SteonMod documentation
SteonMod lets you fuse the games you own: play one game's character in another game's world, or build something new out of pieces of several, with cards and no code. These pages cover playing it, building with it, and making routers, the small free add-ons that teach Fusion a game.
About
- What is SteonMod?SteonMod lets you fuse the games you own : play Minecraft's character in another game's world, drop one game's creatures into a playground, or build a whole new game out of pieces…
- Staying safeFusion runs other programs and changes games, so it's worth knowing exactly what it does. What Fusion does to your games It starts them for you , the way their router says (usuall…
- Fixing problems and FAQFusion tries to say what went wrong in plain words. Here are the common ones and what to do. Fusion doesn't start "Windows protected your PC" when installing: the installer isn't…
Getting started
- Installing FusionWhat you need Windows 10 or 11, 64 bit. A graphics card with DirectX 12 (most from 2016 on). Fusion and your games share it. Enough memory for two games at once. 16 GB of RAM work…
- Your first fusionThis page walks you from the main menu to playing, in about five minutes. The main menu Fusion opens on Play : Experiences show as covers: a picture, what it is, which games it ne…
- My GamesMy Games lists every game Fusion found on your PC and what it can do with each. Steam games are found from your Steam libraries; other games are found by their router. What each s…
- Building with cardsBuild a Scenario in the main menu makes a scenario without writing any file. It has three parts: Left: cards. Every block from every router you have, grouped by game. Cards of gam…
- The sandboxEvery plain scenario is a sandbox, like Garry's Mod: spawn things from any game in it, carry them around, weld them, change them. (Experiences decide what you may do, so some of t…
- DevicesDevices are Fusion's no code building pieces. Put one in the world, change its settings, and it does its job: show a message, count down, react when you walk somewhere, drop props…
- Getting contentContent in the main menu is where routers, scenarios, Experiences, addons and Devices come in. They come from two places: The content hub : steonmod.com's list of signed packages.…
Making routers
- Start hereFor people who connect a game to Fusion, and for the AI agents they work with. Read this page first; it says which other page you need. A router connects one game to Fusion. It sp…
- Porting your passthrough modFor authors of passthrough mods (a SkyCraft port, "Minecraft in ", a ReShade bridge) who want their game in Fusion. Start with making routers.md if you haven't. What you keep is w…
- The Router APIA router splits one game into blocks (see block manifest.md ). The Router API is how a router tells the game's kit where those blocks are inside the game: which character is the p…
- Router manifests and scenariosTwo small TOML files describe everything Fusion needs to fuse games: File Written by Says router.toml (one per game) router makers which blocks a game offers, what each one needs…
- Guest SDKFor programs whose source you have (open source games, Rust rewrites, recomps, your own game), and for your own plugin inside a closed game (a BepInEx or MelonLoader plugin, an SK…
- The agent pack (for AI agents)name: fusion router description: Make, fix or extend a Fusion router (routers/ /router.toml, router.lua, or a game plugin on Fusion's guest SDK) for any game, or bring a passthrou…
- Cheaper AI agentsWritten 2026 10 03 from research done that day (sources at the end). The user's goal: making a fusion in Fusion should cost a developer's AI agent far fewer tokens than today's ha…
- Packages and publishingBUILD.md step 4.6. Code: crates/fusion core/src/content.rs (format, sources, resolution, install), crates/fusion godot/src/content.rs ( FusionContent ), godot/scripts/content brow…
- Signatures and trustBUILD.md steps 6.1 6.3, VISION.md §9 ("Trust & safety") and §11 (takedown rules). Code: crates/fusion core/src/trust.rs , publish.rs , content.rs ; commands in fusion cli keys , p…
Kits
- Unreal kitMakes an Unreal Engine game a Fusion guest. Built in BUILD.md step 1.4 with VEIN Demo (Unreal 5.6, D3D12) as the first game. It shows the game's world inside Fusion, drawn from Fu…
- Unity kitMakes a Unity game a Fusion guest. Built in BUILD.md step 7.1 with The Long Dark (Unity 6, IL2CPP, Direct3D 11) as the first game. It shows the game's world inside Fusion, drawn b…
- Minecraft (Fabric) kitOur fork of SkyCraft's Fabric mod (MIT, see THIRD PARTY NOTICES.md at the repo root). It started as an exact copy of third party/skycraft/fabric (commit bfcaf17 ) in BUILD.md step…
- Bevy pluginA game made with Bevy (0.19) joins Fusion as a guest by adding one plugin and marking things with components. Its own systems keep running every mechanic; the plugin only shows Fu…
Scripting
- Lua APIAddons are small Lua programs that add things to Fusion: tools, props, game modes, rules. Fusion uses Luau (the Lua used by Roblox), so anything you know from Lua or Garry's Mod m…
Reference
- Fusion protocolHow Fusion and a guest game talk. The exact byte layout is defined in schema/fusion.fidl ; this page explains the ideas. The pieces Piece What it is Who writes Discovery mapping L…
- Schemas and type filesFiles for editors and AI agents. Point your editor's TOML or JSON support at the schemas, and your Lua language server at the type files, and you get completion and errors as you…
- Design decisionsShort records of choices that shaped Fusion, with what was considered and why. Each one is kept as written; a later decision that changes one says so. Decision 0001 Composite gues…
Contributing
- Releasing FusionBUILD.md steps 6.4 6.6. Code: tools/fusion cli/src/release.rs (making a release), tools/fusion launcher ( Fusion.exe : installer, launcher, updater), crates/fusion core/src/releas…