IMM won't launch Stellaris on Linux

[SmartassSkeleton]

Describe the bug
I am running IMM on Arch Linux on Wayland, but I have xWayland installed. I've added a couple of mods, pressed apply. Then I press Launch Game The window immediately closes and this is printed to my terminal:

Preparing to launch game.
Preparing to check whether steam is running, this might take some time.
Checking whether steam is running using direct steam integration method.
Exit on error.

To Reproduce
Steps to reproduce the behavior:

1. Update IMM to latest.
2. Add a couple of mods.
3. Press Apply.
4. Press Launch Game.

Expected behavior
The game should lunch.

Screenshots
N/A

Logs
There are no logs in ~/.config/Mario/IronyModManager-Logs.

Version:

• OS: Arch Linux
• IronyModManager 1.27.149+387cb786c7

[bcssov]

It's failing to talk to steam. Is this proton? Or some sandbox like flatpak?

[SmartassSkeleton]

This is a plain extract of the zip file you provide in this repo. Running ./IronyModManager, no sandbox anywhere.

I've updated using the update capabilities of the mod manager and nothing else.

[bcssov]

Steam is it flatpak or some other sandbox? Does older irony version work?

[SmartassSkeleton]

Thank you for the swift replies, nothing is sandboxed. Steam is installed using pacman.

I've just made a test with an older version of IMM. The collection from the newer version wasn't identified, so I've exported from the new IMM and imported in the older one, the import worked.

Then, I tried to launch, it failed, but it was a little more verbose:

./IronyModManager
2026-02-04 22:10:14.7369|ERROR|IronyModManager.Log.Logger|Version: 1.26.258+b8bc6846ce
OS Description: EndeavourOS
Runtime Identifier: linux-x64
|System.IndexOutOfRangeException: Index was outside the bounds of the array.
   at Gameloop.Vdf.VdfTextReader.ReadToken()
   at Gameloop.Vdf.VdfSerializer.ReadProperty(VdfReader reader)
   at Gameloop.Vdf.VdfSerializer.ReadObject(VdfReader reader)
   at Gameloop.Vdf.VdfSerializer.ReadProperty(VdfReader reader)
   at Gameloop.Vdf.VdfSerializer.ReadObject(VdfReader reader)
   at Gameloop.Vdf.VdfSerializer.ReadProperty(VdfReader reader)
   at Gameloop.Vdf.VdfSerializer.Deserialize(TextReader textReader)
   at Gameloop.Vdf.VdfConvert.Deserialize(TextReader reader, VdfSerializerSettings settings)
   at Gameloop.Vdf.VdfConvert.Deserialize(String value, VdfSerializerSettings settings)
   at IronyModManager.Services.Registrations.SteamDirectory.LoadVDF(String path) in IronyModManager.Services\Registrations\SteamDirectory.cs:line 393
Preparing to launch game.
Preparing to check whether steam is running, this might take some time.
Checking whether steam is running using direct steam integration method.
[S_API] SteamAPI_Init(): Loaded '/home/smartassskeleton/.local/share/Steam/linux64/steamclient.so' OK.
Setting breakpad minidump AppID = 281990
SteamInternal_SetMinidumpSteamID:  Caching Steam ID:  76561198001670578 [API loaded no]
Done exiting.

I'm not really sure what does API loaded no means, but I guess you can make sense of it?

[bcssov]

The VDF error looks like a known VDF parsing limit, which was fixed in 1.27.
The Steam communication log itself looks fine, so that's likely not the issue.

Since even 1.26 fails to launch the game, this points more toward a permissions or environment issue rather than a regression.

Steamworks.net might have a Linux-specific issue on some OS versions; I see there's a newer release from December. I'll update to that, and you could try that version once a new version of Irony is pushed out.

[SmartassSkeleton]

Thank you! I really appreciate this!

Is there a way to make the logs even more verbose then this? I could find the issue myself if I had more information to work with. The issue may really be some env, or permission issue on my side.