I have the same issue.

This appears consistently across all launch attempts, for every game, regardless of Proton version.

What was tried (all unsuccessful):

1. Verified integrity of Steam Linux Runtime 4.0 and Proton via per-game properties — passes 0/0, no actual files downloaded.
2. Deleted appmanifest_4183110.acf and the runtime folder, restarted Steam → stuck at "Downloading content (0%)" indefinitely.
3. Nuclear option: deleted manifests and folders for both runtime 3.0 (sniper, 1628350) and 4.0 (4183110), cleared appcache/ entirely → Proton Experimental redownloaded fine, but runtime 4.0 still stuck at 0%.
4. Attempted steamcmd +force_install_dir ~/.local/share/Steam +login <user> +app_update 4183110 validate +quit → ERROR! Failed to install app '4183110' (Invalid platform), even with +@sSteamCmdForcePlatformType linux.
5. Tried steam steam://install/4183110 while Steam was running → no install dialog appeared.
6. Checked libraryfolders.vdf — app 4183110 is completely absent from the registered apps list, suggesting Steam never successfully registered the runtime.

Notable observation: App 4183110 never appears in ~/.local/share/Steam/steamapps/ at all — no manifest, no folder, no partial download. Steam's downloader silently fails at 0% with no error logged

Forgot to add my system specs:

System specs:

• OS: CachyOS
• CPU: AMD Ryzen 7 9800X3D
• GPU: NVIDIA RTX 5080 (NVIDIA open drivers 595.71)
• RAM: 32GB
• Kernel: Linux 7.0.9

Thank you so much! Would love to poke around in any further logs or avenues for diagnostics.

Update: Found a workaround that works on CachyOS and should work on your system too

Root cause (confirmed via config.vdf):

Steam records app 4183110 as downloaded with "completed": true and "overall_percent_complete": 100, but "buildid": 0 instead of the expected 22818298. This means Steam's download pipeline completes the transfer internally but the post-install step that writes appmanifest_4183110.acf and the actual files to disk silently fails. Steam then permanently believes the runtime is installed while nothing exists on disk, causing every subsequent download attempt to silently hang at 0%.

All standard recovery attempts fail because of this:

• Verifying integrity passes 0/0 (nothing to verify)
• Deleting the manifest and restarting Steam → stuck at "Downloading content (0%)" indefinitely
• Nuclear wipe of manifests + appcache/ → same result
• steamcmd +app_update 4183110 validate → ERROR: Failed to install app (Invalid platform)
• steam steam://install/4183110 → no dialog appears

Workaround:

Step 1 — Open the Steam console. Either launch Steam with steam -console or run steam steam://open/console while Steam is already open. A Console tab will appear in the Steam window.

Step 2 — In the Steam console input field, run:

download_depot 4183110 4183111

Wait for it to complete. It will output something like:

Depot download complete : "/path/to/Steam/ubuntu12_32/steamapps/content/app_4183110/depot_4183111"

Step 3 — Move the downloaded files into place:

mkdir -p ~/.local/share/Steam/steamapps/common/"Steam Linux Runtime 4.0"
cp -r ~/.local/share/Steam/ubuntu12_32/steamapps/content/app_4183110/depot_4183111/* \
  ~/.local/share/Steam/steamapps/common/"Steam Linux Runtime 4.0"/

Step 4 — Create the missing appmanifest. On bash:

cat > ~/.local/share/Steam/steamapps/appmanifest_4183110.acf << 'EOF'
"AppState"
{
	"appid"		"4183110"
	"Universe"		"1"
	"name"		"Steam Linux Runtime 4.0"
	"StateFlags"		"4"
	"installdir"		"Steam Linux Runtime 4.0"
	"SizeOnDisk"		"748703422"
	"buildid"		"22818298"
	"LastUpdated"		"1779282445"
	"UpdateResult"		"0"
	"BytesToDownload"		"0"
	"BytesDownloaded"		"0"
}
EOF

On fish shell:

echo '"AppState"
{
	"appid"		"4183110"
	"Universe"		"1"
	"name"		"Steam Linux Runtime 4.0"
	"StateFlags"		"4"
	"installdir"		"Steam Linux Runtime 4.0"
	"SizeOnDisk"		"748703422"
	"buildid"		"22818298"
	"LastUpdated"		"1779282445"
	"UpdateResult"		"0"
	"BytesToDownload"		"0"
	"BytesDownloaded"		"0"
}' > ~/.local/share/Steam/steamapps/appmanifest_4183110.acf

Step 5 — Restart Steam. The runtime will be recognized immediately — no re-download needed.

You can confirm it worked by checking:

cat ~/.local/share/Steam/logs/compat_log.txt | grep "4183110" | tail -5

It should now show Command prefix for tool 4183110 set to: instead of unsupported version 0.

System info (for reference):

• OS: CachyOS (Arch-based, rolling)
• CPU: AMD Ryzen 7 9800X3D
• GPU: NVIDIA RTX 5080, open drivers 595.71.05
• RAM: 32GB
• Kernel: 7.0.9
• Steam: 1.0.0.85-6
• Filesystem: btrfs
• Desktop: niri (Wayland + XWayland)

Hope this helps!

