[Bug] Linux sandbox (bash) permanently fails — cloud workspace not provisioning for Windows Cowork sessions (6+ sessions affected)

[chatkecerdasan]

Preflight Checklist

• I have searched existing issues and this hasn't been reported yet
• This is a single bug report (please file separate reports for different bugs)
• I am using the latest version of Claude Code

What's Wrong?

The isolated Linux sandbox fails to start in every Cowork session on Windows. Every bash call returns immediately: "Workspace unavailable. The isolated Linux environment failed to start." This has persisted across 6+ consecutive sessions over multiple weeks with no recovery.

What Should Happen?

The Linux sandbox should start successfully when a Cowork session begins, allowing Claude to execute bash commands, run Python scripts, and perform shell operations. Sessions should have cwd set to /sessions//mnt/ as was the case before the April 2026 app update.

Error Messages/Logs

Workspace unavailable. The isolated Linux environment failed to start. You can still use file tools directly.

Steps to Reproduce

1. Open Claude Cowork desktop app on Windows (Microsoft Store version)
2. Start any new conversation session
3. Ask Claude to perform any task requiring bash/shell/Python execution
4. Observe Claude calls mcp__workspace__bash
5. Result: immediate failure — "Workspace unavailable. The isolated Linux environment failed to start."
6. Failure is instant with no retry, no startup delay, sandbox never becomes available

Claude Model

Sonnet (default)

Is this a regression?

Yes, this worked in a previous version

Last Working Version

Version before Claude_1.5354.0.0_x64 (last working sessions before 29 April 2026)

Claude Code Version

Claude Cowork 1.5354.0.0 (Microsoft Store, not Claude Code CLI)

Platform

Other

Operating System

Windows

Terminal/Shell

Other

Additional Information

IMPORTANT: This bug is in Claude Cowork (desktop app), not Claude Code CLI.

KEY FINDINGS:

1. Session cwd format changed after app update:

   • BEFORE (working): /sessions//mnt/
   • AFTER (broken): C:\Users\NKB.PRBNS.2111.0025\AppData\Roaming\Claude\local-agent-mode-sessions...

2. No local sandbox exists — installation inspection confirms:
   Path: C:\Program Files\WindowsApps\Claude_1.5354.0.0_x64__pzs8sxrjxfjjc
   Contents: app/ and assets/ folders only
   NO WSL, Docker, container runtime, or sandbox binary found
   %AppData%\Claude does not exist on this machine
   Windows Event Viewer shows ZERO Claude entries

   Conclusion: Linux workspace is a REMOTE/CLOUD service.
   The failure is server-side — nothing to fix locally.

3. Affected sessions (6 confirmed):
   local_7922f495, local_b8a680cb, local_83d21f4b,
   local_b2a16a18, local_b98a6bbc, local_b5a3f165

4. Working sessions (before update):
   local_749d8921, local_b55ec58e, local_9f5155d2, local_95848dc1

5. Anthropic Support Conversation ID: 215474175581735

6. App update date: 29 April 2026 — correlates exactly with regression start

[github-actions]

Found 2 possible duplicate issues:

1. [BUG] Cowork mode - Linux bash sandbox never starts on Windows (Workspace unavailable since first launch) #55649
2. [BUG] Cowork desktop app — bash workspace fails to start repeatedly across sessions #55404

This issue will be automatically closed as a duplicate in 3 days.

• If your issue is a duplicate, please close it and 👍 the existing issue instead
• To prevent auto-closure, add a comment or 👎 this comment

🤖 Generated with Claude Code

[github-actions]

This issue has been automatically closed as a duplicate of #55649.

If this is incorrect, please re-open this issue or create a new one.

🤖 Generated with Claude Code

[mederic-coreai]

« +1 same symptom on Surface Book 3 / Windows 11 Pro / i7-1065G7. Identified root cause as 5-second timeout race between Claude Desktop and CoworkVMService startup. Detailed trace and PowerShell workaround posted in #48661 ([link to your comment]). Sharing in case it helps others land on the right fix faster than nuking their install. »