[Regression][Remote] VS Code and iOS threads no longer sync bidirectionally after VS Code restart

What issue are you seeing?

Codex Remote no longer keeps the same thread/history visible between VS Code on the PC and the ChatGPT mobile app on iPhone.

This previously worked: I could start a Codex chat on the PC, open the same chat on mobile, see live progress, and continue the same conversation from either device.

Now the state appears split between devices:

• If I start a Codex task/chat in VS Code on the PC, I cannot see its current progress / messages correctly on mobile.
• If I start a Codex Remote chat on mobile, it is not visible/resumable in VS Code on the PC after restarting VS Code.
• On mobile, opening the affected remote chat can fail with the German error:

Fehler beim Laden der Nachrichten: Der Codex-Server hat einen Fehler zurückgegeben.

(English: “Error loading messages: The Codex server returned an error.”)

This looks like a regression in Remote thread/session indexing or reattachment across clients rather than the intended cross-device Remote behavior.

Environment

• Desktop client: VS Code with Codex / ChatGPT extension
• Mobile client: ChatGPT iOS app
• iOS: 26.6
• ChatGPT iOS app build observed: 30960470514
• Exact VS Code extension version: not captured yet
• Desktop OS/build: not captured yet
• Date reproduced: 2026-08-12

Steps to reproduce

PC → mobile

1. Open a project in VS Code and start a Codex task/chat.
2. Let the task continue running / producing progress.
3. Open ChatGPT on iPhone and go to Codex Remote for the same PC/project.
4. Open the corresponding chat.
5. The current task/progress is not reliably visible; in at least one case the mobile app shows Fehler beim Laden der Nachrichten: Der Codex-Server hat einen Fehler zurückgegeben.

Mobile → PC

1. Start a Codex Remote chat/task from the ChatGPT iOS app against the connected PC.
2. Confirm it is usable on mobile.
3. Restart VS Code on the PC.
4. Open the Codex/ChatGPT extension.
5. The mobile-started thread is not visible/resumable there as the same conversation.

Expected behavior

Remote should keep one coherent thread/session across VS Code and the ChatGPT mobile app:

• a task started on PC should be visible on mobile with its live/current state;
• a task started on mobile should remain visible/resumable in VS Code after restarting VS Code;
• both clients should attach to the same thread/history rather than showing different conversation state;
• restarting VS Code should not break the cross-device association.

Regression

The same workflow worked previously: the same chat could be used from both mobile and PC and progress was visible across devices. The problem is therefore a regression rather than a request for new functionality.

Related issues

This appears related to prior Remote thread visibility/indexing problems such as #23351, but that issue was closed as completed. It may also overlap with cross-client session divergence reported in #31114. The current symptom is specifically a bidirectional visibility/resume regression involving VS Code + iOS and VS Code restart.

Additional information

A screenshot is available showing the mobile error message. I can provide the exact VS Code extension version, desktop OS/build, Remote host diagnostics, or feedback/session ID if maintainers need them.

Start by reproducing the two Codex Remote flows between the VS Code extension and ChatGPT iOS app, including the VS Code restart. Collect the missing extension and desktop versions plus Remote diagnostics, then compare thread visibility and message loading before and after restart. Done means one task remains visible, resumable, and history-consistent in both clients.