player.mainHandStack and, in theory, all other references to the players selected slot / stack will return the hotbar managers selection if there's an active request. This is different compared to the way it worked in 1.20.4 as previously it only altered the interaction managers selected slot

Author: beanbag44

src/main/java/com/lambda/mixin/entity/PlayerInventoryMixin.java

@@ -0,0 +1,46 @@
+/*
+ * Copyright 2025 Lambda
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+package com.lambda.mixin.entity;
+
+import com.lambda.interaction.request.hotbar.HotbarManager;
+import com.lambda.interaction.request.hotbar.HotbarRequest;
+import com.llamalad7.mixinextras.injector.ModifyExpressionValue;
+import net.minecraft.entity.player.PlayerInventory;
+import org.objectweb.asm.Opcodes;
+import org.spongepowered.asm.mixin.Mixin;
+import org.spongepowered.asm.mixin.injection.At;
+import org.spongepowered.asm.mixin.injection.Inject;
+import org.spongepowered.asm.mixin.injection.callback.CallbackInfoReturnable;
+
+@Mixin(PlayerInventory.class)
+public class PlayerInventoryMixin {
+    @SuppressWarnings({"MixinAnnotationTarget", "UnresolvedMixinReference"})
+    @ModifyExpressionValue(method = "*", at = @At(value = "FIELD", target = "Lnet/minecraft/entity/player/PlayerInventory;selectedSlot:I", opcode = Opcodes.GETFIELD))
+    private int modifySelectedSlot(int original) {
+        final HotbarRequest hotbarRequest = HotbarManager.INSTANCE.getActiveRequest();
+        if (hotbarRequest == null) return original;
+        return hotbarRequest.getSlot();
+    }
+
+    @Inject(method = "getSelectedSlot", at = @At("HEAD"), cancellable = true)
+    private void redirectGetSelectedSlot(CallbackInfoReturnable<Integer> cir) {
+        final HotbarRequest hotbarRequest = HotbarManager.INSTANCE.getActiveRequest();
+        if (hotbarRequest == null) return;
+        cir.setReturnValue(hotbarRequest.getSlot());
+    }
+}

src/main/kotlin/com/lambda/interaction/request/breaking/BreakManager.kt

@@ -62,7 +62,6 @@ import com.lambda.interaction.request.breaking.BrokenBlockHandler.destroyBlock
 import com.lambda.interaction.request.breaking.BrokenBlockHandler.pendingActions
 import com.lambda.interaction.request.breaking.BrokenBlockHandler.setPendingConfigs
 import com.lambda.interaction.request.breaking.BrokenBlockHandler.startPending
-import com.lambda.interaction.request.hotbar.HotbarManager
 import com.lambda.interaction.request.interacting.InteractionManager
 import com.lambda.interaction.request.placing.PlaceManager
 import com.lambda.interaction.request.rotating.RotationRequest
@@ -304,7 +303,7 @@ object BreakManager : RequestHandler<BreakRequest>(
                             it.couldReBreak.update()
                             it.shouldProgress = !it.progressedThisTick &&
                                     tickStage in it.breakConfig.breakStageMask &&
-                                    rotated || !it.isPrimary
+                                    (rotated || !it.isPrimary)
                         }
                     }
                     .also {
@@ -817,7 +816,7 @@ object BreakManager : RequestHandler<BreakRequest>(
         config: BreakConfig,
         item: ItemStack? = null
     ) = runSafe {
-        val delta = calcItemBlockBreakingDelta(player, world, pos, item ?: player.inventory.getStack(HotbarManager.serverSlot))
+        val delta = calcItemBlockBreakingDelta(player, world, pos, item ?: player.mainHandStack)
         //ToDo: This setting requires some fixes / improvements in the player movement prediction to work properly. Currently, it's broken
 //        if (config.desyncFix) {
 //            val nextTickPrediction = buildPlayerPrediction().next()

src/main/kotlin/com/lambda/interaction/request/hotbar/HotbarManager.kt

@@ -20,7 +20,6 @@ package com.lambda.interaction.request.hotbar
 import com.lambda.context.SafeContext
 import com.lambda.event.Event
 import com.lambda.event.EventFlow.post
-import com.lambda.event.events.InventoryEvent
 import com.lambda.event.events.TickEvent
 import com.lambda.event.events.UpdateManagerEvent
 import com.lambda.event.listener.SafeListener.Companion.listen
@@ -45,7 +44,7 @@ object HotbarManager : RequestHandler<HotbarRequest>(
     private var maxSwapsThisTick = 0
     private var swapDelay = 0
 
-    private var activeRequest: HotbarRequest? = null
+    var activeRequest: HotbarRequest? = null
 
     override fun load(): String {
         super.load()
@@ -60,10 +59,6 @@ object HotbarManager : RequestHandler<HotbarRequest>(
             activeInfo.keepTicks--
         }
 
-        listen<InventoryEvent.HotbarSlot.Update>(priority = Int.MIN_VALUE) {
-            it.slot = activeRequest?.slot ?: return@listen
-        }
-
         return "Loaded Hotbar Manager"
     }
 

src/main/resources/lambda.mixins.common.json

@@ -15,6 +15,7 @@
     "entity.FireworkRocketEntityMixin",
     "entity.LivingEntityMixin",
     "entity.PlayerEntityMixin",
+    "entity.PlayerInventoryMixin",
     "input.KeyBindingMixin",
     "input.KeyboardMixin",
     "input.MouseMixin",