VS2022 sign-in fails after auth backend migration to app.devin.ai (localhost callback + show-auth-token broken)

[devin-ai-integration]

Describe the bug

Sign-in from the Visual Studio 2022 plugin fails. After clicking Sign in, the browser opens to the Windsurf "Getting started" page, and Visual Studio eventually fails with a "Failed to get the Authentication Token… Do you want to retry?" prompt. Sign-in never completes.

Root cause (investigated)

Windsurf authentication has been migrated onto Devin's login system (app.devin.ai). The VS plugin's sign-in opens:

https://www.windsurf.com/profile?response_type=token&redirect_uri=http://127.0.0.1:<port>/auth&state=...&scope=openid%20profile%20email&redirect_parameters_type=query

and waits for the token to be POSTed back to a local listener at http://127.0.0.1:<port>/auth (see CodeiumVS/LanguageServer/LanguageServer.cs:183-196). With the new flow, www.windsurf.com/profile 302-redirects through https://app.devin.ai/auth/windsurf/continue?..., and the original localhost redirect_uri is not honored end-to-end, so the token never returns to VS → "Retry".

The manual-token fallback is also broken: the "Sign in with authentication token" dialog's help link opens

https://www.codeium.com/profile?response_type=token&redirect_uri=show-auth-token&state=...

(CodeiumVS/Windows/EnterTokenDialogWindow.cs:47-54). For a logged-in user this now bounces to the "Getting started" page instead of rendering the token on https://windsurf.com/show-auth-token. A token=... value is briefly visible in the URL during the redirect (so a token IS issued), but the page does not display it for copy/paste.

Steps to reproduce

1. Install the Windsurf (formerly Codeium) extension in Visual Studio 2022 (17.5.5+).
2. With a personal Windsurf account that is already logged in via the browser, click Sign in (or Extensions → Windsurf → Sign in with authentication token and use the help link).
3. Browser opens to "Getting started"; VS times out and shows the "Retry" prompt. No token is captured.

Expected behavior

The plugin should complete sign-in against the current (Devin-backed) auth flow, or the show-auth-token page should render a copyable token for the manual-token dialog.

Environment

• IDE: Visual Studio 2022
• Plugin: Windsurf Plugin (formerly Codeium) for Visual Studio (Codeium.CodeiumVS)
• Account type: personal
• OS: Windows

Notes

Likely related to #106 (login not recognized after successful web sign-in). This report adds the specific root cause: the auth backend migration to app.devin.ai and the broken show-auth-token rendering.