[BUG] Cowork: Linux bash sandbox never finishes booting on macOS — every command returns "Workspace still starting"

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?

In Claude Desktop, when I'm using the Cowork mode and need to run shell commands, the isolated Linux sandbox never finishes booting. Every shell/bash tool call returns:

Workspace still starting. The isolated Linux environment is booting in the background
(usually 10–30 seconds). Try again shortly.

This persists indefinitely — far beyond the expected 10–30 seconds — across many
consecutive retries spread over several minutes. The VM never becomes ready, so no
command can run inside it.

What Should Happen?

The Cowork Linux VM should finish booting within 10–30 seconds, after which bash commands execute inside the Ubuntu guest successfully.

Error Messages/Logs

Workspace still starting. The isolated Linux environment is booting in the background
(usually 10–30 seconds). Try again shortly.

Steps to Reproduce

1. Open Claude Desktop on macOS (Apple Silicon).
2. Open a Cowork session with a connected workspace folder.
3. Ask Claude to run any shell command (e.g. echo ready).
4. Observe: the command returns "Workspace still starting" and never succeeds, no matter how long you wait or how many times you retry.

Claude Model

Opus

Is this a regression?

No, this never worked

Last Working Version

_No response_

Claude Code Version

Claude 1.11847.5

Platform

Anthropic API

Operating System

macOS

Terminal/Shell

Terminal.app (macOS)

Additional Information

_No response_