diff --git a/internal/paper1_21_11/src/main/java/com/lishid/openinv/internal/paper1_21_11/container/menu/OpenEnderChestMenu.java b/internal/paper1_21_11/src/main/java/com/lishid/openinv/internal/paper1_21_11/container/menu/OpenEnderChestMenu.java
index dc45137e..163a24ea 100644
--- a/internal/paper1_21_11/src/main/java/com/lishid/openinv/internal/paper1_21_11/container/menu/OpenEnderChestMenu.java
+++ b/internal/paper1_21_11/src/main/java/com/lishid/openinv/internal/paper1_21_11/container/menu/OpenEnderChestMenu.java
@@ -59,14 +59,14 @@ public ItemStack quickMoveStack(Player player, int index) {
   }
 
   @Override
-  public void clicked(int i, int j, ClickType clickType, Player player) {
+  public void clicked(int slotIndex, int button, ClickType clickType, Player player) {
     if (viewOnly) {
       if (clickType == ClickType.QUICK_CRAFT) {
         sendAllDataToRemote();
       }
       return;
     }
-    super.clicked(i, j, clickType, player);
+    super.clicked(slotIndex, button, clickType, player);
   }
 
 }
diff --git a/internal/paper1_21_11/src/main/java/com/lishid/openinv/internal/paper1_21_11/container/menu/OpenInventoryMenu.java b/internal/paper1_21_11/src/main/java/com/lishid/openinv/internal/paper1_21_11/container/menu/OpenInventoryMenu.java
index 3bc0f134..b2fc2d0e 100644
--- a/internal/paper1_21_11/src/main/java/com/lishid/openinv/internal/paper1_21_11/container/menu/OpenInventoryMenu.java
+++ b/internal/paper1_21_11/src/main/java/com/lishid/openinv/internal/paper1_21_11/container/menu/OpenInventoryMenu.java
@@ -26,14 +26,14 @@ public OpenInventoryMenu(
   }
 
   @Override
-  public void clicked(int i, int j, ClickType clickType, Player player) {
+  public void clicked(int slotIndex, int button, ClickType clickType, Player player) {
     if (viewOnly) {
       if (clickType == ClickType.QUICK_CRAFT) {
         sendAllDataToRemote();
       }
       return;
     }
-    super.clicked(i, j, clickType, player);
+    super.clicked(slotIndex, button, clickType, player);
   }
 
 }
diff --git a/internal/paper26_3/src/main/java/com/lishid/openinv/internal/paper26_3/container/BaseOpenInventory.java b/internal/paper26_3/src/main/java/com/lishid/openinv/internal/paper26_3/container/BaseOpenInventory.java
index e7b11c94..c7451dba 100644
--- a/internal/paper26_3/src/main/java/com/lishid/openinv/internal/paper26_3/container/BaseOpenInventory.java
+++ b/internal/paper26_3/src/main/java/com/lishid/openinv/internal/paper26_3/container/BaseOpenInventory.java
@@ -187,7 +187,7 @@ public ServerPlayer getOwnerHandle() {
   @Override
   public org.bukkit.inventory.Inventory getBukkitInventory() {
     if (bukkitEntity == null) {
-      bukkitEntity = new OpenPlayerInventory(this);
+      bukkitEntity = new OpenPlayerInventory(factory, this);
     }
     return bukkitEntity;
   }
diff --git a/internal/paper26_3/src/main/java/com/lishid/openinv/internal/paper26_3/container/bukkit/OpenPlayerInventory.java b/internal/paper26_3/src/main/java/com/lishid/openinv/internal/paper26_3/container/bukkit/OpenPlayerInventory.java
index 9c957e92..16551fa4 100644
--- a/internal/paper26_3/src/main/java/com/lishid/openinv/internal/paper26_3/container/bukkit/OpenPlayerInventory.java
+++ b/internal/paper26_3/src/main/java/com/lishid/openinv/internal/paper26_3/container/bukkit/OpenPlayerInventory.java
@@ -1,12 +1,20 @@
 package com.lishid.openinv.internal.paper26_3.container.bukkit;
 
+import com.github.jikoo.openinv.internal.container.slot.InventoryFactory;
 import com.google.common.base.Preconditions;
 import com.lishid.openinv.internal.paper26_3.container.BaseOpenInventory;
 import net.minecraft.core.NonNullList;
+import net.minecraft.server.level.ServerPlayer;
+import net.minecraft.world.Container;
 import net.minecraft.world.entity.EquipmentSlot;
 import net.minecraft.world.entity.player.Inventory;
+import net.minecraft.world.inventory.Slot;
+import net.minecraft.world.item.Item;
+import net.minecraft.world.item.Items;
+import org.bukkit.Material;
 import org.bukkit.craftbukkit.inventory.CraftInventory;
 import org.bukkit.craftbukkit.inventory.CraftItemStack;
+import org.bukkit.craftbukkit.inventory.CraftItemType;
 import org.bukkit.entity.Player;
 import org.bukkit.event.inventory.InventoryType;
 import org.bukkit.inventory.ItemStack;
@@ -14,13 +22,22 @@
 import org.jspecify.annotations.NullMarked;
 import org.jspecify.annotations.Nullable;
 
+import java.util.HashMap;
 import java.util.List;
+import java.util.Map;
+import java.util.function.BiPredicate;
 
 @NullMarked
 public class OpenPlayerInventory extends CraftInventory implements PlayerInventory {
 
-  public OpenPlayerInventory(BaseOpenInventory inventory) {
+  protected final InventoryFactory<ServerPlayer, net.minecraft.world.item.ItemStack, Container, Slot, EquipmentSlot> factory;
+
+  public OpenPlayerInventory(
+      InventoryFactory<ServerPlayer, net.minecraft.world.item.ItemStack, Container, Slot, EquipmentSlot> factory,
+      BaseOpenInventory inventory
+  ) {
     super(inventory);
+    this.factory = factory;
   }
 
   @Override
@@ -29,16 +46,34 @@ public BaseOpenInventory getInventory() {
   }
 
   @Override
-  public ItemStack[] getContents() {
-    return asCraftMirror(getInventory().getOwnerHandle().getInventory().getContents());
+  public @Nullable ItemStack[] getContents() {
+    return asCraftMirror(getInventory().getContents());
   }
 
   @Override
   public void setContents(@Nullable ItemStack[] items) {
-    Inventory internal = getInventory().getOwnerHandle().getInventory();
+    Container internal = getInventory();
     int size = internal.getContainerSize();
     Preconditions.checkArgument(items.length <= size, "items.length must be <= %s", size);
 
