[BUG] Cowork Plugin cache never cleaned up per session, causing sessiondata.img to fill up and all new conversations to fail

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?

What's Wrong?

Every conversation creates a new user directory under /sessions/<name>/ inside the VM
and caches all installed plugins there. These directories are never cleaned up after
the conversation ends. Over time, sessiondata.img (fixed at 8.5GB) fills up
internally and all new conversations fail.

Note: this is distinct from #28128 (ENOSPC on temp files within a session). The root
cause here is plugin cache accumulation across sessions, not temp file bloat within a
single session.

What Actually Happens?

After ~80 conversations, every new conversation fails immediately with:
RPC error: ensure user: useradd failed: exit status 12: useradd: cannot create
directory /sessions/<session-name>

coworkd.log on startup shows:
[coworkd] user recovery complete: recovered=81 skipped=8 failed=0

81 old session directories are still present on disk, each containing a full copy of
all installed plugins.

What Should Happen?

What Should Happen?

Plugin cache directories under /sessions/<name>/mnt/.local-plugins/ and
/sessions/<name>/mnt/.remote-plugins/ should be cleaned up when a conversation ends,
or shared/deduplicated across sessions rather than copied fresh each time.

Error Messages/Logs

RPC error: ensure user: useradd failed: exit status 12: useradd: cannot create directory /sessions/stoic-jolly-fermat

Steps to Reproduce

Steps to Reproduce

1. Install several plugins in Claude Desktop
2. Have ~80+ conversations over time
3. Every new conversation fails with the RPC error above
4. Restarting the app does not help — the image is full

The plugin directories eating the space (per session):
/sessions/<name>/mnt/.skills
/sessions/<name>/mnt/.remote-plugins/
/sessions/<name>/mnt/.local-plugins/cache/
/sessions/<name>/mnt/.local-plugins/marketplaces/

With many plugins installed, each session's cache is substantial. 81 sessions × N
plugins = 8.5GB exhausted.

Impact

Scales inversely with plugin count — power users with many plugins will hit this much
sooner than ~80 sessions. Effectively, the more you use Claude Desktop's plugin
ecosystem, the faster you get bricked.

Workaround

1. Fully quit Claude Desktop
2. mv "~/Library/Application

Support/Claude/vm_bundles/claudevm.bundle/sessiondata.img"
~/Desktop/sessiondata.img.bak

1. Restart Claude Desktop (recreates the image fresh)
2. Delete .bak to reclaim ~8.5GB

Environment

• Claude Desktop version: 1.1.4498
• macOS: Darwin 25.3.0
• sessiondata.img size at failure: 8.5GB
• Sessions accumulated: 81

Claude Model

Not sure / Multiple models

Is this a regression?

Yes, this worked in a previous version

Last Working Version

_No response_

Claude Code Version

• Claude Desktop version: 1.1.4498

Platform

Anthropic API

Operating System

macOS

Terminal/Shell

Terminal.app (macOS)

Additional Information

<img width="593" height="239" alt="Image" src="https://github.com/user-attachments/assets/ae55ac3f-544f-44cb-9293-f21f1009c870" />