[Problem/Bug]: NTLM login dialog doesn't pop up

What happened?

We have a UWP application with Webview2 control. When loading an URL from the Webview2 which responses NTLM authentication challenge, the Webview2 doesn't pops up the NTLM login dialog, so the request always fails with 401 status code.

If opening the same URL on Edge browser, the login dialog can pop up correctly. See the screenshot from Edge browser:

Importance

Blocking. My app's basic functions are not working due to this issue.

Runtime Channel

Stable release (WebView2 Runtime)

Runtime Version

126.0.2592.61

SDK Version

1.0.1264.42

Framework

WinUI2/UWP

Operating System

Windows 10

OS Version

No response

Repro steps

We have a UWP application with Webview2 control. When loading an URL from the Webview2 which responses NTLM authentication challenge, the Webview2 doesn't pops up the NTLM login dialog, so the request always fails with 401 status code.

If opening the same URL on Edge browser, the login dialog can pop up correctly.

Repros in Edge Browser

No, issue does not reproduce in the corresponding Edge version

Regression

No, this never worked

Last working version (if regression)

No response

Start with the UWP application’s WebView2 control and load a URL that returns an NTLM authentication challenge using WebView2 Runtime 126.0.2592.61 on Windows 10. Compare the result with the same URL in the corresponding Edge version; done means the WebView2 request no longer fails with 401 and the NTLM login dialog appears.