From d61de63482f780de40cd3c337fd8e4a874da6b59 Mon Sep 17 00:00:00 2001
From: LexManos <LexManos@gmail.com>
Date: Sat, 3 Jan 2026 12:24:53 -0800
Subject: [PATCH] Allow accessing Registry context from TagValueOutput

---
 .../level/block/entity/BlockEntity.java.patch |  2 +-
 .../level/storage/TagValueOutput.java.patch   | 25 +++++++++++++++++++
 .../capabilities/CapabilityProvider.java      | 12 +++++++++
 3 files changed, 38 insertions(+), 1 deletion(-)
 create mode 100644 patches/minecraft/net/minecraft/world/level/storage/TagValueOutput.java.patch

diff --git a/patches/minecraft/net/minecraft/world/level/block/entity/BlockEntity.java.patch b/patches/minecraft/net/minecraft/world/level/block/entity/BlockEntity.java.patch
index 23b5bde849..f199babc96 100644
--- a/patches/minecraft/net/minecraft/world/level/block/entity/BlockEntity.java.patch
+++ b/patches/minecraft/net/minecraft/world/level/block/entity/BlockEntity.java.patch
@@ -43,7 +43,7 @@
      }
  
      protected void saveAdditional(ValueOutput p_407573_) {
-+        if (getCapabilities() != null && this.level != null) p_407573_.storeNullable("ForgeCaps", CompoundTag.CODEC, serializeCaps(this.level.registryAccess()));
++        if (getCapabilities() != null) p_407573_.storeNullable("ForgeCaps", CompoundTag.CODEC, serializeCaps(p_407573_));
      }
  
      public final CompoundTag saveWithFullMetadata(HolderLookup.Provider p_331193_) {
diff --git a/patches/minecraft/net/minecraft/world/level/storage/TagValueOutput.java.patch b/patches/minecraft/net/minecraft/world/level/storage/TagValueOutput.java.patch
new file mode 100644
index 0000000000..2f00de52bf
--- /dev/null
+++ b/patches/minecraft/net/minecraft/world/level/storage/TagValueOutput.java.patch
@@ -0,0 +1,25 @@
+--- a/net/minecraft/world/level/storage/TagValueOutput.java
++++ b/net/minecraft/world/level/storage/TagValueOutput.java
+@@ -17,15 +_,21 @@
+     private final ProblemReporter problemReporter;
+     private final DynamicOps<Tag> ops;
+     private final CompoundTag output;
++    public final HolderLookup.@org.jspecify.annotations.Nullable Provider lookup;
+ 
+     TagValueOutput(ProblemReporter p_407091_, DynamicOps<Tag> p_407083_, CompoundTag p_409593_) {
++        this(p_407091_, p_407083_, p_409593_, null);
++    }
++
++    TagValueOutput(ProblemReporter p_407091_, DynamicOps<Tag> p_407083_, CompoundTag p_409593_, HolderLookup.@org.jspecify.annotations.Nullable Provider lookup) {
+         this.problemReporter = p_407091_;
+         this.ops = p_407083_;
+         this.output = p_409593_;
++        this.lookup = lookup;
+     }
+ 
+     public static TagValueOutput createWithContext(ProblemReporter p_409887_, HolderLookup.Provider p_409738_) {
+-        return new TagValueOutput(p_409887_, p_409738_.createSerializationContext(NbtOps.INSTANCE), new CompoundTag());
++        return new TagValueOutput(p_409887_, p_409738_.createSerializationContext(NbtOps.INSTANCE), new CompoundTag(), p_409738_);
+     }
+ 
+     public static TagValueOutput createWithoutContext(ProblemReporter p_405875_) {
diff --git a/src/main/java/net/minecraftforge/common/capabilities/CapabilityProvider.java b/src/main/java/net/minecraftforge/common/capabilities/CapabilityProvider.java
index 50a886bf2d..c6d6263720 100644
--- a/src/main/java/net/minecraftforge/common/capabilities/CapabilityProvider.java
+++ b/src/main/java/net/minecraftforge/common/capabilities/CapabilityProvider.java
@@ -13,6 +13,8 @@ import net.minecraft.world.item.ItemStack;
 import net.minecraft.world.level.Level;
 import net.minecraft.world.level.block.entity.BlockEntity;
 import net.minecraft.world.level.chunk.LevelChunk;
+import net.minecraft.world.level.storage.TagValueOutput;
+import net.minecraft.world.level.storage.ValueOutput;
 import net.minecraftforge.common.util.LazyOptional;
 import net.minecraftforge.event.AttachCapabilitiesEvent;
 import net.minecraftforge.event.ForgeEventFactory;
@@ -176,6 +178,16 @@ public abstract class CapabilityProvider<B extends ICapabilityProviderImpl<B>> i
         return capabilities;
     }
 
+
+    protected final @Nullable CompoundTag serializeCaps(ValueOutput output) {
+        if (isLazy && !initialized)
+            return lazyData;
+        var disp = getCapabilities();
+        if (disp == null || !(output instanceof TagValueOutput tagOutput) || tagOutput.lookup == null)
+            return null;
+        return disp.serializeNBT(tagOutput.lookup);
+    }
+
     protected final @Nullable CompoundTag serializeCaps(HolderLookup.Provider registryAccess) {
         if (isLazy && !initialized)
             return lazyData;