@Quinta0 - thank you very much, particularly for giving the fish variant! Arc Raiders now launches.

Any thoughts on what happened? For me, I suspect it was something to do with enabling / disabling shader cache, and 'Clear Download Cache'.

Note: I still do not see the Steam Linux Runtime in my library, which I did before. It does appear in Settings > Storage.

@dcog989 I honestly don't know, since I've not disabled shader cache yet the issue appeared, i did although change the version of proton experimental from the public one to the bleeding edge so it could be that maybe?

i did although change the version of proton experimental

Yeah, I was also playing with that - I've been trying to solve an infuriating, intermittent hang / Crash To Desktop. Hoping the latest CachyOS Proton solves it.

Thanks again. :)

@dopreo did you manage to run your games now?

im stuck with the same problem, but before i try this maybe this can help identifying the culprit

cat ~/.local/share/Steam/logs/compat_log.txt | grep "4183110" | tail -5
:16:50] Registering tool steamlinuxruntime_4, AppID 4183110
[2026-05-29 22:20:34] Registering tool steamlinuxruntime_4, AppID 4183110
[2026-05-29 22:24:34] Mapping AppID 4183110 to tool "Proton-GE Latest" with priority 250
[2026-05-29 22:24:39] Registering tool steamlinuxruntime_4, AppID 4183110
[2026-05-29 22:24:39] Posting queued app config changed callback 4183110

so if i understand correctly SLR4 was mapped to tool proton-ge which is not possible to set in the steam client ( i used proton-plus to map all my apps to proton-ge recently). steam also showing SLR4 being available for windows

anybody knows where to remap this to its default setting?

so my config.vdf is showing
slr4
"4183110"
{
"name" "Proton-GE Latest"
"config" ""
"priority" "250"
}

but for slr3
"1628350"
{
"ShaderCacheSize" "0"
}
since it is in a completely different tab im unsure how to fix that properly, my guess is that protonplus has somehow missed to update slr4 to ignored apps when editing leading to this misconfig

EDIT: removed the slr4 config and i can install slr4 again, the error does not show up any more

The only thing that still bothers me is that the ShaderCacheSize is not configed any more can anyone confirm this is being set for slr4?

@givname Good find! You're right that ProtonPlus incorrectly assigned a compatibility tool to SLR4, which is a runtime container and shouldn't have one. Glad removing that block from config.vdf fixed it.

Regarding ShaderCacheSize not being configured for SLR4 it seems like that's expected and nothing to worry about. The shader cache setting is only relevant for actual games, not runtime containers. SLR3 having it set is likely a leftover from a previous misconfiguration rather than something that should be there.

i dont understand why its being configed for every other slr though, i just set it for 4 too

I started having the same issue yesterday with Bazzite and proton-cachyos latest which was installed by ProtonPlus. I tried a million things to fix it but couldn't get SLR4.0 to download or run, but I had been successfully using this version of proton just fine the past few days. I was getting 'compatibility tool configuration failed' on launch, reinstalled proton-cachyos via protonplus and switched to the downloading content stuck at 0% on launch. If I am reading this thread correctly, it sounds like an issue with how ProtonPlus is installing the extra proton variant which is based on Proton 11 which requires SLR4?

What would be the proper way to fix this? Uninstall all of the SLR, all of the compatibility tools and reinstall with protonup-qt?

@ShyRobbie Sorry for the late reply, but that's a really plausible theory. ProtonPlus likely iterates over all installed compatibility tools when you install/update one, and writes entries for all of them into config.vdf including SLR4, which it shouldn't touch. If it assigns a Proton tool to SLR4 by mistake, Steam can no longer use SLR4 as a runtime container, breaking any Proton version that depends on it (like proton-cachyos which requires SLR4).

For the proper way to fix it its a bit of a MacGyver: you don't need to uninstall everything the issue is likely just a bad entry in config.vdf that ProtonPlus wrote when it installed/updated proton-cachyos. Check this first (with Steam closed):

grep -A5 '"4183110"' ~/.local/share/Steam/config/config.vdf

If you see something like:

"4183110"
{
    "name"    "proton-cachyos" (or any Proton tool)
    ...
}

...delete that block, save the file, and restart Steam. SLR4 is a runtime container and should never have a compatibility tool assigned to it ProtonPlus appears to be incorrectly writing an entry for it when managing other tools.

If that block isn't there, or if removing it doesn't fix it, follow the manual workaround in my earlier comment to force-install SLR4 via download_depot.

Update: Found a workaround that works on CachyOS and should work on your system too

thanks!
that workaround worked for me too on CachyOS to run games successfully, after uninstalled stock proton-cachyos-slr to install it with ProtonPlus instead.
maybe I did a mistake to chose a compat tool for a runtime (didn't remember its name, but it wasn't "Steam Linux Runtime 4.0" ) that shows as a game. it seems ProtonPlus tool is far from stable state.
what I'm not sure in that is your appmanifest_4183110.acf content could make as an issue too later, as its content is probably does not match for the newest "Steam Linux Runtime 4.0".
Does that "~/.local/share/Steam/ubuntu12_32/steamapps/content/app_4183110/depot_4183111/" directory can be deleted after the copy?