codex

Installation
SKILL.md

Codex Skill Guide

Models

Model Notes
gpt-5.4 Default & recommended — frontier reasoning + coding
gpt-5.3-codex Strong coding focus
gpt-5.3-codex-spark Extra fast; ChatGPT Pro only (research preview)
  • Set default: model = "gpt-5.4" in ~/.codex/config.toml
  • Override per-run: codex -m gpt-5.4 or /model in-session
  • Reasoning effort: --config model_reasoning_effort="high|medium|low" (or set in config)
    • Low → fast, well-scoped tasks; Medium/High → complex changes or debugging; Extra High → long agentic tasks

Best Practices

Related skills
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First Seen
Apr 7, 2026