicting performance mods, including:
  • Sodium/Embeddium Dynamic Lights
  • Sodium/Embeddium Options API
  • Sodium Extra
  • Lithium
  • ModernFix

The issue persisted even after:

• Generating a new world using the same seed (7778674254872562037)
• Creating a new CurseForge instance with the same mod list minus the removed mods
• Reaching the same coordinates (x=2431, z=-3602) where the crash consistently occurs

This confirms the crash is triggered by deterministic worldgen logic in Repurposed Structures using this seed — not due to chunk corruption or leftover data.

We had no issues with Repurposed Structures in Minecraft 1.21. The crash only started occurring after updating to 1.21.1 and exploring previously unexplored chunks. This suggests that something specific to the 1.21.1 version — either in world gen timing or structural registration — may be triggering the issue.

Crash occurs with:

• New and old instance
• New and old world
• Vanilla seed: '7778674254872562037'
• Coordinates: 'x = 2431, y = 113, z = -3602'
• Both Lithium and ModernFix removed

By disabling Repurposed Structures you can go to the coordinates without crashing.

Crash Log:

Caused by: java.lang.IllegalStateException: Requested chunk unavailable during world generation at com.telepathicgrunt.repurposedstructures.world.features.Skeletons.method_13151(Skeletons.java:28)

Root Cause

The mod attempts to access adjacent chunks via 'getChunk(...)' or similar during structure generation without verifying that the chunk is loaded or available.

When a structure spans multiple chunks (like Skeletons), this causes a crash if the chunk isn’t generated yet — instead of waiting or skipping safely.

Steps to Reproduce

1. Create a new world in Minecraft 1.21.1 with seed '7778674254872562037'
2. Enable Repurposed Structures in the modlist
3. Teleport to '2431 113 -3602'
4. Crash occurs on worldgen when the structure tries to spawn

We really love this mod, it's a must have on our long-term server, and we’d really appreciate a patch for this issue. Let us know if you need help reproducing or testing.

Please share full latest.log and not a one line snippet. Snippets doesn’t give me enough context for the specific calling path that led to the issue

I forgot to attach it, sorry!

This is the log my friend (who hosts the world with Essential) got from our last attempt to fix the problem.

latest (host) 6.log

knot/net.minecraft.class_1613.handler$dic000$moremobvariants$onInitialize(class_1613.java:556) ~[client-intermediary.jar:?]

Can you remove more mob variants please and then try again? I believe your issue is a duplicate of this pinned issue report: #347

It works! I never thought that mod was giving me the damn problem, thank you so much!!!