Why the Codex harness matters

Alexander Embiricos, the product lead for Codex at OpenAI, shares practical workflows for getting the most out of this AI coding agent. In this episode, he demonstrates how both non-technical users and experienced engineers can leverage Codex to accelerate development, from making simple code changes to building production-ready applications. Alex walks through real examples of using Codex in VS Code and terminal environments, implementing parallel workflows with Git worktrees, and creating detailed implementation plans for complex projects. He also reveals how OpenAI uses Codex internally, including how they built the Sora Android app in just 28 days, and offers insights on automated code review and the future of AI-assisted development.

What you’ll learn:

1. How to set up and use Codex in VS Code and terminal environments for both simple and complex coding tasks
2. A practical workflow for running multiple Codex instances in parallel using Git worktrees to avoid conflicts
3. How to create detailed implementation plans using the Plans.md technique for complex engineering projects
4. Why context is critical when prompting Codex—and how to provide the right information for better results
5. How OpenAI uses automated code review to accelerate development while maintaining high quality standards
6. The key differences between vibe coding for prototypes versus building production-ready applications with AI
7. How the new GPT-5.2 model improves Codex’s capabilities with faster reasoning and better problem-solving

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Detailed workflow walkthrough from this episode:

https://chatprd.ai/how-i-ai/advanced-codex-workflows-with-openai-alex-embiricos

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In this episode, we cover:

(00:00) Introduction to Alex and Codex

(02:06) Getting started with Codex

(04:54) Using Codex for parallel tasks

(07:34) Understanding Git worktrees

(09:51) Terminal shortcuts and command-line efficiency

(12:16) How OpenAI built the Sora Android app with Codex

(15:37) Using PLANS.md for problem solving

(17:57) The importance of high agency

(22:22) Deciding between what needs a plan and what doesn’t

(26:42) How to multiply the impact of Codex

(28:08) Implementing automated code review with GitHub

(31:58) Delivering the benefits of AGI to all humanity

(34:35) Accelerating developer productivity

(36:38) Recap and final thoughts

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Tools referenced:

• Codex: https://openai.com/blog/openai-codex

• VS Code: https://code.visualstudio.com/

• Cursor: https://cursor.com/

• Git: https://git-scm.com/

• GitHub: https://github.com/

• Atlas: https://openai.com/atlas

• ChatGPT: https://chat.openai.com/

• Slack: https://slack.com/

• Linear: https://linear.app/

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Other references:

• Sora Android app: https://openai.com/blog/sora

• GPT-5.2 model: https://openai.com/index/introducing-gpt-5-2/

• SWE-bench: https://openai.com/index/introducing-swe-bench-verified/

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Where to find Alexander Embiricos:

LinkedIn: https://www.linkedin.com/in/embirico

X: https://x.com/embirico

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Where to find Claire Vo:

ChatPRD: https://www.chatprd.ai/

Website: https://clairevo.com/

LinkedIn: https://www.linkedin.com/in/clairevo/

X: https://x.com/clairevo

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Production and marketing by https://penname.co/. For inquiries about sponsoring the podcast, email jordan@penname.co.