[Windows] Queuing a follow-up in a side chat fails with "ephemeral thread does not support queued submissions"

What version of the Codex App are you using (From “About Codex” dialog)?

26.908.4834.0

What subscription do you have?

plus

What platform is your computer?

Microsoft Windows NT 10.0.19045.0 x64

What issue are you seeing?

In the Codex App on Windows, I cannot queue a follow-up message while a side chat is actively responding.

When I submit a new message in the focused side chat with Queue as the active follow-up mode, the app shows this error:

ephemeral thread does not support queued submissions: 01a0965f-52e2-7830-b476-50338e1ca5ef

The follow-up message is not added to the side chat queue and does not run after the active response finishes. This prevents me from preparing the next instruction while the side chat is working. I remember this workflow working previously, but I have not identified the first affected app version.

I am not assuming that an ephemeral side chat must be persisted. The user-facing problem is that the side-chat composer exposes the Queue behavior, but the submission is rejected only after I send it.

What steps can reproduce the bug?

1. Launch the Codex App on Windows.
2. Open an existing Codex chat and start a side chat.
3. Send a prompt that causes the side chat to begin responding.
4. Before that response finishes, enter a follow-up message in the same side chat.
5. Submit the follow-up with Queue as the active follow-up mode.
6. Observe the red error banner stating ephemeral thread does not support queued submissions: <thread-id>.
7. Observe that the follow-up message is not added to the side chat queue.

What is the expected behavior?

While a side chat is focused and responding, a queued follow-up should remain attached to that side chat and run after the current response finishes.

If Queue is intentionally unsupported for side chats, the app should disable or hide that action before submission, preserve the draft, and explain the limitation with a user-facing message instead of returning a low-level thread error.

Additional information

No response

Reproduce the Windows Codex App flow with an active side-chat response, then trace the focused side-chat composer’s Queue submission path and the source of the ephemeral thread does not support queued submissions error. Done means queued follow-ups work for side chats, or Queue is disabled or hidden there, the draft is preserved, and the limitation is explained without a low-level error.