codex-cli

Codex CLI

Use this skill when the user asks this agent to talk to Codex, consult Codex, delegate a coding/review/research task to Codex CLI, or ask Codex to generate an image.

The core interface is:

codex exec "prompt"

For automation, prefer non-interactive codex exec over interactive codex.

First Check

Before using Codex CLI, verify it is available:

command -v codex
codex --version
codex exec --help

If codex is missing, tell the user Codex CLI is not available in this environment and stop. Do not simulate a Codex response.

If codex exec --help is available, use it as the source of truth for the installed CLI flags. Codex CLI changes over time.

One-Off Task Workflow

Use this for normal delegation:

codex exec -C "$PWD" -s read-only "Review this repository and identify likely bugs"

For tasks that may edit files, use the sandbox the user requested or the host agent allows:

codex exec -C "$PWD" -s workspace-write "Implement the requested change"

For a response file:

codex exec -C "$PWD" -o /tmp/codex-last-message.md "Summarize this project"

For machine-readable events:

codex exec -C "$PWD" --json -o /tmp/codex-last-message.md "Analyze this project"

If the prompt is long, pass it via stdin:

codex exec -C "$PWD" - < /tmp/prompt.txt

When using shell commands from another agent, avoid dangerous flags unless the user explicitly asked for them. Prefer read-only for review, planning, critique, image generation, and analysis.

Prompt Shape

For non-trivial tasks, shape the delegated prompt with OpenAI's Codex best-practices structure:

Goal:
Context:
Constraints:
Done when:

Keep the prompt scoped to one task. For complex implementation work, ask Codex for a plan first in read-only mode, then run a separate write task after the plan is accepted.

Session Resume

Codex emits a session id in normal startup output and in JSONL events as thread.started.