claude-code - 💡(How to fix) Fix [BUG] Cowork "Virtualization is not available" on EC2 Windows t3.large — nested virtualization not supported on Nitro instances [1 participants]

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. 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

• Error appears immediately, restarting does not help

TL;DR

The issue can be addressed by updating the error message to clearly state that Cowork is not supported on EC2 instances due to the lack of nested virtualization support.

Guidance

• Verify that the instance type used does not support nested virtualization, as indicated by the aws ec2 modify-instance-attribute --attribute nestedVirtualization command returning "Unknown attribute".
• Check the official documentation for supported instance types and virtualization requirements for Cowork.
• Consider using a different instance type that supports nested virtualization, if available.
• Update the error message to reflect the incompatibility with EC2 instances, rather than suggesting a restart or BIOS fix.

Example

No code snippet is provided as it is not necessary for this issue.

Notes

The issue is specific to EC2 instances with the Nitro hypervisor, which do not support nested virtualization. This limitation is a known constraint and should be clearly communicated to users.

Recommendation

Apply workaround: Update the error message to clearly state the incompatibility with EC2 instances. This will help prevent confusion and provide a clearer understanding of the issue.