Browser preview pane cannot authenticate against HTTP Basic Auth (native dialog unsupported)

Description

When previewing a local (or staging) app that is protected by HTTP Basic Auth (e.g. via Next.js middleware) using the Claude Desktop app's built-in Browser preview pane, the native Basic Auth login dialog cannot be interacted with. Entering the correct username/password does not work, and the raw 401 response body ("Authentication required.") is shown instead of a usable page.

Embedding credentials directly in the URL (http://user:pass@host:port/...) was also tried as a workaround and did not work either.

Steps to reproduce

1. Run a local dev server for an app that enforces HTTP Basic Auth (e.g. a Next.js app with a middleware.js that checks Authorization headers and returns 401 with WWW-Authenticate: Basic).
2. Open the app's URL in the Claude Desktop Browser preview pane.
3. Try to log in via the native Basic Auth prompt with valid credentials.

Expected behavior

The Browser preview pane should support HTTP Basic Auth, either by rendering an interactive native-style prompt that can be filled in, or by providing some way to supply credentials programmatically (e.g. via a tool parameter) so authenticated pages can be previewed and verified.

Actual behavior

The Basic Auth prompt cannot be completed. The page instead shows the plain 401 response body ("Authentication required."), and there is no way to authenticate and proceed to the actual app content within the preview pane.

Impact

It is not possible to visually verify UI changes in Basic-Auth-protected environments using the Browser preview pane. The current workaround is to temporarily disable Basic Auth server-side just for verification, which is undesirable since it means testing happens without the real auth guard in place.

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🤖 Filed via Claude Code