Your first real edit

In Level 4 you got comfortable asking Claude about code — what does this do, where is that defined, why is it written this way. This level is the next move: asking Claude to change code.

When Claude wants to change a file, it proposes the change first. You see it. You decide. The file doesn’t move until you say yes.

That single rule is the foundation of every later lesson in this level. Hold onto it.

What an edit actually looks like

You ask for something specific:

rename the variable `usr` to `user` in src/auth.ts

Claude reads the file, figures out the change, and then pauses to show you what it wants to write — not a paragraph describing the change, but the actual line-by-line difference between what’s there now and what it wants to put there. That difference is called a diff, and the next lesson is all about reading one.

You either accept it or you don’t.

Tourist vs collaborator

In Level 4 you were a tourist. You walked around a codebase asking questions. Nothing you said could break anything — the worst that could happen was a wrong answer.

This level is different. You’re now editing real files. The blast radius is real.

But notice what isn’t different: Claude still doesn’t change anything without your permission. That gate is always there. The work changes — the trust model doesn’t.

About the permission prompt

You’ll see the permission prompt (from Lesson 2.6) every time Claude wants to write to a file in this level. For now: read what it shows you, click allow once if it looks right, move on.

Level 6 is the whole story of when to widen that gate, when to keep it narrow, and what to never allow without thinking. For Level 5, default mode. One change at a time. Allow once.

What’s next

Claude is going to show you diffs constantly from here on. The next lesson is the actual reading — what + and − mean, what context lines are, and why scanning a diff is not the same as reading one.