How I Plan Every Claude Code and Codex Project

The goal of planning is clarity: what you want to build, how it should work, and what success looks like. Use your agent to develop that clarity, turn it into a useful spec, then build and verify the first milestone.

Start with a conversation

Planning != Plan mode. You can plan well by talking with your agent. Explain the idea, use voice if it helps, and ask the agent to interview you about your goals, constraints and preferences.

This is planning as an interactive process. Let the agent’s questions expose gaps in your thinking; your first prompt does not need to contain every requirement. The brainstorm skill helps structure that conversation.

Use the brainstorm skill →

Turn clarity into a useful spec

A good project spec has three components:

• Project goals: What are you trying to achieve, and what will each milestone enable?
• Product requirements (PRD): Who is it for, what problem does it solve, and what must it do? Capture these in a Product Requirements Document.
• Engineering design (EDD): How will it be built? Capture the tech stack, engineering requirements, architecture and system design in an Engineering Design Document.

Use a project spec for shared direction and constraints, and feature specs for focused requirements. Specs need to be useful, not perfect. Keep separate documentation of how the product currently works.

Use the create-spec skill →

Build in small, verifiable steps

Move from the idea to a spec, then to a minimum viable product (MVP) or first milestone. Break the work into smaller issues in an external project-management tool.

For each piece, use RPIT: Research → Plan → Implement → Test. Investigate the unknowns, choose an approach, build, and check the result against the spec.

Ask the agent to keep running notes on Design decisions, Deviations, Tradeoffs, and Open questions so you can review how the plan changed during implementation.