Active time: Approximately 20–30 minutes. The agent may take additional time to make the change.

Today’s outcome: Add one “Clear completed tasks” button and prove that the new feature works without breaking the existing app.

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**Quick links: LinkedIn lessons · WhatsApp group · The Builder Course website .

Setup . Day 1 . Day 2 . Day 3**

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💡 Using Claude Code?

This lesson uses Codex. If you already use Claude Code, run claude instead of codex.

Replace AGENTS.md with CLAUDE.md everywhere it appears, including inside copied prompts. The remaining steps are the same. The supported setup and demonstrations use Codex.

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Yesterday, you inspected the files the agent created.

Today, you will make one deliberate product change.

The agent will still do the coding, but you will decide what the change must do and how you will know it works.

Why this matters

A first version is rarely the final version.

Coding agents can make changes quickly. Your responsibility is to keep each change bounded, define the result and check that the rest of the product still works.

Today’s feature is the same for everyone: one button that removes completed tasks while leaving unfinished tasks in place.

You will not receive a completely finished prompt this time. You will supply the button wording and write the finish line yourself.

This is your first step from following a worked example to directing a change.

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Follow along Demo Video

https://supercut.ai/share/thebuildercourse/iEq7zsVOcSFgqg4uz6ZvHM

Before you begin

Open the same challenge folder in VS Code.

Confirm that you can see:

Open index.html in your browser and confirm that the Day 2 version still works.

Add one task, mark it complete and delete it. If any of those actions fail, repair Day 2 before starting today’s change.

Take one screenshot of the current app. This is your before evidence.

Your required action