Codex VS Code extension 26.506.31421 shows blank chat webview on Windows 11 Hyper-V VM, while 26.318.11754 works

<img width="1603" height="1025" alt="Image" src="https://github.com/user-attachments/assets/c001a263-b450-40a5-89c9-a89c5b262e66" />

What version of the IDE extension are you using?

26.506.31421

What subscription do you have?

Plus

Which IDE are you using?

VS Code 1.120 (but the issue is present also in 1.115 and subsequent)

What platform is your computer?

Windows 11 Pro VM in HyperV on Windows 11 Pro

What issue are you seeing?

Summary

The Codex VS Code extension does not render the chat webview on a Windows 11 VM running on Hyper-V.

The issue is reproducible with the latest Codex extension version 26.422.30944, but an older version, 26.318.11754, works correctly on the same VM.

The same VS Code version and the same Codex extension version work correctly on another Windows PC, so this does not look like a general regression for all Windows installations. It seems related to running inside a Hyper-V Windows 11 VM or to the rendering/webview environment exposed to Electron/Chromium inside the VM.

Environment

Failing environment

• OS: Windows 11 Pro running inside a Hyper-V VM
• VS Code: 1.120.0 user setup
• Codex extension: openai.chatgpt@26.506.31421
• Previous working Codex extension version: openai.chatgpt@26.318.11754
• Session type: both Console and RDP

VS Code About:

Version: 1.120.0 (user setup)
Commit: 0958016b2af9f09bb4257e0df4a95e2f90590f9f
Date: 2026-05-12T20:17:22Z
Electron: 39.8.8
ElectronBuildId: 13870025
Chromium: 142.0.7444.265
Node.js: 22.22.1
V8: 14.2.231.22-electron.0
OS: Windows_NT x64 10.0.26200

What steps can reproduce the bug?

Steps to reproduce

1 - Start from a clean Windows 11 Hyper-V VM.
2 - Install VS Code 1.120.0 user setup.
3 - Install Codex extension openai.chatgpt@26.506.31421.
4 - Open the Codex chat panel.
5 - The panel opens, but the chat UI does not render.

The issue is reproducible even on a newly created Windows 11 VM with a clean VS Code installation.

What is the expected behavior?

The Codex chat webview should render normally and show the full chat interface.

After opening the Codex panel in VS Code, I expect to see the conversation UI, model selector, input box, and normal Codex controls, as happens with extension version 26.318.11754 on the same VM and with version 26.422.30944 on another Windows PC.

The extension should either work inside a Windows 11 Hyper-V VM or, if this environment is unsupported, fail with a clear diagnostic/error message instead of showing a blank or incomplete webview.

Additional information

Troubleshooting already performed

I tried the following and the issue still reproduces:

• Reinstalled VS Code.
• Removed VS Code user data.
• Tested with a clean VS Code user data directory:

code --user-data-dir C:\Temp\vscode-clean-user --extensions-dir C:\Temp\vscode-clean-ext

• Tested with only the Codex extension installed:

openai.chatgpt@26.506.31421

• Disabled GPU acceleration.
• Forced a clean extension directory.
• Tested a brand-new Windows 11 Hyper-V VM with clean VS Code installation.
• Verified that the same VS Code and Codex versions work correctly on another Windows PC.
• Verified that the VS Code Markdown Preview webview works correctly.
• Verified that the session is Console, not only RDP:

$env:SESSIONNAME
Console

• Added GPU-P / GPU partitioning to the VM.
• Installed AMD GPU drivers in the guest VM.
• The AMD GPU is now recognized by Windows in the VM, but the Codex webview still does not render.

Additional notes

This does not appear to be caused by:

• VS Code profile corruption
• Settings Sync
• other VS Code extensions
• normal VS Code webview failure, because Markdown Preview works
• VS Code version mismatch
• Codex version mismatch
• Chrome browser version
• RDP / Enhanced Session rendering

The strongest remaining signal is that the failure only happens inside Windows 11 Hyper-V VMs, including a newly created clean VM.

Hypothesis

The newer Codex webview introduced after 26.318.11754 may depend on a rendering, WebGL, service worker, browser API, or Electron/Chromium behavior that does not work correctly inside this Hyper-V Windows 11 VM environment.

The extension host starts, but the Codex webview does not complete rendering.

Could you please check whether the newer Codex webview has a dependency or initialization path that may fail under Hyper-V / GPU-P / virtualized graphics environments?