BepInEx plugin for Facepunch.Steamworks split-screen multiplayer

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README.md

SplituxFacepunch

BepInEx plugin for splitux that enables local split-screen multiplayer in games using Facepunch.Steamworks.

Features

Identity Spoofing: Each instance gets a unique Steam ID and display name
Facepunch Library Patches: Patches SteamClient.SteamId, SteamClient.Name, IsValid, IsLoggedOn
Photon Auth Bypass: Sets AuthType=255 (None) for games using Photon networking
Runtime Patches: Apply game-specific patches via config (no recompilation needed)

How It Works

Splitux generates a BepInEx/config/splitux.cfg for each game instance. The plugin reads this config and applies:

Facepunch Settings - Toggle switches for known library patches
Runtime Patches - Game-specific class/method patches using Harmony

Configuration Format

[Identity]
player_index=0
account_name=Player 1
steam_id=76561198000000001

[Facepunch]
spoof_identity=true
force_valid=true
photon_bypass=true

[RuntimePatches]
patch.0.class=SteamManager
patch.0.method=DoSteam
patch.0.action=force_steam_loaded

patch.1.class=GameManager
patch.1.property=DisableSteamAuthorizationForPhoton
patch.1.action=force_true

Available Actions

Action	Description
`force_true`	Force bool return to true
`force_false`	Force bool return to false
`skip`	Skip original method entirely
`force_steam_loaded`	Set steamLoaded=true, steamId/steamName to spoofed values
`fake_auth_ticket`	Return fake Steam auth ticket string
`photon_auth_none`	Set Photon AuthType=255, random UserId
`log_call`	Log method calls (debug)

Splitux Handler Example

name: "Across The Obelisk"
steam_appid: 1385380
exec: "AcrossTheObelisk.exe"

facepunch_settings:
  spoof_identity: true
  force_valid: true
  photon_bypass: true

runtime_patches:
  - class: "SteamManager"
    method: "DoSteam"
    action: "force_steam_loaded"
  - class: "GameManager"
    property: "DisableSteamAuthorizationForPhoton"
    action: "force_true"
  - class: "NetworkManager"
    method: "GetSteamAuthTicket"
    action: "fake_auth_ticket"
  - class: "GameManager"
    method: "SteamNotConnected"
    action: "skip"

Supported Games

Games using Facepunch.Steamworks:

Across The Obelisk
(more as tested)

Building

dotnet build src/SplituxFacepunch.csproj -c Release

Output: src/bin/Release/net472/SplituxFacepunch.dll

License

MIT