Claude-skill-registry custom-mob-spawn-egg

Use when adding spawn eggs or fixing spawn egg visual bugs (black square, grayscale, invisible).

install

source · Clone the upstream repo

git clone https://github.com/majiayu000/claude-skill-registry

Claude Code · Install into ~/.claude/skills/

T=$(mktemp -d) && git clone --depth=1 https://github.com/majiayu000/claude-skill-registry "$T" && mkdir -p ~/.claude/skills && cp -r "$T/skills/data/custom-mob-spawn-egg" ~/.claude/skills/majiayu000-claude-skill-registry-custom-mob-spawn-egg && rm -rf "$T"

manifest: skills/data/custom-mob-spawn-egg/SKILL.md

Custom Mob Spawn Egg Implementation Guide

Purpose: Ensure all required steps are completed when adding a spawn egg for a custom mob. Spawn eggs require multiple registration points across Fabric, NeoForge, and multi-version resource files. Missing any step causes visual bugs (grayscale, invisible texture).

Spawn Egg Implementation Checklist

When adding a spawn egg for a new custom mob, all of the following steps must be completed:

1. Item Registration (ModItems.java)

ModItems.java

for each version.

1.21.2 (requires

.setId()

public static final RegistrySupplier<Item> MOB_NAME_SPAWN_EGG = ITEMS.register(
    "mob_name_spawn_egg",
    () -> new com.chronodawn.items.DeferredSpawnEggItem(
        ModEntities.MOB_NAME,
        0xAABBCC, // Background color
        0xDDEEFF, // Spots color
        new Item.Properties()
                .setId(ResourceKey.create(Registries.ITEM,
                    ResourceLocation.fromNamespaceAndPath(ChronoDawn.MOD_ID, "mob_name_spawn_egg")))
    )
);

1.21.1 / 1.20.1 (simpler, no

.setId()

public static final RegistrySupplier<Item> MOB_NAME_SPAWN_EGG = ITEMS.register(
    "mob_name_spawn_egg",
    () -> new com.chronodawn.items.DeferredSpawnEggItem(
        ModEntities.MOB_NAME,
        0xAABBCC, // Background color
        0xDDEEFF, // Spots color
        new Item.Properties()
    )
);

2. Initialize Spawn Egg (ModItems.java)

Add the

initializeSpawnEgg()

call inside the

initializeSpawnEggs()

method:

if (MOB_NAME_SPAWN_EGG.get() instanceof com.chronodawn.items.DeferredSpawnEggItem) {
    ((com.chronodawn.items.DeferredSpawnEggItem) MOB_NAME_SPAWN_EGG.get()).initializeSpawnEgg();
}

3. Creative Tab Entry (ModItems.java)

Add to the

populateCreativeTab()

method:

if (MOB_NAME_SPAWN_EGG.isPresent()) {
    output.accept(MOB_NAME_SPAWN_EGG.get());
}

4. Item Model File (CRITICAL)

Without this file, the spawn egg will be completely invisible in the inventory.

Create

models/item/mob_name_spawn_egg.json

in all version resource directories:

common-1.20.1/src/main/resources/assets/chronodawn/models/item/

common-1.21.1/src/main/resources/assets/chronodawn/models/item/

common-1.21.2/src/main/resources/assets/chronodawn/models/item/

common-1.21.4/src/main/resources/assets/chronodawn/models/item/

Content (identical for all versions):

{
  "parent": "item/template_spawn_egg"
}

No custom texture file is needed - Minecraft generates the spawn egg texture procedurally from the two color values.

4a. Item Definition File (1.21.4 ONLY - CRITICAL)

1.21.4 introduced a new item definition system. Without this file, spawn egg colors will not display correctly.

Create

items/mob_name_spawn_egg.json

in the 1.21.4 resource directory:

common-1.21.4/src/main/resources/assets/chronodawn/items/

Note: This is a separate directory from

models/item/

- both files are required for 1.21.4.

Content:

{
  "model": {
    "type": "minecraft:model",
    "model": "minecraft:item/template_spawn_egg",
    "tints": [
      {
        "type": "minecraft:constant",
        "value": 10194798
      },
      {
        "type": "minecraft:constant",
        "value": 14329120
      }
    ]
  }
}

Color Value Conversion: The

tints

array uses decimal values, not hex:

First tint (index 0): Background color
Second tint (index 1): Spots color
Convert hex to decimal:
```
0x9B8B6E
```
→
```
10194798
```
,
```
0xDAA520
```
→
```
14329120
```
JavaScript conversion:
```
parseInt("9B8B6E", 16)
```
→
```
10194798
```

IMPORTANT: Colors must be specified in BOTH:

Java code (hex):
```
0x9B8B6E, 0xDAA520
```
in ModItems.java
JSON file (decimal):
```
10194798, 14329120
```
in items/*.json

5. NeoForge Color Handler Registration (CRITICAL)

Without this, the spawn egg will appear grayscale on NeoForge. Fabric handles this automatically via vanilla mechanisms, but NeoForge requires explicit registration.

File:

neoforge-base/src/main/java/com/chronodawn/neoforge/client/ChronoDawnClientNeoForge.java

Add

ModItems.MOB_NAME_SPAWN_EGG.get()

to the item list in the

onRegisterItemColors

method:

@SubscribeEvent
public static void onRegisterItemColors(RegisterColorHandlersEvent.Item event) {
    event.register(
        (stack, tintIndex) -> {
            if (stack.getItem() instanceof com.chronodawn.items.DeferredSpawnEggItem egg) {
                int color = egg.getColor(tintIndex);
                return 0xFF000000 | color;
            }
            return 0xFFFFFFFF;
        },
        // ... existing spawn eggs ...
        ModItems.MOB_NAME_SPAWN_EGG.get()  // <-- Add here
    );
}

6. Language Files

Add entries to both

en_us.json

and

ja_jp.json

for all 3 versions:

"item.chronodawn.mob_name_spawn_egg": "Mob Name Spawn Egg"

Common Issues

Symptom	Cause	Fix
Spawn egg invisible, or black square (dark purple on hover)	Missing item model JSON	Add `models/item/xxx_spawn_egg.json` with `"parent": "item/template_spawn_egg"`
Grayscale on NeoForge only	Missing NeoForge color handler	Add to `onRegisterItemColors` in `ChronoDawnClientNeoForge.java`
Correct on NeoForge, broken on Fabric	Missing `initializeSpawnEgg()` call	Add to `initializeSpawnEggs()`
No name displayed	Missing lang entry	Add to `en_us.json` / `ja_jp.json`
Not in creative tab	Missing creative tab entry	Add to `populateCreativeTab()`
Colors wrong on 1.21.4 only	*Missing items/.json with tints**	Add `items/xxx_spawn_egg.json` with tints array (1.21.4 only)
Colors mismatch between versions	Hex/decimal mismatch	Ensure Java (hex) and JSON (decimal) colors match

Why NeoForge Needs Explicit Color Registration

Minecraft spawn eggs use

tintIndex

(0 = background, 1 = spots) to colorize the template texture at runtime. Fabric integrates with vanilla's

ColorProviderRegistry

automatically through

DeferredSpawnEggItem

, but NeoForge uses its own event system (

RegisterColorHandlersEvent.Item

) which requires manual registration. The alpha channel (

0xFF000000 |

) must also be added explicitly on NeoForge.