Your first task: plan, diff and permissions

Mr Manuel has a bakery on the street below and has never had a page on the Internet. You are going to make him one, just for fun, with a made-up name, opening hours and address. It is the first real task with an agent, and the page is not what matters: the habit is. Plan first, diff next, and only then yes.

This is how it looks on 6 October 2026; your screen may differ. Look for the button with the same name.

The request

You will write this to the agent, but not yet. First, the right mode.

Create a simple HTML page for the bakery on my street, with a made-up name, opening hours and address. One file only, index.html, no external libraries. Before you create anything, show me the plan.

Step 1: the right mode

Open the terminal, go into the folder and check where you are:

cd experiencias
pwd

Claude Code. Open it like this:

claude --permission-mode manual

Below the text box you should see ⏸ manual mode on: the agent asks permission before editing files or running commands. This matters because recent versions start in auto mode, where a second model approves actions for you. To learn, you want it to be you. Then press Shift + Tab until ⏸ plan mode on appears (or start your message with /plan). Now paste the request.

Codex. Open it with codex. Type /permissions and choose Read Only: it can read and run commands that change nothing, but it must ask you before changing files. (Auto is something else: it edits and runs commands inside the folder without asking.) Then type /plan, press Enter and paste the request.

Sources: Claude Code permission modes, Codex approvals and security and Codex commands.

Step 2: read the plan

The agent reads the (empty) folder and answers with a plan. A good plan for this says, more or less:

• it will create one file, index.html;
• what it will put in it: name, opening hours, address, a bit of colour;
• that it will not download anything or touch anything outside the folder.

If the plan mentions several files, installing things or libraries, tell it what you want to change. In Claude Code choose No, keep planning and write the correction; in Codex just reply in the conversation.

When the plan is good:

• Claude Code: choose Yes, manually approve edits. Do not choose the option that mentions auto mode.
• Codex: if it asks whether to put the plan into practice, say yes; if it does not ask, type “You can go ahead with the plan.” It stays in Read Only, so it must ask you before saving.

Step 3: the diff before you accept

Now the agent wants to create index.html and asks your permission. Claude Code shows you what it will write. In Codex, the request may not show the whole file: before you accept, ask “Show me the full contents of the file first”. Because the file is new, every line appears with a + (lesson 0/03). Before you say yes, look at:

• the name, the opening hours and the address (made up, as you asked);
• lines that fetch things from other sites, such as <script src="https://…">;
• the name and the place of the file: index.html, inside experiencias.

Accept or refuse each action. If it asks to run a command you do not understand, refuse and ask what it does. If it asks to open the browser, you can refuse and open it yourself.

In Codex, if the folder is in Git (lesson 1/05), the /diff command then shows everything that changed at once.

Step 4: see the result

Open the page in the browser. Double-click index.html in the file explorer, or, in the terminal, inside experiencias:

• Windows: start index.html
• Mac: open index.html
• Linux: xdg-open index.html

A small change

Now ask for a change:

Change Saturday's opening hours to 7:00–13:00. Do not touch anything else.

This time the diff has lines with − (the old hours) and with + (the new ones). If more lines appear than the Saturday ones, refuse and ask why.