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Fix cross-region teleportation in SpreadPlayersCommand #35

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Fix cross-region teleportation in SpreadPlayersCommand #35

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74ab001
Fix cross-region teleportation in SpreadPlayersCommand
UnlimitedBytes Jan 10, 2026
cd1df24
Run getSpawnY on target region thread in SpreadPlayersCommand
UnlimitedBytes Jan 10, 2026
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50 changes: 50 additions & 0 deletions ...r/minecraft-patches/sources/net/minecraft/server/commands/SpreadPlayersCommand.java.patch
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Original file line number Diff line number Diff line change
@@ -0,0 +1,50 @@
--- a/net/minecraft/server/commands/SpreadPlayersCommand.java
+++ b/net/minecraft/server/commands/SpreadPlayersCommand.java
@@ -30,6 +_,7 @@
import net.minecraft.world.level.block.state.BlockState;
import net.minecraft.world.phys.Vec2;
import net.minecraft.world.scores.Team;
+import io.multipaper.shreddedpaper.ShreddedPaper;

public class SpreadPlayersCommand {
private static final int MAX_ITERATION_COUNT = 10000;
@@ -205,6 +_,8 @@

if (!flag) {
for (SpreadPlayersCommand.Position position1 : positions) {
+ // ShreddedPaper - isSafe does read-only block access; blocking to sync would cause deadlock
+ // when command runs on a region thread, so we accept the minor race condition here
if (!position1.isSafe(level, maxHeight)) {
position1.randomize(random, minX, minZ, maxX, maxZ);
flag = true;
@@ -246,17 +_,19 @@
position = positions[i++];
}

- entity.teleportTo(
- level,
- Mth.floor(position.x) + 0.5,
- position.getSpawnY(level, maxHeight),
- Mth.floor(position.z) + 0.5,
- Set.of(),
- entity.getYRot(),
- entity.getXRot(),
- true
- , org.bukkit.event.player.PlayerTeleportEvent.TeleportCause.COMMAND // CraftBukkit - handle teleport reason
- );
+ // ShreddedPaper start - compute spawn Y on correct region thread, then teleport
+ final float entityYRot = entity.getYRot();
+ final float entityXRot = entity.getXRot();
+ final SpreadPlayersCommand.Position finalPosition = position;
+ BlockPos targetPos = BlockPos.containing(position.x, maxHeight, position.z);
+ ShreddedPaper.runSync(level, targetPos, () -> {
+ int spawnY = finalPosition.getSpawnY(level, maxHeight);
+ entity.getBukkitEntity().teleportAsync(
+ new org.bukkit.Location(level.getWorld(), Mth.floor(finalPosition.x) + 0.5, spawnY, Mth.floor(finalPosition.z) + 0.5, entityYRot, entityXRot),
+ org.bukkit.event.player.PlayerTeleportEvent.TeleportCause.COMMAND
+ );
+ });
+ // ShreddedPaper end - compute spawn Y on correct region thread, then teleport
double d1 = Double.MAX_VALUE;

for (SpreadPlayersCommand.Position position1 : positions) {