[BUG] Cowork tool sandbox VM fails to start on macOS 26 — missing com.apple.vm.networking entitlement (v1.11847.5)

[Wildpixels]

Description

Cowork launches and chat works normally, but the Linux bash VM used to execute tools (file operations, code execution, etc.) fails to start. Cowork chat incorrectly identifies this as a remote server issue, but the root cause is a missing code-signing entitlement on the local app bundle.

Root Cause

The app is signed with com.apple.security.virtualization but is missing com.apple.vm.networking. On macOS 26, the Virtualization framework requires this entitlement for the guest VM to access the network. Without it, macOS silently blocks all VM network traffic, so the bridge sockets between host and guest never connect and the tool sandbox times out.

Reproduction

1. Install Claude Desktop v1.11847.5 on macOS 26.5.1
2. Open Cowork and start a chat — chat works fine
3. Trigger any tool that requires the bash sandbox (e.g. file read, code execution)
4. Tool execution fails — Cowork chat reports a remote server error (misleading)

Verify the missing entitlement:

codesign -d --entitlements - /Applications/Claude.app 2>&1 | grep -i "vm.networking"
# returns nothing

Environment

• Claude Desktop: v1.11847.5
• macOS: 26.5.1 (Build 25F80)
• Chip: Apple M3

Current Entitlements (relevant subset)

com.apple.security.virtualization = true
com.apple.vm.networking           = MISSING

Workarounds Attempted (all failed)

• Deleting sessiondata.img (VM bundle reset)
• Deleting entire ~/Library/Application Support/Claude/vm_bundles/
• Killing all Claude processes + clearing stale /tmp/claude-* sockets
• Reinstalling workspace via built-in button

Expected Fix

Re-sign the app bundle with the com.apple.vm.networking entitlement.

[Wildpixels]

Some update:
Updated (with the in-app updater) to Claude 1.12603.1 (3df4fd)

Problem persists with now an explicit pop up window with this message:
"Failed to start Claude's workspace
Download failed. Check your internet connection and try again.
Restarting Claude or your computer sometimes resolves this. If it persists, you can reinstall the workspace."

After clicking reinstall the workspace, Claude restarts and I can see a download happening, but it keeps having the same error.
Manually deleting the VM with "rm -rf ~/Library/Application\ Support/Claude/vm_bundles" and relaunching Claude also trigger the redownload. Checking the com.apple.vm.networking entitlement does not return anything, so likely it is still missing.

[Wildpixels]

VM launch issue fixed in Claude 1.13576.0 (1290fc) 2026-06-16T05:46:10.000Z

[github-actions]

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