Arclight not respecting level seed from server.properties. Always the same seed no matter what.

[ecoterrorist]

I have tried that...

• I am using the latest Arclight build

• I have read the FAQ and Troubleshooting, they didn't solve my issue

• I have searched existing Issues and found no duplicates

• The mods and/or plugins I use support my Minecraft version

• I have installed all required dependencies for the mods and/or plugins

• I have updated all mods and/or plugins to their latest versions

• This issue cannot be reproduced on a Spigot server
  (Mod-related issues are considered non-reproducible on Spigot)

• This issue cannot be reproduced on the Mod Loader server (Forge/NeoForge/Fabric)
  (Plugin-related issues are considered non-reproducible on mod loaders)

Minecraft Version

1.20.1

Arclight Version

arclight-1.20.1-1.0.6-SNAPSHOT-6de9fec

OS Version

Windows 10 AND Debian

Java Version

java 21.0.11 2026-04-21 LTS
Java(TM) SE Runtime Environment (build 21.0.11+9-LTS-211)
Java HotSpot(TM) 64-Bit Server VM (build 21.0.11+9-LTS-211, mixed mode, sharing)

Related Mods and/or Plugins (Name & Version)

NO mods
NO plugins

Issue Description

A freshly installed arclight server does not respect the level-seed property of the server.properties file or the level.dat files of imported worlds. This is true for an arclight server with no mods, no plugins, no custom configuration, no custom JVM arguments- nothing at all beyond what comes out of the box. Even with a newly generated server.properties file that has no seed argument specified (in which case the server should generate a random one).

Running the command /seed ALWAYS yields this output: Seed: [-2103864312]. It's always the same seed.

Going beyond simply running "/seed", I have visually confirmed that the seed is always the same by generating chunks with the Chunky mod and a world map with Bluemap.

The issue cannot be replicated on a similar Forge 1.20.1 server. Seeds behave as expected.

EDIT: I've discovered that purely numerical seeds still work as anticipated. Any non-numerical letters or characters result in the same "default" seed.

Steps to Reproduce

1. Install and run a fresh Arclight 1.20.1 server
2. Run the console command /seed
3. Observe that the output is "Seed: [-2103864312]"
4. Stop the server, delete the world folder, and set the level-seed property of server.properties to any custom value.
5. Start the server, and run /seed again
6. Observe that the output is still "Seed: [-2103864312]"

Server Logs

latest.log

The Server Pack for Reproduce

No response