Valve has released a new Proton Experimental update with compatibility fixes for several Windows games running on Linux and Steam Deck.
The September 4, 2026 update makes Cool People Club playable through Proton while restoring compatibility for Lunacid: Tears of the Moon and Ligo after recent Proton 11 regressions.
It also addresses controller problems in Far Cry 4, restores Grand Theft Auto III intro videos, fixes the in game HUD in RaceRoom Racing Experience, and resolves smaller visual and font issues in two other games.
| Game | Change in latest Proton Experimental update |
|---|---|
| Cool People Club | Now playable |
| Lunacid: Tears of the Moon | Playable again |
| Ligo | Playable again |
| Far Cry 4 | Controller reliability fixed |
| Grand Theft Auto III | Intro videos work again |
| RaceRoom Racing Experience | Race HUD restored |
| Achron | Missing font warning fixed |
| The I of the Dragon | Carpet rendering issue fixed |
Lunacid and Ligo Are Playable Again
Two of the more important changes address regressions introduced with Proton 11.
Lunacid: Tears of the Moon had stopped working correctly following recent compatibility changes. The new Proton Experimental build restores the game to a playable state.
Ligo receives the same treatment and can once again run through Proton.
Regression fixes are particularly important for Steam Deck because games that previously worked can sometimes break after changes to Proton, Wine, graphics libraries, or game updates.
Proton Experimental gives Valve a way to distribute these fixes before they reach a more stable Proton release.
Far Cry 4 Controller Support Is More Reliable
The update also addresses controller problems in Far Cry 4.
Valve says the game's controller should now work reliably again when running through Proton.
Controller compatibility can be especially important on Steam Deck, where the integrated controls are the primary input method.
A game may technically launch through Proton while still providing a poor handheld experience if buttons, analog sticks, triggers, or controller detection do not operate correctly.
The latest fix should remove one of those barriers for Far Cry 4 players using Linux based systems.
GTA 3 Intro Videos Have Been Restored
Grand Theft Auto III receives a video playback fix.
The game's intro videos should now display correctly again after being affected by a Proton 11 regression.
Video playback has historically been one of the more complicated parts of Windows game compatibility on Linux because games can depend on specific codecs, media frameworks, and proprietary formats.
In this case, the issue did not necessarily prevent the entire game from running, but restoring the videos makes the experience more complete.
RaceRoom Racing Experience Gets Its HUD Back
RaceRoom Racing Experience also receives a regression fix.
The game's HUD should now load correctly during races.
A missing HUD can make a racing game difficult to use because important information such as position, timing, vehicle status, and other race data may no longer be visible.
The Proton Experimental update restores that interface during gameplay.
Two Smaller Rendering and Font Problems Are Fixed
Valve has also addressed issues affecting Achron and The I of the Dragon.
Achron should no longer display a warning about missing fonts.
The I of the Dragon receives a rendering correction for graphical problems affecting carpet textures.
These are smaller fixes than restoring an unplayable game, but they show how Proton updates continue to target individual compatibility problems rather than only whether a game launches.
Cool People Club Is Newly Playable
Cool People Club joins the list of games that can now run through Proton Experimental.
The changelog does not provide detailed performance information or a Steam Deck compatibility rating, so being listed as playable should not automatically be treated as the same thing as receiving Valve's Steam Deck Verified status.
It does mean that the Proton team has resolved the compatibility problems that previously prevented the game from functioning correctly through the Windows compatibility layer.
Proton Experimental Updates Automatically
If Proton Experimental is already installed, Steam should download the latest version automatically.
Steam Deck owners who do not have it installed can find Proton Experimental through Steam and add it to their system.
You can then select it manually for individual games through Steam's compatibility settings when you need a newer fix that has not yet reached the regular Proton branch.
Because Proton Experimental receives changes more quickly, it can sometimes fix a broken game sooner, although its faster development cycle also means new regressions can occasionally appear.
The September 4 update is mainly focused on correcting those kinds of regressions, with Lunacid: Tears of the Moon, Ligo, Grand Theft Auto III, and RaceRoom Racing Experience all recovering functionality that had recently been affected.
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