Welcome to the MonDive

Today in MonDive, we’re diving into OpenAI Codex, OpenAI’s AI teammate for building, fixing, testing, and improving real projects not just writing code in a chat.

We’ll cover why Codex matters, how to access it, what the key settings mean, and how to use plugins. Then we’ll walk through a beginner-friendly project where Codex helps build an AI newsletter launch kit from landing page to promo asset.

Alright, let’s dive in.

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Why use OpenAI Codex?

Think of OpenAI Codex as a coding teammate that helps you get real work done, not just brainstorm code.

It can help you:

• Fix bugs without digging through every file yourself

• Write new features based on clear instructions

• Explain confusing code in a project you are working on

• Run checks and tests so changes are easier to trust

• Prepare cleaner updates that are easier to review

Codex works best when the task is clear and specific. Instead of making big, messy changes across your whole project, it helps you handle focused updates that are easier to check, test, and review. That makes it useful for real coding work where you want speed, but still want to stay in control of what changes in your project.

How to Access OpenAI Codex

The easiest way to start with Codex is to download the Codex app.

• Go to the OpenAI Codex page.

• Click Download for Windows or the download button for your device.

• Install the Codex app on your computer.

• Open the app and sign in with your ChatGPT account.

You can also access Codex through the terminal, an IDE like VS Code or Cursor, and GitHub-connected cloud workflows, but for beginners, the Codex app is the easiest place to start because it gives you a more visual and simple way to work with your projects.

Codex Subscription and Usage Limits

Codex is not fully unlimited. OpenAI says Codex is included with ChatGPT Plus, Pro, Business, Enterprise, and Edu plans. Free and Go users may also get Codex for a limited time, but regular access is mainly tied to paid ChatGPT plans

Set Up Plugins

Plugins are like extra tools you can connect to Codex. They let Codex do more than just edit code. With the right plugins, Codex can open websites, use your browser, create docs, work with GitHub, or even help publish a project.

For this workflow, the useful plugins are:

• Browser — lets Codex open websites, test pages, click buttons, take screenshots, and check if something works visually.

• Chrome — lets Codex use your real Chrome browser, which is useful when a website needs your login, browser session, or real account access.

• Google Drive — lets Codex create and work with Docs, Sheets, Slides, plans, reports, and research files directly from your Drive.

• GitHub — lets Codex work with repositories, review pull requests, check code changes, and help manage development work.

• HeyGen — useful for creating promo videos, motion graphics, product videos, or marketing assets from a prompt.

To add them:

• Open the Codex app

• Click the Plugins section on the left side

• Search for the plugin you need

• Click the plus button

• Select the plugin

• Sign in or give permission if asked

Important Codex Settings to Know

Before you start building with Codex, there are a few settings you should understand.

• Plan Mode
  Turn this on when you want Codex to explain the plan before making changes. This is useful for beginners because you can review what Codex wants to do before it starts editing anything.

• Pursue Goal
  Use this when you want Codex to keep working toward a bigger result instead of stopping after one small answer. This is helpful for longer tasks like building a page, fixing multiple issues, or improving a project step by step.

• Ask for Approval
  This is the safer option. Codex will ask before sensitive actions, like editing external files or using the internet. Use this when you want more control.

• Approve for Me
  Codex can continue more smoothly and only ask when something may be unsafe. This is faster, but beginners should use it carefully.

• Full Access
  This gives Codex the most freedom, including access to the internet and files on your computer. Only use this when you trust the task and understand what Codex is doing.

• Reasoning Level: Low, Medium, High, Extra High
  This controls how much thinking Codex uses. Low is faster for simple tasks. Medium is good for normal work. High or Extra High is better for harder builds, debugging, or complex project changes.

• Model Selection
  This lets you choose which Codex model to use. In the screenshot, GPT-5.5 is selected. Use the stronger model for bigger tasks and harder fixes.

• Speed Setting
  This controls how fast Codex works. Faster settings are useful for quick edits, while slower or deeper settings can be better when accuracy matters more.

Build an AI Newsletter Launch Kit With Codex

Codex works best when you treat it less like a code generator and more like an assistant.

For this project, we’ll use it to create the core pieces of a simple AI newsletter launch: a landing page, a marketing plan, and a promo video. This is a good example because it shows Codex helping with the full workflow around an idea, not just one piece of code.

Step 1: Create the Landing Page

Start with the first thing people will see: the landing page.

The goal is simple. Codex should create a clean page that explains the newsletter, makes it easy to understand the value, and gives visitors a place to sign up.

Prompt:

Create a simple landing page for an AI newsletter.

The newsletter is called [Your Newsletter Name].

Make it modern, clean, and beginner-friendly.

Include:
- a strong headline
- a short subheadline
- an email signup box
- a feature section
- a clear call-to-action button

Use a Deep Navy color scheme.

Before building, show me the plan first.

After Codex shows the plan, quickly check that the page includes the right sections. Then approve the build.

Step 2: Improve the Landing Page

The first version gives you something to work with.

Now ask Codex to improve it like a designer, copywriter, and marketer. This is where the page starts to feel more polished.

Prompt:

Review the landing page you created.

Look at:
- the design
- the headline
- the copy
- the signup section
- the layout
- anything that feels confusing

Make the page cleaner, easier to read, and more professional.

Keep the same Deep Navy color style.
Do not make it complicated.

Step 3: Create the Newsletter Email

Once the landing page is ready, use Codex to create the actual newsletter.

This step shows how Codex can move from building the page to creating the content behind the product. Instead of starting from a blank email, you can ask Codex to research recent AI updates and turn them into a simple, useful newsletter draft.

Prompt:

Create an AI newsletter that includes simple lessons that are useful and practical for our readers.

Pull recent information from articles, YouTube videos, and any other place where AI information might be.

Compile it into a final email that is easily digestible and actionable for the readers.

Step 4: Create a Marketing Plan

Once the page is ready, Codex can help with the strategy around the newsletter.

This turns the project from a simple page into something you can actually launch and promote. Use Google Drive if you want Codex to create the plan as a real document.

Prompt:

Create a new Google Doc with a full marketing plan for this AI newsletter.

The plan should include:
- target audience
- newsletter positioning
- launch strategy
- content ideas
- social media plan
- growth channels
- weekly action plan
- simple ways to get the first subscribers

Make it practical, beginner-friendly, and easy to follow.

Now you have more than a landing page. You have a plan for who the newsletter is for, how to position it, and how to start growing it.

Step 5: Create a Promo Video

The final step is to turn the newsletter into something you can promote.

Use HeyGen or another video plugin to create a short video that matches the style of the landing page.

Prompt:

Use HeyGen or Hyperframes to create a 30-second promo video for this AI newsletter.

The video should:
- match the green color style of the landing page
- explain why the newsletter is useful
- show that it helps beginners keep up with AI
- include simple motion graphics
- avoid overlapping text or messy visuals

Do not add voiceover for now.

This gives you a simple launch asset for social media, a product teaser, or a newsletter announcement.

By the end, Codex has helped create the page, improve the message, build the launch plan, and produce a promo asset around the same idea.

Know someone who may be interested?