Decompiling Stardew Valley

For most development, Visual Studio's Peek Definition provides on-the-fly access to decompiled game code. Full decompilation is only needed if you want to:

• Work with game code in a separate project
• Debug complex server-side interactions
• Develop modifications beyond SMAPI's capabilities

Long-term Goals

Recompiling the game is currently exploratory work rather than a fully supported workflow. However, having a fully recompilable version of Stardew Valley could enable:

• Custom debugging symbols (*.pdb files) for step-through debugging with breakpoints inside Stardew Valley code
• Internal .NET upgrades potentially improving performance and enabling access to newer C# language features for server-side mods
• Advanced customizations beyond what SMAPI allows

Experimental

This should be viewed as exploratory documentation of what might be achievable, rather than a supported or fully functional workflow.

Decompiling the Game

To decompile Stardew Valley, run the decompilation script:

bash ./tools/decompile-sdv.sh

This script will use decompilation tools to extract the C# source code from the Stardew Valley assemblies.

Semantic search over the decompiled code

Once decompiled, the stardew-decompiled Serena project lets an AI agent navigate the game code by symbol. Its config is committed at decompiled/sdv-<version>/.serena/project.yml; when a new game version lands (rare), move that .serena folder into the new version's directory — the project_name stays stable, so nothing else changes.

Recompiling (Work in Progress)

Work in Progress

The recompilation process is still experimental and may require significant troubleshooting.

If you want to attempt recompiling the decompiled code:

1. Decompile the Game

Follow the decompilation steps above.

2. Fix Compiler Errors

The decompiled code will likely have immediate compiler errors. For version 1.6.15, this typically involves:

• Commenting out problematic code sections
• Fixing 2-3 references to non-existent dependencies
• Addressing type conversion issues

3. Create global.json

In the decompilation root directory, create a global.json file:

{
  "sdk": {
    "version": "6.0.403"
  }
}

4. Adjust Project Settings

Modify the .csproj file to use preview language features:

<LangVersion>preview</LangVersion>

5. Copy Game Files

Copy remaining files from your Steam installation into <decompRoot>/bin.

Common Fixes

Here are some common fixes needed when recompiling:

HashUtility Fix

The HashUtility class needs to be rewritten to use System.IO.Hashing.XxHash32 instead of the deprecated System.Data.HashFunction:

using System;
using System.IO.Hashing;
using System.Text;

namespace StardewValley.Hashing;

public class HashUtility : IHashUtility
{
    public int GetDeterministicHashCode(string value)
    {
        if (value == null) throw new ArgumentNullException(nameof(value));
        byte[] data = Encoding.UTF8.GetBytes(value);
        return GetDeterministicHashCode(data);
    }

    public int GetDeterministicHashCode(params int[] values)
    {
        if (values == null) throw new ArgumentNullException(nameof(values));
        byte[] array = new byte[values.Length * 4];
        Buffer.BlockCopy(values, 0, array, 0, array.Length);
        return GetDeterministicHashCode(array);
    }

    public int GetDeterministicHashCode(byte[] data)
    {
        if (data == null) throw new ArgumentNullException(nameof(data));
        byte[] hash = XxHash32.Hash(data);
        return BitConverter.ToInt32(hash, 0);
    }
}

PropertyType Fixes

If you encounter type conversion issues with PropertyType, try adding .ToString() to the affected conversions.

Contributing

If you find solutions to recompilation issues, consider contributing your findings.