xinput1_3.dll is the controller (gamepad) library from the DirectX 9-era runtime. Modern Windows includes newer XInput versions but not this file, so games built against it refuse to start — even if you never plug in a controller, because the game checks for the library at launch regardless.
Brand-new games showing this error are usually packaged with an older engine or a mod that needs the file — the fix is identical. If the error names xinput1_4 or uinput instead, those ship with Windows; run `sfc /scannow` to repair them.
I play with keyboard and mouse. Why does the game need a controller file? The game loads the library at startup whether or not a controller is connected. Missing file = launch stops, input device irrelevant.
Is xinput1_3.dll part of Windows? It was, in the Windows 7 era. On Windows 10/11 it arrives via the DirectX End-User Runtime or a game’s bundled installer.