[Portal 2] Mouse cursor not locked into window (vulkan)

[rugk]

Your system information

• Steam client version (build number or date): 1769025840
• Distribution (e.g. Ubuntu): Fedora 43/Bluefin (GNOME with wayland)
• Opted into Steam client beta?: No
• Have you checked for system updates?: Yes
• Steam Logs: steam-logs.tar.gz
• GPU: Intel (integrated)

Please describe your issue in as much detail as possible:

The mouse cursor should be locked into the game/screen (in full screen mode). When you have multiple monitors, otherwise, when you move your mouse to the side to change your view, it goes to the other screen making playing the game actually quite to impossible (or very frustrating).

Steam-Betabranch:  Client (stabil)
Steam-Version:  1769025840
Steam-Client: Build-Datum:  Mi., 21. Jan. 18:12 UTC -08:00
Datum des Steam-Web-Builds:  Mi., 21. Jan. 20:41 UTC -08:00
Steam-API-Version:  SteamClient023

$ flatpak info com.valvesoftware.Steam

Steam - Launcher for the Steam software distribution service

          ID: com.valvesoftware.Steam
         Ref: app/com.valvesoftware.Steam/x86_64/stable
        Arch: x86_64
      Branch: stable
     Version: 1.0.0.84
     License: LicenseRef-proprietary
      Origin: flathub
  Collection: org.flathub.Stable
Installation: system
   Installed: 60.0?MB
     Runtime: org.freedesktop.Platform/x86_64/25.08
         Sdk: org.freedesktop.Sdk/x86_64/25.08

      Commit: 2ba439dcb2dfc2db0ecbd80a97b5a3cb1cfaa8a172dfcad59e0d9e6cd40c867b
      Parent: ac7e5fde7bf413de33cf972f274b16df591d2d44a9bb64e724bd2fb0aa6b2570
     Subject: steam_wrapper: Don't build in isolation (fbd0220e56e7)
        Date: 2026-01-21 11:01:35 +0000

Steps for reproducing this issue:

0. (Have multiple monitors attached.)
1. Download and start Portal 2. (or any mod of it)
2. Add gamemoderun %command% -vulkan in the stat options in Steam of that game to make it work more smoothly (had the wrong aspect ratio and choose the wrong screen otherwise)
3. Now it basically works quite flawless,, except that it has the wrong resolution (I guess highest) set in the game.

I have not modified the compatibility runtime, but when I click it, it seems to use "scout 1.0":

More information

Possibly related (issues I found but do not have this issue reported): ValveSoftware/steam-for-linux#8652 ValveSoftware/steam-for-linux#6179