Just a guide. Not a prescription.
- Upfront planning, especially systems design and architecture
- Hard problems that can be solved cleanly in one pass
- Code and technical design reviews
- Finishing touches, especially cleaning up gaps left by Opus 4.5
- Tough bug hunts that require careful reasoning
- Long-running tasks I can leave overnight (and go to sleep)
- Big refactors where changes need to be surgical (precise and controlled)
- Backend-heavy work with complex business or domain logic
- Reviewing and understanding mid to large brownfield/legacy codebases using Codex through context gathering
- Execution, turning Codex plans and specs into working code
- Rapid prototyping and iteration
- Close collaboration with fast back-and-forth over long sessions
- Frontend development
- Knowledge work using Agent Skills
- Working with open models through Anthropic-style APIs
- Small to medium refactors
Together, they cover very different strengths, and using both in the right places makes a noticeable difference.