[Bug] Server Watchdog Crash / Deadlock during world generation when used with C2ME

[SilkyPanda]

Environment

• Minecraft Version: 26.1.2
• Fabric Loader: 0.19.3
• Surveyor Version: 1.2.4+26.1
• C2ME Version: 0.4.0-alpha.0.44+26.1.2
• Java Version: 25

Description of the Bug

When using Surveyor alongside C2ME (Concurrent Chunk Management Engine), generating world features on background worldgen threads causes a deadlock and triggers a Minecraft Server Watchdog crash.

During structure feature placement on a C2ME worker thread (c2me-worker-0), a Point of Interest (POI) block state update triggers updatePOIOnBlockStateChange. Surveyor's handler on onPointOfInterestAdded attempts to call LandmarkComponentTypes.forBlock(), which calls Level.getChunk()/Level.getBlockState().

Because this synchronous chunk query occurs inside an off-thread world generation task, CompletableFuture.join() stalls waiting for the chunk, causing the worker thread and the server main thread to hang indefinitely until Watchdog crashes the server.

Crash Trace / Thread Dump

Relevant stack trace from worker thread c2me-worker-0:

Task trace for thread "c2me-worker-0" Id=30 (obtained on a best-effort basis)
    Sync load chunk [160, 36] to status minecraft:full in world minecraft:overworld (create=true) (1.003 min elapsed)
    Upgrading chunk [160, 36] to minecraft:features in world minecraft:overworld (1.003 min elapsed)
"c2me-worker-0" daemon prio=4 Id=30 WAITING on java.util.concurrent.CompletableFuture$Signaller@43bf18ba
	at java.base@25.0.3/jdk.internal.misc.Unsafe.park(Native Method)
	at java.base@25.0.3/java.util.concurrent.CompletableFuture.join(CompletableFuture.java:2138)
	at knot//net.minecraft.server.level.ServerChunkCache.getChunkOffThread(ServerChunkCache.java:2748)
	at knot//net.minecraft.world.level.Level.getChunk(Level.java:212)
	at knot//net.minecraft.world.level.Level.getBlockState(Level.java:9069)
	at knot//folk.sisby.surveyor.landmark.component.LandmarkComponentTypes.forBlock(LandmarkComponentTypes.java:47)
	at knot//net.minecraft.server.level.ServerLevel.mdf78614$surveyor$lambda$onPointOfInterestAdded$0$14(ServerLevel.java:19479)
	at knot//folk.sisby.surveyor.landmark.Landmark.create(Landmark.java:29)
	at knot//folk.sisby.surveyor.landmark.Landmark.global(Landmark.java:33)
	at knot//net.minecraft.server.level.ServerLevel.handler$fgg000$surveyor$onPointOfInterestAdded(ServerLevel.java:19477)
	at knot//net.minecraft.server.level.ServerLevel.updatePOIOnBlockStateChange(ServerLevel.java:1453)
	at knot//net.minecraft.server.level.WorldGenRegion.setBlock(WorldGenRegion.java:263)
	at knot//net.minecraft.world.level.levelgen.structure.templatesystem.StructureTemplate.placeInWorld(StructureTemplate.java:281)