[BUG] Cowork VM disk full on session start - ENOSPC blocks all Bash commands

Environment

• Session: determined-keen-albattani
• Project: PowerPoint Generator
• Model: claude-opus-4-6
• Platform: macOS (Cowork)
• Date: 2026-03-22

Description

The Cowork VM internal disk is completely full at session start. Every Bash tool invocation fails before executing any command because the tool infrastructure cannot create its required temp directory. No shell commands can run at all - not even diagnostic commands like df -h.

Error

Every Bash call fails identically with:

ENOSPC: no space left on device, mkdir '/sessions/determined-keen-albattani/tmp/claude-XXXX'

This occurs before the user command executes. The mkdir is performed by the Bash tool infrastructure itself, not the user command.

Key Facts

• Bash was broken from the very first command. Zero successful Bash calls in the entire session.
• The session directory is nearly empty. Glob confirms only dotfiles (.profile, .bashrc, .bash_logout) and the mounted user folder exist. No node_modules, no build artifacts, no PDFs, no leftover files.
• The /sessions/.../tmp/ directory is empty.
• The mounted folder (user Mac filesystem) has plenty of space. Write tool successfully creates files on the mount.
• /dev/shm has available space. Write tool can create files there. But the Bash tool temp directory path is hardcoded to the session path.
• Zero builds were attempted. This was a fresh session with no prior work done.

Diagnosis

The disk was full before the session started. Since the session directory is clean and no user activity occurred, the problem is in the base image or container runtime - either the image is too large for the disk allocation, the disk quota is too small, or ephemeral storage was not provisioned.

Impact

Complete blocker for any task requiring shell execution:

• Node.js builds (npm install, node scripts)
• Package installation (npm, pip)
• Python script execution
• File conversions (LibreOffice, pdftoppm)
• Git operations
• All diagnostic commands (df, ls, rm, du)

Tools that still work: Read, Write, Edit, Glob, Grep, MCP tools.

Workaround

Built a full 22-slide PptxGenJS presentation by writing scripts to the mounted Mac folder and executing them via mcp__Control_your_Mac__osascript (do shell script). This works but is significantly slower and more fragile.

Reproduction Steps

1. Open Cowork mode with the PowerPoint Generator project
2. Try any Bash command: ls, df -h, echo test
3. All fail with: ENOSPC: no space left on device, mkdir '/sessions/determined-keen-albattani/tmp/claude-XXXX'
4. Confirm Write tool works on mounted folder but not on session directory
5. Confirm /dev/shm has available space via Write tool

Suggestions

1. Configurable TMPDIR for Bash tool - allow temp directory creation at /dev/shm/ or /tmp/ instead of /sessions/.../tmp/
2. Disk space monitoring - surface df -h in session metadata
3. Auto-cleanup on session start
4. Increase disk allocation for build-heavy workflows
5. Pre-install common tools (LibreOffice, pdftoppm) in the VM image