diff --git a/src/main/java/net/minecraftforge/client/StencilManager.java b/src/main/java/net/minecraftforge/client/StencilManager.java
index 6807f6bdb4..2e496f8afe 100644
--- a/src/main/java/net/minecraftforge/client/StencilManager.java
+++ b/src/main/java/net/minecraftforge/client/StencilManager.java
@@ -7,6 +7,10 @@ package net.minecraftforge.client;
 
 import java.util.BitSet;
 
+/// @deprecated This class is scheduled for removal in 26.4 due to a lack of adoption by mods, in order to ease porting.
+///             Please reach out to the Forge team if you are relying on this and would like to see it remain in Forge.
+///             We may keep it or add it back in a future version if there is enough demand.
+@Deprecated(forRemoval = true, since = "26.4")
 public final class StencilManager
 {
     private static final BitSet BITS = new BitSet(8);
diff --git a/src/main/java/net/minecraftforge/client/model/pipeline/TransformingVertexPipeline.java b/src/main/java/net/minecraftforge/client/model/pipeline/TransformingVertexPipeline.java
index ac12f4a906..481a2050f3 100644
--- a/src/main/java/net/minecraftforge/client/model/pipeline/TransformingVertexPipeline.java
+++ b/src/main/java/net/minecraftforge/client/model/pipeline/TransformingVertexPipeline.java
@@ -10,9 +10,12 @@ import com.mojang.math.Transformation;
 import org.joml.Vector3f;
 import org.joml.Vector4f;
 
-/**
- * Vertex pipeline element that applies a transformation to incoming geometry.
- */
+/// Vertex pipeline element that applies a transformation to incoming geometry.
+///
+/// @deprecated This class is scheduled for removal in 26.4 due to a lack of adoption by mods, in order to ease porting.
+///             Please reach out to the Forge team if you are relying on this and would like to see it remain in Forge.
+///             We may keep it or add it back in a future version if there is enough demand.
+@Deprecated(forRemoval = true, since = "26.4")
 public class TransformingVertexPipeline extends VertexConsumerWrapper
 {
     private final Transformation transformation;
diff --git a/src/main/java/net/minecraftforge/client/model/pipeline/VertexConsumerWrapper.java b/src/main/java/net/minecraftforge/client/model/pipeline/VertexConsumerWrapper.java
index e83e6ac067..c1a45d03df 100644
--- a/src/main/java/net/minecraftforge/client/model/pipeline/VertexConsumerWrapper.java
+++ b/src/main/java/net/minecraftforge/client/model/pipeline/VertexConsumerWrapper.java
@@ -11,7 +11,12 @@ import com.mojang.blaze3d.vertex.VertexConsumer;
  * Wrapper for {@link VertexConsumer} which delegates all operations to its parent.
  * <p>
  * Useful for defining custom pipeline elements that only process certain data.
+ *
+ * @deprecated This class is scheduled for removal in 26.4 due to a lack of adoption by mods, in order to ease porting.
+ *             Please reach out to the Forge team if you are relying on this and would like to see it remain in Forge.
+ *             We may keep it or add it back in a future version if there is enough demand.
  */
+@Deprecated(forRemoval = true, since = "26.4")
 public class VertexConsumerWrapper implements VertexConsumer {
     protected final VertexConsumer parent;
 
diff --git a/src/main/java/net/minecraftforge/common/UsernameCache.java b/src/main/java/net/minecraftforge/common/UsernameCache.java
index d328ed15ad..cee2f7ef7f 100644
--- a/src/main/java/net/minecraftforge/common/UsernameCache.java
+++ b/src/main/java/net/minecraftforge/common/UsernameCache.java
@@ -36,9 +36,14 @@ import org.jetbrains.annotations.Nullable;
  * last known username.<br>
  * For convenience, {@link #getMap()} is provided to get an immutable copy of
  * the caches underlying map.
+ *
+ * @deprecated This class is scheduled for removal in 26.4 due to a lack of adoption by mods, in order to ease porting.
+ *             Please reach out to the Forge team if you are relying on this and would like to see it remain in Forge.
+ *             We may keep it or add it back in a future version if there is enough demand.
  */
+@Deprecated(forRemoval = true, since = "26.4")
 public final class UsernameCache {
-    private static Map<UUID, String> map = new HashMap<>();
+    private static HashMap<UUID, String> map = new HashMap<>();
 
     private static final Path saveFile = FMLLoader.getGamePath().resolve("usernamecache.json");
     private static final Gson gson = new GsonBuilder().setPrettyPrinting().create();
diff --git a/src/main/java/net/minecraftforge/common/property/Properties.java b/src/main/java/net/minecraftforge/common/property/Properties.java
index dfa87da024..8f6ca2d439 100644
--- a/src/main/java/net/minecraftforge/common/property/Properties.java
+++ b/src/main/java/net/minecraftforge/common/property/Properties.java
@@ -9,6 +9,10 @@ import net.minecraft.client.renderer.block.dispatch.ModelState;
 import net.minecraft.world.level.block.state.properties.BooleanProperty;
 import net.minecraftforge.client.model.data.ModelProperty;
 
