[BUG] Cowork "Virtualization is not available" on EC2 Windows t3.large — nested virtualization not supported on Nitro instances

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?

Cowork is unusable on AWS EC2 Windows instances. The error "Claude's workspace requires Virtual Machine Platform, but the virtualization service isn't responding" appears and cannot be resolved because EC2 Nitro instances (e.g. t3.large) do not support nested virtualization — meaning Cowork's VM can never initialize.

Environment:

• Instance type: t3.large (AWS EC2, Nitro hypervisor)
• OS: Windows Server (Administrator account)
• Virtual Machine Platform: Enabled
• CoworkVMService: Running
• %APPDATA%\Claude: Never created — VM never initializes
• systeminfo Hyper-V: "A hypervisor has been detected. Features required for Hyper-V will not be displayed."

What Should Happen?

Either Cowork works on EC2, or the error message clearly states "Cowork is not supported on cloud VMs / EC2 instances" rather than misleadingly suggesting a BIOS/restart fix.

Error Messages/Logs

Virtualization is not available

Claude's workspace requires Virtual Machine Platform, but the virtualization service isn't responding. Restart your computer to resolve this.

Steps to Reproduce

• Launch a t3.large EC2 Windows instance
• Install Claude Desktop
• Open Cowork tab
• Error appears immediately, restarting does not help
• aws ec2 modify-instance-attribute --attribute nestedVirtualization returns Unknown attribute for t3

Claude Model

Opus

Is this a regression?

No, this never worked

Last Working Version

_No response_

Claude Code Version

2.1.59 (Claude Code)

Platform

Anthropic API

Operating System

Windows

Terminal/Shell

PowerShell

Additional Information

_No response_