ChatGPT app freezes on large threads when switching window focus

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

Version 26.721.41059

What subscription do you have?

Pro 5x

What platform is your computer?

Darwin 25.4.0 arm64 arm

What issue are you seeing?

On a large session [813 MB JSONL file], the ChatGPT app's javascript thread often freezes for a very long time trying to rerender the conversation on window focus change. This does not occur through the Codex VSCode extension or the codex cli. If a prompt is in progress, it will render at a speed of one token per several minutes.

What steps can reproduce the bug?

1. Open a very large thread in the Codex app
2. Attempt to send a prompt that triggers "Working for ...s" and switch focus to another app.
3. Switch focus back to the Codex app and it will often freeze.

[inconsistently?]

What is the expected behavior?

The Codex app should not freeze for a long period of time.

Additional information

_No response_