Codex/ChatGPT Desktop App crashing on loading older chats

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

26.820.60940

What subscription do you have?

Business

What platform is your computer?

Microsoft Windows NT 10.0.26200.0 x64

What issue are you seeing?

Summary

After updating the Windows ChatGPT/Codex desktop application to version 26.820.60940, opening certain existing/older conversations causes the application to become unresponsive and effectively crash/terminate. Newer or newly created conversations can be used, but selecting affected historical conversations consistently reproduces the failure.

Windows Error Reporting records the failure as MoAppHang for the Codex package rather than a conventional application exception.

Environment:

• About dialog version: 26.820.60940
• Microsoft Store package: OpenAI.Codex_26.820.7780.0_x64__2p2nqsd0c76g0
• Chromium runtime reported by WER: 151.0.7922.170
• OS: Microsoft Windows NT 10.0.26200.0 x64
• Subscription: ChatGPT Business

Reproduction

1. Launch ChatGPT/Codex Desktop normally.
2. Select an existing conversation from the sidebar/project history.
3. The application begins attempting to restore/load the conversation.
4. For affected conversations, the UI stops responding and the application eventually disappears or must be terminated/restarted.
5. Relaunching and selecting the same conversation reproduces the problem.

This is repeatable with multiple existing conversations.

Expected behavior

Existing conversations should load normally and remain usable after an application update.

Actual behavior

Loading affected existing conversations causes the desktop application to hang. Windows Error Reporting records:

Event Name: MoAppHang

P1: OpenAI.Codex_26.820.7780.0_x64__2p2nqsd0c76g0
P2: praid:App
P3: 151.0.7922.170

The Windows Application event log also contains repeated Chromium Event ID 256 entries while the application is running/reproducing the problem.

Example informational Chromium event:

[43896:38992:0826/230442.732:INFO:
chrome\browser\extensions\extension_garbage_collector.cc:188]
Garbage collection for extensions on file thread is complete.

I do not believe that individual INFO event is necessarily the error itself, but it establishes that the affected desktop UI is running under the bundled Chromium runtime.

Troubleshooting performed

I tested launching the application with Chromium DirectComposition disabled:

$pkg = Get-AppxPackage -Name 'OpenAI.Codex' |
    Sort-Object Version -Descending |
    Select-Object -First 1

Start-Process `
    (Join-Path $pkg.InstallLocation 'app\ChatGPT.exe') `
    -ArgumentList '--disable-direct-composition'

This did not change the behavior. The affected historical conversations still cause the application to hang.

Therefore this does not appear to be the same issue as reports where --disable-direct-composition restores rendering on Windows.

I have also observed historical LiveKernelEvent entries on this machine, but the relevant dumps predate this Codex regression by months or more and do not correlate temporally with reproduction, so I do not currently believe they are related.

Additional observations

• The regression began after updating to the current desktop release.
• The failure is triggered specifically by attempting to restore/load existing conversation state.
• The application does not report a useful user-visible error before becoming unresponsive.
• WER classifies the current failure as MoAppHang, not an access violation.
• Disabling DirectComposition does not mitigate the issue.
• The affected conversations should not contain inherently invalid data; they were usable before the application update.

This may be related to conversation/session restoration rather than Chromium rendering itself.

There are other recent reports involving Windows desktop conversation restoration, including older conversations failing to load and a separate case where a failed thread/read operation is followed by an Electron main-process crash. I cannot determine whether this has the same root cause.

What steps can reproduce the bug?

1. Install/update Windows ChatGPT/Codex Desktop to 26.820.60940.
2. Launch the application.
3. Select an existing historical conversation that was previously usable.
4. Wait for the conversation to load.
5. The application becomes unresponsive and eventually closes or must be restarted.
6. Relaunch the application and select the same conversation.
7. The behavior reproduces consistently.

Launching ChatGPT.exe with --disable-direct-composition does not change the result.

What is the expected behavior?

_No response_

Additional information

_No response_