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3.5

The Diff

Estimated time: 20 minTool: GitHub, Claude Pro
After this drill, you can:

After this drill, you can read a GitHub diff — the record of what changed in your code — with AI assistance and understand what changed and why.

Why this matters

Every change to your codebase creates a diff — a precise record of what was added, removed, and modified. Reading diffs is the developer's primary accountability tool: it shows you exactly what Lovable (or Claude Code in Module 5) did on your behalf. You do not need to understand the code — but you do need to be able to read the record of changes. This is the governance layer of building with AI.

How to do it

  1. 1

    Open your GitHub repository and navigate to the Commits tab

    You should see a list of commits — each one representing a change Lovable made when you sent a prompt. Click on the most recent commit.

  2. 2

    Look at the diff — green lines are additions, red lines are deletions

    Spend 2 minutes trying to understand what changed without AI help. Note what you can and cannot understand.

  3. 3

    Use the Diff Reader prompt with Claude to get an explanation

    Paste the diff text into Claude and ask it to explain what changed and why.

  4. 4

    Ask one follow-up question about a specific change you do not understand

    This builds the habit of interrogating changes — not just accepting them.

The prompt

PROMPT — Read and Explain a DiffModel: Claude Pro
Here is a code diff from my web application. Please explain:

1. What files were changed and what is each file responsible for?
2. What specifically changed in the code — explain in plain language (no jargon)
3. What user-visible behavior does this change create or fix?
4. Is there anything in this diff that looks potentially risky or unexpected?

[PASTE THE DIFF FROM GITHUB]

Success criteria

  • ✓You opened GitHub and found the commit history for your app
  • ✓You can describe what changed in one commit in plain language
  • ✓You asked at least one interrogating follow-up question
  • ✓You understand why reading diffs matters for working with AI

Common mistakes

Pasting the GitHub URL instead of the diff text

→ Claude cannot access URLs. In GitHub, click on a commit, then click '...' and 'View file' or just select all the text in the diff view and copy it.

Only reading the most recent commit

→ The most interesting diffs are from your iteration rounds — look at Iteration 3 or 4 where the core logic changed. Those are worth understanding.