Cowork workspace fails to start - Cowork SDK missing from macOS arm64 installer (likely duplicate of #31647)

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?

m64 installer (likely duplicate of #31647)
Environment:

• macOS 26.4.1 (build 25E253)
• Apple Silicon (arm64)
• Claude Desktop: Claude 1.5354.0 (9a9e3d) 2026-04-29T01:14:34.000Z

Symptom:
"Failed to start Claude's workspace - Download failed. Check your internet connection and try again."

What's actually failing:
The error message is misleading. Logs show the VM image downloads and validates correctly (~13 GB, checksums pass). The actual failure is in the SDK prepare step.

Diagnostic output:

$ ls /Applications/Claude.app/Contents/Resources/app.asar.unpacked/node_modules/ | grep -i -E "claude-code|cowork|swift"
(no output - SDK is missing from app bundle)

$ ls -la ~/Library/Application\ Support/Claude/claude-code-vm/
total 0
drwx------@ 3 ... .
drwx------@ 42 ... ..
drwx------@ 2 ... 2.1.121 ← empty (only . and ..)

Log excerpt from ~/Library/Logs/Claude/cowork_vm_node.log:
[info] [cache] rootfs.img checksum validated
[info] All files ready in /Users/.../claudevm.bundle
[error] [VM:steps] download_and_sdk_prepare failed: Download failed.

Steps already taken:

• Deleted vm_bundles, let it re-download (works, but same error)
• Deleted claude-code-vm cache folder
• Full app uninstall (drag to Trash, empty Trash)
• Reboot
• Fresh install from claude.ai/download
• All produce identical empty 2.1.121/ folder, confirming SDK isn't shipping in the installer

• Claude Desktop: 1.5354.0 (build 9a9e3d, released 2026-04-29) — confirmed latest via in-app update check
• Expected Cowork SDK: 2.1.121 (per .sdk-version), latest available: 2.1.128

Likely duplicate of #31647 (macOS Cowork runtime missing from app bundle).

What Should Happen?

After installing Claude Desktop from claude.ai/download, the Cowork SDK runtime should be present in the app bundle at /Applications/Claude.app/Contents/Resources/app.asar.unpacked/node_modules/, and on first launch it should extract into ~/Library/Application Support/Claude/claude-code-vm/<version>/.

The workspace should then start successfully and be usable for code execution and file tools.

Error Messages/Logs

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.

Steps to Reproduce

1. On macOS 26.4.1 (Apple Silicon), download Claude Desktop from https://claude.ai/download
2. Install Claude.app to /Applications
3. Launch Claude and sign in
4. Open the Cowork workspace (or trigger any tool that requires the VM, e.g. code execution)
5. Observe the error: "Failed to start Claude's workspace - Download failed. Check your internet connection and try again."

Verification that the SDK is missing from the installer:

ls /Applications/Claude.app/Contents/Resources/app.asar.unpacked/node_modules/ | grep -i -E "claude-code|cowork|swift"
→ returns no output

ls -la ~/Library/Application\ Support/Claude/claude-code-vm/
→ shows version folder (e.g. 2.1.121) that is empty (only . and ..)

tail ~/Library/Logs/Claude/cowork_vm_node.log
→ shows VM image downloads and validates successfully, then download_and_sdk_prepare fails immediately after "All files ready"

The bug reproduces on every fresh install. Steps already attempted that do NOT resolve it:

• Deleting ~/Library/Application Support/Claude/vm_bundles/ and re-downloading
• Deleting ~/Library/Application Support/Claude/claude-code-vm/
• Full uninstall (Trash + Empty Trash), reboot, fresh install from claude.ai/download

No minimal code example is needed — the bug is in the installer payload itself, not in any user code or file. Reproduction requires only a fresh download and install on macOS arm64.

Claude Model

Opus

Is this a regression?

Yes, this worked in a previous version

Last Working Version

_No response_

Claude Code Version

Claude 1.5354.0 (9a9e3d)

Platform

Anthropic API

Operating System

macOS

Terminal/Shell

Terminal.app (macOS)

Additional Information

_No response_