You can create a script that uses the Classic Agent and the Open Agent. Recording primarily depends on the default agent while replaying the script primarily depends on the window declaration of the underlying control. If you create a script that does not use window declarations, the default agent is used to replay the script.
The Select Application dialog box opens.
You can also use the function Connect([sMachine, sAgentType]) in a script to connect a machine explicitly with either the Classic Agent or the Open Agent. Using the connect function changes the default agent temporarily for the current test case, but it does not change the default agent of your project. However, this does not override the agent that is used for replay, which is defined by the window declaration.