codex

What the source does

• FilesystemNone observedNo reads or writes in the source
• NetworkNone observedNo outbound calls in the source
• ShellNone observedNo commands run in the source
• DependenciesPinnedNothing floats
• SecretsNone foundNo keys in source

Five audit layers

Gates applied: no behavioural pass.

Audit 0.4.1 · source sha da8eb817ebd2 · 17 Oct 2026Report an issue or request a re-scan

• Publisherskills-directory GitHub organizationOwner of the repository this skill is read from
• Source folderskills-directory/skill-codexThe exact folder we audited
• LicenceMITAs the repository states it
• Commit pinned for this verdictda8eb817ebd2A new audit runs when the source changes
• Repository statusNot archivedLast push 33 days ago
• Sandboxed runNot runSkills are read, not executed; layer L4 is skipped

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

---
name: codex
description: 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 Skill Guide

## Running a Task
1. For a new session (resumes inherit the prior model/effort — see step 5), ask the user (via `AskUserQuestion`) which **model** AND which **reasoning effort** to use, in a **single prompt with two questions**. When the user expresses no preference, default to `gpt-6-astra` at `high`.
   - **Model** — default `gpt-6-astra`:
     - *GPT-6:* `gpt-6-astra` (frontier / most capable — **default**)
     - *GPT-5.6:* `gpt-5.6-sol` (reliable agentic workhorse), `gpt-5.6-terra` (balanced, everyday), `gpt-5.6-luna` (fast & affordable)
     - *Legacy (kept for compatibility):* `gpt-5.5`, `gpt-5.4`, `gpt-5.4-mini`, `gpt-5.3-codex-spark`, `gpt-5.3-codex`
   - **Reasoning effort** — default `high`: `low`, `medium`, `high`, `xhigh`, `max`, `ultra`.
     - `max`/`ultra` require a GPT-6 or GPT-5.6 model; `ultra` is only on `astra`/`sol`/`terra` (`luna` caps at `max`); legacy models cap at `xhigh`.
     - `ultra` = maximum reasoning **with automatic task delegation** (slowest and most expensive — reserve for the hardest jobs).
     - If the chosen effort exceeds the chosen model's maximum, fall back to that model's highest supported effort and tell the user.
2. Select the sandbox mode required for the task; default to `--sandbox read-only` unless edits or network access are necessary.
3. Assemble the command with the appropriate options:
   - `-m, --model <MODEL>`
   - `--config model_reasoning_effort="<low|medium|high|xhigh|max|ultra>"` (max/ultra only on GPT-6 / GPT-5.6 models; ultra only on astra/sol/terra — see step 1)
   - `--sandbox <read-only|workspace-write|danger-full-access>`
   - `--full-auto`
   - `-C, --cd <DIR>`
   - `--skip-git-repo-check`
   - `"your prompt here"` (as final positional argument)
4. Always use --skip-git-repo-check.
5. When continuing a previous session, use `codex exec --skip-git-repo-check resume --last` via stdin. When resuming don't use any configuration flags unless explicitly requested by the user e.g. if he species the model or the reasoning effort when requesting to resume a session. Resume syntax: `echo "your prompt here" | codex exec --skip-git-repo-check resume --last 2>/dev/null`. All flags have to be inserted between exec and resume.
6. **IMPORTANT**: By default, append `2>/dev/null` to all `codex exec` commands to suppress thinking tokens (stderr). Only show stderr if the user explicitly requests to see thinking tokens or if debugging is needed.
7. **IMPORTANT (stdin)**: `codex exec` always reads stdin and concatenates it with the positional prompt -- even when the prompt is fully supplied as a positional argument. If stdin is not closed, codex blocks forever. When invoking from a harness (background tasks, hooks, scripts where stdin is not a TTY but also not closed), explicitly redirect stdin: append `</dev/null` to the command, e.g. `codex exec ... "prompt" </dev/null 2>/dev/null`. Symptom of getting this wrong: zero bytes of stdout, zero CPU accumulated, process appears hung indefinitely.
8. Run the command, capture stdout/stderr (filtered as appropriate), and summarize the outcome for the user.
9. **After Codex completes**, inform the user: "You can resume this Codex session at any time by saying 'codex resume' or asking me to continue with additional analysis or changes."

### Quick Reference
| Use case | Sandbox mode | Key flags |
| --- | --- | --- |
| Read-only review or analysis | `read-only` | `--sandbox read-only 2>/dev/null` |
| Apply local edits | `workspace-write` | `--sandbox workspace-write --full-auto 2>/dev/null` |
| Permit network or broad access | `danger-full-access` | `--sandbox danger-full-access --full-auto 2>/dev/null` |
| Resume recent session | Inherited from original | `echo "prompt" \| codex exec --skip-git-repo-check resume --last 2>/dev/null` (no flags allowed) |
| Run from another directory | Match task needs | `-C <DIR>` plus other flags `2>/dev/null` |

## Execution timeouts

Codex produces **no intermediate output** — it writes the result only at completion. If the process is killed before finishing, the output file is silently empty (no error).

**Preferred approach:** run synchronously — eliminates timeout risk entirely and the conversation waits for the result anyway.

**If running in background**, set the execution timeout based on reasoning effort:

| Reasoning effort | Timeout |
|---|---|
| `low` | 150s |
| `medium` | 300s |
| `high` | 600s |
| `xhigh` | 1200s |
| `max` | 1800s |
| `ultra` | 1800s |

## 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 2>/dev/null`. 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.

## Critical Evaluation of Codex Output

Codex is powered by OpenAI models with their own knowledge cutoffs and limitations. Treat Codex as a **colleague, not an authority**.

### Guidelines
- **Trust your own knowledge** when confident. If Codex claims something you know is incorrect, push back directly.
- **Research disagreements** using WebSearch or documentation before accepting Codex's claims. Share findings with Codex via resume if needed.
- **Remember knowledge cutoffs** - Codex may not know about recent releases, APIs, or changes that occurred after its training data.
- **Don't defer blindly** - Codex can be wrong. Evaluate its suggestions critically, especially regarding:
  - Model names and capabilities
  - Recent library versions or API changes
  - Best practices that may have evolved

### When Cod

Excerpt, first 6,000 characters of SKILL.md, verbatim from the audited commit. It is text from someone else’s repository, quoted so you can judge it before your agent reads it.

1. 2026-10-17
   ✓SAFE B 89 / 100

   first audit · source da8eb817ebd2

Questions about codex

• github.com/skills-directory/skill-codex — the audited source at commit da8eb817ebd2 and every finding aboveObserved · 17 Oct 2026

Spotted something wrong? Report a correction · Methodology