codex

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. If unclear, ask the user (via AskUserQuestion) what they want reviewed or changed.

2. Assemble the codex command with appropriate options:

   • -m, --model gpt-5.3-codex (default model)
   • -c model_reasoning_effort="xhigh" (default reasoning effort; options: none, minimal, low, medium, high, xhigh)
   • --sandbox <mode> - use read-only for reviews, workspace-write for edits, danger-full-access for network/broad access
   • --full-auto - only for write operations, not needed for read-only
   • -C, --cd <DIR> - run from a different directory

3. When continuing a previous session, use resume syntax:

   codex exec resume --last "your prompt here" 2>/dev/null
   

   Add --skip-git-repo-check if running outside a git repo. Do not use configuration flags when resuming unless explicitly requested - the session inherits original settings.

4. For code reviews, prefer the dedicated review subcommand:

   codex exec review --base main "Review instructions" 2>/dev/null
   

   Options: --uncommitted (staged/unstaged/untracked), --base <branch>, --commit <sha>.

5. IMPORTANT: Append 2>/dev/null to suppress thinking tokens (stderr). Only show stderr if debugging is needed.

6. Run the command, summarize the outcome for the user.

7. After Codex completes, inform the user: "You can resume this Codex session at any time by saying 'codex resume'."

Quick Reference

Use case	Command example
Code review	codex exec review --base main 2>/dev/null
Review uncommitted	codex exec review --uncommitted 2>/dev/null
Review a commit	codex exec review --commit abc123 2>/dev/null
Apply edits	codex exec --sandbox workspace-write --full-auto "Refactor..." 2>/dev/null
Full access	codex exec --sandbox danger-full-access --full-auto "..." 2>/dev/null
Resume	codex exec resume --last "continue with..." 2>/dev/null
Different dir	codex exec -C /path/to/dir --sandbox read-only "..." 2>/dev/null

Following Up

• When output includes actionable findings or the user might want changes applied, offer to resume the session.
• When resuming, pass the new prompt as an argument - the session keeps its original model, reasoning effort, and sandbox mode.

Auto-Fixing Critical Bugs in PR Reviews

When codex identifies HIGH severity bugs during PR reviews, automatically fix them without asking for permission:

1. Identify severity: Parse codex output for "High" or "HIGH" severity bugs
2. Auto-fix workflow:

   # Resume codex session with fix instructions
   codex exec resume --last --sandbox workspace-write --full-auto "Fix all HIGH severity bugs identified in the review. For each bug, apply the necessary code changes." 2>/dev/null
   

3. Commit fixes: After codex applies fixes, commit with descriptive message
4. Report: Tell user what was fixed

Severity guidelines:

• HIGH: Auto-fix (data loss, security holes, correctness bugs, broken functionality)
• MEDIUM: Ask user first (performance issues, tech debt, unclear impact)
• LOW: Report only (style suggestions, minor improvements)

Safety notes:

• Only auto-fix in review/PR context (not exploratory coding)
• Always commit fixes immediately after applying
• User can revert commits if needed
• If codex fix fails or is unclear, stop and ask user

Example:

Codex found: "High - Date constraints never reach Qdrant"
→ Automatically resume codex to fix
→ Commit: "Fix: Push date constraints to Qdrant query"
→ Report: "Fixed HIGH severity date filtering bug in query.py"

Error Handling

• Stop and report failures when codex exits non-zero; request direction before retrying.
• Before using --full-auto, --sandbox danger-full-access, or --skip-git-repo-check, ask for user permission unless already given.
• When output includes warnings or partial results, summarize and ask how to proceed.