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--- 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. Uses GPT-5.5 by default for state-of-the-art software engineering. --- # Codex Skill Guide ## Running a Task 1. Default to `gpt-5.5` model. Ask the user (via `AskUserQuestion`) which reasoning effort to use (`xhigh`,`high`, `medium`, or `low`). User can override model if needed (see Model Options below). If `gpt-5.5` is unavailable in your environment, fall back to `gpt-5.4`. 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="<high|medium|low>"` - `--sandbox <read-only|workspace-write|danger-full-access>` - `--full-auto` - `-C, --cd <DIR>` - `--skip-git-repo-check` 3. Always use --skip-git-repo-check. 4. 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. 5. **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. 6. Run the command, capture stdout/stderr (filtered as appropriate), and 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' 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` | ## Model Options | Model | Best for | Notes | | --- | --- | --- | | `gpt-5.5` ⭐ | **Newest frontier (default)**: Complex coding, computer use, knowledge work, research workflows | Latest flagship. Available via ChatGPT sign-in and API auth (since 2026-04). Recommended starting point. | | `gpt-5.4` | Flagship alternative for professional work | Available across all Codex platforms. Use as fallback when `gpt-5.5` is not in the picker. | | `gpt-5.4-mini` | Fast, efficient mini model for responsive coding tasks and subagents | Lower-cost option for lighter workloads, sub-agents, cleanup tasks. | | `gpt-5.3-codex` | Industry-leading coding model for complex software engineering | Powers GPT-5.4's coding abilities. Use when coding-specific quality is paramount. | | `gpt-5.3-codex-spark` | Real-time coding iteration (text-only research preview) | ChatGPT Pro subscribers only. Optimized for near-instant coding iteration. | | `gpt-5.2` | Legacy general-purpose | Previous default; available for tasks needing deeper reasoning under prior behavior. | **Selection guide**: Start with `gpt-5.5` for most tasks. Drop to `gpt-5.4` when 5.5 isn't available. Use `gpt-5.3-codex` when you need maximum coding quality without 5.5 reasoning overhead. Use `gpt-5.4-mini` for sub-agents and cleanup workloads. > Verify exact context window / pricing on the official model card — values may shift as preview/stable status changes. **Reasoning Effort Levels**: - `xhigh` - Ultra-complex tasks (deep problem analysis, complex reasoning, deep understanding of the problem) - `high` - Complex tasks (refactoring, architecture, security analysis, performance optimization) - `medium` - Standard tasks (refactoring, code organization, feature additions, bug fixes) - `low` - Simple tasks (quick fixes, simple changes, code formatting, documentation) **Cached Input Discount**: Repeated context is heavily discounted with cache lasting up to 24 hours. Verify current rates on the official OpenAI pricing page. ## 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. ## Error Handling - Stop and report failures whenever `codex --version` or a `codex exec` command exits non-zero; request direction before retrying. - Before you use high-impact flags (`--full-auto`, `--sandbox danger-full-access`, `--skip-git-repo-check`) ask the user for permission using AskUserQuestion unless it was already given. - When output includes warnings or partial results, summarize them and ask how to adjust using `AskUserQuestion`. ## CLI Version Requires a recent Codex CLI version for GPT-5.5 model support. Check version: `codex --version` and update with `npm install -g @openai/codex@latest` if needed. Use `/model` slash command within a session to switch, or set default in `~/.codex/config.toml`.