When it goes wrong: undo, restart and understand the error

You asked the agent to change only Saturday's opening hours on the bakery page. It changed the hours, yes. But it also swapped the colours, deleted the address and added an order form that nobody asked for. And you, in a hurry, accepted.

It happens to everyone. Here are the three commonest cases and what to do.

This is how it looks on 6 October 2026; your screen may differ. Look for the button with the same name.

Case 1: it changed what you did not want, and you want to go back

Claude Code has automatic restore points. Each request you make creates one. To go back:

1. Type /rewind, or press Esc twice with the text box empty.
2. In the list, choose the request before which you want to go back.
3. Choose Restore code (puts the files back and keeps the conversation), Restore conversation (only the conversation) or Restore code and conversation (both).

Guide: Claude Code checkpointing.

There are limits. Changes made by terminal commands (deleting, moving or copying files) are not recorded. And restore points are no substitute for Git: they are kept for a while, then disappear.

Codex has no equivalent button for files. The documentation itself advises you to create restore points with Git before and after each task (Codex CLI).

With Git (in both agents), the folder must be in Git with an earlier commit: the subject of lesson 1/05. Keep three things apart:

• Look, changing nothing: git status says which files changed and git diff shows the lines.
• Save a point, with git add and git commit: lesson 1/05.
• Go back: the only step that wipes work.

To put the file back as it was at the last commit:

git restore --source=HEAD index.html

Without --source=HEAD, git restore takes the version from the staging area (what you marked with git add), which may already have the changes you wanted to undo. And with --source=HEAD the marked version stays there anyway; to drop it too, git restore --source=HEAD --staged --worktree -- index.html.

Without any of this, you can still ask the agent:

Undo the changes you made to index.html in the last request. Show me the diff before you apply it.

It often works, but it depends on the conversation's memory: don't count on it for anything important.

Case 2: the agent insists on the same mistake

You ask, it fails. You explain, it fails the same way. You explain better: same again.

The conversation fills up with failed attempts, and the agent keeps leaning on them. The fix is a clean sheet:

• Claude Code: /clear starts a new conversation.
• Codex: /new starts a new conversation (/clear does too, and clears the screen).

And the new request should be smaller, with what you have learned:

In the file index.html, change only Saturday's opening hours to 7:00–13:00. Do not touch the colours, the address or anything else. Last time, when changing the hours, the address was deleted; check that it stays the same.

A rule that works well: two failed attempts at the same point, new conversation with a smaller request.

Case 3: a red error appeared

First understand, only then fix. Copy the error and ask:

Explain this error to me without fixing it. Tell me in plain English what it means, which file and which line it is in, and what you think caused it. Do not change any file.

[paste the error here]

Why not ask for “fix” straight away? Because the agent sometimes “solves” the error by deleting the part that causes it, and the problem just moves elsewhere. Use what you learned in lesson 0/03: the last line says what, and the file and line say where.

To keep it from changing files, ask this in plan mode (Claude Code) or with /permissions on Read Only (Codex). If it still asks to change something, say no.

When to stop and ask a person for help

Stop and ask someone who knows when:

• the agent wants to use sudo, delete things outside experiencias, change system settings or switch off the antivirus;
• the error talks about passwords, keys, payments or other people's data;
• something changed outside the experiencias folder;
• three new conversations gave the same problem;
• you are already accepting without reading, because you are tired. That counts.

Mistakes here are cheap

The experiencias folder exists for this. If everything gets tangled, you delete the folder in the file explorer, create another and start again. You lose nothing important; you only spend agent usage, which counts towards your account's limits or your API key's bill. Every mistake here is one you will not make on the real bakery page or the parish council site. Try things, break them, go back: that is how you learn when to trust the agent.