[BUG] Cowork mode sandbox stuck — Bash tool fails to mount virtiofs share repeatedly (Windows)

### Preflight Checklist

- [x] I have searched [existing issues](https://github.com/anthropics/claude-code/issues?q=is%3Aissue%20state%3Aopen%20label%3Abug) 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?

bash failed on resume, create, and re-resume. resume: RPC error -1: failed to mount /mnt/.virtiofs-root/shared/c/... as outputs: source path ... is under Plan9 share "c" which is not mounted; create: RPC error -1: ensure user: user already exists unexpectedly: uid=1416 gid=1416

### What Should Happen?

The Bash tool (mcp__workspace__bash) should successfully mount the session's outputs/uploads folders from the local Windows drive (C:) into the Linux sandbox, so that scripts (e.g. Python/openpyxl) can read and write files in the connected workspace folder. A scheduled task that reads an Excel master DB, generates new statement files, and writes back to the workspace folder should complete without manual intervention. If a mount transiently fails, the tool should recover automatically on retry rather than failing identically 5 times in a row within the same session, and restarting the Claude app or rebooting the OS should be sufficient to restore a working sandbox.

### Error Messages/Logs

```shell
bash failed on resume, create, and re-resume. resume: RPC error -1: failed to mount /mnt/.virtiofs-root/shared/c/Users/user/AppData/Local/Packages/Claude_pzs8sxrjxfjjc/LocalCache/Roaming/Claude/local-agent-mode-sessions/7719ff93-0c58-41b6-8386-154b039b3089/3c6e1ff9-466d-4ed8-8ab0-fc3b19663b38/local_4a862ab6-8937-4e83-a21c-cdb87251b21d/outputs as outputs: source path /mnt/.virtiofs-root/shared/c/Users/user/AppData/Local/Packages/Claude_pzs8sxrjxfjjc/LocalCache/Roaming/Claude/local-agent-mode-sessions/7719ff93-0c58-41b6-8386-154b039b3089/3c6e1ff9-466d-4ed8-8ab0-fc3b19663b38/local_4a862ab6-8937-4e83-a21c-cdb87251b21d/outputs is under Plan9 share "c" which is not mounted; create: RPC error -1: ensure user: user adoring-lucid-faraday already exists unexpectedly: uid=1416 gid=1416
```

### Steps to Reproduce

Open a Cowork mode session in the Claude desktop app, with a local folder connected (e.g. Desktop\자동화).
In that session, have a scheduled task registered that manipulates files in the workspace folder (a Python script reading/writing an Excel file), then trigger that task. (Alternatively, just make any chat request that invokes the mcp__workspace__bash tool.)
The Bash tool fails with the following error:
bash failed on resume, create, and re-resume. resume: RPC error -1: failed to mount /mnt/.virtiofs-root/shared/c/... as outputs: source path ... is under Plan9 share "c" which is not mounted; create: RPC error -1: ensure user: user already exists unexpectedly: uid=1416 gid=1416
Retry the Bash tool call in the same session — the identical error recurs (reproduced 5 times in a row).
By contrast, file tools (Read/Write/Glob) accessing the same workspace folder work normally — so file access itself is fine; only the Bash/Linux sandbox mount is failing.
Fully quit and restart the Claude desktop app — the issue persists.
Reboot Windows entirely and retry in the same session — the identical error still recurs.
(Unconfirmed) Whether opening a brand-new conversation/session resolves it has not yet been tested — if you haven't tried this yet, do so and add the result, since it would clarify whether the issue is scoped to one wedged session or is systemic.

### Claude Model

Sonnet (default)

### Is this a regression?

Yes, this worked in a previous version

### Last Working Version

_No response_

### Claude Code Version

2.1.267

### Platform

Anthropic API

### Operating System

Windows

### Terminal/Shell

PowerShell

### Additional Information

_No response_

Start by reproducing the failure from a Windows Claude desktop Cowork session through mcp__workspace__bash, using the logged virtiofs and Plan9 mount errors as the entry point. Compare resume, create, and re-resume behavior, including repeated retries and a new session. Done means the Bash tool mounts the workspace outputs/uploads folders and recovers from transient failures without requiring manual intervention.

索引モデルが issue の本文から書いたものです。