[FEATURE] Cowork: Allow folder selection outside home directory (custom allowed paths)

Preflight Checklist

• [x] I have searched existing requests and this feature hasn't been requested yet
• [x] This is a single feature request (not multiple features)

Problem Statement

Users with multi-drive setups (work partitions on D:\, L:\, M:\) cannot use Cowork because folder selection is restricted to %USERPROFILE%. All my project files live on separate drives — Cowork is unusable for my actual workflow.

Attempting to select folders outside the home directory shows: "The selected folder is outside your home directory. Only folders within your home directory can be used."

Directory junctions and symlinks (e.g., mklink /J "%USERPROFILE%\AI-Hub" "L:\AI-Hub") are resolved to their real target path and still rejected.

Environment: Windows 11 Pro 25H2 (Build 26200), Claude Desktop v1.1.3963 (MSIX), Drives: L:\ (1TB workspace), M:\ (4TB assets), C:\ (OS only)

Note: The Code tab correctly allows folder selection on any drive — this restriction is Cowork-specific.

Proposed Solution

Allow users to configure additional allowed paths for Cowork, similar to how the Filesystem MCP server accepts an allowedDirectories array in claude_desktop_config.json.

Example configuration:

{
  "cowork": {
    "allowedDirectories": [
      "L:\\AI-Hub",
      "M:\\System Assets"
    ]
  }
}

Cowork's sandboxed VM approach is understood — the request is to allow mounting non-home directories into that sandbox. This would unblock adoption for any user whose workspace isn't under %USERPROFILE%.

Alternative Solutions

Workaround attempted: Created a directory junction (mklink /J "%USERPROFILE%\AI-Hub" "L:\AI-Hub"). Cowork resolves the junction to its real target path and still rejects it. No viable workaround exists — I use Chat + MCP tools instead, which works but lacks Cowork's agentic multi-step capabilities and polished document skills.

Priority

High - Significant impact on productivity

Feature Category

Configuration and settings

Use Case Example

1. I have a 1TB drive (L:\) dedicated to my AI workspace with scripts, knowledge docs, and project files
2. I open Claude Desktop → Cowork tab
3. I want to point Cowork at L:\AI-Hub\Knowledge (30+ markdown files) and say "Create a Table of Contents index as a formatted Word doc and flag any files not updated in 30 days"
4. Cowork rejects the folder because it's not under C:\Users\MidnightPrzm
5. I'm forced to use Chat + MCP instead, losing Cowork's document generation skills (.xlsx, .pptx, .docx) and agentic multi-step execution

Additional Context

• Code tab allows any drive — Cowork is the only mode with this restriction
• Cowork's VM mounts the selected folder — allowing configurable mount paths should be architecturally feasible
• This affects any user with external drives, NAS mounts, or non-C: work partitions
• Claude Desktop v1.1.3963, Windows 11 Pro 25H2 Build 26200