Codex CLI

Codex runs non-interactively through codex exec. A new run starts a separate Codex session in the selected working directory, streams progress to stderr, and prints its final response to stdout. Redirect stderr to /tmp/codex.err so the turn log stays out of the caller context. A run is done when the process exits; stdout is the reply. If the command fails, read /tmp/codex.err.

Run a task

Use gpt-6.1-sol with high reasoning effort by default:

codex -a never \
  -C <working-directory> \
  -m gpt-6.1-sol \
  -c model_reasoning_effort=high \
  exec --skip-git-repo-check "<request>" \
  </dev/null 2>/tmp/codex.err

-a never is a global flag and therefore appears before exec. It keeps an unattended run from waiting for interactive approval; failed operations return to Codex instead.

--skip-git-repo-check lifts Codex's trusted-directory check; without it an unattended run fails before doing any work.

</dev/null> keeps piped stdin from being appended to the prompt. For a long request, write it to a file and pass - < file in place of the quoted prompt and </dev/null — inline quoting breaks on quotes and newlines.

Model and reasoning

Available models, in ascending capability and cost: gpt-6-luna, gpt-6.1-sol. Set the model explicitly with -m on every run.

Reasoning effort accepts medium, high, xhigh, or max (not low). Higher effort gives the model more room to deliberate and generally increases latency. Set it explicitly with -c model_reasoning_effort=<level>.

Use gpt-6.1-sol with high effort for most delegated tasks. Use gpt-6-luna with xhigh or max for simple but tedious tasks to improve reliability at low cost.

Continue a session

resume --last continues the most recent session in that working directory. A thread ID continues a specific one. The thread id is on the session id: line in /tmp/codex.err. Keep model and effort unless the caller picks different values.

codex -a never \
  -C <working-directory> \
  -m gpt-6.1-sol \
  -c model_reasoning_effort=high \
  exec resume --skip-git-repo-check --last "<follow-up>" \
  </dev/null 2>/tmp/codex.err

codex -a never \
  -C <working-directory> \
  -m gpt-6.1-sol \
  -c model_reasoning_effort=high \
  exec resume --skip-git-repo-check <thread-id> "<follow-up>" \
  </dev/null 2>/tmp/codex.err

Review code

Pass either one scope flag or a prompt. --help lists both; the CLI still rejects that combination (exit 2).

codex -a never \
  -C <working-directory> \
  -m gpt-6.1-sol \
  -c model_reasoning_effort=high \
  exec review --skip-git-repo-check --uncommitted \
  </dev/null 2>/tmp/codex.err

Other shapes: review --base <branch>, review --commit <sha>, review "<instructions>".

Command reference

Use codex exec --help, codex exec resume --help, and codex exec review --help for the command surface installed on the machine.