[BUG] Cowork sandbox disk at 100% capacity — base image too large for allocated disk

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 at 100% capacity (9.2 GB used / 9.8 GB total, only 44 MB free) before any user work is done. The base image itself consumes virtually all available disk space, making the sandbox unusable for any task that requires writing files or installing packages.

What Should Happen?

The sandbox should have meaningful free disk space available for user work after the base image is loaded. A reasonable minimum would be 2-3 GB free.

Error Messages/Logs

Filesystem: /dev/sdc — Size: 9.8G, Used: 9.2G, Avail: 44M, Use%: 100%

Largest consumers in base image:
- /usr/lib/firmware: 1.2 GB
- /usr/lib/x86_64-linux-gnu: 832 MB
- /usr/lib/modules: 601 MB
- /snap/lxd + /var/lib/snapd: ~1 GB
- /usr/local/lib/python3.10/dist-packages: 718 MB
- /usr/local/bin/claude binary: 225 MB
- /var/lib/apt/lists: 289 MB
- /var/log/journal: 105 MB
- /usr/share/doc: 171 MB

User session files: only 4.7 MB
Cleanup blocked: sandbox user has no sudo, no_new_privileges enforced, all system paths root-owned.

Steps to Reproduce

1. Open a Cowork session
2. Run: df -h /sessions
3. Observe disk is at 100% capacity
4. Run: du -sh /* 2>/dev/null | sort -rh
5. Observe that the base image alone consumes 9.2 GB

Claude Model

Sonnet (default)

Is this a regression?

Yes, this worked in a previous version

Last Working Version

Unknown — discovered on April 23, 2026

Claude Code Version

Claude Cowork (desktop app)

Platform

Anthropic API

Operating System

Windows

Terminal/Shell

Other

Additional Information

Account email: qiao.mufan.p1@dc.tohoku.ac.jp

The issue cannot be resolved from within the session. The sandbox enforces no_new_privileges, sudo is blocked, and all reclaimable directories (APT cache, journal logs, package docs) are root-owned. A human engineer needs to either increase the disk allocation or reduce the base image footprint.