nucleus-xinput-steampatch

XInput proxy DLL that filters controllers per game instance, surviving Steam overlay function hooking.

Built for Nucleus Co-op split-screen scenarios where each instance should see only its assigned controller.

Fixed issue emerged by latest Windows/Steam updates (circa 15.04.2026), where controller input goes to every Nucleus instance, regardless of settings or HidHide.

Quick How-To for NucleusCoop!

Copy whole repo or just get xinput1_3.dl_ files from x64/x86 dirs. Backup NucleusCoop\utils\XInputPlus\x86 and x64 dirs. Copy and replace those two files to NucleusCoop\utils\XInputPlus\x86 and x64 respectively.

Problem

When using XInputPlus-style proxy DLLs to separate controllers between game instances, Steam overlay (gameoverlayrenderer.dll) overwrites the proxy's XInputGetState export with a JMP detour to its own handler. Steam's handler calls the system xinput1_4.dll directly, completely bypassing the proxy's controller filtering. This causes all instances to respond to all controllers.

This happens even when the Steam overlay is disabled in Steam settings — the DLL is still injected and hooks are still installed.

What doesn't work

Approach	Why it fails
Using HidHide to hide duplicated controlers in system	No duplicated controlers in system, but input still goes to every instance
Disabling Steam Input for the given game	No effect, still duplicated input
Restoring original function bytes	Steam re-hooks immediately (every frame)
Reading bytes from DLL on disk	The compiler emits JMP thunks — disk bytes are also JMPs
Goldberg Steam Emulator	Bundled version too old for modern Steamworks SDK
Stub gameoverlayrenderer.dll in game folder	Steam injects via full absolute path, ignores local DLL
Disabling overlay in Steam settings	DLL is still injected and hooks still installed

Solution

Instead of fighting Steam's hook, take it over:

1. A background thread sleeps 3 seconds (giving Steam time to install its hooks)
2. Reads the JMP rel32 target address from our hooked XInputGetState — this is Steam's internal handler
3. Overwrites the JMP to point at our filtering trampoline instead
4. Our trampoline applies the controller map from XInputPlus.ini, then calls Steam's handler with the remapped index
5. Monitors for 60 seconds in case Steam re-hooks

Call flow

Game calls XInputGetState(0)
  → [our xinput1_3.dll export]
    → [JMP — rewritten to point at our trampoline]
      → hooked_getstate(0)
        → g_map[0] == -1? → return ERROR_DEVICE_NOT_CONNECTED
        → g_map[0] == 2?  → call Steam_handler(2, pState)
          → Steam overlay internals
            → system xinput1_4.dll

Building

Requires Visual Studio Build Tools (or full Visual Studio) with the C++ desktop workload.

build.bat

Produces 4 DLLs:

x86\xinput1_3.dll    x86\xinput1_4.dll
x64\xinput1_3.dll    x64\xinput1_4.dll

Choose the DLL matching your game's architecture (x86/x64) and XInput version (1_3/1_4). Most older games (XNA, Unity 4) use xinput1_3.dll. Newer games often use xinput1_4.dll.

Usage with Nucleus Co-op

1. Build or download the DLLs
2. Pick the correct variant for your game (e.g. x86\xinput1_3.dll for Terraria)
3. Replace NucleusCoop\utils\XInputPlus\x86\xinput1_3.dl_ (or the x64 equivalent) with the built DLL
   (Nucleus renames .dl_ → .dll when copying to game instances)
4. Ensure the game handler has Game.XInputPlusDll = ["xinput1_3.dll"] (or xinput1_4.dll)
5. Launch via Nucleus as usual

The DLL writes a log file (xinput_proxy.log) next to itself for diagnostics.

Troubleshooting

The proxy writes xinput_proxy.log in the same directory as the DLL. Nucleus cleans up instance folders after the game exits, so copy the log while the game is still running.

Instance folders are located at: NucleusCoop\content\<GameName>\Instance0\, Instance1\, etc.

What to look for in the log

Log line	Meaning
XInput proxy loaded	DLL is being loaded — basic setup works
Counter-hooked XInputGetState: Steam(...) -> filter(...)	Steam overlay was detected and counter-hooked — this is the fix working
XInputGetState not hooked by Steam	No Steam hook found — proxy filtering works directly without counter-hook
Re-hooked XInputGetState (pass N)	Steam re-applied its hook and we patched it again
Failed to load xinput1_4.dll	System XInput DLL not found — should not happen on any Windows 10/11

Common issues

• Log file is empty or missing — the DLL isn't being loaded. Check that the .dl_ file in utils\XInputPlus\x86\ (or x64\) was replaced correctly and that Game.XInputPlusDll in the handler matches the DLL name.
• Log shows Controller1 = 0 for all controllers — Nucleus assigned no controllers to this instance (keyboard+mouse instance). This is correct behavior.
• Counter-hook installs but controller still controls both instances — the game may load XInput from a different DLL name. Check which xinput*.dll the game imports (use a tool like Dependencies or dumpbin /imports).

Files

File	Purpose
xinput1_3.c	Proxy DLL source — filtering + counter-hook (x86 & x64)
xinput1_3.def	Export definitions for xinput1_3.dll
xinput1_4.def	Export definitions for xinput1_4.dll (adds XInputGetAudioDeviceIds)
build.bat	Build script — produces all 4 variants

Tested with

• Terraria (XNA Framework 4.0, x86, xinput1_3) via Nucleus Co-op v2.4.1
• Windows 11 Pro, Steam overlay enabled and disabled
• Single physical Xbox controller, one instance keyboard+mouse / one controller
• Single physical Playstation Dualsense/DualSense Edge + DS4Windows, one instance keyboard+mouse / one controller

Architecture support

• x86: Steam overlay uses E9 (JMP rel32) hooks — fully tested
• x64: Steam overlay uses FF 25 (indirect JMP with 8-byte address) or E9 — supported, not yet field-tested

License

MIT