codex

name	codex
description	Codex CLI (codex exec) を非対話的に呼び出す。GPT-5.4 によるコード実装、レビュー、設計分析に使用する。「codex で実装して」「codex でレビュー」「Codex に聞いて」などのリクエストで使用する。

You invoke OpenAI Codex CLI in headless (non-interactive) mode from within Claude Code using codex exec. Use GPT-5.4 for code implementation, review, architecture analysis, security checks, and other tasks.

Prerequisites

• codex CLI is installed and authenticated (codex login or OPENAI_API_KEY set)
• The working directory should be a git repository (or use --skip-git-repo-check)

Modes

Review mode (read-only)

For code review, analysis, second opinions. Codex cannot modify files.

codex exec --sandbox read-only --ephemeral [OPTIONS] "PROMPT"

Implementation mode (workspace-write)

For code generation and implementation. Codex can create and modify files in the workspace.

codex exec --full-auto --ephemeral [OPTIONS] "PROMPT"

--full-auto is equivalent to --sandbox workspace-write with auto-approval of file writes.

Common flags

Flag	Purpose
--ephemeral	Do not persist session to disk (always include)
-m MODEL	Override model (default: gpt-5.3-codex)
--skip-git-repo-check	Allow running outside a git repo
-C DIR	Set working directory
-o FILE	Write final message to a file
--json	Output JSON Lines event stream
--output-schema FILE	Force structured output with JSON Schema
-i IMAGE	Attach image file to the prompt
-c key=value	Override config (e.g. -c model_reasoning_effort="xhigh")

Workflow

For implementation

1. Identify the files/features to implement
2. Write a detailed prompt with requirements, file paths, and design constraints
3. Run codex exec --full-auto --ephemeral -C PROJECT_DIR "PROMPT" via Bash (timeout: 300000ms)
4. Verify the generated files with Read tool
5. Run tests/linting to validate quality
6. Report results to the user

For review

1. Parse the user's request to determine the task type
2. Run codex exec --sandbox read-only --ephemeral "PROMPT" via Bash (timeout: 120000ms)
3. Present the result to the user
4. If the user wants to act on suggestions, implement them

Built-in review command

codex exec review

Reviews the current diff against the base branch without needing a custom prompt.

Implementation prompt tips

• Include the full file path where code should be written
• Reference existing files that Codex should read for context
• Specify the language, framework, and coding style
• Include type signatures, interfaces, or examples from the codebase
• Be specific about error handling and edge cases
• One task per invocation for best results

Important notes

• Set timeout to 120000-300000ms for codex exec calls (implementation takes longer)
• Progress logs go to stderr, final answer goes to stdout
• Token usage is shown at the end of the output
• If the user has ChatGPT Plus/Pro, Codex usage is included in the subscription
• If using API key, each call consumes OpenAI API credits
• --dangerously-bypass-approvals-and-sandbox はサンドボックスを無効化し、ファイルシステム全体への書き込みを許可するため使わない
• Codex requires a git repo by default; add --skip-git-repo-check for non-repo directories