Codex Desktop: delegated task callback can make the previous assistant response disappear

What version of the Codex App are you using?

26.818.61809

What subscription do you have?

ChatGPT subscription (exact tier intentionally omitted from this public report)

What platform is your computer?

Darwin 25.5.0 arm64 arm

What issue are you seeing?

In a long-running Codex Desktop conversation that coordinates separate visible tasks, an assistant response can disappear from the rendered chat when a delegated task callback arrives at approximately the same time.

The assistant response may already be visible or finishing. When the callback is injected as a new conversation turn, the UI switches to the new turn and the prior assistant response is no longer visible. This has reproduced multiple times after updating to 26.818.61809.

The underlying worker/task continues normally. The symptom appears limited to conversation rendering or turn-state synchronization, but it causes user-facing answers to be lost from the visible history.

No private repository content, conversation text, phone numbers, or internal thread identifiers are included in this report.

What steps can reproduce the bug?

1. Open a long-running Codex Desktop conversation.
2. Have that conversation coordinate one or more separate visible Codex tasks that send callbacks to the main conversation.
3. Ask the main conversation a question while a delegated task is close to completing or reporting material progress.
4. Allow the main assistant response to render or nearly finish.
5. Let the delegated task callback arrive during or immediately after that response.
6. Observe that the callback starts a new turn and the previous assistant response disappears from the visible chat.

Observed repeatedly in the same conversation. The problem is timing-sensitive but becomes frequent when multiple delegated tasks report back during active user interaction.

What is the expected behavior?

A delegated-task callback should append a new durable turn without removing, hiding, or replacing any completed or currently rendered assistant response. If events arrive concurrently, the UI should preserve deterministic chronological ordering and all completed response content.

Additional information

This may be related to renderer/app-server turn-state synchronization issues reported in:

• #13135 (assistant response hidden until UI interaction)
• #24287 (active turn/trace state can become invisible or detach)
• #24467 (stale streaming state after completed/interrupted turns)

The distinguishing trigger here is arrival of a delegated visible-task callback while the main conversation is rendering or completing another response.

A useful regression test would race:

• completion/persistence of assistant turn A;
• injection of delegated-task callback turn B;
• renderer reconciliation;

and assert that turn A remains durably visible before and after turn B is appended.

Start by tracing the Codex Desktop renderer and app-server turn-state synchronization around delegated visible-task callback injection. Add the suggested regression test racing completion and persistence of assistant turn A with callback turn B and renderer reconciliation; done means turn A remains durably visible before and after turn B is appended.