# Codex CLI > Run OpenAI Codex CLI for coding tasks and second-opinion audits. Use when a user asks to run/ask/use Codex, says "codex prompt", or wants Claude to delegate a logic/code review to OpenAI models. Use when this capability is needed. - Skill: `tomevault-io/codex-cli-2` (Agent Skill, multi-file: 2 files) - Install (CLI): `npx skillmds@latest add tomevault-io/codex-cli-2` - Raw SKILL.md: https://api.skillmd.com/api/skills/tomevault-io/codex-cli-2/raw - Safety review: pending - Works with: Claude Code, Claude.ai, OpenAI Codex - Category: AI & ML - Author: tomevault-io (https://skillmd.com/u/tomevault-io) - Updated: 2026-09-17 - Page: https://skillmd.com/skills/tomevault-io/codex-cli-2 --- # Codex CLI Run OpenAI Codex CLI locally for second-opinion audits, code review, and non-interactive task execution. ## Prerequisites Codex CLI must be installed and authenticated: 1. **Install:** `npm install -g @openai/codex` 2. **Auth:** `codex login` 3. **Verify:** `codex --version` ## Core Execution Pattern Use `codex exec` for delegated prompts (non-interactive): ```bash codex exec "Your prompt here" ``` When the user says "codex prompt", treat it as: ```bash codex exec "" ``` ## Model Guidance Prefer `gpt-5.4` unless the user asks for a different model. Default reasoning effort is **medium**. Only escalate when explicitly needed: - Use `medium` for most coding, reviews, refactors, second-opinion audits, and one-off tasks - Use `high` only for: repeated/failing tasks that need deeper analysis, complex multi-step planning, or when the user explicitly asks for deeper reasoning ```bash codex exec -c 'model="gpt-5.4"' -c 'model_reasoning_effort="medium"' "Your prompt" ``` Fallback note: - If `gpt-5.4` is unavailable, fall back to the newest available GPT-5 or Codex model - Keep reasoning effort explicit for reproducible behavior ## Critical: Argument Compatibility Rules These rules prevent CLI errors. Follow them exactly. ### `codex exec` - `-m` flag works: `codex exec -m gpt-5.4 "prompt"` - `-c` config overrides work: `codex exec -c 'model="gpt-5.4"' "prompt"` - Stdin with `-` replaces the prompt — do NOT pass both `-` and a quoted prompt string - Correct stdin: `cat file.txt | codex exec -s read-only -c 'model="gpt-5.4"' -` - WRONG: `cat file.txt | codex exec -s read-only - "Some extra prompt"` (two positional args) ### `codex review` - `-m` flag does NOT work with `codex review` — use `-c 'model="gpt-5.4"'` instead - `--commit ` and `[PROMPT]` are MUTUALLY EXCLUSIVE — cannot combine them - `--base ` and `[PROMPT]` CAN be combined - `--uncommitted` and `[PROMPT]` CAN be combined - WRONG: `codex review --commit abc123 "Review for security"` (will error) - Correct: `codex review --commit abc123 -c 'model="gpt-5.4"'` - Correct: `codex review --base main "Focus on security"` ### Workaround for reviewing commits with custom instructions Since `--commit` cannot take a prompt, pipe the diff to `codex exec` instead: ```bash git diff ~1.. > /tmp/diff.txt && cat /tmp/diff.txt | codex exec -s read-only -c 'model="gpt-5.4"' -c 'model_reasoning_effort="medium"' - ``` This is the recommended pattern for reviewing specific commits with custom review instructions. ## Commands ### Non-Interactive Execution ```bash # Basic task (default model + medium effort) codex exec -c 'model="gpt-5.4"' -c 'model_reasoning_effort="medium"' "Audit this logic for edge cases" # Full-auto mode (sandboxed, lower friction) codex exec --full-auto -c 'model="gpt-5.4"' -c 'model_reasoning_effort="medium"' "Implement the requested refactor" # Read-only sandbox (analysis only) codex exec -s read-only -c 'model="gpt-5.4"' -c 'model_reasoning_effort="medium"' "Find bugs in this code path" # Workspace-write sandbox codex exec -s workspace-write -c 'model="gpt-5.4"' -c 'model_reasoning_effort="medium"' "Apply the fix and update tests" # Custom working directory codex exec -C /path/to/project -c 'model="gpt-5.4"' "Evaluate this repository" # Save final output to file codex exec -o output.txt -c 'model="gpt-5.4"' "Summarize key risks" # Pipe context from stdin (no additional prompt argument!) cat context.txt | codex exec -s read-only -c 'model="gpt-5.4"' -c 'model_reasoning_effort="medium"' - # Pipe diff for commit review with custom instructions git diff HEAD~1..HEAD > /tmp/diff.txt && cat /tmp/diff.txt | codex exec -s read-only -c 'model="gpt-5.4"' -c 'model_reasoning_effort="medium"' - ``` ### Code Review Use `codex review` for repository diffs. Model must be set via `-c`, not `-m`. ```bash # Review uncommitted changes codex review --uncommitted -c 'model="gpt-5.4"' -c 'model_reasoning_effort="medium"' # Review against a base branch codex review --base main -c 'model="gpt-5.4"' -c 'model_reasoning_effort="medium"' # Review a specific commit (NO prompt allowed with --commit) codex review --commit abc123 -c 'model="gpt-5.4"' -c 'model_reasoning_effort="medium"' # Custom review instructions (only with --base or --uncommitted, NOT --commit) codex review --uncommitted -c 'model="gpt-5.4"' "Focus on security issues" codex review --base main -c 'model="gpt-5.4"' "Check for performance regressions" ``` ## Important Flag Placement `--search` and `-a/--ask-for-approval` are top-level flags. Put them before `exec` or `review`. Correct: ```bash codex --search -a on-request exec "Your prompt" codex --search -a on-request review --uncommitted ``` WRONG: ```bash codex exec --search "Your prompt" codex exec -a on-request "Your prompt" ``` ## Useful Flags | Flag | Description | |------|-------------| | `-c 'model="gpt-5.4"'` | Set model (works everywhere, preferred over `-m`) | | `-m` | Model shorthand (works with `exec` only, NOT `review`) | | `-s` | Sandbox: `read-only`, `workspace-write`, `danger-full-access` | | `-a` | Approval policy (top-level flag, before subcommand) | | `-C` | Working directory | | `-o` | Write last message to file | | `--full-auto` | Sandboxed auto-execution (`-a on-request -s workspace-write`) | | `--json` | JSONL event output | | `--search` | Enable web search tool (top-level flag) | | `--add-dir` | Additional writable directories | | `-c key=value` | Override any config value | ## Best Practices - Default to `medium` reasoning effort — it covers most use cases well - Only escalate to `high` for repeated failures, complex planning, or explicit user request - Prefer `codex exec` for delegated prompts instead of interactive `codex` - Start with `-s read-only` for audits and second opinions - Use `--full-auto` only when you expect autonomous edits - Always use `-c 'model="gpt-5.4"'` (not `-m`) for `codex review` commands - For commit reviews with custom instructions, pipe `git diff` to `codex exec -` - Keep prompts explicit about expected output format - Add `-o` when another tool or agent must consume the result - Run `codex review --uncommitted` before committing as a quick extra pass - Run background tasks with `run_in_background` and check output via file path --- > Converted and distributed by [TomeVault](https://tomevault.io/claim/georgekhananaev) — claim your Tome and manage your conversions.