FUSE

FUSE is a modding layer for Railroader. It loads FUSE packages — custom maps, routes, scenery, industries, and audio — and runs your existing legacy mods through a built-in compatibility layer. It runs on Unity Mod Manager.

Documentation

Full documentation is in docs/.

• New to FUSE: Getting Started · FAQ
• Coming from Railloader or another legacy stack: Migrating From Legacy Mods
• Reference: Settings · Console Commands · Troubleshooting
• Authoring: Package Author Guide · Converter · External Editor
• Contributing: CONTRIBUTING.md · Architecture

What it adds

• Custom maps — whole replacement worlds, picked from a map dropdown on the New Game screen
• Routes and track — extensions, new segments, switches, turntables
• World scenery — buildings, map labels, speed signs, telegraph poles
• Operations — industries, loads, stations, passenger stops, team tracks, interchanges
• Progression — sections, delivery phases, and unlock-gated map features
• Audio — whistles, horns, and bells

FUSE itself adds no content. It is the layer that loads content packages.

Your existing mods keep working

Packages built for Railloader, Strange Customs, ConfusingSupplements, For Your Convenience, and Alina's Map Mod load through FUSE's compatibility layer. Package authors can also convert them to the FUSE format with the converter — see docs/FUSE_CONVERTER.md.

Requirements

• Railroader 2025.1.x
• Unity Mod Manager (UMM)

Installation

1. Install Unity Mod Manager and point it at your Railroader install.
2. Download FUSE-v<version>.zip from the releases page or from Nexus Mods.
3. Install it:
   • GitHub download: drag the zip onto UMM's Mods tab, or extract its FUSE folder to Railroader/Mods/FUSE.
   • Nexus download: extract the zip and run FUSE-Installer.exe, or copy the adjacent FUSE folder to Railroader/Mods/FUSE by hand. When you are done, Railroader/Mods/FUSE/FUSE.dll and Railroader/Mods/FUSE/Info.json should both exist.
4. Start Railroader and load a map.

Open the console and run /fuse.report to confirm it loaded. The FUSE icon also appears in the top bar, and FUSE writes its own FUSE.log next to Railroader's Player.log.

Do not nest the folder. Railroader/Mods/FUSE/FUSE/FUSE.dll is wrong and FUSE will not load.

For the longer version, including the optional converter and installer tools, see docs/INSTALL.md.

Installing content packages

Each FUSE package is its own folder under Railroader/Mods, installed exactly like FUSE itself. Install any asset packs a package lists as required, then run /fuse.loaded to confirm FUSE picked them up.

FUSE respects Unity Mod Manager's enabled checkbox — a package you disable in UMM is marked disabled by FUSE, and its track and data files are not loaded.

Updating

1. Back up your saves and the current Railroader/Mods/FUSE folder.
2. Replace the FUSE mod folder with the new build.
3. Re-run the matching converter when the converter or schema version changes.
4. Start the game and check /fuse.report.

Do not mix legacy and converted FUSE copies of the same route unless you are deliberately testing conflicts.

Uninstalling

1. Exit Railroader.
2. Remove or disable converted *.FUSE packages first.
3. Remove or disable Railroader/Mods/FUSE.
4. Restore the previous mod folders and save backup if needed.
5. Start the game and verify the legacy stack or vanilla game loads normally.

Good to know

• Multiplayer is compatibility mode only. FUSE does not sync package contents over the network. Every host and client applies its own local package stack, matching the legacy Railloader expectation that everyone has the same mods installed. Non-host clients log a warning the first time they apply runtime world changes. Servers that want strict client blocking can set Settings.BlockNonHostMultiplayerClientWorldApply to true.
• FUSE does not add rolling stock or locomotive/car mods, apart from audio definitions it can import.
• The in-game editor was retired in 1.0. Authoring happens in the standalone external editor; FUSE still discovers and loads custom map packages at runtime.
• Arbitrary legacy script mods are not supported — only data, asset, audio, and supported runtime component packages.
• Mid-session scene-path suppression cannot be re-enabled.
• Three-way switches are unsupported, because Railroader does not treat them as normal graph switches.

Having trouble?

Work through docs/TROUBLESHOOTING.md first, then file a report with the bug report form, which requires the diagnostics below before it will submit:

• FUSE.log
• Player.log
• The output of /fuse.report
• The output of /fuse.loaded when package state matters
• The output of /fuse.conflicts when conflicts are reported
• The converter conversion-report.json and conversion-report.md for the affected package
• Screenshots and the exact mod/package list

Support priority goes to issues reproducible with a minimal converted package, or against a documented legacy route covered by the converter.

Runtime diagnostics

The top-bar FUSE icon opens the FUSE menu. The Status tab shows the latest load report; the Tools tab carries the Object Inspector, dependency/asset/diagnostics reports, scenery benchmarks, and Runtime Actions (Reload Track/Data, Reload Terrain, Rebuild Caches) for testing and recovery. Check FUSE.log after using a reload action.

