CLI: Enter intermittently inserts a newline instead of submitting; Ctrl+M does the same

What version of Codex CLI is running?

codex-cli 0.153.4 (verified with codex --version on the reporting machine).

What subscription do you have?

Not provided.

Which model were you using?

Not recorded for the affected input events.

What platform is your computer?

Ubuntu 26.04.1 LTS, Linux, x86_64.

What terminal emulator and version are you using (if applicable)?

Not yet confirmed. Multiplexer and remote-input involvement have not been established.

What issue are you seeing?

While composing a message in the Codex terminal interface, pressing plain Enter sometimes inserts a newline instead of submitting the message. When this happens, there is no clear way to send the composed prompt.

Ctrl+M was suggested as a workaround and was tried, but it also inserted a newline. It did not resolve the problem.

This is an intermittent user-observed input-handling problem. The underlying cause has not been identified.

What steps can reproduce the bug?

A deterministic reproduction is not yet available. The observed sequence is:

1. Compose a message during an interactive Codex session.
2. Press Enter expecting to submit it.
3. Sometimes a newline is inserted instead, and the message remains in the composer.
4. Try Ctrl+M; in the reported occurrence, it also inserts a newline instead of submitting.

The exact trigger, relationship to pasting or typing speed, and effect of pausing before Enter have not been established.

What is the expected behavior?

The submit key should send the message consistently. If the composer deliberately switches to a mode where Enter inserts newlines, the interface should clearly indicate that mode and provide an obvious, working submit action.

Additional information

• No reliable workaround has been confirmed.
• Paste detection was considered only as a hypothesis; it has not been established as the cause.
• Related usability report: #36585 concerns an alternative submit binding after intentionally configuring Enter for newlines. This report concerns intermittent behavior during normal message composition; whether the two share a cause is unknown.
• No conversation logs or private configuration are attached.

Start by reproducing the input behavior in the interactive Codex terminal interface on Ubuntu, testing plain Enter and Ctrl+M while noting whether pasting or typing speed affects it. Investigate the input path once a reliable trigger is found; done means Enter consistently submits, or any newline mode clearly indicates how to submit.