# Codex CLI

> Use when the user asks to run Codex CLI (codex exec, codex resume) or references OpenAI Codex for code analysis, refactoring, or automated editing

- Skill: `rafaelcalleja/codex-cli-2` (Agent Skill)
- Install (CLI): `npx skillmds@latest add rafaelcalleja/codex-cli-2`
- Raw SKILL.md: https://api.skillmd.com/api/skills/rafaelcalleja/codex-cli-2/raw
- Safety review: pending (external: skill-scanner PASS, skillspector PASS)
- Works with: Claude Code, Claude.ai, OpenAI Codex
- Category: Coding & Dev Tools
- Author: rafaelcalleja (https://skillmd.com/u/rafaelcalleja)
- Updated: 2026-09-21
- Page: https://skillmd.com/skills/rafaelcalleja/codex-cli-2

---


# Codex Skill Guide

## Running a Task
1. Ask the user (via `AskUserQuestion`) which model to run: `gpt-5.1` or `gpt-5.1-codex` or `gpt-5.1-codex-max` or `gpt-5.1-mini`.
2. Ask the user (via `AskUserQuestion`) which reasoning effort to use: `low`, `medium`, or `high`.
3. Select the sandbox mode required for the task; default to `--sandbox read-only` unless edits or network access are necessary.
4. Assemble the command with the appropriate options:
    - `-m, --model <MODEL>`
    - `--config model_reasoning_effort="<low|medium|high>"`
    - `--sandbox <read-only|workspace-write|danger-full-access>`
    - `--full-auto`
    - `-C, --cd <DIR>`
    - `--skip-git-repo-check`
5. When continuing a previous session, use `codex exec resume --last` via stdin. **IMPORTANT**: When resuming, you CANNOT specify model, reasoning effort, or other flags—the session retains all settings from the original run. Resume syntax: `echo "your prompt here" | codex exec resume --last`
6. Run the command, capture stdout/stderr, and summarize the outcome for the user.

### Quick Reference
| Use case | Sandbox mode | Key flags |
| --- | --- | --- |
| Read-only review or analysis | `read-only` | `--sandbox read-only` |
| Apply local edits | `workspace-write` | `--sandbox workspace-write --full-auto` |
| Permit network or broad access | `danger-full-access` | `--sandbox danger-full-access --full-auto` |
| Resume recent session | Inherited from original | `echo "prompt" \| codex exec resume --last` (no flags allowed) |
| Run from another directory | Match task needs | `-C <DIR>` plus other flags |

## Following Up
- After every `codex` command, immediately use `AskUserQuestion` to confirm next steps, collect clarifications, or decide whether to resume with `codex exec resume --last`.
- When resuming, pipe the new prompt via stdin: `echo "new prompt" | codex exec resume --last`. The resumed session automatically uses the same model, reasoning effort, and sandbox mode from the original session.
- Restate the chosen model, reasoning effort, and sandbox mode when proposing follow-up actions.

## Error Handling
- Stop and report failures whenever `codex --version` or a `codex exec` command exits non-zero; request direction before retrying.
- Before you use high-impact flags (`--full-auto`, `--sandbox danger-full-access`, `--skip-git-repo-check`) ask the user for permission using AskUserQuestion unless it was already given.
- When output includes warnings or partial results, summarize them and ask how to adjust using `AskUserQuestion`.