+    if (items.length < size) {
+      // If size matches normal player inventory size, redirect to it.
+      Container ownerInternal = getInventory().getOwnerHandle().getInventory();
+      if (items.length == ownerInternal.getContainerSize()) {
+        internal = ownerInternal;
+        size = items.length;
+      }
+    } else {
+      // Otherwise, ensure that the display-only slots are not in use.
+      for (int index = 0; index < size; ++index) {
+        ItemStack itemStack = items[index];
+        if (itemStack == null || itemStack.isEmpty()) {
+          continue;
+        }
+        validateSet(index);
+      }
+    }
+
     for (int index = 0; index < size; ++index) {
       if (index < items.length) {
         internal.setItem(index, CraftItemStack.asNMSCopy(items[index]));
@@ -48,8 +83,21 @@ public void setContents(@Nullable ItemStack[] items) {
     }
   }
 
+  protected void validateSet(int index) {
+    InventoryType.SlotType slotType = getInventory().getSlotType(index);
+    if (slotType == InventoryType.SlotType.OUTSIDE || slotType == InventoryType.SlotType.RESULT) {
+      throw new IllegalArgumentException("A plugin tried to put an item in a display slot. That would delete it!");
+    }
+  }
+
+  @Override
+  public void setItem(int index, @Nullable ItemStack item) {
+    validateSet(index);
+    super.setItem(index, item);
+  }
+
   @Override
-  public ItemStack[] getStorageContents() {
+  public @Nullable ItemStack[] getStorageContents() {
     return asCraftMirror(getInventory().getOwnerHandle().getInventory().getNonEquipmentItems());
   }
 
@@ -63,6 +111,294 @@ public void setStorageContents(@Nullable ItemStack[] items) throws IllegalArgume
     }
   }
 
