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The Ultimate Guide to ChatGPT Codex: OpenAI's Claude Code Killer

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Dec 8, 2025

Guest

Carl Vellotti

This discussion features Carl Vellotti, a full-stack product manager and prototyping expert with a knack for developer tooling. He dives into the potent capabilities of ChatGPT Codex versus Claude Code. Carl breaks down how non-technical PMs can get started with Codex CLI and offers practical tips on using it for documentation, meetings, and prototyping. He shares hands-on demonstrations of integrating Codex in IDEs and how to streamline workflows using templates, voice dictation, and Socratic questioning for effective PRDs.

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ADVICE

Start Codex From Your Terminal

Install Codex CLI with npm and launch it by typing codex in your terminal to access ChatGPT outside the browser.
Use the IDE (Cursor or VS Code) to watch Codex create and edit files in real time for faster prototyping.

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INSIGHT

Folder Context Beats Manual Uploads

Codex can read and analyze all files in a project folder without manual uploads, letting it synthesize interviews and create documents.
This makes folder-based context far more powerful than copying text into a browser chat.

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ADVICE

Use YOLO Mode For Long Tasks

Use approvals/full-access (YOLO) mode to let Codex run long tasks without prompting for permission repeatedly.
Keep Codex scoped to one directory to reduce risk when running with full access.

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Getting started with Codex CLI

01:34 • 2min

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Selecting models and settings

03:06 • 2min

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Preparing a demo project and files

05:15 • 42sec

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Using Codex to read and summarize files

05:57 • 3min

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IDE integration and Cursor demo

Web search, permissions and comparisons

10:32 • 1min

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Launching Codex inside an IDE

11:46 • 33sec

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Codex vs Cloud Code head-to-head

12:19 • 2min

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Approval modes and YOLO hack

14:45 • 2min

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Handling images and clipboard inputs

16:59 • 3min

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Writing styles: documents vs code

20:24 • 3min

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Running code and connecting APIs

23:50 • 2min

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Template-driven meeting summaries

Socratic questioning to build better PRDs

32:58 • 3min

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Using voice dictation and Whisperflow

35:50 • 4min

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Review examples and generate PRD

39:21 • 4min

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Codex file workflows and limitations

43:18 • 3min

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Agents, parallelism, and workarounds

46:04 • 2min

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Parallel YouTube transcript summarization demo

47:41 • 6min

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When Codex shines: prototyping and coding

53:24 • 3min

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Top PM use cases for Codex

56:35 • 2min

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Living in the terminal and final tips

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Today’s Episode

Claude Code hit $1B ARR in 6 months. But OpenAI is not just giving up.

ChatGPT’s new Codex is the most powerful way for product managers to build prototypes.

And it’s a far better way to use ChatGPT than the browser.

So every PM should know how to use it.

Today, I brought back the man behind my Claude Code tutorial, Carl Vellotti, for a full guide on how to use ChatGPT Codex for PMs:

This might be the most important podcast you watch all year.

(And not a single other PM podcast has even talked about this tool)

Your Newsletter Subscriber Bonus

For subscribers, each episode I also write up a newsletter version of the podcast. Thank you for having me in your inbox.

Today’s guide covers:

* Getting Started: The Non-Technical PM’s Guide to Codex CLI

* Classic PM Tasks: Documents, Meetings & PRDs with Codex

* Advanced Prototyping: From Vibe Coder to Vibe Engineer

This is your complete Codex roadmap.

1. How to Get Started - The Non-Technical PM’s Guide to Codex CLI

If you’ve never touched a terminal, this is for you.

1a. Open Codex in an IDE

Carl opens Cursor and shows files Codex creates in real-time.

Workflow: Open project folder in Cursor → Terminal (Control + backtick) → Type codex.

Now you see files created, preview documents, navigate visually.

As Carl Says:

“Open it in an IDE. Easiest way to see what it’s actually doing.”

1b. The YOLO Mode Hack

Codex asks for permission constantly—every website, every command.

Solution:

codex --yolo

Full access mode. No prompts. Just execution.

“Haven’t broken my computer yet. We’re in this directory so it won’t leave.”

1c. Codex vs Claude Code

Same task on both: Search web, summarize differences.

Claude Code: 3 searches simultaneously, ~2 minCodex: One site at a time, asks permissions, ~4 min

Claude Code is faster, hides details. Codex shows every command—more verbose.

“It’s Apple versus Microsoft. Claude does things in a nicer interface. Codex shows you everything.”

2. How to Handle Classic PM Tasks with Codex

Codex shines at daily PM work.

2a. File Analysis Without Uploading

Run Codex from a folder, it accesses everything. No uploading.

Carl has demo folder (Taskflow) with interviews, notes, PRDs.

“What user interviews completed?” → Codex lists them“Top 3 pain points?” → Returns: voice input reliability, integration gaps, template workflow

Creates document with direct quotes—no manual file providing.

2b. Template-Driven Workflows

Solution: Create /templates folder with markdown files.

Example: Discussion Points, Action Items, Risks & Blockers, Next Steps

Use: Summarize @meeting-notes using @template

Same format every time. Works for PRDs, one-pagers, research summaries.

2c. Socratic Questioning for Better PRDs

Problem: Asking Codex to write a PRD produces garbage without proper thinking.

Solution: Socratic template makes Codex ask YOU questions first.

Questions: “Why is this helpful? Data, feedback, or strategic?” “What must work for V1?” “Edge cases?”

You answer. AI embeds your thinking.

Then Codex reviews context, templates, example PRDs, and writes.

Carl: “Goes from kind of there to a really good PRD almost right out of the box.”

3. Advanced Codex Techniques for Future Vibe Engineers

This is where Codex separates from the browser.

3a. Design Systems with Storybook

Vibe coder problem: “Make title pink” → wrong shade → 20 iterations → still janky

Vibe engineer solution: Storybook (npm run storybook)

See components visually, change colors instantly, see changes live without redeploying.

Carl changes recipe title to pink: read-only mode to see plan, then YOLO mode to execute. Updates in Storybook immediately.

Pre-built components: Use Shadcn UI for production-grade React components. Calendar, date picker, dropdown—all done.

“All the logic and difficult things, you get for free.”

3b. Test-Driven Development is The Unlock

Problem: AI says “Done!” but it’s broken. AI will lie and set variables to true to pass tests.

Solution: Write tests BEFORE building.

Red-Green-Refactor: Tests fail → Build until pass → Improve code

Carl’s macro calculator:

Tests: API returns calories, empty recipe returns null, missing data shows “N/A”, API fails retries 3x, divide by servings correctly

Told Codex: “Build to make tests pass.”

35 minutes. Zero touch. All tests green. Feature worked.

Carl: “If you write tests FIRST, they can’t cheat.”

3c. An Example - The TikTok Recipe Bot

Carl built this for his girlfriend: TikTok recipe extractor.

Problem: Recipe videos on TikTok. No written recipe. Just “comment and I’ll DM.”

Solution: Paste URL → Codex downloads video → Sends to Gemini (only model that processes video) → Gemini extracts recipe → Codex formats to PDF

How: Detailed implementation spec: architecture, data flow, APIs, error handling, retry logic, tests.

Gave to Codex in GPT-5 Codex mode. Left 35 minutes.

Built entire feature. Tests passed. Worked first try.

Carl:

“First time I saw the dream—give it a medium-sized feature and it just builds it.”

Where to Find Carl Vellotti