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The Lost Cities - DevTool

Build Lost Cities packs in game, or open one you already have. Write your files with comments and .json5, and have mistakes caught at load time with a line number. Small bugs have optional fixes. KubeJS compatible.
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lostcities_devtool-1.21-1.21.1-3.2.0-8.x.jar

File namelostcities_devtool-1.21-1.21.1-3.2.0-8.x.jar
Uploader
RinkyNoobleRinkyNooble
Uploaded
Nov 7, 2026
Downloads
12
Size
391.5 KB
Mod Loaders
NeoForge
File ID
9484432
Type
R
Release
Supported game versions
  • 1.21.1
  • 1.21

Curse Maven Snippet

NeoForge

implementation "curse.maven:the-lost-cities-devtool-1654265:9484432"

Learn more about Curse Maven

What's new

3.2.0-8.x

For The Lost Cities 8.0.0 to 8.4.6, on Minecraft 1.21 and 1.21.1 with NeoForge 21.0 or 21.1. Needs Java 21 or newer.

The DevTool on NeoForge for the first time. Everything in 3.1.2-7.5 is here, with no new commands and no new settings. One file covers both Minecraft versions.

Your game Your Lost Cities Download
1.21.11, NeoForge 9.4.0 to 9.5.6 3.2.0-9.x
1.21 or 1.21.1, NeoForge 8.0.0 to 8.4.6 3.2.0-8.x
1.20.1, Forge 7.5.1 to 7.5.6 3.1.2-7.5-beta
1.20.1, Forge 7.4.12 3.0.0

Every Lost Cities 8.x works

The 8.x line changed a lot along the way, so some things depend on which one you have.

Your Lost Cities What is different
8.3.0 and newer Everything applies
8.2.6 The full street fix does nothing, because this version does not have that bug
8.0.0 to 8.2.5 The full street fix and the belowpart fix both do nothing. This code has no such bug and no such test. The log says so at startup
Before 8.3.0 A building keeps the floor count you gave its plot, although these versions have no overrideFloors. Under a profile other than the exported one, a higher minimum can still add floors

The workshop catalogue and the key reference describe 8.4.6. On an older Lost Cities, /lcdev workshop go says so, and any key your version does not read is ignored.

Moving down to an older Lost Cities in the same instance can stop it starting, because of the config a newer one left behind. Clearing config/lostcities cures it.

Different from Minecraft 1.20.1

A wrong-typed field in a pack file now stops the server. On 1.20.1 Lost Cities ignored it. On 1.21 Minecraft refuses the file at startup and names it. That covers a monorail part written as a list, a word under top or floor, a number under top, and a true or false under floor.

The load check now says this, and it flags "top": 1, which 1.20.1 accepted. Lost Cities only reads these files when the server starts, so an edit like this shows up on /reload as a warning about your next restart.

Known problems that are not this mod

Problem Where What to do
Chunks fail with Index -1 out of bounds for length 16 Lost Cities 8.3.0 to 8.3.2, with or without this mod Update to 8.3.3 or newer
The server never finishes stopping, if a chunk is being force loaded at that moment NeoForge 21.0 and 21.1, with no mods at all Wait a few seconds after /forceload before /stop

This mod has no additional files