CubeAnvil Join the waitlist
EARLY ACCESS Windows 10/11 · Fabric 1.20.1 & 1.21.1

Describe it. Forge it. Play it.

CubeAnvil is the Windows workspace where an AI agent writes your Minecraft Fabric mod, builds it, launches the game and tests it — while you review every single change.

Join the early-access list See how it works
Native Windows app Your files stay on your PC Every change undoable

Built for the real Fabric toolchain

Fabric 1.20.1 · Java 17 Fabric 1.21.1 · Java 21 Fabric Loom Gradle, warm daemon Yarn mappings Local projects
One feedback loop

From a sentence to a sword in your hand.

No tab maze, no copy-pasting stack traces. The idea, the code, the build and the running game live in a single window.

01 — OPEN

Start a project or bring your own

Create a prepared Fabric workspace for 1.20.1 or 1.21.1, or import a mod you already have. The right Java and Fabric setup is handled for you.

02 — DESCRIBE

Say what you want, in plain language

An item, a recipe, a block, a mob, a bug to fix. Attach a texture, a spec or a screenshot if it helps — the agent reads it too.

03 — REVIEW

Watch every change land

The agent's actions stream into the chat as it works. Open any file, edit it yourself, and undo with one click if you disagree.

04 — RUN

Launch Minecraft and try it

CubeAnvil builds the mod and starts the Fabric test client right inside the app. The agent can run commands and take screenshots to check its own work.

What's inside

An agent with the whole workbench.

Not a chatbot beside your editor. The agent has real tools — files, builds, the Minecraft API and the running game — and you see each one it uses.

An agent that actually plays your game

After a build, the agent can reload the client, run commands, send input and take a screenshot to confirm the result — then fix what it sees.

agent › build_project ✓ passed agent › game_restart client up in 14s agent › game_command /give @p crystalrealms:crystal_sword agent › game_screenshot saved · sword glows as expected agent › undo_point ✓ saved

Reads the real Minecraft API

Looks up classes and methods in Loom's Yarn-mapped sources instead of guessing.

class SwordItem extends ToolItem public postHit(ItemStack, LivingEntity, LivingEntity) // net.minecraft.item

Every change is reversible

Each edit is journaled. Roll back the last change, or a whole task.

Add Crystal Swordnow
Register recipeundo
Add Crystal Ore2m

Two Minecraft profiles

Pick your target version; the matching Java is set up automatically.

Minecraft1.21.1
RuntimeJava 21

Textures from a sentence

Ask for an item or block texture and get a transparent, vanilla-style PNG saved straight into your mod.

Promptblue crystal sword

Safe by default

New and imported projects start restricted until you trust them. The agent can't leave the workspace.

Project filesRead and edit inside the trusted folder
Everything outsidePaths are validated and blocked

Drop in anything you have

Concept art, design docs, spreadsheets, even another mod's JAR — the agent reads the contents, safely, without unpacking them to disk.

PNGconcept.png PDFspec.pdf DOCXlore.docx XLSXloot.xlsx PPTXpitch.pptx JARother-mod.jar

Plan first, then build

Switch to Plan mode and the agent only analyses. Read the plan, adjust it, and press Implement when you like it.

The agent's three-step plan with an Implement plan button

Minecraft settings, built in

Tune render distance, FPS, VSync, graphics and more for your test client without leaving the app. Changes save automatically.

The Minecraft settings panel with sliders and toggles
The real app

A workspace that stays out of your way.

Projects and files on the left, Minecraft in the middle, the agent on the right. Dark, fast and focused. These are real screenshots.

CubeAnvil while the agent works: a task checklist, its plan and a live list of actions such as editing files and generating an image A finished task in CubeAnvil: the agent summarises the new Storm Crystal item and the checks it passed The built-in code editor with a Java game test file open next to the project explorer Plan mode: the agent proposes a three-step plan and waits for you to implement it Minecraft settings built into CubeAnvil: render distance, frame rate, VSync, graphics and more
Task change history dialog with a Revert task button
You stay in control

AI that shows its work.

Powerful tools are only useful if you can trust them. CubeAnvil makes the agent's actions visible, bounded and reversible.

Visible actions

Every file read, edit, build and game command shows up in the work log as it happens.

Trusted workspaces

Imported projects stay restricted until you explicitly trust the folder.

Change history

Undo the last change or revisit a past task from the history window.

Action trace — Add the Crystal SwordCompleted
01
Read CrystalRealms.javaREAD · project file inspected
✓
02
Create CrystalSword.javaEDIT · new item class
✓
03
Register item and recipeEDIT · 3 files updated
✓
04
Build passedCHECK · no errors found
✓
05
Undo point createdSAVE · history updated
✓
Planned access

Simple plans, AI included.

The idea: one subscription covers the app and the AI usage, with no API keys to juggle. Plans are not final and nothing is charged today. Tell us which one fits you in the form below.

Free

$0

For learning and the occasional experiment.

  • Small monthly AI allowance
  • Economy model
  • Local projects, full editor
Get early access
Most popular

Builder

~$13/ month

For regular mod development.

  • Larger monthly AI allowance
  • More model choices
  • Stronger models for harder tasks
  • Game testing and texture tools
Join the waitlist

Pro

~$25/ month

For ambitious and frequent projects.

  • Highest monthly allowance
  • Access to the top flagship models
  • Room for long, heavy projects
Get early access

Prices are planned and approximate. Allowances and models may change before launch. Nothing is charged today.

Questions

Good to know.

Is CubeAnvil available now?
Not publicly yet — it's in active development. Join the early-access list and we'll email you when there's meaningful launch news.
Which platforms and Minecraft versions are supported?
CubeAnvil is a native Windows 10/11 app. It targets Minecraft Fabric, with prepared profiles for 1.20.1 (Java 17) and 1.21.1 (Java 21).
Do I need to know Java or how to mod?
No. Describe what you want in plain language and the agent writes and wires the code. If you do know Java, you can open and edit every file yourself — the agent works in your real project folder.
Where do my files live? Can the AI touch the rest of my PC?
Projects stay in the folder you choose. Imported projects start restricted until you trust them, and the agent's file access is limited to the workspace.
What if the AI breaks something?
Each change is recorded. You can undo the last change straight from the chat, or review past tasks from the history window.
Do I need my own AI API key?
No. The planned subscriptions include AI usage, so there is nothing to configure.
Does it support NeoForge or Forge?
Fabric comes first. Other loaders may follow after the first release.
Early access

Be first at the anvil.

Leave your email and tell us how you mod. We'll only write when there is real news — a build to try, or launch.

Your experience
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