Hi @thaovan
This is expected behaviour. This happens to avoid the extra clicks for the user which has earlier opted for an specific IDP and completed the login in the past. This creates a cookie called glide_sso_id which contains the SysID of the IDP SSO ID (in your case your OIDC SSO SysID). If this cookie is present, it will always redirect the instance access to the IDP's single sign in URL which is expected behaviour.
This cookie gets created everytime user selects the IDP and completes the login process and this is out of box behaviour as well. If you do not want to redirect the users to IDP directly, you can choose any of the below options whichever suits your requirememts -
1 - You can think of changing the logout page in your IDP configuration to login.do or some other page which contains the link of the login page (instance/login.do). This will make sure the users are redirected to login page after logout from the IDP. But if user accesses the instance url, it will still redirect to IDP login page directly since sso_id cookie is present in the browser.
2 - You can think of customising the logout page to let the cookie be expired/removed upon landing on the logout page. Once the cookie is removed, it will not redirect to any IDP, unless you set any IDP record as auto-redirect IDP.
These are kind of workarounds, and its not something available oob, so before opting to it, please make sure to test above suggested workarounds thoroughly to avoid any further issues.
Cheers!
