VPE logon page : how to set correctly USERNAME and DOMAIN prior to call the AD ...

HI, Yes the SAML works when I don't try to change the value USERNAME of the logon page. If I fill the USERNAME value of the logon page with the information I catch in the URL (via an irule) then AD authent works but saml failed. I guess than, doing that (changing USERNAME value), I have also changed other requested values going to the saml : strange (for me) As a reminder I'm trying to implement the ADFS rule on the BIGIP-F5 It run well but the logon page is not pre-filled with the username value givin by the user when connecte to portal.office.com So I have set an irule which get the username and pre-fill the logon page But doing that saml no more run ! I'm not so long of the success but I'm blocked on this problem. cu