[BUG] Desktop app Cloudflare Turnstile 403 loop on Windows 11

Preflight Checklist

• [x] I have searched existing issues and this hasn't been reported yet
• [x] This is a single bug report (please file separate reports for different bugs)
• [x] I am using the latest version of Claude Code

What's Wrong?

The desktop app cannot connect. It loops on "Performing security verification." The application log records a repeating Cloudflare managed-challenge ("Just a moment…") interstitial returning HTTP 403 on every navigation to claude.ai and on every event-logging batch flush. The challenge is never cleared, so the app reloads continuously.

Chrome, Edge, and Firefox all load claude.ai and authenticate normally from the same machine, network, and public IP. The failure is specific to the app's embedded browser.

With all local network and client configuration excluded, and with system browsers succeeding on the identical network and account, the failure appears to be an interaction between the app's web view and the Cloudflare challenge — not resolvable through local configuration.

main.log.txt

What Should Happen?

Claude's internal browser should pass the Cloudflare challenge.

Error Messages/Logs

See attached "Main.log.txt" file, or contact me for details.

Steps to Reproduce

Launch Claude desktop app, or install/reinstall it.

Claude Model

Opus

Is this a regression?

Yes, this worked in a previous version

Last Working Version

_No response_

Claude Code Version

Claude desktop app version 1.12603.1.0 (MSIX package).

Platform

Anthropic API

Operating System

Windows

Terminal/Shell

PowerShell

Additional Information

Steps already taken (local causes ruled out):

• No system or WinHTTP proxy configured.
• hosts file clean.
• No TLS-interception certificate in the trust store; no third-party antivirus.
• IPv6 preference toggled — no change.
• DNS switched to 1.1.1.1 — no change.
• MSIX container / app data cleared.
• In-app Repair and Reset both failed.
• Full uninstall and clean reinstall of the package completed — no change.

Additional detail:
A single GPU-process crash appears in the log, but the 403 loop both precedes and follows it, so it is not the cause.

main.log.txt