+  @SuppressWarnings("NonApiType")
+  @Override
+  public HashMap<Integer, ItemStack> all(Material material) {
+    Preconditions.checkNotNull(material, "Material cannot be null");
+    Item item = CraftItemType.bukkitToMinecraft(material);
+    Preconditions.checkNotNull(item, "Material must be an item");
+
+    BaseOpenInventory inventory = getInventory();
+    int size = inventory.getOwnerHandle().getInventory().getNonEquipmentItems().size();
+
+    HashMap<Integer, ItemStack> slots = new HashMap<>();
+    for (int index = 0; index < size; ++index) {
+      net.minecraft.world.item.ItemStack itemStack = inventory.getItem(index);
+      if (!itemStack.isEmpty() && item.equals(itemStack.getItem())) {
+        slots.put(index, factory.asBukkitMirror(itemStack));
+      }
+    }
+
+    return slots;
+  }
+
+  @SuppressWarnings("NonApiType")
+  @Override
+  public HashMap<Integer, ItemStack> all(@Nullable ItemStack item) {
+    HashMap<Integer, ItemStack> slots = new HashMap<>();
+
+    if (item == null) {
+      return slots;
+    }
+
+    net.minecraft.world.item.ItemStack itemStack = CraftItemStack.unwrap(item);
+    BaseOpenInventory inventory = getInventory();
+    int size = inventory.getOwnerHandle().getInventory().getNonEquipmentItems().size();
+
+    for (int index = 0; index < size; ++index) {
+      net.minecraft.world.item.ItemStack slotItemStack = inventory.getItem(index);
+      if (ItemMatcher.EXACT.predicate.test(itemStack, slotItemStack)) {
+        slots.put(index, factory.asBukkitMirror(slotItemStack));
+      }
+    }
+
+    return slots;
+  }
+
+  @Override
+  public int first(Material material) {
+    Item item = CraftItemType.bukkitToMinecraft(material);
+    Preconditions.checkNotNull(item, "Material must be an item");
+    net.minecraft.world.item.ItemStack itemStack = new net.minecraft.world.item.ItemStack(item);
+    int size = getInventory().getOwnerHandle().getInventory().getNonEquipmentItems().size();
+    return first(itemStack, ItemMatcher.TYPE, 0, size);
+  }
+
+  @Override
+  public int first(ItemStack item) {
+    net.minecraft.world.item.ItemStack itemStack = CraftItemStack.unwrap(item);
+    int size = getInventory().getOwnerHandle().getInventory().getNonEquipmentItems().size();
+    return first(itemStack, ItemMatcher.EXACT, 0, size);
+  }
+
+  @Override
+  public int firstEmpty() {
+    BaseOpenInventory inventory = getInventory();
+    int size = inventory.getOwnerHandle().getInventory().getNonEquipmentItems().size();
+    return first(net.minecraft.world.item.ItemStack.EMPTY, ItemMatcher.EMPTY, 0, size);
+  }
+
+  private int first(net.minecraft.world.item.ItemStack itemStack, ItemMatcher matcher, int startIndex, int endIndex) {
+    for (int index = startIndex; index < endIndex; ++index) {
+      net.minecraft.world.item.ItemStack inventoryStack = inventory.getItem(index);
+      if (matcher.predicate.test(itemStack, inventoryStack)) {
+        return index;
+      }
+    }
+    return -1;
+  }
+
+  @SuppressWarnings("ImmutableEnumChecker") // Ignore Google's style preference for predicate-like enums
+  private enum ItemMatcher {
+    EMPTY((ignored, b) -> b.isEmpty()),
+    TYPE(net.minecraft.world.item.ItemStack::isSameItem),
+    SIMILAR(net.minecraft.world.item.ItemStack::isSameItemSameComponents),
+    EXACT((a, b) -> net.minecraft.world.item.ItemStack.isSameItemSameComponents(a, b) && a.count() == b.count());
+
+    private final BiPredicate<net.minecraft.world.item.ItemStack, net.minecraft.world.item.ItemStack> predicate;
+
+    ItemMatcher(BiPredicate<net.minecraft.world.item.ItemStack, net.minecraft.world.item.ItemStack> predicate) {
+      this.predicate = predicate;
+    }
+  }
+
+  @SuppressWarnings("NonApiType")
+  @Override
+  public HashMap<Integer, ItemStack> addItem(ItemStack... items) {
+    Preconditions.checkNotNull(items, "items cannot be null");
+    HashMap<Integer, ItemStack> leftover = new HashMap<>();
+
+    BaseOpenInventory inventory = getInventory();
+    int storageSize = inventory.getOwnerHandle().getInventory().getNonEquipmentItems().size();
+
+    for (int index = 0; index < items.length; ++index) {
+      addItem(items, index, storageSize, leftover);
+    }
+
+    return leftover;
+  }
+
+  private void addItem(
+      ItemStack[] items,
+      int leftoverIndex,
+      int storageSize,
+      Map<Integer, ItemStack> leftover
+  ) {
+    ItemStack bukkitStack = items[leftoverIndex];
+    Preconditions.checkNotNull(bukkitStack, "ItemStack cannot be null");
+    if (bukkitStack.isEmpty()) {
+      return;
+    }
+    net.minecraft.world.item.ItemStack nmsStack = CraftItemStack.unwrap(bukkitStack);
+    Preconditions.checkNotNull(nmsStack, "ItemStack cannot be empty");
+
+    int maxStackSize = inventory.getMaxStackSize(nmsStack);
+    int stackCount = nmsStack.count();
+
+    // Try to fill existing stacks first. Waste of time for items that don't stack.
+    if (maxStackSize > 1) {
+      stackCount = addPartial(storageSize, nmsStack, maxStackSize, stackCount);
+      if (nmsStack.count() < 1) {
+        // All done adding, next item.
+        return;
+      }
+    }
+
+    // Add to empty slots.
+    stackCount = addEmpty(storageSize, stackCount, maxStackSize, nmsStack);
+
+    if (stackCount > 0) {
+      bukkitStack.setAmount(stackCount);
+      leftover.put(leftoverIndex, bukkitStack);
+    }
+  }
+
+  private int addPartial(
+      int storageSize,
+      net.minecraft.world.item.ItemStack nmsStack,
+      int maxStackSize,
+      int stackCount
+  ) {
+    for (
+        int firstPartial = first(nmsStack, ItemMatcher.SIMILAR, 0, storageSize);
+        firstPartial < storageSize && firstPartial > -1;
+        firstPartial = first(nmsStack, ItemMatcher.SIMILAR, firstPartial + 1, storageSize)
+    ) {
+      net.minecraft.world.item.ItemStack existing = inventory.getItem(firstPartial);
+      int existingCount = existing.count();
+      if (existingCount >= maxStackSize) {
+        continue;
+      }
+
+      int fit = maxStackSize - existingCount;
+
+      if (fit >= stackCount) {
+        nmsStack.setCount(0);
+        existing.setCount(existingCount + stackCount);
+        return 0;
+      }
+
+      stackCount -= fit;
+      nmsStack.setCount(stackCount);
+      existing.setCount(maxStackSize);
+    }
+    return stackCount;
+  }
+
+  private int addEmpty(
+      int storageSize,
+      int stackCount,
+      int maxStackSize,
+      net.minecraft.world.item.ItemStack nmsStack
+  ) {
+    for (
+        int firstEmpty = firstEmpty();
+        firstEmpty < storageSize && firstEmpty > -1;
+        firstEmpty = first(net.minecraft.world.item.ItemStack.EMPTY, ItemMatcher.EMPTY, firstEmpty, storageSize)
+    ) {
+      if (stackCount <= maxStackSize) {
+        inventory.setItem(firstEmpty, nmsStack.copy());
+        return 0;
+      }
+
+      var newStack = nmsStack.copy();
+      stackCount -= maxStackSize;
+      nmsStack.setCount(stackCount);
+      newStack.setCount(maxStackSize);
+      inventory.setItem(firstEmpty, newStack);
+    }
+
+    return stackCount;
+  }
+
+  @SuppressWarnings("NonApiType")
+  @Override
+  public HashMap<Integer, ItemStack> removeItem(ItemStack... items) {
+    Preconditions.checkNotNull(items, "items cannot be null");
+    HashMap<Integer, ItemStack> leftover = new HashMap<>();
+
+    BaseOpenInventory inventory = getInventory();
+    int storageSize = inventory.getOwnerHandle().getInventory().getNonEquipmentItems().size();
+
+    for (int index = 0; index < items.length; ++index) {
+      removeItem(items[index], index, storageSize, leftover);
+    }
+
+    return leftover;
+  }
+
+  private void removeItem(
+      ItemStack bukkitStack,
+      int leftoverIndex,
+      int storageSize,
+      Map<Integer, ItemStack> leftover
+  ) {
+    Preconditions.checkNotNull(bukkitStack, "ItemStack cannot be null");
+    if (bukkitStack.isEmpty()) {
+      return;
+    }
+    net.minecraft.world.item.ItemStack nmsStack = CraftItemStack.unwrap(bukkitStack);
+    Preconditions.checkNotNull(nmsStack, "ItemStack cannot be empty");
+
+    int stackCount = nmsStack.count();
+
+    for (
+        int first = first(nmsStack, ItemMatcher.SIMILAR, 0, storageSize);
+        first < storageSize && first > -1;
+        first = first(nmsStack, ItemMatcher.SIMILAR, first + 1, storageSize)
+    ) {
+      net.minecraft.world.item.ItemStack existing = inventory.getItem(first);
+      int existingCount = existing.count();
+      if (existingCount > stackCount) {
+        existing.setCount(existingCount - stackCount);
+        bukkitStack.setAmount(0);
+        return;
+      }
+
+      stackCount -= existingCount;
+      inventory.setItem(first, net.minecraft.world.item.ItemStack.EMPTY);
+
+      if (stackCount <= 0) {
+        break;
+      }
+    }
+
+    bukkitStack.setAmount(stackCount);
+
+    if (stackCount > 0) {
+      leftover.put(leftoverIndex, bukkitStack);
+    }
+  }
+
+  @Override
+  public void remove(Material material) {
+    Item item = CraftItemType.bukkitToMinecraft(material);
+    Preconditions.checkNotNull(item, "Material must be an item");
+
+    if (!item.equals(Items.AIR)) {
+      removeAll(new net.minecraft.world.item.ItemStack(item), ItemMatcher.SIMILAR);
+    }
+  }
+
+  @Override
+  public void remove(ItemStack bukkitStack) {
+    net.minecraft.world.item.ItemStack nmsStack = CraftItemStack.unwrap(bukkitStack);
+
+    if (!nmsStack.isEmpty()) {
+      removeAll(nmsStack, ItemMatcher.EXACT);
+    }
+  }
+
+  private void removeAll(net.minecraft.world.item.ItemStack itemStack, ItemMatcher matcher) {
+    int storageSize = getInventory().getOwnerHandle().getInventory().getNonEquipmentItems().size();
+    for (int index = 0; index < storageSize; ++index) {
+      net.minecraft.world.item.ItemStack content = inventory.getItem(index);
+      if (matcher.predicate.test(itemStack, content)) {
+        inventory.setItem(index, net.minecraft.world.item.ItemStack.EMPTY);
+      }
+    }
+  }
+
   @Override
   public InventoryType getType() {
     return InventoryType.PLAYER;
@@ -74,7 +410,7 @@ public Player getHolder() {
   }
 
   @Override
-  public ItemStack[] getArmorContents() {
+  public @Nullable ItemStack[] getArmorContents() {
     return asCraftMirror(getInventory().getOwnerHandle().getInventory().getArmorContents());
   }
 
@@ -91,7 +427,7 @@ public void setArmorContents(@Nullable ItemStack[] items) {
   }
 
