Switching between threads is very slow

[ImanYZ]

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

Version 260206.1448 (565)

What subscription do you have?

ChatGPT Pro

What issue are you seeing?

After updating Codex last night, switching between threads is super slow and not responsive.

What steps can reproduce the bug?

I have multiple tabs in the Codex App on my MacBook Pro M4 Max.
Every thread is on a different project, in totally separate folders, without sharing anything.
Some of the threads are on git repos, and some are not.
When I send a prompt in one thread and switch to another thread, for a while the Codex app is frozen.
If I send prompts in two separate threads, they get super slow, and sometimes the app crashes and closes.
I did not experience these issues before updating the Codex app last night.

What is the expected behavior?

No response

Additional information

No response

[github-actions]

Potential duplicates detected. Please review them and close your issue if it is a duplicate.

• App UI gets stuck after some work (background work continues) #11000
• Codex app crashes on macOS shortly after launch #10996

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[awlee01]

+1 - app currently unusable for me

[ImanYZ]

After updating the app to the new version, I cannot use it anymore!

[tomoliveri]

+1 app completely unusable (MacOS)

[gulla0]

+1
The app is hung and completely unusable. Restarting the app does not resolve the issue. Archiving project threads also has no effect. The problem persists across relaunches.

[liampongracz]

Yes please fix this, its bad. 2021 M1 MBP

[gunnartorfis]

Have to put a +1 here, it is barely usable at least when you have multiple big threads going.

[virgildotcodes]

Same experience, M1 Max.

Just discovered that in one particular thread, there was a very large diff of unstaged changes that seemed to be choking the whole app's performance. Getting rid of that solved the performance issues on that thread at least.

[michaeltyson]

I’m seeing very similar behavior, but in the Codex IDE extension running inside Cursor, not the standalone Codex desktop app.

In my case:

• Switching between long-running threads causes a full UI freeze for 10–30 seconds.
• The freeze happens immediately on selecting the thread, even before sending a new prompt.
• CPU spikes during the switch.
• The behavior worsens with longer transcripts.

From observation, it appears that the entire conversation is being loaded and rendered synchronously when switching threads. If the desktop app is using a similar rendering model, that might explain why multiple large threads cause the UI to hang or crash.

By contrast, Cursor’s native chat interface progressively hydrates messages (loading recent content first and backfilling on scroll), which avoids blocking the UI thread.

If the Codex app and extension are eagerly hydrating full transcripts on thread switch, implementing:

• Message virtualization
• Incremental/lazy loading
• Background hydration off the main thread

would likely resolve both the freezing and the memory growth issues people are reporting.

Happy to provide more detailed reproduction info from the extension side if helpful.

[faraponov-agima]

+1
I'm running into the same performance issues. The lag is making it difficult to use.

[9yo]

+ 1