"The Razor @namespace trap"

• C#: type Hud not found / can't reference your PanelComponent.
• Razor resolves the wrong type (Sandbox built-in) and you get baffling "no such member" errors.
• Plain .cs classes without a namespace work; .razor siblings don't show up beside them.

.razor files do NOT land in the global namespace the way namespace-free plain .cs classes do. They get a RootNamespace / folder-derived namespace.

Related: never name classes after Sandbox built-ins (PlayerController, etc.). A global-namespace name may compile, but razor resolves Sandbox.* first.

Scene/bootstrap JSON references custom components by plain class name when the class has no namespace ("__type": "MyBootstrap"). Keep bootstrap-referenced classes namespace-free if your scene already binds that way.

In every .razor:

@namespace YourGame

In Assembly.cs (or equivalent):

global using YourGame;

Then C# and other razor files can see Hud, InventoryPanel, etc.

Rename player/camera/inventory-ish classes away from Sandbox API names before you fight phantom member errors.

The Razor generator emits classes into a project-derived namespace unless you override it. global using puts that namespace in scope for the rest of the game assembly so panel types behave like your other gameplay types. Explicit @namespace also stops accidental collisions with Sandbox.UI names.