Commonwealth Online is an experimental Fallout 4 multiplayer mod built around a dedicated relay server (Minecraft-style hosting), designed for larger sessions (16+ players at near-full release).

The project has a working multiplayer foundation: connected clients can see each other as synced proxy actors, observe movement and animation, and share appearance, clothing, and weapons. Gameplay systems such as quests, inventory, settlements, and VATS are not synced yet.

For how this project relates to DoxyCoSync (peer-to-peer co-op for small groups), see docs/project-comparison.md. The creators collaborate on research; the mods target different scales and architectures.

Project Goals

First Prototype

• Load a native Fallout 4 plugin through F4SE
• Connect to a local test server
• Send local player position data
• Receive remote player transform data
• Represent another connected player using a placeholder actor
• Restrict all testing to a custom test cell

Long-Term Ideas

• Basic LAN multiplayer test mode
• Remote player movement sync
• Basic animation state sync
• Basic chat or debug messages
• Host-controlled test cell
• Simple co-op combat arena

Non-Goals

This project is not currently trying to support:

• Full Fallout 4 campaign co-op
• Quest synchronization
• Settlement synchronization
• Full NPC/world state synchronization
• VATS synchronization
• Public server/MMO gameplay
• Compatibility with large modlists

Those systems are extremely complex and are outside the scope of the first prototype.

Repository Layout

docs/             Project documentation and research notes
plugin/           Native F4SE/CommonLibF4 plugin work
creation-kit/     Creation Kit plugin files, Papyrus scripts, and test cell notes
server/           External multiplayer test server
protocol/         Network packet design and sync documentation
tools/            Helper scripts and utilities
test-data/        Example packets and test data
screenshots/      Development screenshots

Requirements

This project is expected to require:

• Fallout 4 on PC
• Fallout 4 Script Extender, F4SE
• Fallout 4 Creation Kit
• Visual Studio 2022 or newer
• CMake or another supported C++ build system
• A CommonLibF4-based plugin template
• Git
• A clean Fallout 4 test profile

Recommended Development Setup

Use a separate Fallout 4 installation or a dedicated modding profile for testing.

Recommended setup:

Fallout 4
F4SE
Creation Kit
Mod Organizer 2 or Vortex
Visual Studio
Git

Use a clean test save and avoid testing with a full personal modlist.

Legal Notice

This repository does not include Fallout 4 game files, Bethesda assets, F4SE binaries, or any proprietary game code.

Users are responsible for owning Fallout 4 and installing required external tools themselves.

Status

Current status:

Functional multiplayer foundation
Dedicated Python relay server
Remote player proxy actors (movement, appearance, apparel, weapons)
Server profiles, LAN discovery, world time/weather sync
Quest, inventory, settlement, and combat sync not yet implemented

License

To be decided.