@DebuggerServiceRegistration(
path = "CallStackView",
types = {TreeModel.class, NodeModel.class}
)
public class MyCallStackModel implements TreeModel, NodeModel
{
....
}

public class MyDebugger extends ActionsProviderSupport
{
    public MyDebugger(ContextProvider context)
    {
        MyCallStackModel callStack =
            context.lookupFirst("CallStackView", TreeModel.class);

        // callStack is null...
    }
}

However, when registering MyCallStackModel the old fashioned way, i.e. via folders:

META-INF.debugger.MySession.CallStackView (folder)
  - org.netbeans.spi.viewmodel.TreeModel (file)
      - org.mycompany.mydebugger.MyCallStackModel (file content)
...

everything works just fine.

So it seems that when using the annotation for registering a debugger service, it fails to register it within the lookup. The problem description also applies to other services such as BreakpointsView, LocalsView etc.