   @Override
-  public ItemStack[] getExtraContents() {
+  public @Nullable ItemStack[] getExtraContents() {
     return asCraftMirror(List.of(getInventory().getOwnerHandle().getInventory().equipment.get(EquipmentSlot.OFFHAND)));
   }
 
diff --git a/internal/paper26_3/src/main/java/com/lishid/openinv/internal/paper26_3/container/bukkit/OpenPlayerInventorySelf.java b/internal/paper26_3/src/main/java/com/lishid/openinv/internal/paper26_3/container/bukkit/OpenPlayerInventorySelf.java
index 1d7eb3b4..70e05b95 100644
--- a/internal/paper26_3/src/main/java/com/lishid/openinv/internal/paper26_3/container/bukkit/OpenPlayerInventorySelf.java
+++ b/internal/paper26_3/src/main/java/com/lishid/openinv/internal/paper26_3/container/bukkit/OpenPlayerInventorySelf.java
@@ -1,28 +1,169 @@
 package com.lishid.openinv.internal.paper26_3.container.bukkit;
 
+import com.github.jikoo.openinv.internal.container.slot.InventoryFactory;
+import com.google.common.base.Preconditions;
 import com.lishid.openinv.internal.paper26_3.container.BaseOpenInventory;
+import net.minecraft.server.level.ServerPlayer;
+import net.minecraft.world.Container;
+import net.minecraft.world.entity.EquipmentSlot;
+import net.minecraft.world.inventory.Slot;
+import org.bukkit.Material;
+import org.bukkit.craftbukkit.inventory.CraftItemStack;
 import org.bukkit.inventory.ItemStack;
 import org.jspecify.annotations.NullMarked;
 import org.jspecify.annotations.Nullable;
 
+import java.util.HashMap;
+
 @NullMarked
 public class OpenPlayerInventorySelf extends OpenPlayerInventory {
 
   private final int offset;
 
-  public OpenPlayerInventorySelf(BaseOpenInventory inventory, int offset) {
-    super(inventory);
+  public OpenPlayerInventorySelf(
+      InventoryFactory<ServerPlayer, net.minecraft.world.item.ItemStack, Container, Slot, EquipmentSlot> factory,
+      BaseOpenInventory inventory,
+      int offset
+  ) {
+    super(factory, inventory);
     this.offset = offset;
   }
 
+  @Override
+  public int getSize() {
+    return super.getSize() - offset;
+  }
+
   @Override
   public @Nullable ItemStack getItem(int index) {
     return super.getItem(offset + index);
   }
 
+  @Override
+  public @Nullable ItemStack[] getStorageContents() {
+    return new ItemStack[0];
+  }
+
+  @Override
+  public void setStorageContents(@Nullable ItemStack[] items) throws IllegalArgumentException {
+    Preconditions.checkArgument(items.length == 0, "items.length must be <= 0");
+  }
+
+  @Override
+  public @Nullable ItemStack[] getContents() {
+    @Nullable ItemStack[] contents = new ItemStack[getSize()];
+    for (int i = 0; i < contents.length; ++i) {
+      contents[i] = getItem(i);
+    }
+    return contents;
+  }
+
+  @Override
+  public void setContents(@Nullable ItemStack[] items) {
+    int size = getSize();
+    Preconditions.checkArgument(items.length <= size, "items.length must be <= %s", size);
+
+    for (int index = 0; index < size; ++index) {
+      ItemStack itemStack = items[index];
+      if (itemStack == null || itemStack.isEmpty()) {
+        continue;
+      }
+      validateSet(index);
+    }
+
+    for (int index = 0; index < size; ++index) {
+      if (index < items.length) {
+        inventory.setItem(offset + index, CraftItemStack.asNMSCopy(items[index]));
+      } else {
+        inventory.setItem(offset + index, net.minecraft.world.item.ItemStack.EMPTY);
+      }
+    }
+  }
+
   @Override
   public void setItem(int index, @Nullable ItemStack item) {
     super.setItem(offset + index, item);
   }
 
+  @Override
+  public boolean contains(Material material) {
+    // Only checks the storage contents.
+    return false;
+  }
+
+  @Override
+  public boolean contains(ItemStack item) {
+    return false;
+  }
+
+  @Override
+  public boolean contains(Material material, int amount) {
+    return false;
+  }
+
+  @Override
+  public boolean contains(ItemStack item, int amount) {
+    return false;
+  }
+
+  @Override
+  public boolean containsAtLeast(ItemStack item, int amount) {
+    return false;
+  }
+
+  @SuppressWarnings("NonApiType")
+  @Override
+  public HashMap<Integer, ItemStack> all(Material material) {
+    // No storage contents, no results.
+    return new HashMap<>();
+  }
+
+  @SuppressWarnings("NonApiType")
+  @Override
+  public HashMap<Integer, ItemStack> all(@Nullable ItemStack item) {
+    return new HashMap<>();
+  }
+
+  @Override
+  public int first(Material material) {
+    return -1;
+  }
+
+  @Override
+  public int first(ItemStack item) {
+    return -1;
+  }
+
+  @Override
+  public int firstEmpty() {
+    return -1;
+  }
+
+  @SuppressWarnings("NonApiType")
+  @Override
+  public HashMap<Integer, ItemStack> addItem(ItemStack... items) {
+    HashMap<Integer, ItemStack> map = new HashMap<>();
+    for (int index = 0; index < items.length; ++index) {
+      map.put(index, items[index]);
+    }
+    return map;
+  }
+
+  @SuppressWarnings("NonApiType")
+  @Override
+  public HashMap<Integer, ItemStack> removeItem(ItemStack... items) {
+    return addItem(items);
+  }
+
+  @Override
+  public void remove(Material material) {
+    Preconditions.checkNotNull(material, "Material cannot be null");
+    Preconditions.checkArgument(material.isItem(), "Material must be an item");
+  }
+
+  @Override
+  public void remove(ItemStack itemStack) {
+    // Sure did.
+  }
+
 }
diff --git a/internal/paper26_3/src/main/java/com/lishid/openinv/internal/paper26_3/container/menu/BaseOpenInventoryMenu.java b/internal/paper26_3/src/main/java/com/lishid/openinv/internal/paper26_3/container/menu/BaseOpenInventoryMenu.java
index d013f0c6..9c34d8cb 100644
--- a/internal/paper26_3/src/main/java/com/lishid/openinv/internal/paper26_3/container/menu/BaseOpenInventoryMenu.java
+++ b/internal/paper26_3/src/main/java/com/lishid/openinv/internal/paper26_3/container/menu/BaseOpenInventoryMenu.java
@@ -112,7 +112,7 @@ protected CraftInventoryView<OpenChestMenu<BaseOpenInventory>, Inventory> create
     if (viewOnly) {
       bukkitInventory = new OpenDummyPlayerInventory(container);
     } else if (ownContainer) {
-      bukkitInventory = new OpenPlayerInventorySelf(container, offset);
+      bukkitInventory = new OpenPlayerInventorySelf(factory, container, offset);
     } else {
       bukkitInventory = container.getBukkitInventory();
     }
diff --git a/internal/spigot26_3/build.gradle.kts b/internal/spigot26_3/build.gradle.kts
index d7721ce4..763925d0 100644
--- a/internal/spigot26_3/build.gradle.kts
+++ b/internal/spigot26_3/build.gradle.kts
@@ -20,8 +20,10 @@ tasks.withType<JavaCompile>().configureEach {
 apply<SpigotSetup>()
 
