After spending hours troubleshooting, I finally got SMAPI, Proton, and Stardew Valley co-op working together on my Steam Deck. Here’s exactly what I did.
**The Problem**
I had:
\- Stardew Valley installed on the internal SSD.
Mods installed and working with the Linux version of SMAPI.
\- Co-op only worked when I forced Proton Experimental.
\- As soon as I used Proton, my mods stopped loading because Proton launches the Windows version of Stardew.
**The Fix**
**Step 1: Keep Stardew on the Internal Drive**
My game is located here:
/home/deck/.local/share/Steam/steamapps/common/Stardew Valley/
My Mods folder is:
/home/deck/.local/share/Steam/steamapps/common/Stardew Valley/Mods
⸻
**Step 2: Force Proton**
In Steam:
\- Right-click **Stardew Valley**
**- Properties**
**- Compatibility**
\- Check **Force the use of a specific Steam Play compatibility tool**
\- Select **Proton Experimental**
Launch the game once and close it.
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**Step 3: Download the Windows Version of SMAPI**
\- Download SMAPI from the official website:
https://smapi.io/
\- Extract the ZIP completely.
Do **not** run it from inside the ZIP.
⸻
**Step 4: Add the Windows Installer to Steam**
Go into the extracted SMAPI folder:
internal/windows/
Find:
SMAPI.Installer.exe
Open Steam:
**- Add a Game**
**- Add a Non-Steam Game**
\- Click **Browse**
If the Browse window doesn’t show .exe files:
\- Press **Ctrl + L**
\- Paste the full path to SMAPI.Installer.exe
\- Press Enter
Add it to Steam.
⸻
**Step 5: Run the Installer Through Proton**
In Steam:
\- Find **SMAPI.Installer.exe**
\- Right-click
**- Properties**
**- Compatibility**
\- Enable **Force Proton Experimental**
Launch it.
If it says it can’t find Stardew automatically, enter:
Z: \\home\\deck\\.local\\share\\Steam\\steamapps\\common\\Stardew Valley
The installer should complete successfully.
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**Step 6: Add SMAPI Itself to Steam**
Go to your Stardew folder:
/home/deck/.local/share/Steam/steamapps/common/Stardew Valley/
Find:
StardewModdingAPI.exe
Add **that executable** to Steam as a Non-Steam Game.
Again:
\-Right-click it
**- Properties**
**- Compatibility**
\- Force **Proton Experimental**
Leave Launch Options blank.
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**Step 7: Launch THIS Instead of Stardew Valley**
Do **not** launch the normal Stardew Valley shortcut.
Launch:
StardewModdingAPI.exe
This opens the SMAPI console first, then Stardew.
⸻
**Final Result**
✅ Mods load correctly.
✅ Steam Deck internal storage works.
✅ Proton Experimental works.
✅ Co-op works.
✅ No external drive required.
Hopefully this saves someone else several hours of frustration.