+/// @deprecated This class is scheduled for removal in 26.4 due to a lack of adoption by mods, in order to ease porting.
+///             Please reach out to the Forge team if you are relying on this and would like to see it remain in Forge.
+///             We may keep it or add it back in a future version if there is enough demand.
+@Deprecated(forRemoval = true, since = "26.4")
 public class Properties {
     /**
      * Property indicating if the model should be rendered in the static renderer or in the TESR. AnimationTESR sets it to false.
diff --git a/src/main/java/net/minecraftforge/common/util/CenterChunkPosComparator.java b/src/main/java/net/minecraftforge/common/util/CenterChunkPosComparator.java
index d8891d6dc3..4fb7532e4d 100644
--- a/src/main/java/net/minecraftforge/common/util/CenterChunkPosComparator.java
+++ b/src/main/java/net/minecraftforge/common/util/CenterChunkPosComparator.java
@@ -8,8 +8,15 @@ package net.minecraftforge.common.util;
 import net.minecraft.server.level.ServerPlayer;
 import net.minecraft.world.level.ChunkPos;
 
+import java.util.Comparator;
+
 // Sorter to load nearby chunks first
-public class CenterChunkPosComparator implements java.util.Comparator<ChunkPos> {
+
+/// @deprecated This class is scheduled for removal in 26.4 due to a lack of adoption by mods, in order to ease porting.
+///             Please reach out to the Forge team if you are relying on this and would like to see it remain in Forge.
+///             We may keep it or add it back in a future version if there is enough demand.
+@Deprecated(forRemoval = true, since = "26.4")
+public class CenterChunkPosComparator implements Comparator<ChunkPos> {
     private final int x;
     private final int z;
 
diff --git a/src/main/java/net/minecraftforge/common/util/HexDumper.java b/src/main/java/net/minecraftforge/common/util/HexDumper.java
index 97cde42156..530751597c 100644
--- a/src/main/java/net/minecraftforge/common/util/HexDumper.java
+++ b/src/main/java/net/minecraftforge/common/util/HexDumper.java
@@ -7,6 +7,8 @@ package net.minecraftforge.common.util;
 
 import io.netty.buffer.ByteBuf;
 
+import java.util.Arrays;
+
 /**
  * Utility class for creating a nice human readable dump of binary data.
  *
@@ -42,7 +44,7 @@ public class HexDumper {
         return inst.finish();
     }
 
-    private static class Instance {
+    private static final class Instance {
         private static final String HEX = "0123456789ABCDEF";
         private final int marked;
         private final StringBuilder buf;
@@ -57,8 +59,7 @@ public class HexDumper {
                                         + (lines * 2)        // \t and \n per line
                                         + (marked == -1 ? 0 : lines)); // ' ' or < at the start of each line
 
-            for (int x = 0; x < ascii.length; x++)
-                ascii[x] = ' ';
+            Arrays.fill(ascii, ' ');
         }
 
         public void add(byte data) {
diff --git a/src/main/java/net/minecraftforge/common/util/ItemStackMap.java b/src/main/java/net/minecraftforge/common/util/ItemStackMap.java
index 99e3beddf1..806afa21e9 100644
--- a/src/main/java/net/minecraftforge/common/util/ItemStackMap.java
+++ b/src/main/java/net/minecraftforge/common/util/ItemStackMap.java
@@ -12,6 +12,10 @@ import net.minecraft.world.item.ItemStackLinkedSet;
 
 import java.util.Map;
 
+/// @deprecated This class is scheduled for removal in 26.4 due to a lack of adoption by mods, in order to ease porting.
+///             Please reach out to the Forge team if you are relying on this and would like to see it remain in Forge.
+///             We may keep it or add it back in a future version if there is enough demand.
+@Deprecated(forRemoval = true, since = "26.4")
 public class ItemStackMap {
 
     public static <V> Map<ItemStack, V> createTypeAndTagLinkedMap() {
diff --git a/src/main/java/net/minecraftforge/common/util/JsonUtils.java b/src/main/java/net/minecraftforge/common/util/JsonUtils.java
index 302e86d8e1..c519c4e659 100644
--- a/src/main/java/net/minecraftforge/common/util/JsonUtils.java
+++ b/src/main/java/net/minecraftforge/common/util/JsonUtils.java
@@ -29,6 +29,10 @@ import net.minecraft.nbt.CompoundTag;
 import net.minecraft.util.GsonHelper;
 import org.jetbrains.annotations.Nullable;
 
