| name | codex |
| description | Second opinion from a different model (OpenAI Codex). Use when exploring different design choices (more diversity with heterogenous models), debugging hard problems, or when the user wants a second perspective, you want second perspective, are stuck, ... |
Codex — Second Opinion
Run OpenAI's Codex CLI non-interactively from Claude Code. Different model family = different blind spots, different strengths.
Example use cases
- To increase diversity of opinions when exploring design choices
- Code review or architecture critique
- Debugging when stuck — different model may see different patterns
- User explicitly asks for a second perspective
Command
_id=$(date +%s%N); codex exec -s read-only -c 'sandbox_permissions=["disk-full-read-access"]' -c 'model_reasoning_effort="xhigh"' -o "/tmp/codex-${_id}.md" "<prompt>" > "/tmp/codex-${_id}-log.md" 2>&1
-s read-only + disk-full-read-access — can read any file on disk, not write (no codebase conflicts)-o — final answer to file. _id = epoch-nanosecond timestamp-c 'model_reasoning_effort="xhigh"' — always xhigh-C <dir> — working directory (defaults to cwd, set when reviewing a different project)
Run via Bash with run_in_background: true. You already have _id from the command — read /tmp/codex-${_id}.md directly. Log at /tmp/codex-${_id}-log.md if debugging.
How to Prompt Codex
Codex has zero context from your session. Everything it needs must be in the prompt or readable from the filesystem.
Give it orientation first:
- Tell it to read
./CLAUDE.md (project root) for project context, knowledge map, and conventions
- Point it to
CONTEXT.md, decisions/, and agent/tasks/ when relevant — written records is more efficient than re-explaining what's already documented
- Name the specific files and directories to review — it can read them, but won't know which ones matter unless told
Add session context it can't get from files:
- Describe the current approach, decisions made, constraints discovered — things only in your conversation
- State the question clearly: what you want reviewed, what kind of answer you want
Request structured output:
- "List the top 5 issues, each with: what's wrong, where, and how you'd fix it"
- "Pros and cons of this approach as a numbered list"
- Not: "What do you think?"
GPT-5 is sensitive to contradictory instructions — more so than other models. Keep prompts clean and unambiguous.
