Codex desktop: editing an existing message fails with “Failed to edit message”

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

Unknown / not captured at the time of the report

What subscription do you have?

Not provided

What platform is your computer?

macOS

What issue are you seeing?

Editing an existing user message in the Codex desktop app fails. After clicking Send in the message editor, a red toast says "Failed to edit message". The editor remains open with the modified text and Cancel / Send buttons; the edit cannot be submitted.

The screenshot also shows "You stopped after 0s" below the editor. It is unknown whether this is related to the failure.

What steps can reproduce the bug?

Observed workflow:

1. Open an existing conversation in the Codex desktop app.
2. Edit a previously sent user message.
3. Change the message text and click Send.
4. Observe "Failed to edit message" and the editor remaining open.

Exact triggering conditions and reproduction frequency have not been established.

What is the expected behavior?

The edited message should be saved successfully and the conversation should continue from the edited message.

Additional information

Reported on September 7, 2026. The edited message contains multiline Chinese text. No root cause is asserted.

Related reports found during search: #26514 and #25961 describe side-chat editing failures; #41657 describes a Windows history/resume failure. It has not been established whether this macOS report shares their triggering conditions or root cause.

The screenshot contains unrelated private conversation content, so the relevant UI text is transcribed above instead of uploading the full screenshot.

Start by reproducing the edit workflow in the Codex desktop app on macOS: open an existing conversation, edit a user message, and select Send. Compare the behavior with the related reports #26514 and #25961, while checking whether multiline Chinese text or the “You stopped after 0s” state matters. Done means the edited message saves and the conversation continues from it.