 dependencies {
-  compileOnly(libs.spigotapi)
-  extensions.getByType(SpigotDependencyExtension::class.java).version = "26.3-R0.1-SNAPSHOT"
+  val spigotVersion = "26.3-R0.1-SNAPSHOT"
+  extensions.getByType(SpigotDependencyExtension::class.java).version = spigotVersion
+  val spigotApi = libs.spigotapi.get()
+  compileOnly("${spigotApi.group}:${spigotApi.name}:$spigotVersion")
   compileOnly("com.mojang:logging:1.7.12")
   compileOnly("com.mojang:brigadier:1.3.11")
   compileOnly("com.mojang:datafixerupper:10.0.21")
diff --git a/internal/spigot26_3/src/main/java/com/github/jikoo/openinv/internal/spigot26_3/container/bukkit/OpenPlayerInventory.java b/internal/spigot26_3/src/main/java/com/github/jikoo/openinv/internal/spigot26_3/container/bukkit/OpenPlayerInventory.java
index 89f4cbfe..3f825fca 100644
--- a/internal/spigot26_3/src/main/java/com/github/jikoo/openinv/internal/spigot26_3/container/bukkit/OpenPlayerInventory.java
+++ b/internal/spigot26_3/src/main/java/com/github/jikoo/openinv/internal/spigot26_3/container/bukkit/OpenPlayerInventory.java
@@ -3,9 +3,14 @@
 import com.github.jikoo.openinv.internal.spigot26_3.container.OpenInventory;
 import com.google.common.base.Preconditions;
 import net.minecraft.core.NonNullList;
+import net.minecraft.world.Container;
 import net.minecraft.world.entity.player.Inventory;
+import net.minecraft.world.item.Item;
+import net.minecraft.world.item.Items;
+import org.bukkit.Material;
 import org.bukkit.craftbukkit.inventory.CraftInventory;
 import org.bukkit.craftbukkit.inventory.CraftItemStack;
+import org.bukkit.craftbukkit.inventory.CraftItemType;
 import org.bukkit.entity.Player;
 import org.bukkit.event.inventory.InventoryType;
 import org.bukkit.inventory.ItemStack;
@@ -13,6 +18,10 @@
 import org.jspecify.annotations.NullMarked;
 import org.jspecify.annotations.Nullable;
 
+import java.util.HashMap;
+import java.util.Map;
+import java.util.function.BiPredicate;
+
 @NullMarked
 public class OpenPlayerInventory extends CraftInventory implements PlayerInventory {
 
@@ -26,16 +35,34 @@ public OpenInventory getInventory() {
   }
 
   @Override
-  public ItemStack[] getContents() {
-    return asCraftMirror(getInventory().getOwnerHandle().getInventory().getContents());
+  public @Nullable ItemStack[] getContents() {
+    return asCraftMirror(getInventory().getContents());
   }
 
   @Override
-  public void setContents(ItemStack[] items) {
-    Inventory internal = getInventory().getOwnerHandle().getInventory();
+  public void setContents(@Nullable ItemStack[] items) {
+    Container internal = getInventory();
     int size = internal.getContainerSize();
     Preconditions.checkArgument(items.length <= size, "items.length must be <= %s", size);
 
+    if (items.length < size) {
+      // If size matches normal player inventory size, redirect to it.
+      Container ownerInternal = getInventory().getOwnerHandle().getInventory();
+      if (items.length == ownerInternal.getContainerSize()) {
+        internal = ownerInternal;
+        size = items.length;
+      }
+    } else {
+      // Otherwise, ensure that the display-only slots are not in use.
+      for (int index = 0; index < size; ++index) {
+        ItemStack itemStack = items[index];
+        if (itemStack == null || itemStack.getType() == Material.AIR || itemStack.getAmount() <= 0) {
+          continue;
+        }
+        validateSet(index);
+      }
+    }
+
     for (int index = 0; index < size; ++index) {
       if (index < items.length) {
         internal.setItem(index, CraftItemStack.asNMSCopy(items[index]));
@@ -45,13 +72,26 @@ public void setContents(ItemStack[] items) {
     }
   }
 
+  protected void validateSet(int index) {
+    InventoryType.SlotType slotType = getInventory().getSlotType(index);
+    if (slotType == InventoryType.SlotType.OUTSIDE || slotType == InventoryType.SlotType.RESULT) {
+      throw new IllegalArgumentException("A plugin tried to put an item in a display slot. That would delete it!");
+    }
+  }
+
+  @Override
+  public void setItem(int index, @Nullable ItemStack item) {
+    validateSet(index);
+    super.setItem(index, item);
+  }
+
   @Override
-  public ItemStack[] getStorageContents() {
+  public @Nullable ItemStack[] getStorageContents() {
     return asCraftMirror(getInventory().getOwnerHandle().getInventory().getNonEquipmentItems());
   }
 
   @Override
-  public void setStorageContents(ItemStack[] items) throws IllegalArgumentException {
+  public void setStorageContents(@Nullable ItemStack[] items) throws IllegalArgumentException {
     NonNullList<net.minecraft.world.item.ItemStack> list = getInventory().getOwnerHandle().getInventory().getNonEquipmentItems();
     int size = list.size();
     Preconditions.checkArgument(items.length <= size, "items.length must be <= %s", size);
@@ -60,6 +100,294 @@ public void setStorageContents(ItemStack[] items) throws IllegalArgumentExceptio
     }
   }
 
