[BUG] Cowork: VirtioFS mount fails for users with macOS username "shared" — path collision with /Users/Shared/

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?

Cowork fails to mount any folder for users whose macOS username is "shared". Every folder selection produces a VirtioFS mount error because the home directory path /Users/shared/ collides with the macOS system directory /Users/Shared/ (macOS uses a case-insensitive filesystem).
The VM refuses to create the Shared path component under /mnt/.virtiofs-root/, presumably because it treats it as a reserved or protected system path.

What Should Happen?

Cowork should mount folders from the user's home directory regardless of the username.

Error Messages/Logs

RPC error: failed to mount ../Shared/Documents/Dewey_Classes as Dewey_Classes: source path does not exist and could not be created: /mnt/.virtiofs-root/Shared/Documents/Dewey_Classes: mkdir /mnt/.virtiofs-root/Shared: operation not permitted
Same error for any folder location within the home directory (tested Documents, Desktop).
Folders outside the home directory cannot be selected — the Cowork folder picker displays "this folder is outside of your directory."

Steps to Reproduce

Have a macOS user account with the username "shared" (home directory: /Users/shared/)
Open Cowork and start a new task
Select any folder within the home directory
Mount fails immediately with the above error

Claude Model

None

Is this a regression?

Yes, this worked in a previous version

Last Working Version

_No response_

Claude Code Version

Claude Desktop (latest version, February 2026)

Platform

Anthropic API

Operating System

macOS

Terminal/Shell

Terminal.app (macOS)

Additional Information

macOS allows "shared" as a username, but /Users/Shared/ is also a system-level shared directory. The case-insensitive filesystem treats these as the same path.
No workaround exists — all home directory paths fail, and Cowork rejects folders outside the home directory.
Claude Code CLI works fine since it doesn't use VirtioFS.
The only current workaround is creating a separate macOS user account, which is impractical for daily use.