VS Code background-agent panel does not update when native subagents are spawned

What version of the IDE extension are you using?

openai.chatgpt-26.707.91948-darwin-arm64

Which IDE are you using?

Visual Studio Code 1.129.0

What platform is your computer?

macOS (Apple Silicon / arm64)

What issue are you seeing?

The VS Code extension's “background agents” panel does not update immediately when the current Codex session creates new active native subagents.

What steps can reproduce the bug?

1. Start a Codex task inside the VS Code extension.
2. Have the main agent invoke the native multi-agent spawn API and create two subagents (in my reproduction, nicknamed Feynman and Epicurus).
3. While the same session remains open, inspect the “background agents” panel above the composer.
4. Observe that neither newly created subagent appears.
5. Leave the session to the session list and reopen the same session while both agents are still running.
6. Observe that both agents now appear in the “background agents” panel.

What is the expected behavior?

The background-agent panel should update immediately when a new active subagent is created in the current session, without navigating away from or reopening the session.

What is the actual behavior?

The panel remains stale until the session is left and reopened. Until then, the user cannot observe, open, or stop freshly spawned background agents from the IDE UI.

Impact

This prevents real-time monitoring and control of active native subagents from the VS Code extension and makes it easy to miss work that is running in the background.

Additional information

This may indicate a UI hydration or realtime-subscription/update issue, but I am not asserting a root cause.

A related but distinct open issue is #31971, “VS Code reload re-adds closed subagents to the "background agents" count”: https://github.com/openai/codex/issues/31971. That report concerns completed/closed agents incorrectly reappearing after reload; this report concerns newly active agents not appearing during the live session until reload/reopen.