+  @SuppressWarnings("NonApiType")
+  @Override
+  public HashMap<Integer, ItemStack> all(Material material) {
+    Preconditions.checkNotNull(material, "Material cannot be null");
+    Item item = CraftItemType.bukkitToMinecraft(material);
+    Preconditions.checkNotNull(item, "Material must be an item");
+
+    OpenInventory inventory = getInventory();
+    int size = inventory.getOwnerHandle().getInventory().getNonEquipmentItems().size();
+
+    HashMap<Integer, ItemStack> slots = new HashMap<>();
+    for (int index = 0; index < size; ++index) {
+      net.minecraft.world.item.ItemStack itemStack = inventory.getItem(index);
+      if (!itemStack.isEmpty() && item.equals(itemStack.getItem())) {
+        slots.put(index, CraftItemStack.asCraftMirror(itemStack));
+      }
+    }
+
+    return slots;
+  }
+
+  @SuppressWarnings("NonApiType")
+  @Override
+  public HashMap<Integer, ItemStack> all(@Nullable ItemStack item) {
+    HashMap<Integer, ItemStack> slots = new HashMap<>();
+
+    if (item == null) {
+      return slots;
+    }
+
+    net.minecraft.world.item.ItemStack itemStack = CraftItemStack.asNMSCopy(item);
+    OpenInventory inventory = getInventory();
+    int size = inventory.getOwnerHandle().getInventory().getNonEquipmentItems().size();
+
+    for (int index = 0; index < size; ++index) {
+      net.minecraft.world.item.ItemStack slotItemStack = inventory.getItem(index);
+      if (ItemMatcher.EXACT.predicate.test(itemStack, slotItemStack)) {
+        slots.put(index, CraftItemStack.asCraftMirror(slotItemStack));
+      }
+    }
+
+    return slots;
+  }
+
+  @Override
+  public int first(Material material) {
+    Item item = CraftItemType.bukkitToMinecraft(material);
+    Preconditions.checkNotNull(item, "Material must be an item");
+    net.minecraft.world.item.ItemStack itemStack = new net.minecraft.world.item.ItemStack(item);
+    int size = getInventory().getOwnerHandle().getInventory().getNonEquipmentItems().size();
+    return first(itemStack, ItemMatcher.TYPE, 0, size);
+  }
+
+  @Override
+  public int first(ItemStack item) {
+    net.minecraft.world.item.ItemStack itemStack = CraftItemStack.asNMSCopy(item);
+    int size = getInventory().getOwnerHandle().getInventory().getNonEquipmentItems().size();
+    return first(itemStack, ItemMatcher.EXACT, 0, size);
+  }
+
+  @Override
+  public int firstEmpty() {
+    OpenInventory inventory = getInventory();
+    int size = inventory.getOwnerHandle().getInventory().getNonEquipmentItems().size();
+    return first(net.minecraft.world.item.ItemStack.EMPTY, ItemMatcher.EMPTY, 0, size);
+  }
+
+  private int first(net.minecraft.world.item.ItemStack itemStack, ItemMatcher matcher, int startIndex, int endIndex) {
+    for (int index = startIndex; index < endIndex; ++index) {
+      net.minecraft.world.item.ItemStack inventoryStack = inventory.getItem(index);
+      if (matcher.predicate.test(itemStack, inventoryStack)) {
+        return index;
+      }
+    }
+    return -1;
+  }
+
+  @SuppressWarnings("ImmutableEnumChecker") // Ignore Google's style preference for predicate-like enums
+  private enum ItemMatcher {
+    EMPTY((ignored, b) -> b.isEmpty()),
+    TYPE(net.minecraft.world.item.ItemStack::isSameItem),
+    SIMILAR(net.minecraft.world.item.ItemStack::isSameItemSameComponents),
+    EXACT((a, b) -> net.minecraft.world.item.ItemStack.isSameItemSameComponents(a, b) && a.count() == b.count());
+
+    private final BiPredicate<net.minecraft.world.item.ItemStack, net.minecraft.world.item.ItemStack> predicate;
+
+    ItemMatcher(BiPredicate<net.minecraft.world.item.ItemStack, net.minecraft.world.item.ItemStack> predicate) {
+      this.predicate = predicate;
+    }
+  }
+
+  @SuppressWarnings("NonApiType")
+  @Override
+  public HashMap<Integer, ItemStack> addItem(ItemStack... items) {
+    Preconditions.checkNotNull(items, "items cannot be null");
+    HashMap<Integer, ItemStack> leftover = new HashMap<>();
+
+    OpenInventory inventory = getInventory();
+    int storageSize = inventory.getOwnerHandle().getInventory().getNonEquipmentItems().size();
+
+    for (int index = 0; index < items.length; ++index) {
+      addItem(items, index, storageSize, leftover);
+    }
+
+    return leftover;
+  }
+
+  private void addItem(
+      ItemStack[] items,
+      int leftoverIndex,
+      int storageSize,
+      Map<Integer, ItemStack> leftover
+  ) {
+    ItemStack bukkitStack = items[leftoverIndex];
+    Preconditions.checkNotNull(bukkitStack, "ItemStack cannot be null");
+    if (bukkitStack.getType() == Material.AIR || bukkitStack.getAmount() <= 0) {
+      return;
+    }
+    net.minecraft.world.item.ItemStack nmsStack = CraftItemStack.asNMSCopy(bukkitStack);
+    Preconditions.checkNotNull(nmsStack, "ItemStack cannot be empty");
+
+    int maxStackSize = inventory.getMaxStackSize(nmsStack);
+    int stackCount = nmsStack.count();
+
+    // Try to fill existing stacks first. Waste of time for items that don't stack.
+    if (maxStackSize > 1) {
+      stackCount = addPartial(storageSize, nmsStack, maxStackSize, stackCount);
+      if (nmsStack.count() < 1) {
+        // All done adding, next item.
+        return;
+      }
+    }
+
+    // Add to empty slots.
+    stackCount = addEmpty(storageSize, stackCount, maxStackSize, nmsStack);
+
+    if (stackCount > 0) {
+      bukkitStack.setAmount(stackCount);
+      leftover.put(leftoverIndex, bukkitStack);
+    }
+  }
+
+  private int addPartial(
+      int storageSize,
+      net.minecraft.world.item.ItemStack nmsStack,
+      int maxStackSize,
+      int stackCount
+  ) {
+    for (
+        int firstPartial = first(nmsStack, ItemMatcher.SIMILAR, 0, storageSize);
+        firstPartial < storageSize && firstPartial > -1;
+        firstPartial = first(nmsStack, ItemMatcher.SIMILAR, firstPartial + 1, storageSize)
+    ) {
+      net.minecraft.world.item.ItemStack existing = inventory.getItem(firstPartial);
+      int existingCount = existing.count();
+      if (existingCount >= maxStackSize) {
+        continue;
+      }
+
+      int fit = maxStackSize - existingCount;
+
+      if (fit >= stackCount) {
+        nmsStack.setCount(0);
+        existing.setCount(existingCount + stackCount);
+        return 0;
+      }
+
+      stackCount -= fit;
+      nmsStack.setCount(stackCount);
+      existing.setCount(maxStackSize);
+    }
+    return stackCount;
+  }
+
+  private int addEmpty(
+      int storageSize,
+      int stackCount,
+      int maxStackSize,
+      net.minecraft.world.item.ItemStack nmsStack
+  ) {
+    for (
+        int firstEmpty = firstEmpty();
+        firstEmpty < storageSize && firstEmpty > -1;
+        firstEmpty = first(net.minecraft.world.item.ItemStack.EMPTY, ItemMatcher.EMPTY, firstEmpty, storageSize)
+    ) {
+      if (stackCount <= maxStackSize) {
+        inventory.setItem(firstEmpty, nmsStack.copy());
+        return 0;
+      }
+
+      var newStack = nmsStack.copy();
+      stackCount -= maxStackSize;
+      nmsStack.setCount(stackCount);
+      newStack.setCount(maxStackSize);
+      inventory.setItem(firstEmpty, newStack);
+    }
+
+    return stackCount;
+  }
+
+  @SuppressWarnings("NonApiType")
+  @Override
+  public HashMap<Integer, ItemStack> removeItem(ItemStack... items) {
+    Preconditions.checkNotNull(items, "items cannot be null");
+    HashMap<Integer, ItemStack> leftover = new HashMap<>();
+
+    OpenInventory inventory = getInventory();
+    int storageSize = inventory.getOwnerHandle().getInventory().getNonEquipmentItems().size();
+
+    for (int index = 0; index < items.length; ++index) {
+      removeItem(items[index], index, storageSize, leftover);
+    }
+
+    return leftover;
+  }
+
+  private void removeItem(
+      ItemStack bukkitStack,
+      int leftoverIndex,
+      int storageSize,
+      Map<Integer, ItemStack> leftover
+  ) {
+    Preconditions.checkNotNull(bukkitStack, "ItemStack cannot be null");
+    if (bukkitStack.getType() == Material.AIR || bukkitStack.getAmount() <= 0) {
+      return;
+    }
+    net.minecraft.world.item.ItemStack nmsStack = CraftItemStack.asNMSCopy(bukkitStack);
+    Preconditions.checkNotNull(nmsStack, "ItemStack cannot be empty");
+
+    int stackCount = nmsStack.count();
+
+    for (
+        int first = first(nmsStack, ItemMatcher.SIMILAR, 0, storageSize);
+        first < storageSize && first > -1;
+        first = first(nmsStack, ItemMatcher.SIMILAR, first + 1, storageSize)
+    ) {
+      net.minecraft.world.item.ItemStack existing = inventory.getItem(first);
+      int existingCount = existing.count();
+      if (existingCount > stackCount) {
+        existing.setCount(existingCount - stackCount);
+        bukkitStack.setAmount(0);
+        return;
+      }
+
+      stackCount -= existingCount;
+      inventory.setItem(first, net.minecraft.world.item.ItemStack.EMPTY);
+
+      if (stackCount <= 0) {
+        break;
+      }
+    }
+
+    bukkitStack.setAmount(stackCount);
+
+    if (stackCount > 0) {
+      leftover.put(leftoverIndex, bukkitStack);
+    }
+  }
+
+  @Override
+  public void remove(Material material) {
+    Item item = CraftItemType.bukkitToMinecraft(material);
+    Preconditions.checkNotNull(item, "Material must be an item");
+
+    if (!item.equals(Items.AIR)) {
+      removeAll(new net.minecraft.world.item.ItemStack(item), ItemMatcher.SIMILAR);
+    }
+  }
+
+  @Override
+  public void remove(ItemStack bukkitStack) {
+    net.minecraft.world.item.ItemStack nmsStack = CraftItemStack.asNMSCopy(bukkitStack);
+
+    if (!nmsStack.isEmpty()) {
+      removeAll(nmsStack, ItemMatcher.EXACT);
+    }
+  }
+
+  private void removeAll(net.minecraft.world.item.ItemStack itemStack, ItemMatcher matcher) {
+    int storageSize = getInventory().getOwnerHandle().getInventory().getNonEquipmentItems().size();
+    for (int index = 0; index < storageSize; ++index) {
+      net.minecraft.world.item.ItemStack content = inventory.getItem(index);
+      if (matcher.predicate.test(itemStack, content)) {
+        inventory.setItem(index, net.minecraft.world.item.ItemStack.EMPTY);
+      }
+    }
+  }
+
   @Override
   public InventoryType getType() {
     return InventoryType.PLAYER;
@@ -76,7 +404,7 @@ public ItemStack[] getArmorContents() {
   }
 
