Just for sanity sake

Common/src/main/java/com/hypherionmc/craterlib/core/networking/CraterPacketNetwork.java

@@ -15,14 +15,27 @@ public class CraterPacketNetwork {
 
     private final PacketRegistry packetRegistry;
     public static CraterPacketNetwork INSTANCE;
+    private static DeferredPacketRegistrar delayedHandler;
 
     public CraterPacketNetwork(PacketRegistry registry) {
         INSTANCE = this;
         this.packetRegistry = registry;
+        getDelayedHandler().registerQueuedPackets(registry);
+    }
+
+    private static DeferredPacketRegistrar getDelayedHandler() {
+        if (delayedHandler == null) {
+            delayedHandler = new DeferredPacketRegistrar();
+        }
+        return delayedHandler;
     }
 
     public static <T> PacketRegistrar registerPacket(ResourceLocation id, Class<T> messageType, BiConsumer<T, FriendlyByteBuf> encoder, Function<FriendlyByteBuf, T> decoder, Consumer<PacketContext<T>> handler) {
-        return INSTANCE.packetRegistry.registerPacket(id, messageType, encoder, decoder, handler);
+        if (INSTANCE != null) {
+            return INSTANCE.packetRegistry.registerPacket(id, messageType, encoder, decoder, handler);
+        } else {
+            return getDelayedHandler().registerPacket(id, messageType, encoder, decoder, handler);
+        }
     }
 
     public PacketRegistry getPacketRegistry() {

Common/src/main/java/com/hypherionmc/craterlib/core/networking/DeferredPacketRegistrar.java

@@ -0,0 +1,41 @@
+package com.hypherionmc.craterlib.core.networking;
+
+import com.hypherionmc.craterlib.core.networking.data.PacketContext;
+import com.hypherionmc.craterlib.core.networking.data.PacketHolder;
+import com.hypherionmc.craterlib.core.networking.data.PacketSide;
+import net.minecraft.network.FriendlyByteBuf;
+import net.minecraft.resources.ResourceLocation;
+
+import java.util.HashMap;
+import java.util.Map;
+import java.util.function.BiConsumer;
+import java.util.function.Consumer;
+import java.util.function.Function;
+
+/**
+ * Based on https://github.com/mysticdrew/common-networking/tree/1.20.4
+ */
+public class DeferredPacketRegistrar implements PacketRegistrar {
+
+    private static final Map<Class<?>, PacketHolder<?>> QUEUED_PACKET_MAP = new HashMap<>();
+
+    @Override
+    public PacketSide side() {
+        return PacketSide.CLIENT;
+    }
+
+    @Override
+    public <T> PacketRegistrar registerPacket(ResourceLocation packetIdentifier, Class<T> messageType, BiConsumer<T, FriendlyByteBuf> encoder, Function<FriendlyByteBuf, T> decoder, Consumer<PacketContext<T>> handler) {
+        PacketHolder<T> container = new PacketHolder<>(packetIdentifier, messageType, encoder, decoder, handler);
+        QUEUED_PACKET_MAP.put(messageType, container);
+        return this;
+    }
+
+
+    public void registerQueuedPackets(PacketRegistry packetRegistration) {
+        if (!QUEUED_PACKET_MAP.isEmpty()) {
+            packetRegistration.PACKET_MAP.putAll(QUEUED_PACKET_MAP);
+            QUEUED_PACKET_MAP.forEach((aClass, container) -> packetRegistration.registerPacket(container));
+        }
+    }
+}