Indestructible Spawners

Spawners, trial spawners and vaults become as indestructible as bedrock. Or, if you prefer, give them a custom hardness for each difficulty.

Server-side only: install it on the server (or in your own game for singleplayer). Players don't need it.

Features

By default, in every difficulty, spawners, trial spawners and vaults:

• can't be mined outside creative mode (the mining progress stops right away, as on bedrock);
• resist every explosion like bedrock: TNT, creepers, end crystals, beds, respawn anchors, ghast fireballs, Wither skulls (blue ones included). Like bedrock, they also shield the blocks behind them;
• can't be destroyed by the Wither charging through blocks;
• can't be destroyed by the Ender Dragon flying through them.

Creative players can still break them, as with bedrock.

Configuration

One hardness value per block (spawner, trial spawner, vault) and per difficulty:

For reference, vanilla hardness is 5 for spawners and 50 for trial spawners, vaults and obsidian. 0 breaks them almost instantly (the speed multiplier is capped at x1024, the maximum of the attribute). Hardcore worlds use the Hard value.

Singleplayer and LAN

With Mod Menu and Cloth Config installed, the settings are available in game. Changes apply immediately. Both mods are optional.

Dedicated server

Edit config/indestructiblespawners.json, then restart the server:

{
  "spawner": {
    "peaceful": -1.0,
    "easy": -1.0,
    "normal": -1.0,
    "hard": -1.0
  },
  "trial_spawner": {
    "peaceful": -1.0,
    "easy": -1.0,
    "normal": -1.0,
    "hard": -1.0
  },
  "vault": {
    "peaceful": -1.0,
    "easy": -1.0,
    "normal": -1.0,
    "hard": -1.0
  }
}

Invalid values (below -1, or between -1 and 0) and missing blocks are replaced by the default and logged. A config file from version 1.0.0 (a single set of values) is migrated automatically: its values are copied to all three blocks.

How it works

• Mining: the block's hardness is never changed, since vanilla clients would keep using the vanilla value and desync (blocks breaking, then reappearing). Instead, while a player mines a protected block, their block_break_speed attribute gets a temporary multiplier of vanilla hardness / configured hardness (0 when indestructible). Attributes are synced to the client, so both sides compute the same progress. The modifier is removed as soon as the player stops mining.
• Server-side guarantee: on top of that, the server refuses to break an indestructible block for a player outside creative, whatever the client sends.
• Explosions: indestructible blocks get bedrock's blast resistance, applied where every explosion reads it, so it also works with mods that replace the vanilla explosion code (such as Lithium). As a last safety net, they are removed from the final list of blocks an explosion destroys.
• Wither and Ender Dragon: vanilla uses the #minecraft:wither_immune and #minecraft:dragon_immune tags for this, but tags can't depend on the difficulty, so the mod adds its own check next to them.

Known limitation

The speed multiplier reaches the client after a network round trip. With very fast mining (Efficiency V netherite pickaxe plus Haste II) and a high ping, the client can predict a spawner breaking before it learns the new speed. The server refuses and the spawner comes back, but the client may show an empty cage, without the spinning mob, until the chunk reloads. This is purely visual: the spawner keeps working.

Compatibility

• Minecraft 1.21.2 to 1.21.11, Fabric Loader 0.20.1+. Fabric API is not required.
• Other mods that change block_break_speed keep working: the multiplier stacks with theirs.
• Compatible with Lithium's explosion optimizations.

License

MIT