How do I install the Codex skill?

Run npx skillmds@latest add ericpardee/codex in your terminal (requires Node.js), paste this page's agent-chat prompt into Claude, Cursor, or any MCP-connected agent, or download the SKILL.md file and copy it into your agent's skills directory.

Is Codex safe to use?

This skill has not completed SkillMD's automated safety review yet. Capability flags: docs only. SkillMD never runs a skill's scripts for you; review the SKILL.md before installing.

Which AI agents work with Codex?

This skill is tagged as working with Claude Code, Claude.ai, OpenAI Codex. SKILL.md is an open format, so most agents that read a skills directory can load it too.

Is Codex free to use?

Yes. Installing skills from SkillMD is free, and the skill stays under its author's original license.

ericpardee (@ericpardee) published this skill. Their other Agent Skills are listed on their SkillMD profile.

Codex by ericpardee — Agent Skill

Name: Codex
Rating: 4.2 (5 reviews)
Author: ericpardee

File contents

Codex CLI

Reference for driving codex exec correctly from an agent session. For a full review gate with a fix-or-rebut loop, use the codex-gate skill instead.

Invocation rules

Do not pass -m. ~/.codex/config.toml sets the default model; override it only when the user names a model. Pair reviews with -c model_reasoning_effort="xhigh" (options: none, minimal, low, medium, high, xhigh).
Always redirect stdin from /dev/null. codex exec appends stdin to the prompt, so without the redirect it blocks on an open terminal and looks like a slow reasoning pass until killed. The tell is empty stdout with Reading additional input from stdin... on stderr.
Append 2>/dev/null to hide thinking tokens (stderr). Show stderr only when debugging.
Sandbox: --sandbox read-only for reviews, workspace-write for edits, danger-full-access only for work that needs the network. --full-auto applies to write runs only. Ask before --full-auto, danger-full-access, or --skip-git-repo-check unless the user already granted it.
-C <dir> runs from another directory; --skip-git-repo-check is needed outside a repository.
Pass -o <file> when the final message must survive scrollback.

Reviews

codex exec review accepts a scope flag (--base <branch>, --commit <sha>, --uncommitted) or a custom prompt, never both; combining them fails arg parsing with the argument '--base <BRANCH>' cannot be used with '[PROMPT]' (codex-cli 0.146 through 0.154). So:

Codex's own review instructions on a scope: codex exec review --base main </dev/null 2>/dev/null
Your own instructions: plain codex exec with the scope stated in the prompt, for example codex exec --sandbox read-only "<instructions>. Review only the changes on this branch relative to main; see them with git diff main...HEAD." </dev/null 2>/dev/null

Resuming

codex exec resume --last "<prompt>" </dev/null 2>/dev/null continues the previous session with its original model, reasoning effort, and sandbox; do not pass configuration flags when resuming unless the user asks. After any run, tell the user the session can be resumed this way.

Quick reference

Use case	Command
Review a branch	`codex exec review --base main </dev/null 2>/dev/null`
Review uncommitted work	`codex exec review --uncommitted </dev/null 2>/dev/null`
Review one commit	`codex exec review --commit abc123 </dev/null 2>/dev/null`
Review with your own instructions	`codex exec --sandbox read-only "<instructions> Review only <scope>." </dev/null 2>/dev/null`
Apply edits	`codex exec --sandbox workspace-write --full-auto "Refactor ..." </dev/null 2>/dev/null`
Resume	`codex exec resume --last "continue with ..." </dev/null 2>/dev/null`
Another directory	`codex exec -C /path --sandbox read-only "..." </dev/null 2>/dev/null`

After a run

Summarize the outcome. When the output has actionable findings, offer to resume the session to apply them; do not apply or commit changes on the user's behalf without being asked. Stop and report when codex exits non-zero or returns partial results, and ask how to proceed.

---name: codexdescription: Use when the user asks to run Codex CLI (codex exec, codex resume) or references OpenAI Codex for code analysis, refactoring, or automated editing---# Codex CLIReference for driving `codex exec` correctly from an agent session. For afull review gate with a fix-or-rebut loop, use the `codex-gate` skill instead.## Invocation rules- Do not pass `-m`. `~/.codex/config.toml` sets the default model; override it only when the user names a model. Pair reviews with `-c model_reasoning_effort="xhigh"` (options: `none`, `minimal`, `low`, `medium`, `high`, `xhigh`).- Always redirect stdin from `/dev/null`. `codex exec` appends stdin to the prompt, so without the redirect it blocks on an open terminal and looks like a slow reasoning pass until killed. The tell is empty stdout with `Reading additional input from stdin...` on stderr.- Append `2>/dev/null` to hide thinking tokens (stderr). Show stderr only when debugging.- Sandbox: `--sandbox read-only` for reviews, `workspace-write` for edits, `danger-full-access` only for work that needs the network. `--full-auto` applies to write runs only. Ask before `--full-auto`, `danger-full-access`, or `--skip-git-repo-check` unless the user already granted it.- `-C <dir>` runs from another directory; `--skip-git-repo-check` is needed outside a repository.- Pass `-o <file>` when the final message must survive scrollback.## Reviews`codex exec review` accepts a scope flag (`--base <branch>`, `--commit <sha>`,`--uncommitted`) or a custom prompt, never both; combining them fails argparsing with `the argument '--base <BRANCH>' cannot be used with '[PROMPT]'`(codex-cli 0.146 through 0.154). So:- Codex's own review instructions on a scope: `codex exec review --base main </dev/null 2>/dev/null`- Your own instructions: plain `codex exec` with the scope stated in the prompt, for example `codex exec --sandbox read-only "<instructions>. Review only the changes on this branch relative to main; see them with git diff main...HEAD." </dev/null 2>/dev/null`## Resuming`codex exec resume --last "<prompt>" </dev/null 2>/dev/null` continues theprevious session with its original model, reasoning effort, and sandbox; do notpass configuration flags when resuming unless the user asks. After any run,tell the user the session can be resumed this way.## Quick reference| Use case | Command || --- | --- || Review a branch | `codex exec review --base main </dev/null 2>/dev/null` || Review uncommitted work | `codex exec review --uncommitted </dev/null 2>/dev/null` || Review one commit | `codex exec review --commit abc123 </dev/null 2>/dev/null` || Review with your own instructions | `codex exec --sandbox read-only "<instructions> Review only <scope>." </dev/null 2>/dev/null` || Apply edits | `codex exec --sandbox workspace-write --full-auto "Refactor ..." </dev/null 2>/dev/null` || Resume | `codex exec resume --last "continue with ..." </dev/null 2>/dev/null` || Another directory | `codex exec -C /path --sandbox read-only "..." </dev/null 2>/dev/null` |## After a runSummarize the outcome. When the output has actionable findings, offer toresume the session to apply them; do not apply or commit changes on theuser's behalf without being asked. Stop and report when `codex` exits non-zeroor returns partial results, and ask how to proceed.

Frequently asked questions

Codex