tomevault-io OpenAI Codex
OpenAI Codex CLI is an open-source command-line coding agent that runs locally, providing AI-powered code generation, debugging, and task automation directly in the terminal. It uses advanced reasoning models (GPT-5-Codex by default) to read, modify, and execute code in the local environment.
Critical Operating Requirements
Always use these five requirements together:
- Information gathering - Codex should be used to understanding how things work, the root cause for why things are happening in specific ways, validating feedback to the user as a peer/second pair of eyes to confirm assumptions
- Include at the end of any prompt: "Do not make any modification to the codebase"
- Non-interactive exec mode - Use
codex --yolo exec --skip-git-repo-check -o ./specs/logs/codex-$(date +%Y-%m-%d-%H%M)-<spec-slug>.md "<task>"for automation, logging and session resumption
Best Practices
Prompting Techniques
- Be specific: Include programming language, constraints, or optimization goals
- Good: “Create a Python REST API with FastAPI, include rate limiting”
- Poor: “Make an API”
- Provide context: Reference specific files, functions, or requirements
- Good: “Add authentication middleware to routes.js using JWT”
- Poor: “Add auth”
- Use constraints: Specify frameworks, style guides, or performance requirements
- Good: “Refactor using functional programming, optimize for speed”
- Poor: “Make it better”
Exec Mode (Non-Interactive)
Use codex exec for invocations. This mode runs without interactive prompts and streams results to stdout.
Availability
Install via Homebrew:
brew update && brew upgrade codex
Permission Errors
Network Access
Ensure one of:
- Proper configuration in ~/.codex/config.toml
Git Repository Requirement
codex --yolo exec --skip-git-repo-check "task"
Summary
Every Codex operation should: 1. Use codex exec (not interactive mode) 2. Log output to file 3. Support session resumption with resume --last
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