use-codex

name	use-codex
description	Use when running OpenAI Codex via the codex CLI (copilot CLI fallback) for code analysis, refactoring, or editing. Triggers on "run codex", "codex analyze", "ask codex", "copilot with codex".

Codex Skill Guide

Always run Codex through the codex-run.sh helper. The helper auto-detects its backend: it uses the native codex CLI when installed, and falls back to the copilot CLI otherwise. Always invoke the helper - never call codex or copilot directly - so backend detection and flag mapping stay correct.

• codex backend (preferred): OpenAI ChatGPT subscription, no per-request billing multiplier. Uses codex's own configured default model unless -m is passed.
• copilot backend (fallback): GitHub Copilot, billed with a per-request multiplier - see below.

Dispatch Contract (shared)

Background dispatch and waiting (TaskOutput-only waiting), following up, error handling, and the always-use--f prompt rule are defined once in /Users/bob/.claude/skills/use-codex/references/dispatch-contract.md. Read it before dispatching; it applies verbatim to this skill.

Codex-specific delta: each run is independent by default; --resume-thread (codex backend only, requires -o) continues a prior codex session so its context carries over.

Multiplier Policy (copilot backend only)

This applies only when the helper falls back to copilot. GitHub Copilot bills models with a per-request multiplier. The CLI does not expose multipliers locally, so the helper hardcodes a curated 1x default rather than auto-picking the highest version (which silently lands on premium tiers - gpt-5.5 once burned 25% of a monthly quota in one run).

• copilot default: gpt-5.4 (1x). Always use unless the user has explicitly approved a different model.
• Before passing -m to opt into a higher-multiplier model (e.g. gpt-5.5 for harder reasoning), confirm with the user via AskUserQuestion. State the model name and that it carries a higher Copilot multiplier.
• Verify current multipliers in the GitHub Copilot dashboard if unsure - they change.
• The codex backend has no multiplier, so -m on codex needs no quota confirmation.

Running a Task

Every run is non-interactive. By default each call is a fresh, one-shot Codex session; --resume-thread continues a prior codex session (codex backend only).

1. Select the permission mode required for the task; default to no special flags (read-only) unless edits are necessary.
2. Assemble the codex-run.sh command with appropriate helper flags:
   • -m, --model MODEL to override the model; on the copilot backend, ask the user first if the override is a higher-multiplier model
   • -f, --file FILE to pass the prompt (preferred - avoids shell escaping)
   • -a, --allow-tools to auto-approve tool use (codex: workspace-write sandbox)
   • -y, --yolo for full permissions (codex: bypass approvals and sandbox)
   • -d, --dir DIR to allow access to a specific directory (repeatable)
   • -o, --output FILE to capture output to a file
   • -s, --silent for clean scripting output (copilot backend only; ignored on codex)
   • --emit-thread-id FILE to capture the codex thread id from the JSON path (codex backend only; requires -o)
   • --resume-thread VALUE to resume a codex thread (VALUE is the thread id, or a file whose first line is the id; codex backend only; requires -o)
3. Run the command, capture output, and summarize the outcome for the user.

Quick Reference (helper flags)

Use case	Key flags
Read-only analysis	-f prompt.txt
Auto-approve tools	-a -f prompt.txt
Full auto (edits + tools)	-y -f prompt.txt
Allow specific directory	-d <DIR> -f prompt.txt
Scripting (clean output)	-s -f prompt.txt

Helper Script

# Write prompt to temp file (see the shared dispatch contract), then run
~/.claude/skills/use-codex/scripts/codex-run.sh -f /tmp/codex-prompt.txt

# With auto-approve tools
~/.claude/skills/use-codex/scripts/codex-run.sh -a -f /tmp/codex-prompt.txt

# Override model (on copilot backend, only after user approval - higher multiplier may apply)
~/.claude/skills/use-codex/scripts/codex-run.sh -m gpt-5.5 -f /tmp/codex-prompt.txt

# Full permissions
~/.claude/skills/use-codex/scripts/codex-run.sh -y -f /tmp/codex-prompt.txt

# Capture output to file
~/.claude/skills/use-codex/scripts/codex-run.sh -a -o /tmp/result.txt -f /tmp/codex-prompt.txt

Run ~/.claude/skills/use-codex/scripts/codex-run.sh --help for all options.