
Modrinth · Minecraft mod
SecondBrain
AI-powered NPCs that chat and play like real players
Quick answer
Which SecondBrain release matches 1.20.4 Fabric?
SecondBrain 1.0.9 targets 1.20.4 with Fabric. Installation on the client is optional. Installation on the dedicated server is optional. 1 required mod needs a matching file.
Where it goes
Is SecondBrain required on the client, server, or both?
Installation on the client is optional. Installation on the dedicated server is optional.
The source marks this as usable on both the client and server.
What else does SecondBrain 1.0.9 need?
1.0.9 on 1.20.4 Fabric. Every mod below is checked against that same setup.
Install Fabric API first, but 1 required mod has no matching file for this setup. Do not mix loader builds to force a match.
We only count dependency files that match this setup. A file for another loader does not fill the gap.
Before you install it
Add SecondBrain without breaking your instance.
Built for SecondBrain 1.0.9 on 1.20.4 Fabric. Pick another file and the loader, install side or required mods may change.
- 01
Stick to this file
Use 1.0.9. It targets 1.20.4 with Fabric; another release may have different loader, side or dependency requirements.
- 02
Bring the mods it needs
Install Fabric API first, but 1 required mod has no matching file for this setup. Do not mix loader builds to force a match.
- 03
Put it on the correct side
Installation on the client is optional. Installation on the dedicated server is optional.
- 04
Pick the file you checked
Use the “Get this file” button beside 1.0.9. It opens that exact file at the source.
About this project
What does SecondBrain add?
SecondBrain

A Fabric mod that brings intelligent NPCs to your minecraft world. Create player-like characters controlled by LLMs that respond to your chat messages and perform basic player actions.
This mod works fully serverside. It must also be installed on a client for setup.
Requirements
- Minecraft Version: 1.20.1/1.21.1
- Running Ollama server OR Player2 App OR an OpenAi Key
Mod Installation
- Download the Mod:
- Get the latest version of the
SecondBrainmod from the Modrinth page.
- Get the latest version of the
- Install the Mod:
- Place
secondbrain.jarin yourmodsfolder on your minecraft fabric server and client.
- Place
- Launch Minecraft:
- Start the Minecraft client and the server, and you're ready!
Usage with Ollama/OpenAi
Note: Player must be an operator to execute the following commands
GUI
- Open the gui with the
/secondbraincommand and create/spawn, despawn/delete or edit the NPCs there. - Also edit the base configuration there.
Commands (Deprecated)
Warning: This command uses default ollama/openai settings!
Spawn NPCs:Use the/secondbrain add <npcname> <openai|ollama>(currently only ollama is supported) command to create an NPC. (Example: `/secondbrain add sailex428 OLLAMA)
Remove NPCs:Use the/secondbrain remove <npcname>command to remove an NPC from the game world.
Interact with NPCs:
- Just write in the chat to interact with the NPC.
Setup Ollama
Ollama (Local LLM)
Download Ollama:
- Visit Ollamas Website and download the installer for your operating system.
Install and Run Ollama:
- Follow the setup instructions to install.
- Start Ollama and ensure it's running in the background.
Connect to the Mod:
- Use the gui to create/edit an NPC and put in the address to your ollama server (complete url with http://...;
if you're running your ollama on your local pc then you can just use the one that's already typed in)
- Use the gui to create/edit an NPC and put in the address to your ollama server (complete url with http://...;
Setup OpenAi (Paid)
- Create API Key
- Visit OpenAi's website, sign up/log in and create a API key
- Copy the created key
- Use the Key in the mod
- Open the GUI and create an NPC with the LLM Type
OPENAIand paste key into the Key field. (The key wont be ever shared with any other clients that has access to the GUI, also not your client. It will be saved in a secondbrain config file on the server)
- Open the GUI and create an NPC with the LLM Type
Usage with Player2 App
The mod will automatically sync the selected Characters from the player2 App to NPCs in your singleplayer world.
If you updated a description/name in the player2 App you can sync these changes with the command/secondbrain player2 SYNC
It's not possible to change any configs from the Character with this mod.
Interact with NPCs
- Write messages in the chat or directly to a specific NPC
- Press and hold alt (win) or opt (macOS) key to talk directly to the LLM/AI
- Activate Text-To-Speech for any NPC in the config gui to hear the LLM/AI output
Setup Player2 (Free, Limited)
Download Player2 App
- Visit player2's website and download the App for your operating system.
Start the App and select Characters
- Start the downloaded App and select the Characters you wanna use as NPCs
License
This project is licensed under the LGPL-3.0
Disclaimer
Credits
This project utilizes components from the following projects:
Thank you to the developers of these projects for their amazing work!
Project description from Modrinth.
Pick your setup
SecondBrain by Minecraft version and loader
Choose the version and loader you play, then open the matching release.
1.21.11
1 loader build1.21.10
1 loader build1.21.8
1 loader build1.21.3
1 loader build1.21.1
1 loader build1.20.4
1 loader build1.20.3
1 loader build1.20.1
1 loader buildCheck the dependencies, then try the file in a copied instance before changing a world you care about.
Recent files
SecondBrain versions and loaders
1.0.9
ai-npc-launcher-1.20.4-v1.0.9-fabric-beta.jar
28 Dec 2024
1.0.8-beta
ai-npc-launcher-1.20.4-v1.0.8-fabric-beta.jar
28 Dec 2024
1.0.7-beta
ai-npc-launcher-1.20.4-v1.0.7-fabric-beta.jar
15 Dec 2024
1.0.6-beta
ai-npc-launcher-1.20.4-v1.0.6-fabric-beta.jar
11 Dec 2024
1.0.5-beta
ai-npc-launcher-1.0.5.jar
16 Nov 2024
1.0.4-beta
ai-npc-launcher-1.0.4.jar
14 Nov 2024
1.0.3-alpha
ai-npc-launcher-1.0.3.jar
12 Nov 2024
1.0.1-alpha
ai-npc-launcher-1.0.1.jar
8 Nov 2024
Looking for an older file? The official Modrinth project page is in Resources.