Cowork macOS: VirtioFS mount fails for all folders — "mkdir /mnt/.virtiofs-root/Gerald: operation not permitted"

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 (both local and OneDrive-synced) with a VirtioFS permission error. The VM cannot create the username directory under /mnt/.virtiofs-root/.
This is a regression — Cowork worked without issues approximately 3–4 weeks ago (around late February 2026). No macOS system changes were made. The issue appeared after a Claude Desktop auto-update.

What Should Happen?

Cowork should successfully mount any folder within the user's home directory via VirtioFS, regardless of the macOS username or folder location (local or cloud-synced). The VM should be able to create the required mount point directory under /mnt/.virtiofs-root/.

Error Messages/Logs

RPC error: failed to mount ../Gerald/Library/CloudStorage/OneDrive-Kapounek/AI/Projekte/MacOS-Dock-Icon-hide-Tool as MacOS-Dock-Icon-hide-Tool: source path does not exist and could not be created: /mnt/.virtiofs-root/Gerald/Library/CloudStorage/OneDrive-Kapounek/AI/Projekte/MacOS-Dock-Icon-hide-Tool: mkdir /mnt/.virtiofs-root/Gerald: operation not permitted

Same error with a purely local folder (no cloud storage involved):

RPC error: failed to mount ../Gerald/Work/AI/Projekte/MacOS-Dock-Icon-hide-Tool as MacOS-Dock-Icon-hide-Tool: source path does not exist and could not be created: /mnt/.virtiofs-root/Gerald/Work/AI/Projekte/MacOS-Dock-Icon-hide-Tool: mkdir /mnt/.virtiofs-root/Gerald: operation not permitted
The key error in both cases: mkdir /mnt/.virtiofs-root/Gerald: operation not permitted

Steps to Reproduce

1. Open Claude Desktop on macOS
2. Switch to Cowork tab
3. Create a new project or open an existing one
4. Select any folder (tested with OneDrive-synced and purely local folders)
5. Mount fails immediately with the above error
6. Clicking "Erneut versuchen" (Retry) reproduces the same error

Claude Model

Opus

Is this a regression?

Yes, this worked in a previous version

Last Working Version

Cowork worked correctly approximately 3–4 weeks ago on the same system with the same folders. No system changes were made. The issue likely appeared after a Claude Desktop auto-update (possibly version 1.1.5749 from March 9, 2026).

Claude Code Version

1.1.8359

Platform

Anthropic API

Operating System

macOS

Terminal/Shell

Terminal.app (macOS)

Additional Information

The error pattern suggests the VM's rootfs does not allow creating new directories under /mnt/.virtiofs-root/. This appears to affect the username-based path scheme (/mnt/.virtiofs-root/<username>/...) that replaced the earlier fixed path (/mnt/.virtiofs-root/shared/).