+/// @deprecated This class is scheduled for removal in 26.4 due to a lack of adoption by mods, in order to ease porting.
+///             Please reach out to the Forge team if you are relying on this and would like to see it remain in Forge.
+///             We may keep it or add it back in a future version if there is enough demand.
+@Deprecated(forRemoval = true, since = "26.4")
 public class JsonUtils {
     // http://stackoverflow.com/questions/7706772/deserializing-immutablelist-using-gson/21677349#21677349
     public enum ImmutableListTypeAdapter implements JsonDeserializer<ImmutableList<?>>, JsonSerializer<ImmutableList<?>> {
diff --git a/src/main/java/net/minecraftforge/common/util/TextTable.java b/src/main/java/net/minecraftforge/common/util/TextTable.java
index 503104290c..65e84148f0 100644
--- a/src/main/java/net/minecraftforge/common/util/TextTable.java
+++ b/src/main/java/net/minecraftforge/common/util/TextTable.java
@@ -15,9 +15,12 @@ import java.util.List;
 import java.util.Objects;
 import java.util.stream.Collectors;
 
-/**
- * Utility to format data into a textual (markdown-compliant) table.
- */
+/// Utility to format data into a textual (markdown-compliant) table.
+///
+/// @deprecated This class is scheduled for removal in 26.4 due to a lack of adoption by mods, in order to ease porting.
+///             Please reach out to the Forge team if you are relying on this and would like to see it remain in Forge.
+///             We may keep it or add it back in a future version if there is enough demand.
+@Deprecated(forRemoval = true, since = "26.4")
 public class TextTable
 {
     public static Column column(String header)
diff --git a/src/main/java/net/minecraftforge/event/entity/EntityTeleportEvent.java b/src/main/java/net/minecraftforge/event/entity/EntityTeleportEvent.java
index e76f3ca58a..cab6e197a7 100644
--- a/src/main/java/net/minecraftforge/event/entity/EntityTeleportEvent.java
+++ b/src/main/java/net/minecraftforge/event/entity/EntityTeleportEvent.java
@@ -93,7 +93,12 @@ public sealed abstract class EntityTeleportEvent implements Cancellable, EntityE
      * This event is {@linkplain Cancellable cancelable}. If the event is cancelled, the entity will not be teleported.
      * <br>
      * This event is only fired on the {@link LogicalSide#SERVER} side.
+     *
+     * @deprecated This event is scheduled for removal in 26.4 due to a lack of adoption by mods, in order to ease porting.
+     *             Please reach out to the Forge team if you are relying on this and would like to see it remain in Forge.
+     *             We may keep it or add it back in a future version if there is enough demand.
      */
+    @Deprecated(forRemoval = true, since = "26.4")
     public static final class EntityRandom extends EntityTeleportEvent {
         public static final CancellableEventBus<EntityRandom> BUS = CancellableEventBus.create(EntityRandom.class);
 
diff --git a/src/main/java/net/minecraftforge/event/entity/living/MonsterDisguiseEvent.java b/src/main/java/net/minecraftforge/event/entity/living/MonsterDisguiseEvent.java
index 7ef0c748bb..2891493259 100644
--- a/src/main/java/net/minecraftforge/event/entity/living/MonsterDisguiseEvent.java
+++ b/src/main/java/net/minecraftforge/event/entity/living/MonsterDisguiseEvent.java
@@ -20,7 +20,12 @@ import net.minecraftforge.eventbus.api.event.characteristic.Cancellable;
  * If this event is cancelled, the Monster will not target the player.
  *
  * @param getPlayer The player that is being checked.
+ *
+ * @deprecated This event is scheduled for removal in 26.4 due to a lack of adoption by mods, in order to ease porting.
+ *             Please reach out to the Forge team if you are relying on this and would like to see it remain in Forge.
+ *             We may keep it or add it back in a future version if there is enough demand.
  */
+@Deprecated(forRemoval = true, since = "26.4")
 public record MonsterDisguiseEvent(Monster getEntity, Player getPlayer) implements Cancellable, LivingEvent, RecordEvent {
     public static final CancellableEventBus<MonsterDisguiseEvent> BUS = CancellableEventBus.create(MonsterDisguiseEvent.class);
 }
diff --git a/src/main/java/net/minecraftforge/event/entity/living/ZombieEvent.java b/src/main/java/net/minecraftforge/event/entity/living/ZombieEvent.java
index 008767457d..ce21db44c8 100644
--- a/src/main/java/net/minecraftforge/event/entity/living/ZombieEvent.java
+++ b/src/main/java/net/minecraftforge/event/entity/living/ZombieEvent.java
@@ -54,7 +54,12 @@ public sealed abstract class ZombieEvent implements EntityEvent, InheritableEven
      *     <li>{@link Result#ALLOW} Zombie is summoned.</li>
      *     <li>{@link Result#DENY} Zombie is not summoned.</li>
      * </ul>
+     *
+     * @deprecated This event is scheduled for removal in 26.4 due to a lack of adoption by mods, in order to ease porting.
+     *             Please reach out to the Forge team if you are relying on this and would like to see it remain in Forge.
+     *             We may keep it or add it back in a future version if there is enough demand.
      */
+    @Deprecated(forRemoval = true, since = "26.4")
     public static final class SummonAidEvent extends ZombieEvent implements HasResult {
         public static final EventBus<SummonAidEvent> BUS = EventBus.create(SummonAidEvent.class);
 
