[BUG] Cowork VM connection timeout on Windows ARM64 — load_swift_api completes in 0ms (no-op), guest agent never connects

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?

Root cause identified in logs: load_swift_api completes in 0ms —
suspiciously fast, suggesting it is a no-op on Windows ARM64 (Swift APIs
are native to macOS/Apple platforms). The guest agent never responds after
this step, causing the 60s timeout.

Secondary issue: After the first timeout, smol-bin.vhdx remains
locked by the failed VM instance (EBUSY), causing subsequent start attempts
to skip the smol-bin copy step entirely.

System Info:

• Device: Windows ARM64 (Microsoft Surface)
• OS: Windows 11 Pro (ARM64)
• Claude Desktop Version: 1.24012.11.0_arm64
• Installation method: MSIX (WindowsApps)

Troubleshooting Already Completed:

• Restarted app and computer multiple times (full restart, not shutdown)
• Reinstalled workspace via in-app option
• Enabled Hyper-V (all components: Microsoft-Hyper-V, HypervisorPlatform,

VirtualMachinePlatform)

• Verified hypervisorlaunchtype = Auto (bcdedit)
• Verified HyperVisorPresent = True
• Installed WSL2 (Default Version: 2)
• Verified all services running: vmcompute, hns, CoworkVMService
• Full AppData wipe attempted
• Confirmed VM bundle is complete and ARM64-compatible

(vmlinuz MZ header = ARM64 kernel, smol-bin.arm64.vhdx present)

Key Log Findings (cowork_vm_node.log):

Attempt 1 — times out at add_plan9_shares:
[VM:steps] vm_boot completed (218ms)
[VM:steps] add_plan9_shares completed (8023ms)
[VM:start] Still waiting for guest connection... 10199ms elapsed
[VM:start] Still waiting for guest connection... 51068ms elapsed
[VM:error] Connection timeout, last completed step: add_plan9_shares

Attempts 2 & 3 — load_swift_api suspicious 0ms + EBUSY:
[VM:steps] load_swift_api started
[VM:steps] load_swift_api completed (0ms) ← likely no-op on Windows
[VM:start] smol-bin.vhdx locked by running VM (EBUSY), skipping copy
[VM:start] Still waiting for guest connection... 10246ms elapsed
[VM:start] Still waiting for guest connection... 51243ms elapsed
[VM:error] Connection timeout, last completed step: load_swift_api
[VM:start] Skipping auto-reinstall (already attempted once)

Hypothesis:
load_swift_api appears to be a macOS/Apple Swift virtualization API
that has no functional implementation on Windows ARM64. It returns
immediately (0ms) without error, but the guest agent communication
layer is never properly initialized, causing the permanent timeout.

Related Issues: #39161, #42784, #44007, #47737, #51277, #65128, #67066

What Should Happen?

Cowork workspace should start and connect to the VM guest agent
successfully, as it does on x64 Windows systems.

Error Messages/Logs

Attempt 1 — times out at add_plan9_shares:

[VM:steps] vm_boot completed (218ms)
[VM:steps] add_plan9_shares completed (8023ms)
[VM:start] Still waiting for guest connection... 10199ms elapsed
[VM:start] Still waiting for guest connection... 51068ms elapsed
[VM:error] Connection timeout, last completed step: add_plan9_shares

Attempts 2 & 3 — load_swift_api 0ms no-op + EBUSY:

[VM:steps] load_swift_api started
[VM:steps] load_swift_api completed (0ms)   ← likely no-op on Windows ARM64
[VM:start] smol-bin.vhdx locked by running VM (EBUSY), skipping copy
[VM:start] Still waiting for guest connection... 10246ms elapsed
[VM:start] Still waiting for guest connection... 51243ms elapsed
[VM:error] Connection timeout, last completed step: load_swift_api
[VM:start] Skipping auto-reinstall (already attempted once)

Steps to Reproduce

1. Install Claude Desktop (MSIX) on any Windows 11 ARM64 device
2. Open Claude Desktop
3. Click on the Cowork tab
4. Observe: "Failed to start Claude's workspace —

VM connection timeout after 60 seconds"

1. Error persists on every subsequent attempt regardless of

restarts, reinstalls, or Hyper-V configuration

Claude Model

Not sure / Multiple models

Is this a regression?

I don't know

Last Working Version

_No response_

Claude Code Version

not claude code related, but cowork

Platform

Anthropic API

Operating System

Windows

Terminal/Shell

Windows Terminal

Additional Information

_No response_