VS Code Codex sidebar hangs when GitHub Copilot Chat is enabled

Summary

The Codex sidebar in VS Code hangs indefinitely on the OpenAI logo whenever GitHub Copilot Chat is enabled. Disabling GitHub Copilot Chat and reloading VS Code makes the Codex sidebar load normally.

This was reproduced after a full VS Code purge/reinstall and after testing with a clean VS Code user-data directory. The Codex CLI and Codex conversations opened through VS Code's Chat view remained usable; the dedicated Codex sidebar was the failing surface.

Environment

• OS: Ubuntu 22.04.5 LTS (X11/GNOME)
• VS Code: 1.129.1 (8a7abeba6e03ea3af87bfbce9a1b7e48fed567b8)
• Codex extension: openai.chatgpt@26.715.31925
• GitHub Copilot Chat: bundled VS Code chat extension (VS Code did not report a separate Marketplace version)

Steps to reproduce

1. Start from a clean VS Code installation/profile.
2. Install and enable openai.chatgpt.
3. Confirm that the dedicated Codex sidebar loads successfully.
4. Enable GitHub Copilot Chat.
5. Reload VS Code and open the dedicated Codex sidebar.
6. Observe that the sidebar remains indefinitely on the OpenAI loading logo.
7. Disable GitHub Copilot Chat and reload VS Code.
8. Observe that the Codex sidebar loads successfully again.

Expected behavior

Codex and GitHub Copilot Chat should coexist without preventing the Codex sidebar Webview from initializing.

Actual behavior

With GitHub Copilot Chat enabled, the Codex sidebar never progresses beyond the OpenAI logo. Disabling Copilot Chat immediately restores the sidebar after reload.

Relevant logs

The VS Code extension-host/renderer logs included:

No bundle location found for extension GitHub.copilot-chat
MainThreadChatAgents2#$updateAgent: No agent with handle 2 registered

During failing starts, the Codex app-server activated and initialized, but the dedicated sidebar did not complete its Webview bootstrap. A Codex conversation Webview could still reach:

[statsig-refresh-diagnostics] React root render requested windowType=extension
[startup][renderer] app routes mounted
maybe_resume_success

Troubleshooting performed

• Verified proxy and HTTPS connectivity to chatgpt.com.
• Confirmed the Codex CLI and model access worked.
• Cleared VS Code Service Worker, Cache, Code Cache, and GPUCache.
• Reinstalled the Codex extension.
• Completely purged VS Code, ~/.config/Code, and ~/.vscode, then reinstalled VS Code and only Codex.
• Tested a separate clean --user-data-dir and --extensions-dir; Codex worked there.
• Re-enabled synced extensions and reproduced the failure.
• Isolated the trigger to GitHub Copilot Chat: enabled = failure; disabled = success.

This may be related to the Webview bootstrap/lifecycle symptoms in #32420, but this report has a repeatable extension-level trigger rather than an intermittent Remote-SSH trigger.