what is the tested games?
i using experimental but i don't have problem

I teste game Teardown (https://store.steampowered.com/app/1167630/Teardown/)
image:

log (with x11 lgging): steam-1167630.zip
log (without x11 lgging): steam-1167630-withoutx-11-logging.zip

Video: Screencast_20250812_190245.zip

system info:

Operating System: Bazzite 42
KDE Plasma Version: 6.4.3
KDE Frameworks Version: 6.16.0
Qt Version: 6.9.1
Kernel Version: 6.15.9-106.bazzite.fc42.x86_64 (64-bit)
Graphics Platform: Wayland
Processors: 16 × 11th Gen Intel® Core™ i7-11700KF @ 3.60GHz
Memory: 16 GiB of RAM (15.4 GiB usable)
Graphics Processor: NVIDIA GeForce RTX 3060
Manufacturer: ASUS

steam info:

Informazioni computer:
Produttore: ASUSTeK COMPUTER INC.
Modello: PRIME H510M-E
Fattore di forma: desktop
Input touch non rilevato
Informazioni sul processore:
Produttore della CPU: GenuineIntel
Marca della CPU: 11th Gen Intel(R) Core(TM) i7-11700KF @ 3.60GHz
Famiglia della CPU: 0x6
Modello della CPU: 0xa7
Stepping della CPU: 0x1
Tipo di CPU: 0x0
Velocità: 4900 MHz
16 processori logici
8 processori fisici
HyperThreading: Supportato
FCMOV: Supportato
SSE2: Supportato
SSE3: Supportato
SSSE3: Supportato
SSE4a: Non supportato
SSE4: Supportato
SSE42: Supportato
AES: Supportato
AVX: Supportato
AVX2: Supportato
AVX52F: Supportato
AVX52PF: Non supportato
AVX52ER: Non supportato
AVX52CD: Supportato
AVX52VNNI: Supportato
SHA: Supportato
CMPXCHG6B: Supportato
LAHF/SAHF: Supportato
PrefetchW: Non supportato
BMI1: Supportato
BMI2: Supportato
F16C: Supportato
FMA: Supportato
Versione del sistema operativo:
"Bazzite (FROM Fedora Atomic)" (64 bit)
Nome del kernel: Linux
Versione del kernel: 6.15.9-106.bazzite.fc42.x86_64
Produttore dell'X Server: The X.Org Foundation
Versione dell'X Server: 12401006
Gestore dell'X Window: KWin
Versione del Runtime di Steam: steam-runtime_1.0.20250519.130917
Informazioni ottenute dal client:
Versione: 1751405894
Stato di accelerazione della GPU per il browser: Attivo
Canvas del browser: Attivo
Rasterizzazione fuori processo del canvas del browser: Attivo
Direct Rendering Display Compositor del browser: Disattivato
Composizione del browser: Attivo
Multiple Raster Threads del browser: Attivo
OpenGL del browser: Attivo
Rasterizzazione del browser: Attivo
RawDraw del browser: Disattivato
Skia Graphite del browser: Disattivato
Decodifica video del browser: Attivo
Codifica video del browser: Disattivato
Vulkan del browser: Disattivato
WebGL del browser: Attivo
WebGL2 del browser: Attivo
WebGPU del browser: Disattivato
WebNN del browser: Disattivato
Scheda video:
Driver: NVIDIA Corporation NVIDIA GeForce RTX 3060/PCIe/SSE2
Versione dei driver: 4.6.0 NVIDIA 575.64.05
Profondità di colore del desktop: 24 bit per pixel
Frequenza di aggiornamento del monitor: 119 Hz
VendorID: 0x10de
DeviceID: 0x2504
Revisione non rilevata
Numero di monitor: 1
Numero di schede video logiche: 1
Risoluzione del display principale: 2560 x 1440
Risoluzione del desktop: 2560 x 1440
Dimensioni del display principale: 27.44" x 15.43" (31.46" diag), 69.7cm x 39.2cm (79.9cm diag)
VRAM principale: 12288 MB
Scheda audio:
Dispositivo audio: Realtek ALC897
Memoria:
RAM: %$s1 MB
Hardware VR:
Visore VR: non rilevato
Varie:
Lingua dell'interfaccia: Italiano
LINGUA: it_IT.UTF-8
Spazio totale disponibile: 952244 MB
Blocco libero più ampio: 468711 MB
Spazio su disco:
Numero di SSD: 1
Dimensioni SSD: 1000G
Numero di SSD: 0
Numero di unità rimovibili: 0

This issue affects every other running app, while any game using Proton 10 or Experimental is running. Mouse button clicks with R2/L2 fail to register in Chrome and Discord, though can be circumvented with the Steam Deck's touchscreen. Nested Desktop fails to acknowledge any input, even touchscreen, when this happens.

what is the tested games? i using experimental but i don't have problem

I teste game Teardown

I get this issue with World of Warcraft and Discord where WoW captures the input over everything else, works fine on other games however.

what is the tested games? i using experimental but i don't have problem
I teste game Teardown

I get this issue with World of Warcraft and Discord where WoW captures the input over everything else, works fine on other games however.

ha ok, but there are not writter

Any word on a fix for this issue?

