When playing CS2 in fullscreen mode using a 4:3 resolution (e.g., 1280x960) on a 2560x1440 (2K) monitor, alt-tabbing out and back into the game causes the mouse cursor to become offset. The screen remains 4:3, but the mouse behaves as if it's in a different resolution — clicking is inaccurate and not aligned with UI elements.

Additional problem (possibly related):
While in CS2's main menu, with the game set to Fullscreen, the mouse is able to move from the primary monitor to the second monitor, as if the game is not truly in exclusive fullscreen mode.
This suggests the game may not be locking the cursor or enforcing fullscreen mode correctly in 4:3 resolutions.

Steps to Reproduce:

Set Windows desktop to 2560x1440 (native resolution)

Launch CS2 in fullscreen at 1280x960 (4:3)

Observe that in the menus, the cursor can move outside the game window to another monitor

Alt-tab out and back into the game

Mouse cursor becomes misaligned with UI

Temporary Workaround:

If Windows is manually set to 1280x960 before launching CS2, the issue does not occur.

This forces Windows and CS2 to run at the same resolution — a workaround, but not ideal.

Tested without success:

Disabling DPI scaling / changing scaling behavior

Using GPU or Display scaling (NVIDIA Control Panel)

Disabling all overlays (Steam, Discord, GeForce)

Using all fullscreen/windowed modes

Full reinstall of CS2

Deleting userdata and config files

Creating and using custom resolutions

Adjusting refresh rates and driver settings

System info:

OS: Windows 11

GPU: NVIDIA RTX 4070 SUPER

Monitor: 2560x1440 (2K), 240HZ

CS2 resolution: 1280x960, Fullscreen (4:3)

Monitor setup: Dual monitors, extended

Expected Behavior:

Fullscreen should lock the cursor to the primary monitor.

Alt-tabbing should not desync the cursor from the visual UI.

Mouse input should always align with screen position.

Please investigate — this severely affects players who rely on 4:3 resolutions for competitive play. The cursor offset and improper fullscreen behavior break immersion and usability.