   @Override
-  public void setArmorContents(ItemStack[] items) {
+  public void setArmorContents(@Nullable ItemStack[] items) {
     getInventory().getOwnerHandle().getBukkitEntity().getInventory().setArmorContents(items);
   }
 
@@ -86,7 +414,7 @@ public ItemStack[] getExtraContents() {
   }
 
   @Override
-  public void setExtraContents(ItemStack[] items) {
+  public void setExtraContents(@Nullable ItemStack[] items) {
     getInventory().getOwnerHandle().getBukkitEntity().getInventory().setExtraContents(items);
   }
 
@@ -117,39 +445,37 @@ public void setChestplate(@Nullable ItemStack chestplate) {
 
   @Override
   public void setLeggings(@Nullable ItemStack leggings) {
-    getInventory().getOwnerHandle().getBukkitEntity().getInventory().setLeggings(leggings);
+    getInventory().getOwner().getInventory().setLeggings(leggings);
   }
 
   @Override
   public @Nullable ItemStack getBoots() {
-    return getInventory().getOwnerHandle().getBukkitEntity().getInventory().getBoots();
+    return getInventory().getOwner().getInventory().getBoots();
   }
 
   @Override
   public void setBoots(@Nullable ItemStack boots) {
-    getInventory().getOwnerHandle().getBukkitEntity().getInventory().setBoots(boots);
+    getInventory().getOwner().getInventory().setBoots(boots);
   }
 
   @Override
   public ItemStack getItemInMainHand() {
-    Inventory internal = getInventory().getOwnerHandle().getInventory();
-    return CraftItemStack.asCraftMirror(internal.getSelectedItem());
+    return getInventory().getOwner().getInventory().getItemInMainHand();
   }
 
   @Override
   public void setItemInMainHand(@Nullable ItemStack item) {
-    Inventory internal = getInventory().getOwnerHandle().getInventory();
-    internal.setSelectedItem(CraftItemStack.asNMSCopy(item));
+    getInventory().getOwner().getInventory().setItemInMainHand(item);
   }
 
   @Override
   public ItemStack getItemInOffHand() {
-    return getInventory().getOwnerHandle().getBukkitEntity().getInventory().getItemInOffHand();
+    return getInventory().getOwner().getInventory().getItemInOffHand();
   }
 
   @Override
   public void setItemInOffHand(@Nullable ItemStack item) {
-    getInventory().getOwnerHandle().getBukkitEntity().getInventory().setItemInOffHand(item);
+    getInventory().getOwner().getInventory().setItemInOffHand(item);
   }
 
