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How to Architect Complex Software Projects with OpenAI's Plans.md Technique

Leverage OpenAI Codex for high-level software architecture by using the `Plans.md` technique. This workflow guides the AI to generate a comprehensive, multi-step implementation plan for large projects before writing any code.

From How I AI

How I AI: 3 Advanced Codex Workflows for Faster, Smarter Development with OpenAI's Alex Embiricos

with Claire Vo

How to Architect Complex Software Projects with OpenAI's Plans.md Technique

Tools Used

Codex

OpenAI's cloud-based AI software engineering agent that can execute code, run tests, and handle complex multi-file tasks autonomously.

Step-by-Step Guide

1

Create a `Plans.md` File

Start by creating a file named Plans.md in your project's root directory. Copy and paste the template from the official OpenAI blog post on the Plans.md technique. This file acts as a meta-prompt, instructing Codex on how to structure a good plan, including creating milestones and considering edge cases.

2

Generate the Implementation Plan

With the Plans.md file in place, prompt Codex to generate a detailed architectural plan for your complex task. Be specific about your goal and tell it to use the Plans.md file as a guide. This allows you to review the entire approach before any code is written.

Prompt:
using Plans.md make a plan to build a Python SDK based off our TypeScript SDK. put it in temp.md
3

Review and Iterate on the Plan

Codex will generate a comprehensive document (e.g., temp.md) outlining the steps. Carefully review this plan. You can have a conversation with Codex in the same thread to refine or change the plan until you are satisfied with the architecture.

4

Execute the Approved Plan

Once the plan is finalized, instruct Codex to begin implementation. The AI will methodically work through the steps it created. This combines human strategic oversight with tireless AI execution for maximum velocity.

Prompt:
implement the plan in sdk_plan.md

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