Which file at your company is a mess?
The Code tab lets Claude work on a folder of files on your computer. You describe the job in plain words and approve what Claude asks to do. You don't need to know how to code.
Think of a customer list with three spellings of one name, dates in mixed styles, or a price sheet with stray symbols. It should be a file you can copy. Using the practice job? Write "messy invoice list".
What can Claude do here that chat can't, and who decides?
Guess first. The reveals come from Anthropic's Claude Code pages.
Show the answer
Read your files, change them and run commands, as far as the mode you pick allows. A command is a typed instruction that starts a small program on your computer, such as one that adds up a column. Claude writes it, so you never have to.
Each conversation in the Code tab is called a session. It keeps its own history and stays tied to the folder you chose.
Show the answer
A request. It shows exactly what will change, line by line, and waits for your answer. In Manual mode Claude asks before it changes a file or runs a command. Accept edits lets file changes through without asking, and Plan reads your files and proposes a plan without changing them. Start in Manual until you trust a task.
Clean the list in the Code tab
Five steps, about 15 minutes. Tick each one when it's done.
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Make a folder and put the file in it.
Create a new folder called invoices and save the messy file into it. Claude can read and change anything in the folder you open, so keep this one to just the file you want fixed.
Or use the practice file
A made-up plumber's invoice list: 10 rows, mixed dates, three spellings of one customer, one repeated row.
- invoices-messy.csv10 rows · under 1 KB
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Open the Code tab and choose the folder.
Click Code at the top of the sidebar. If the tabs show only icons, hover over one to see its name.
Look at the row of controls under the prompt box. Click the first one, which sets where Claude works, and pick your computer: the first entry under Local. Then click the folder control next to it, choose Open folder… and pick your invoices folder.
Are those controls above the prompt box instead? Your app has the older layout. Update it with Check for Updates…, in the Claude menu on a Mac or the Help menu on Windows.
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Set the mode to Manual, then ask.
In the same row, click the mode selector and choose Manual. Paste this and press Enter:
Clean invoices-messy.csv and save the result as a new file called invoices-clean.csv. Don't change the original. Rules: write every date as year-month-day, like 2026-10-03 (dates with dots are day.month.year); amounts as plain numbers with no € sign and a dot for decimals; each customer spelled one way, with a capital letter on each name; paid as yes or no in lowercase; remove any row that is repeated exactly. Then tell me how many rows are in the new file.
The rules sit in the first message, so Claude doesn't have to guess what "clean" means. "Don't change the original" keeps the messy file there to compare.
Press the stop button if Claude starts doing something you didn't ask for. To steer it without stopping, type a correction and press Enter.
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Read each request, then approve or decline it.
In Manual mode Claude stops before each change and waits for you. A request to change a file shows the file's name and the exact lines Claude wants to write. For invoices-clean.csv that's a row of column names and nine invoices.
A request to run a command shows a short line of code. You don't have to read it. Claude usually says in the chat what it's for, such as counting the rows. If you can't tell, decline and ask "What would that do?"
You can say no to any request. Claude stops that step and waits for you to tell it what to do instead.
Once you approve the new file, a count such as +10 -0 appears in the Changes card beside the chat: ten lines added, none removed. Click it, or Changes at the top of the session, to open the changes view. It shows every line Claude added or removed.
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Ask Claude what it did, in plain words.
Send this in the same session and read the answer:
Explain what you did as if I've never seen code. One line per file you created or changed, and one line for anything you ran. Then tell me anything you weren't sure about.
It should say it created invoices-clean.csv and only read invoices-messy.csv. Read the part about what it wasn't sure of, such as how it read "85,50". That's where a cleaning job goes wrong, and you can correct it in one message.
If you see this instead
- Clicking Code shows a prompt to upgrade
- The Code tab needs Pro, Max, Ultra, Team or Enterprise. On some older Enterprise plans only certain seats include it, so ask your admin.
- Clicking Code shows a sign-in prompt or an error
- Finish signing in and restart the app. If an error stays, sign out and back in from the app menu, then quit the app completely and open it again.
- Claude asks for something you didn't expect
- Decline it, then ask: "Why do you need this, and what would it change?" Approve only when the answer fits the job you gave it.
- Claude changed the original file
- In Manual mode that needs your yes, so decline any request that names invoices-messy.csv. If it already happened, put back your copy of the file, or download the practice file again, and paste the prompt again.
Is the clean file right, and is the original untouched?
A clean-looking file can hide a wrong total. Have Claude check the numbers, then look at the files yourself.
With the practice file
Send this in the same session. Claude may ask to run a command to do the sums. Approve it.
You pass when Claude says 1596.00 in all and 1060.00 unpaid, and the files show the same when you look yourself.
Click invoices-clean.csv where Claude names it in the chat. It opens beside the chat as plain text, one invoice per line. Under the row of column names there are 9 invoices. Invoice 1006 is there once, Ion Vasile is spelled the same way on invoices 1002, 1005 and 1009, and every date looks like 2026-10-03.
Then click invoices-messy.csv in Claude's answer from step 5. It still has 10 invoices, with 1006 twice.
Claude adding up its own work proves less than your own count, so do both. Only read in that view: anything you type there is saved on its own. With your own file, count the rows and add up one column by hand.
Two questions from memory
Which mode makes Claude ask before it changes a file or runs a command?
Manual. Accept edits lets file changes through without asking, and Plan only reads and proposes. Earlier versions of the app called Manual "Ask permissions".
Claude asks to do something you didn't expect. What can you do?
Decline it. Claude stops that step and waits. Then ask why it needs it, or tell it what to do instead.
Lesson 5 opens by asking the first one again.
Claude can read and change anything in the folder you open. Open a small folder made for the job, not Documents. Stop with the stop button, and keep a copy of anything you can't recreate.
Course 2 so far
What you've built
- Lesson 1: Tip calculator
- Lesson 2: Browser comparison
- Lesson 3: Scheduled summary
- Lesson 4: Clean invoice list