Confirmation: GameInputRawInputProxy.exe is NEVER created.  SANITIZED.
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Two independent methods, both across the full Minecraft launch + repro window:

1) Microsoft-Windows-Kernel-Process ETW provider (process/image keywords enabled):
   - ProcessStart (EventID 1) events were captured for ~29 processes during the
     window (Minecraft.exe, Minecraft.Windows.exe, xgamehelper.exe, RuntimeBroker,
     etc.).
   - There is NO ProcessStart event for GameInputRawInputProxy.exe.

2) Event-driven WMI process-creation watcher
   (SELECT * FROM __InstanceCreationEvent WITHIN 0.05 WHERE TargetInstance ISA
    'Win32_Process' AND TargetInstance.Name = 'GameInputRawInputProxy.exe'):

   Broker spawn catcher result
   Computer : <MACHINE>
   Window   : 240 s
   RESULT   : NO broker spawn events captured
              (service never created GameInputRawInputProxy.exe).

Conclusion: CreateProcess fails at the kernel level and no process object is ever
created (consistent with STATUS_INVALID_IMAGE_FORMAT returned before process
creation completes).

Control: the SAME GameInputRawInputProxy.exe launches successfully (runs, exits
with its normal handshake code 1) when started:
   - standalone by an interactive administrator
   - as SYSTEM in session 0 (SYSTEM scheduled task)
   - as SYSTEM into interactive session 1 (PsExec -s -i):
       "Starting ...GameInputRawInputProxy.exe ... exited ... with error code 1."
   - with Code Integrity Guard enforced (MicrosoftSignedOnly)