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Day 3 of 52 · about 15 min · Basics

Plan first, then let Claude build

Most bad edits come from solving the wrong problem. A plan takes a minute to read, and fixing a plan is far cheaper than fixing finished code.

You’ll finish with

  • A written plan for a real change, corrected by you
  • The change built from that plan, with the tests passing

You’ll need

  • Claude Code set up with a CLAUDE.md, as on Day 1
  • The practice project, or your own project in git
Start from the practice project as of Day 1 (.zip, 9 KB)

Before you start

Tell us about your setup and the steps change to fit it. Your answers stay in this browser, and you can change them at any time.

Which system are you on?

Commands differ between systems. Pick the one you’ll run Claude Code on.

The steps

One step at a time. When a step’s check matches, tick it and the next one opens.

0 of 4 steps done0%

  1. Step 1 of 4: Switch to plan mode

    Press Shift+Tab until the status bar shows plan mode.

    In plan mode, Claude reads files and writes a plan, but edits stay blocked until you approve it.

    In order:

    1. ⏵⏵ auto mode on

    2. ⏸ manual mode on

    3. ⏵⏵ accept edits on

    4. ⏸ plan mode on

    Each Shift+Tab moves one step. Or start with claude --permission-mode plan.

    Check it worked

    The status bar shows ⏸ plan mode on.

    If it didn’t work

    Shift+Tab does nothing on Windows

    Press Alt+M, or restart with claude --permission-mode plan.

  2. Step 2 of 4: Ask for a plan

    Describe the change and what done looks like; Claude explores and writes a plan.
    Paste into Claude Code
    Add a --deposit option to the quote: a percent of the total that the client pays up front, shown on its own line after Total.

Plan it first: which files change, where the maths goes, and which tests you'll add. Follow CLAUDE.md.

    In order:

    1. You

      You describe the change

    2. Claude

      Claude reads the code

    3. Claude

      Claude presents a plan and asks how to proceed

    Your files stay untouched while Claude plans.

    In your own project, describe a change that touches two or three files.

    Check it worked

    A plan lists the files to change and the tests to add. No file has changed.

  3. Step 3 of 4: Correct the plan

    Check the plan against your rules and send back what’s wrong before any code exists.

    Good sign

    • Deposit maths in src/quote.js
    • Money kept in whole cents
    • A new test for the deposit

    Send it back

    • Maths inside src/cli.js
    • Unrounded decimals
    • No test, or existing tests changed
    Acme Quotes’ rules come from its CLAUDE.md. Check yours against your own.

    To change something, choose No, keep planning and say what to fix. Ctrl+G opens the plan in your editor instead.

    Check it worked

    Claude revises the plan and asks again. Nothing is built yet.

  4. Step 4 of 4: Approve it and check the build

    Approve the plan, let Claude build it, then check the result against the plan.

    Yes, and use auto mode

    • Claude builds without asking
    • A classifier reviews actions instead of you

    Yes, manually approve edits

    • You approve each edit
    • Slower, but you see everything
    Without auto mode, the first option reads Yes, auto-accept edits.

    When Claude finishes, check it yourself:

    Terminal or PowerShell
    npm test
node src/cli.js design:10 dev:24 --discount 10 --deposit 30

    Check it worked

    Practice project: the tests show fail 0, and the quote ends with a 30% deposit of EUR 997.92.

Finish · 4 of 4 steps to go

You planned before you built

Plan when a change touches several files or you’re unsure of the approach. If you could describe the change in one sentence, skip the plan.

What you’ll have checked

  • You corrected a plan before any code existed
  • The build matched the plan and the tests pass

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Claude Code for your team

Want Claude Code set up across your team?

HorizonLux sets up and repairs Claude Code for teams: CLAUDE.md rules, hooks that enforce them and reviewed MCP servers. Book a free call to talk it through.

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Questions

Questions about Day 3

How do I leave plan mode without approving?

Press Shift+Tab again. Plan mode blocks edits, so there is nothing to undo.

Sources

Checked against the official Claude Code docs on .

Independent resource, not affiliated with Anthropic. HorizonLux wrote this lesson; Claude Code is made by Anthropic.