Problem with detecting form: why use headers on HTTP_REQUEST, and not on HTTP_RESPONSE

Hi,

I'm trying to recognise/detect a login form on the back-end application. There is no unique login URI and sometimes the client has a cookie while the back-end asks to log in again.

I have found that the back-end application supplies a HTTP header with the response ("RespondingWithSignonPage"), indicating that a login is required.

Now, I want to enter this into my Form - Client Initiated, Form Detection. I select Header, enter "RespondingWithSignonPage". It doesn't work. Then I read the documentation, and it appears that this relates to headers sent by the client (HTTP_REQUEST), not during the response.

Is my assumption correct? Why would it be like that? How can I detect a form based on the cookies and headers of the client? Seems like they got it reversed?

Thank you Vincent