Symptom
After logging out or after a session timeout, users are redirected to salesforce.com instead of the org login page or a custom logout URL.
Cause
This is expected behavior.
When My Domain > Authentication Configuration > Authentication Service is configured with only ONE login method and that method is not Username-Password, Salesforce deliberately redirects users to salesforce.com on logout.
This is by design to prevent an SSO redirect loop. If users were redirected back to the org login page on an SSO-only org, the login page would immediately re-authenticate them via the Identity Provider, causing an unintended automatic re-login.
Option 1
Add Username-Password as an additional Authentication Service.
Setup > My Domain > Authentication Configuration > Authentication Service > Add Username-Password
Adding Username-Password does not require users to use it. SSO can remain the primary login method.
Option 2
Configure a Custom Logout URL.
Setup > Security > Session Settings > Logout Page Settings > Logout URL
Set this to the desired post-logout redirect destination.
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