On this issue, I noticed that people seem to use:
page = agent.get("http://www.you.com/index_login/", :referer => "http://www.you.com/")
On the sidelines, now that I have tested this answer, it seems that this is not the problem of my real problem: every visit to the site that I clear requires a second look at the pages of the login sequence, even a few seconds after the first login, despite the fact that that I always download and save the full cookie doll in yaml format. But this, of course, will lead to another question.