Jump Duplicator

Jump Duplicator is a server-side Fabric mod for Minecraft Java Edition 26.2. When a survival or adventure player starts a valid jump, nearby non-player entities are copied around the player.

Installation

1. Install Fabric Loader 0.19.3 or newer for Minecraft 26.2.
2. Install Fabric API for Minecraft 26.2 on the server.
3. Put the built jumpduplicator JAR into the server mods folder.
4. Start the server once to create config/jumpduplicator.json.

The mod runs its logic on the logical server. Clients do not need the mod installed for multiplayer servers.

Building

Use the Gradle wrapper:

./gradlew build

On Windows:

.\gradlew.bat build

The remapped mod JAR is written to build/libs/.

Commands

Root command aliases:

• /jumpduplicator
• /jumpdupe
• /jd

Available commands:

• /jumpduplicator help
• /jumpduplicator status
• /jumpduplicator enable
• /jumpduplicator disable
• /jumpduplicator reload
• /jumpduplicator radius <value>
• /jumpduplicator offset <value>
• /jumpduplicator amount <value>
• /jumpduplicator cooldown <ticks>
• /jumpduplicator maxentities <amount>
• /jumpduplicator notify <true|false>
• /jumpduplicator duplicate

Administrative commands require the configured vanilla permission level. /jumpduplicator duplicate manually runs duplication for the executing player.

Configuration

The config file is config/jumpduplicator.json and is created automatically on first launch.

{
  "enabled": true,
  "radius": 16.0,
  "verticalOffset": 1.0,
  "duplicationAmount": 1,
  "cooldownTicks": 1,
  "maximumEntitiesPerJump": 1000,
  "duplicateItems": true,
  "duplicateOnlySingleItems": true,
  "duplicateExperienceOrbs": true,
  "duplicatePassiveMobs": true,
  "duplicateHostileMobs": true,
  "duplicateVillagers": true,
  "duplicateProjectiles": true,
  "duplicateVehicles": true,
  "duplicateArmorStands": true,
  "duplicateTnt": true,
  "duplicateFallingBlocks": true,
  "duplicateOtherEntities": true,
  "copyVelocity": true,
  "copyCustomNbt": true,
  "requirePermission": false,
  "permissionLevel": 2,
  "notifyPlayer": false,
  "skipBosses": true,
  "skipTamedEntities": false,
  "skipNamedEntities": false,
  "safeSpawnCheck": true
}

Invalid values are clamped back to safe ranges during load. Use /jumpduplicator reload to reload the config without restarting.

Performance Warning

Entity duplication can create severe server lag. Keep radius, duplicationAmount, and maximumEntitiesPerJump conservative, especially on public servers or farms with many item entities.

Example Behavior

If a dropped stack of oak logs is within the radius and a player starts a valid jump, a copied item entity appears on the same X/Z position with verticalOffset applied. By default, item stack copies contain only 1 item, even when the original stack contains more.