   @SuppressWarnings("InlineMeSuggester")
@@ -180,12 +506,28 @@ public void setHeldItemSlot(int slot) {
 
   @Override
   public @Nullable ItemStack getItem(org.bukkit.inventory.EquipmentSlot slot) {
-    return getInventory().getOwnerHandle().getBukkitEntity().getInventory().getItem(slot);
+    return switch (slot) {
+      case HAND -> getItemInMainHand();
+      case OFF_HAND -> getItemInOffHand();
+      case FEET -> getBoots();
+      case LEGS -> getLeggings();
+      case CHEST -> getChestplate();
+      case HEAD -> getHelmet();
+      default -> throw new IllegalArgumentException("Unsupported EquipmentSlot " + slot);
+    };
   }
 
   @Override
   public void setItem(org.bukkit.inventory.EquipmentSlot slot, @Nullable ItemStack item) {
-    getInventory().getOwnerHandle().getBukkitEntity().getInventory().setItem(slot, item);
+    switch (slot) {
+      case HAND -> setItemInMainHand(item);
+      case OFF_HAND -> setItemInOffHand(item);
+      case FEET -> setBoots(item);
+      case LEGS -> setLeggings(item);
+      case CHEST -> setChestplate(item);
+      case HEAD -> setHelmet(item);
+      default -> throw new IllegalArgumentException("Unsupported EquipmentSlot " + slot);
+    }
   }
 
 }
diff --git a/internal/spigot26_3/src/main/java/com/github/jikoo/openinv/internal/spigot26_3/container/bukkit/OpenPlayerInventorySelf.java b/internal/spigot26_3/src/main/java/com/github/jikoo/openinv/internal/spigot26_3/container/bukkit/OpenPlayerInventorySelf.java
index 02ef39d5..fb79acd3 100644
--- a/internal/spigot26_3/src/main/java/com/github/jikoo/openinv/internal/spigot26_3/container/bukkit/OpenPlayerInventorySelf.java
+++ b/internal/spigot26_3/src/main/java/com/github/jikoo/openinv/internal/spigot26_3/container/bukkit/OpenPlayerInventorySelf.java
@@ -1,10 +1,15 @@
 package com.github.jikoo.openinv.internal.spigot26_3.container.bukkit;
 
 import com.github.jikoo.openinv.internal.spigot26_3.container.OpenInventory;
+import com.google.common.base.Preconditions;
+import org.bukkit.Material;
+import org.bukkit.craftbukkit.inventory.CraftItemStack;
 import org.bukkit.inventory.ItemStack;
 import org.jspecify.annotations.NullMarked;
 import org.jspecify.annotations.Nullable;
 
+import java.util.HashMap;
+
 @NullMarked
 public class OpenPlayerInventorySelf extends OpenPlayerInventory {
 
@@ -15,14 +20,141 @@ public OpenPlayerInventorySelf(OpenInventory inventory, int offset) {
     this.offset = offset;
   }
 
+  @Override
+  public int getSize() {
+    return super.getSize() - offset;
+  }
+
   @Override
   public @Nullable ItemStack getItem(int index) {
     return super.getItem(offset + index);
   }
 
+  @Override
+  public @Nullable ItemStack[] getStorageContents() {
+    return new ItemStack[0];
+  }
+
+  @Override
+  public void setStorageContents(@Nullable ItemStack[] items) throws IllegalArgumentException {
+    Preconditions.checkArgument(items.length == 0, "items.length must be <= 0");
+  }
+
+  @Override
+  public @Nullable ItemStack[] getContents() {
+    @Nullable ItemStack[] contents = new ItemStack[getSize()];
+    for (int i = 0; i < contents.length; ++i) {
+      contents[i] = getItem(i);
+    }
+    return contents;
+  }
+
+  @Override
+  public void setContents(@Nullable ItemStack[] items) {
+    int size = getSize();
+    Preconditions.checkArgument(items.length <= size, "items.length must be <= %s", size);
+
+    for (int index = 0; index < size; ++index) {
+      ItemStack itemStack = items[index];
+      if (itemStack == null || itemStack.getType() == Material.AIR || itemStack.getAmount() <= 0) {
+        continue;
+      }
+      validateSet(index);
+    }
+
+    for (int index = 0; index < size; ++index) {
+      if (index < items.length) {
+        inventory.setItem(offset + index, CraftItemStack.asNMSCopy(items[index]));
+      } else {
+        inventory.setItem(offset + index, net.minecraft.world.item.ItemStack.EMPTY);
+      }
+    }
+  }
+
   @Override
   public void setItem(int index, @Nullable ItemStack item) {
     super.setItem(offset + index, item);
   }
 
+  @Override
+  public boolean contains(Material material) {
+    // Only checks the storage contents.
+    return false;
+  }
+
+  @Override
+  public boolean contains(ItemStack item) {
+    return false;
+  }
+
+  @Override
+  public boolean contains(Material material, int amount) {
+    return false;
+  }
+
+  @Override
+  public boolean contains(ItemStack item, int amount) {
+    return false;
+  }
+
+  @Override
+  public boolean containsAtLeast(ItemStack item, int amount) {
+    return false;
+  }
+
+  @SuppressWarnings("NonApiType")
+  @Override
+  public HashMap<Integer, ItemStack> all(Material material) {
+    // No storage contents, no results.
+    return new HashMap<>();
+  }
+
+  @SuppressWarnings("NonApiType")
+  @Override
+  public HashMap<Integer, ItemStack> all(@Nullable ItemStack item) {
+    return new HashMap<>();
+  }
+
+  @Override
+  public int first(Material material) {
+    return -1;
+  }
+
+  @Override
+  public int first(ItemStack item) {
+    return -1;
+  }
+
+  @Override
+  public int firstEmpty() {
+    return -1;
+  }
+
+  @SuppressWarnings("NonApiType")
+  @Override
+  public HashMap<Integer, ItemStack> addItem(ItemStack... items) {
+    HashMap<Integer, ItemStack> map = new HashMap<>();
+    for (int index = 0; index < items.length; ++index) {
+      map.put(index, items[index]);
+    }
+    return map;
+  }
+
+  @SuppressWarnings("NonApiType")
+  @Override
+  public HashMap<Integer, ItemStack> removeItem(ItemStack... items) {
+    return addItem(items);
+  }
+
+  @Override
+  public void remove(Material material) {
+    Preconditions.checkNotNull(material, "Material cannot be null");
+    Preconditions.checkArgument(material.isItem(), "Material must be an item");
+  }
+
+  @Override
+  public void remove(ItemStack itemStack) {
+    // Sure did.
+  }
+
 }