Command output not shown to the screen if output is printed before a delay

What version of Codex CLI is running?

codex-cli 0.139.0

What subscription do you have?

Enterprise

Which model were you using?

gpt-5.4-mini

What platform is your computer?

_No response_

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

_No response_

Codex doctor report

What issue are you seeing?

If the agent runs a command that prints out some output _then sleep for a while_, the user will incorrectly see (no output).

› Run exactly this command and report the output:

  echo OUTPUT; sleep 0.5


• Running the exact command now.

• Ran echo OUTPUT; sleep 0.5
  └ (no output)

────────────────────────────────────────────────────────────────────────────────────────────────────

• OUTPUT

────────────────────────────────────────────────────────────────────────────────────────────────────


› Run exactly this command and report the output:

  sleep 0.5; echo OUTPUT


• Running the exact command as given.

• Ran sleep 0.5; echo OUTPUT
  └ OUTPUT

────────────────────────────────────────────────────────────────────────────────────────────────────

• OUTPUT

────────────────────────────────────────────────────────────────────────────────────────────────────

In the second case, it's correct.

What steps can reproduce the bug?

See above.

What is the expected behavior?

The output is shown as OUTPUT in both cases.

Additional information

_No response_