Still no fix?

The lack of any reply from Valve concerning this issue is deeply concerning...

Now there's an even worse issue in certain games: While mouse focus is not stolen in GTAV Enhanced for example, attempting to multitask in any way will cause the current game to stop accepting any input at all, whether by gamepad or mouse and keyboard.

I have this problem too, but slightly different:
Say game A and B are both run with Proton and are both fullscreen, then one of them will steal the focus from the other, but it's perfectly fine outside both games.

I think I did a test back then, this is Wayland specific, happens on all Wayland compositors, while X11 worked.

One workaround is to use custom wine builds, wine-ge-8.26 or wine for FFXIV provided by xivlauncher, or use ProtonGE / ProtonEM with PROTON_ENABLE_WAYLAND=1.

But since wine-ge is not for Steam games, and Wine Wayland is unstable (it will close itself randomly), the workaround is not ideal.

I was able to reproduce the issue. It only seems to affect certain titles and not others. We are looking into it. Thank you for the reports, info, and specific applications affected.

FYI, this input-stealing issue happens in standard Wine too, not just Proton.

From what I tested, the following games have this issue: Amid Evil, Tempest 4000, Dusk, Call of Duty MW2 (2009), Grand Theft Auto IV, Grand Theft Auto V Enhanced (with total input lockout, as previously mentioned), Forsaken Remastered, Killing Time Resurrected, PO'ed Definitive Edition, Prodeus.

Generally, Activision and Rockstar games, as well as Unreal Engine 4 & 5, KEX Engine, and Unity, seem to be the main culprits.

Further tests with my currently-installed games and Proton 10 indicate...

Total input lockout: all inputs stop functioning in both game and external apps

• Far Cry 1
• Grand Theft Auto IV: The Complete Edition
• Grand Theft Auto V Enhanced
• Serious Sam 2 (dubious input detection, even on Proton 9)

Inability to multitask: mouse stops working in external apps, but game input still works

• Amid Evil
• Call of Duty 4: Modern Warfare (2007)
• Call of Duty: Modern Warfare 2 (2009)
• Call of Duty: World At War
• Demonstar: Original Missions
• Descent 3
• Dusk
• Far Cry 2
• F.3.A.R.
• Forsaken Remastered
• Geometry Wars 3: Dimensions Evolved
• Forgive Me Father
• Killing Time Resurrected
• Max Payne
• Max Payne 2: The Fall of Max Payne
• Max Payne 3
• Midnight Club 2
• PO'd Definitive Edition
• Powerslave Exhumed
• Prodeus
• Quake 2 (remaster)
• Quake 4
• RealRTCW (mod for Return to Castle Wolfenstein)
• Red Dead Redemption 2
• Red Faction 2
• Rise of the Triad: Ludicrous Edition
• Severed Steel
• Shadow Warrior (2013)
• System Shock Remake
• System Shock 2: 25th Anniversary Remaster
• Tempest 4000
• Tron 2.0
• Turok 2: Seeds of Evil
• Turok 3: Shadow of Oblivion
• Ultrakill
• Warhammer 40,000: Boltgun
• Wizordum

Fully functional: games that can safely multitask under Proton 10.0-3

• Alice: Madness Returns
• Aliens vs. Predator Classic 2000
• Atari 50
• The Making of Karateka
• Llamasoft: The Jeff Minter Story
• Call of Duty: Modern Warfare 3 (2011)
• Chorus
• Desecrators
• Echo Point Nova
• Evil West
• F.E.A.R. 1, Extraction Point, and Perseus Mandate
• F.E.A.R. 2: Project Origin
• Heretic + Hexen (remaster)
• No Man's Sky
• No More Heroes
• Postal: Brain Damaged
• Project Warlock
• Red Faction 1
• Shadow Man Remastered
• Shakedown: Hawaii
• Star Wars: Dark Forces Remaster
• Turbo Overkill
• Zortch

Any update on this? It’s a very simple ask in 2026 to be able to multitask a messaging app in the background, but with this bug it’s next to impossible.

Edit: I’ll add to the list, my game is R.E.P.O. and my app is Discord (Vesktop) and switching to GE-Proton9-27 did work as a workaround.

Any update on this?

Work is ongoing. Some fixes made it into 11.0-1, which has changed some of the behavior for the better. Focus switching may still require input via mouse/touch control, and there may be input bleedthrough. More fixes have been merged into Gamescope fairly recently, which should further improve switching. You can give that a shot by building/downloading the most recent version or by waiting for it to make it over to stable channels.

Thanks for the further game & app info, much appreciated for future testing.