Windows authentication (Custom user) not working?

Hello,

We just upgraded to latest RDM (2026.2.11.0), and I happened to notice under the workspace datasource settings that we can now use windows authentication to log into SQL server WITH a custom user rather than the current user (different than the custom login feature). I tracked this down to a feature that was released recently with 2026.2.5.0 per change notes here. I tested out this feature, however it doesn't appear to be working as expected. No matter how I fill out the credential fields, the error "Unable to connect to the server. Login failed for user ''" is shown. Notice how it doesn't actually show a username, just a blank string, so something in RDM is not passing along the correct value for whatever reason.


If I save and force close RDM, after re-opening I get the same error and still a blank username. Here's the popup with details expanded:


This would be a very welcomed feature, so would love to get this to work.

Note: We use RDM with 2017 SQL server (not Azure). And I do know for a fact that it works with windows authentication logins.