diff --git a/src/main/java/net/minecraftforge/event/level/ChunkEvent.java b/src/main/java/net/minecraftforge/event/level/ChunkEvent.java
index e0d5861268..6d6be9e9c8 100644
--- a/src/main/java/net/minecraftforge/event/level/ChunkEvent.java
+++ b/src/main/java/net/minecraftforge/event/level/ChunkEvent.java
@@ -68,7 +68,12 @@ public sealed interface ChunkEvent extends LevelEvent
      * the ChunkAccess isLightCorrect to true.<br>
      * <br>
      * The game test for this event is lighting_event_test in net.minecraftforge.debug.chunk<br>
+     *
+     * @deprecated This event is scheduled for removal in 26.4 due to a lack of adoption by mods, in order to ease porting.
+     *             Please reach out to the Forge team if you are relying on this and would like to see it remain in Forge.
+     *             We may keep it or add it back in a future version if there is enough demand.
      */
+    @Deprecated(forRemoval = true, since = "26.4")
     record LightingCalculated(ChunkAccess getChunk) implements ChunkEvent {
         public static final EventBus<ChunkEvent.LightingCalculated> BUS = EventBus.create(ChunkEvent.LightingCalculated.class);
     }
diff --git a/src/main/java/net/minecraftforge/event/level/ChunkTicketLevelUpdatedEvent.java b/src/main/java/net/minecraftforge/event/level/ChunkTicketLevelUpdatedEvent.java
index 72aca59e27..4e160d2db1 100644
--- a/src/main/java/net/minecraftforge/event/level/ChunkTicketLevelUpdatedEvent.java
+++ b/src/main/java/net/minecraftforge/event/level/ChunkTicketLevelUpdatedEvent.java
@@ -31,8 +31,13 @@ import org.jspecify.annotations.NullMarked;
  * @param getOldTicketLevel the previous ticket level the chunk had
  * @param getNewTicketLevel the new ticket level the chunk has
  * @param getChunkHolder the chunk that had its ticket level updated, may be null
+ *
+ * @deprecated This event is scheduled for removal in 26.4 due to a lack of adoption by mods, in order to ease porting.
+ *             Please reach out to the Forge team if you are relying on this and would like to see it remain in Forge.
+ *             We may keep it or add it back in a future version if there is enough demand.
  */
 @NullMarked
+@Deprecated(forRemoval = true, since = "26.4")
 public record ChunkTicketLevelUpdatedEvent(
         ServerLevel getLevel,
         long getChunkPos,
diff --git a/src/main/java/net/minecraftforge/server/command/TextComponentHelper.java b/src/main/java/net/minecraftforge/server/command/TextComponentHelper.java
index 333dedb433..c92ab87817 100644
--- a/src/main/java/net/minecraftforge/server/command/TextComponentHelper.java
+++ b/src/main/java/net/minecraftforge/server/command/TextComponentHelper.java
@@ -14,6 +14,10 @@ import net.minecraftforge.network.ConnectionType;
 import net.minecraftforge.network.NetworkContext;
 import java.util.Locale;
 
+/// @deprecated This class is scheduled for removal in 26.4 due to a lack of adoption by mods, in order to ease porting.
+///             Please reach out to the Forge team if you are relying on this and would like to see it remain in Forge.
+///             We may keep it or add it back in a future version if there is enough demand.
+@Deprecated(forRemoval = true, since = "26.4")
 public class TextComponentHelper {
     private TextComponentHelper() {}