Syntax Version 1

This page describes the changes introduced in Gum syntax version 1: a non-breaking move of runtime classes (SpriteRuntime, TextRuntime, ContainerRuntime, etc.) into a single unified namespace, Gum.GueDeriving.

What Changed

Prior to version 1, runtime classes were split across backend-specific namespaces:

• MonoGameGum.GueDeriving.* (MonoGame, KNI, FNA, Apos.Shapes runtimes)
• SkiaGum.GueDeriving.* (Skia runtimes plus shared types like TextRuntime)
• Gum.GueDeriving.* (Raylib and Sokol)

In version 1, every runtime class moves to Gum.GueDeriving. The same SpriteRuntime is now available regardless of backend.

Non-Breaking by Design

Existing user code is unaffected. The old MonoGameGum.GueDeriving and SkiaGum.GueDeriving namespaces still exist and still expose every runtime class — they just now contain thin [Obsolete] derived shims that forward to the real class in Gum.GueDeriving.

This means:

• using MonoGameGum.GueDeriving; still compiles.
• new SpriteRuntime() still works.
• You will see compiler warnings (CS0618) on each obsolete reference, plus an analyzer warning (GUM001) from the bundled Gum.Analyzers package.

Auto-Migration via Roslyn Analyzer

The Gum NuGet packages ship with a Roslyn analyzer (Gum.Analyzers) that detects old-namespace using directives and offers a one-click code fix:

1. Place the cursor on the warning squiggle under using MonoGameGum.GueDeriving; or using SkiaGum.GueDeriving;.
2. Trigger the lightbulb (Ctrl+. in Visual Studio / Rider).
3. Choose Change to 'using Gum.GueDeriving'.
4. To migrate the entire solution at once, use Fix all in solution.

The analyzer rewrites using directives only. Fully-qualified references like new MonoGameGum.GueDeriving.SpriteRuntime() still raise GUM001 but are not auto-fixed — update those by hand.

Generated Code

When the Gum tool detects that your project references a runtime with GumSyntaxVersion(Version = 1) or higher, generated code emits using Gum.GueDeriving; and fully-qualified references like global::Gum.GueDeriving.SpriteRuntime. Older runtimes (version 0) continue to receive the legacy namespaces.

If auto-detection fails, you can pin a version manually by setting the SyntaxVersion field in ProjectCodeSettings.codsj. See Syntax Versions for details.

Deprecation Timeline

The compatibility shims will remain in place until at least the December 2026 release (this change shipped in May 2026). After that window, the shim namespaces will be marked [Obsolete(error: true)] in a subsequent release, breaking compilation for any code still using them. The exact removal date will be announced in the corresponding monthly migration page.

Before / After

Before:

using MonoGameGum.GueDeriving;

public class MyScreen
{
    public void Setup()
    {
        SpriteRuntime sprite = new SpriteRuntime();
        sprite.Width = 100;
    }
}

After:

using Gum.GueDeriving;

public class MyScreen
{
    public void Setup()
    {
        SpriteRuntime sprite = new SpriteRuntime();
        sprite.Width = 100;
    }
}

The only change is the using directive — the class API is unchanged.

Troubleshooting

RenderingLibrary references stop compiling after migration

If your code is declared inside the Gum.* namespace tree (for example, namespace Gum.GueDeriving; to add a custom runtime, or namespace Gum.MyExtensions; for helpers), unqualified references to the top-level RenderingLibrary namespace may stop resolving:

namespace Gum.GueDeriving;

public class MyCustomRuntime : ContainerRuntime
{
    void Setup()
    {
        RenderingLibrary.Camera camera; // CS0234: 'Camera' does not exist
    }
}

This happens because there is also a Gum.RenderingLibrary namespace (a small set of blend-related helpers), and C# searches the containing namespace chain first — so when your file is inside Gum.*, Gum.RenderingLibrary shadows the top-level RenderingLibrary.

Fix: prefix the global namespace alias:

global::RenderingLibrary.Camera camera;

Or move your code out of the Gum.* namespace tree (for example, into MyGame.Extensions) and import what you need with a using directive. That's the recommended structure for user code anyway.

Most users will not encounter this — code declared in your own namespace (MyGame, Acme.Game, etc.) and importing Gum types via using Gum.GueDeriving; is unaffected.