The Dependency Graph includes equipment and asset/code packages, not only FUSE map data. It reads local FUSE, UMM, RailLoader, and AssetLoader metadata plus the installer's offline Nexus cache, and shows missing/disabled/incompatible requirements with their version bounds. The in-game menu does not contact Nexus.

Useful console commands:

• /fuse.report - show the current human-readable load report
• /fuse.report json - show the current load report as structured JSON
• /fuse.loaded - list loaded packages and apply state
• /fuse.conflicts - show ownership/conflict records
• /fuse.graph - summarize graph state
• /fuse.operations - summarize operations state
• /fuse.progressions - summarize progression state
• /fuse.assets - list discovered asset pack folders
• /fuse.maps - list maps registered by FUSE map packages and the active session map
• /fuse.map.launch <mapId> [railroadName] [reportingMark] - launch a new sandbox session on a registered FUSE map (main menu only)
• /fuse.dumpgraph - write the captured original graph to FUSE-original-graph.json
• /fuse.dumpruntimegraph - write the active post-FUSE graph to FUSE-runtime-graph.json
• /fuse.dumpmandelas - write scene clone and world path data to FUSE-mandelas.json

Experimental commands:

• /fuse.reapply
• /fuse.restore

Experimental commands should not be used during normal play unless testing recovery.

The full reference, including the commands not listed above, is in docs/CONSOLE_COMMANDS.md. Settings are documented in docs/SETTINGS.md.

Supported package types

FUSE supports these package categories:

• Route/data packages with *.fuse.json files
• Map tile overlays
• Custom map packages selectable from a dedicated New Game map dropdown, with Railroader's existing control retained separately for starting progression
• Asset packs, including direct nested asset pack discovery under converted mod folders
• Track graph nodes, segments, spans, areas, groups, removals, and turntables
• World scenery, scene clones, map labels, speed signs, map masks, splineys, telegraph poles, telegraph pole movements, and spawn points
• Operations data: loads, industries, loaders, stations, passenger stops, team tracks, repair tracks, interchanges, interchanged loaders/unloaders, teleport loading, formulaic components, progression industry components, and custom industry components from loaded assemblies
• Progression sections, delivery phases, unlock-triggered map features, mixinto requirements, and map feature enable/disable flows
• Audio packs for whistles, horns, and bells

The FUSE JSON schema lives at schemas/fuse-mod.schema.json. The hand-written schema notes live at schemas/FUSE_JSON_SCHEMA.md.

Supported game version

• Supported Railroader line: 2025.1.x
• Current verified build in logs: 2025.1.0
• Current FUSE schema version: 1.0
• Current converter version: 0.2.0

FUSE logs its version report at startup in FUSE.log.

Known limitations

FUSE repairs many legacy data issues during conversion, but it does not silently hide authoring errors. Unsupported graph shapes, missing hard dependencies, invalid spans, and missing runtime component assemblies should be reported by the converter or runtime instead of being dropped.

See docs/KNOWN_ISSUES.md and docs/TROUBLESHOOTING.md for the current issue list and debugging workflow.

License

Copyright (C) 2026 FUSE Development Group and contributors.

FUSE is free software: you can redistribute it and/or modify it under the terms of the GNU Affero General Public License as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later version.

FUSE is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Affero General Public License for more details.

The full license text is in LICENSE, and is also available at https://www.gnu.org/licenses/agpl-3.0.html.

The AGPL covers FUSE's own source. It does not extend to Railroader, Unity, or Unity Mod Manager, whose assemblies FUSE builds against and which remain under their own proprietary terms; those assemblies are not redistributed here.

Local development

Requirements

• Visual Studio (in the installer, make sure you have SDKs for .NET Framework 4.8 and C# Support)
• A .NET 10 SDK — several projects in the solution target net10.0

To start developing FUSE locally, follow these steps:

1. Clone this repo locally
2. Copy Paths.user.example and save it as Paths.user
3. Open this Paths.user file
4. Update the path entries for your local Railroader installation
5. Open the project in Visual Studio
6. Build the project
   • EnableModDeploy is set to true by default which will automatically build to your Railroader/Mods directory. This setting can be configured inside Paths.user

You do not need Railroader installed to build. Without GameDir set, the build falls back to the checked-in reference assemblies under lib/refs.

See CONTRIBUTING.md for the testing policy, code conventions, and PR process, and docs/ARCHITECTURE.md for how the projects fit together.

Contributing

Contributions are welcome — start with CONTRIBUTING.md. Security issues should be reported privately per SECURITY.md, not through the public issue tracker.

See AGENTS.md for skill and sub-agent routing, and docs/RELEASING.md for how releases are cut.