CobbleStacker

CobbleStacker is a server-side Fabric mod for Minecraft 1.21 designed to significantly reduce entity lag by intelligently stacking mobs, ground items, and spawners. Fully compatible with Cobblemon — all Pokemon are
automatically excluded from stacking.

Mob Stacking

• Automatically merges nearby identical mobs into a single entity with a visible nametag (e.g. "x16 Zombie")
• Respects mob attributes: variant, color, size, baby/adult, tamed owner, profession, and more
• Configurable death behavior: KILL_ONE (kills one and respawns the stack with reduced count) or KILL_ALL (kills the entire stack with multiplied drops and XP)
• Entities with name tags can be excluded from stacking

• Blacklist support by entity type and world

  Item Stacking

• Merges ground items of the same type beyond vanilla limits (up to 1024 per stack by default)
• Custom nametags showing the real item count
• Built-in auto-clear system that removes old item stacks after a configurable time, with a whitelist for valuable items

• Manual clearlag command for instant cleanup

  Spawner Stacking

• Stack multiple spawners of the same type by right-clicking with a spawner in hand
• Floating hologram displays the spawner type and stack count
• Mobs spawned from stacked spawners come out pre-stacked
• Silk Touch support for spawner drops
• Automatic spawner property repair to prevent broken spawners

• Persistent data saved to JSON

  General

• Fully configurable via cobblestacker.json
• Admin commands: /cobblestacker reload, stats, info, kill, clear, clearlag, debug, fixspawner, setstack
• Lightweight and optimized with batch processing, caching, and minimal overhead
• No client-side installation required