The ultimate open-source Fabric utility mod. Experience autonomous building and a modern GUI designed for power users.
Auto-updating loader — always the right build for your Minecraft version. Pick a specific version instead
Features
TaskFlow — the brain of the client
One automation system, every module
Everything Lambda does in the world — walking, mining, placing, swapping items, eating — runs through one shared system. So your modules cooperate instead of each doing their own thing: a build can restock itself from a shulker, walk to the next section and eat on the way, without you touching anything.
Printer
Hand it a schematic and walk away. It finds the materials, moves itself into position and sets every block the right way round.
HighwayTools
Digs and paves for as long as you leave it running — straight or diagonal, floor, walls and ceiling.
InventoryTweaks
One click opens a shulker where you stand. Close it and the box is broken and back in your inventory.
Set up how you want blocks placed, how you rotate and how your hotbar is managed once, in an Automation Profile — and every module follows it. Swap profiles for a different server or a different job and the whole client moves with you, instead of you re-tuning ten modules by hand.
Automation Engine
Load a Litematica schematic and Lambda builds it for you — working out the order to place things, which way each block faces, and where to stand. Megabases and logos without the mouse arm.
Unmatched Performance
Highlight every chest, hole or bedrock block as far as you can see and watch your framerate stay where it was. Lambda draws thousands of blocks at once for what other clients charge you for a handful.
Sophisticated UX
Over 1000 settings you can actually find. Double-tap to search anything, snap your HUD to a grid, and keep whole setups as profiles you switch between in a click.
Safety & Tools
Developed and tested against Grim on 2b2t, so what works here works where you play. Elytra flight, building and movement are tuned on the server they were built for.
Download
One jar, and the client keeps itself current.
Lambda Loader
RecommendedA small jar that goes into your mods folder in place of the Lambda jar. On every launch it fetches the right build for you, so you never download the client by hand again.
Matches your Minecraft
Picks the build for whatever version you launch — no version guessing.
Verified downloads
Every build is checked against our servers before it loads, so you always get the real thing.
Updates itself too
The loader keeps both the client and itself up to date.
Tracks development builds out of the box. Switch it to stable-only under
AutoUpdater → Client Branch in the client.
New here? Follow the installation steps — the loader still needs Fabric API, Kotlin and Baritone alongside it.
Need a specific version instead?
Pinned jars for when you need one exact build — reproducing a bug, staying on a known-good version, or running without the auto-updater. These do not update themselves.
Stable Releases
Development Snapshots
Join the Community
Get support, share configs, and stay updated with development.
Installation
Lambda is a Fabric mod for Minecraft ....
Every jar listed below goes into the same mods folder.
Required mods
Java 21 · Minecraft ...Lambda will not start without these. Match the Minecraft version exactly.
Fabric Loader
The mod loader itself. Install it with the official installer, then launch the Fabric profile.
Fabric API
Core hooks every Fabric mod builds on. Drop the jar into mods.
Fabric Language Kotlin
Lambda is written in Kotlin, so this runtime is mandatory — not optional.
Baritone read this
Pathfinding backend for HighwayTools, Printer and every walking task. Vanilla Baritone has no build for this Minecraft version — use rfresh2's Fabric build, linked here.
Recommended
Not required to launch, but some modules stay idle without them.
Step by step
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1
Install Minecraft ...
Run it once through the official launcher so the version files exist. Java 21 or newer is required.
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2
Install Fabric Loader
Use the Fabric installer and pick Minecraft .... This creates a new launcher profile.
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3
Collect the dependencies
Download Fabric API, Fabric Language Kotlin and Baritone from the cards above. All three are jars — keep them together.
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4
Get Lambda
Grab the Lambda jar from the download section — or the Lambda Loader if you want the client to keep itself up to date.
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5
Drop everything into
modsAll jars live side by side in
.minecraft/mods:.minecraft/mods/ ├── lambda-....jar ├── fabric-api-*.jar ├── fabric-language-kotlin-*.jar ├── baritone-fabric-*.jar └── litematica-*.jar # optional, for PrinterWindows:
%appdata%\.minecraft\mods· Linux:~/.minecraft/mods· macOS:~/Library/Application Support/minecraft/mods -
6
Launch & verify
Start the Fabric profile, join any world and press Y. The Lambda GUI should open.
Game crashes on startup?
- A missing Baritone jar crashes development snapshots. Install it even if you never touch pathfinding.
- Every jar must target Minecraft .... A dependency built for another version is the most common cause of failure.
- Still stuck? Post your
latest.login our Discord — someone will get you running.