[BUG] /desktop fails with "Failed to open Claude Desktop" on Windows while the same deep link works manually

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?

Running /desktop in an interactive CLI session on Windows always fails with
"Failed to open Claude Desktop. Please try opening it manually."

The deep link itself is generated correctly (visible in debug log), and executing
the exact same command manually from the same terminal succeeds and the desktop
app receives the session. Only the CLI-internal launch fails.

What Should Happen?

/desktop should hand the current session off to the Claude Desktop app.

Error Messages/Logs

Error: Failed to open Claude Desktop. Please try opening it manually.

Debug log (claude --debug):
[DEBUG] Opening deep link: claude://resume?session=<session-id>
(no further related lines; the error is shown immediately after)

Steps to Reproduce

1. Windows 11, Claude Code CLI 2.1.210 (npm), Claude Desktop app 1.22209.0.0 (Microsoft Store / MSIX) installed and signed in.
2. Run claude in any project directory (VS Code integrated PowerShell or standalone PowerShell).
3. Run /desktop.
4. Error appears immediately.

Verified while debugging:

• Manual execution of the identical command from the same terminal works (app receives the session, exit 0):

cmd /c start "" "claude://resume?session=<session-id>"

• Reproducing the CLI's spawn in Node from an interactive shell also works:

spawn('cmd', ['/c','start','','claude://resume?session=...'], {windowsHide:true, stdio:'pipe'}) → exit 0

• Install check passes: reg query HKEY_CLASSES_ROOT\claude /ve → exit 0
• No %LOCALAPPDATA%\AnthropicClaude directory (no legacy install)
• VS Code not elevated, no cmd AutoRun, default COMSPEC

Possibly related: the Store app recreates HKCU\Software\Classes\claude with only a
"URL Protocol" value (no shell\open\command) on every activation. Manual start
still succeeds with that key present, but the CLI-internal spawn fails regardless
of the key's state.

Claude Model

None

Is this a regression?

I don't know

Last Working Version

_No response_

Claude Code Version

2.1.210 (Claude Code)

Platform

Anthropic API

Operating System

Windows

Terminal/Shell

PowerShell

Additional Information

Desktop app: 1.22209.0.0 (Microsoft Store / MSIX), Windows 11 Home 10.0.26200.
Happy to provide more debug output if needed.