[BUG] MSIX/Store install does not register claude:// protocol handler → OAuth login loops indefinitely

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?

Environment

OS/build: Windows 11 Pro (10.0.26200)
App version: 1.9659.4.0
Affected package: MSIX/Store build (Claude_..._pzs8sxrjxfjjc)
Working package: Squirrel/native build (same version, from full Claude Setup.exe)
Summary
A clean MSIX/Store install does not create the claude:// protocol handler. HKCU\Software\Classes\claude exists with URL Protocol, but has no shell\open\command subkey, so the OAuth login callback has nowhere to dispatch and the in-app Claude Code login loops forever.

Proof it's packaging-specific
Installing the Squirrel/native build registers the handler correctly:

HKCU\Software\Classes\claude\shell\open\command
(Default) = "...\AppData\Local\AnthropicClaude\app-1.9659.4\claude.exe" "%1"
With the native build, login works.

Notes

Original trigger was an auto-update that failed with a file-lock error 0x80073CF6.
Cannot use /feedback because it requires updating to the version that contains this bug.

What Should Happen?

Expected
MSIX install registers claude\shell\open\command (or otherwise registers the protocol activation) so the OAuth callback resolves and login completes.

Error Messages/Logs

Steps to Reproduce

Repro steps

Clean uninstall; verify no leftovers
Install the MSIX/Store build
Run:
reg query "HKCU\Software\Classes\claude\shell\open\command"
→ returns "not found"
Attempt in-app Claude Code login → loops indefinitely

Claude Model

None

Is this a regression?

Yes, this worked in a previous version

Last Working Version

_No response_

Claude Code Version

1.9659.4

Platform

Anthropic API

Operating System

Windows

Terminal/Shell

PyCharm terminal

Additional Information

_No response_