[Cowork] Sandbox disk stuck at 100% full, not cleared by app or PC restart

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?

The Cowork sandbox disk is stuck at 100% full. Any bash or Python command fails with "No space left on device". This persists across new chats, full app restarts (including killing background processes via Task Manager), and full Windows PC restarts.

df -h inside the sandbox shows:

• /dev/sdc mounted at /sessions: 9.3G used of 9.8G, 0 available, 100% full
• - /dev/sda1 mounted at /: 8.8G used of 9.6G, 93% full

du -sh /sessions only shows 11MB of visible data. 9.3GB is invisible to the user and not clearable from within the sandbox. ls /sessions/ shows 371 leftover session folders going back to 4 May 2026.

What Should Happen?

The Cowork sandbox disk should clear between sessions so bash and Python commands work again. Starting a new chat or restarting the app should reset the sandbox to empty, with disk space available for new commands.

Error Messages/Logs

$ df -h
Filesystem      Size  Used Avail Use% Mounted on
/dev/sdc        9.8G  9.3G     0 100% /sessions
/dev/sda1       9.6G  8.8G  756M  93% /

$ du -sh /sessions
11M	/sessions

$ ls /sessions/ | wc -l
371

Any bash/Python command fails with: bash: cannot create temp file for here-document: No space left on device

Steps to Reproduce

1. Open Claude Cowork (Windows desktop app, research preview)
2. 2. Start a new chat in any project
3. 3. Ask Claude to run df -h in the sandbox
4. 4. Observe: /dev/sdc mounted at /sessions shows 9.3G used of 9.8G, 100% full, 0 available
5. 5. Try any bash or Python command - all fail with "No space left on device"
6. 6. Close the app completely (including background processes via Task Manager)
7. 7. Reopen Claude Cowork, start a new chat
8. 8. Run df -h again - still 100% full
9. 9. Restart the entire Windows PC
10. 10. Reopen Claude Cowork, start a new chat
11. 11. Run df -h again - still 100% full

Note: du -sh /sessions shows only 11MB of visible data, meaning 9.3GB is held by the system and cannot be cleared from within the sandbox. There are 371 leftover session folders in /sessions/ going back to 4 May 2026.

Claude Model

None

Is this a regression?

Yes, this worked in a previous version

Last Working Version

_No response_

Claude Code Version

Claude Cowork (Windows desktop app, research preview - not Claude Code CLI)

Platform

Anthropic API

Operating System

Windows

Terminal/Shell

Windows Terminal

Additional Information

Important context: This is Claude Cowork (research preview mode in the Windows desktop app), NOT Claude Code CLI. These are different products with different sandbox architectures.

Impact: Scheduled automation workflows that rely on Python-based skills (Excel, Word, PDF, screenshots) are completely blocked. Specifically a workflow called "Solve Migration" that updates Excel files and saves screenshots to SharePoint.

User: Christian Madsen, 11 Recruitment, Perth, Western Australia
Contact: cmadsen@11recruitment.com.au

What we need:
Either clear the stuck Cowork sandbox storage on the backend for this account, or document the specific file or folder that can be safely deleted on Windows to force a sandbox reset without losing memory files, projects, skills, or chat history.

Anthropic support has been contacted multiple times but was unable to resolve this as the Cowork sandbox documentation is separate from Claude Code documentation.