codex

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-5.1-codex-max (default model)
   • --config model_reasoning_effort="<level>" where level is: 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:

   echo "your prompt here" | codex exec --skip-git-repo-check resume --last 2>/dev/null
   

   Do not use configuration flags when resuming unless explicitly requested - the session inherits original settings.

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

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

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

Quick Reference

Following Up

• When output includes actionable findings or the user might want changes applied, offer to resume the session.
• When resuming, pipe the new prompt via stdin - 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
   echo "Fix all HIGH severity bugs identified in the review. For each bug, apply the necessary code changes." | codex exec --skip-git-repo-check resume --last --sandbox workspace-write --full-auto 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.