While running the unit tests for ZOSPy, I discovered that calling Application.GetSystemAt(0) throws a System.ArgumentOutOfRangeException . This is rather weird, since the primary system should always be present. Upon further inspection, Application.NumberOfOpticalSystems turned out to be 0.

I tried to reproduce this problem in C#, and succeeded. The problem also occurs in this example:

bool isInitialized = ZOSAPI_Initializer.Initialize();
var connection = new ZOSAPI_Connection();
var application = connection.ConnectAsExtension(0);

Console.WriteLine(application.NumberOfOpticalSystems); // --> 0

var systemZero = application.GetSystemAt(0); // --> Throws ArgumentOutOfRangeException

But not in this one, while the new surface added at the end doesn't appear in the GUI (indicating it is not interacting with the primary system):

bool isInitialized = ZOSAPI_Initializer.Initialize();
var connection = new ZOSAPI_Connection();
var application = connection.ConnectAsExtension(0);

Console.WriteLine(application.NumberOfOpticalSystems); // --> 0

application.CreateNewSystem(SystemType.Sequential);

Console.WriteLine(application.NumberOfOpticalSystems); // --> 1

var systemZero = application.GetSystemAt(0); // Returns a system

systemZero.LDE.InsertNewSurfaceAt(2).Comment = "New surface"; // Nothing happens in the primary system

If I connect in standalone mode instead of extension mode, the number of optical systems is equal to 1 and I can connect to the optical system at position 0.

I would expect the number of optical systems to be 1 in extension mode as well. Is the observed behaviour correct, or is it a bug in the ZOS-API?

Additional information

OpticStudio version: 23 R1.00
Windows 10 Enterprise, Build 19044