Respawn: undo anything in seconds

Your mission

Make a big, risky change to your page, decide you hate it, and respawn back to the version you liked, in under ten seconds.

Why it’s worth it

The fastest builders experiment a lot. “What if the whole page was pixel art?” “What if it was a terminal?” Most of those ideas will flop, and that’s fine, if undoing is free. If every experiment risks wrecking something that worked, you play it safe and build boring stuff.

Claude Code has a respawn system built in. Before every prompt you send, it saves a checkpoint of your files. So you can go wild, and if the result is bad, rewind like it never happened.

How checkpoints work

Every time you send Claude a message, it quietly saves a snapshot of the files it might change. Later you can jump back to any of those moments:

1. Press Esc twice on an empty prompt (or type /rewind).
2. Pick the message you want to go back to. You’ll see a list of your recent prompts.
3. Choose what to restore:
   • Restore code and conversation: full respawn, as if the later messages never happened.
   • Restore code: the files go back, but Claude still remembers the chat. Great for “let’s try that a different way”.
   • Restore conversation: the chat rewinds, but the files stay as they are now.

Build it

Start Claude in your speedrun-lab folder, where your profile page from the last lesson lives.

1. Make something risky. Ask for a dramatic redesign:

Completely redesign index.html as a retro 8-bit arcade cabinet: pixel font,
scanlines, chunky borders. Go all in.

What you’ll see: Claude rewrites big chunks of the page. Refresh your browser to check out the new look. Love it? Cool, keep it and try another wild idea. Hate it? Perfect, that’s what we’re practising.

2. Respawn. Press Esc twice, choose the prompt where you asked for the redesign, and pick Restore code.

What you’ll see: a confirmation that the files were restored. Refresh the browser: your previous version is back, exactly as it was.

3. Try a different direction. Because you restored only the code, Claude still remembers the conversation. So you can say:

OK, not that. Instead, keep my design but add a small pixel-art trophy icon
next to each high score.

What you’ll see: a much smaller change on top of your good version. That’s the rhythm: try boldly, keep what works, respawn from what doesn’t.

The one catch

Checkpoints track the files Claude changes with its own file-editing tools, which is almost everything it does to your files. But sometimes Claude runs a terminal command instead: deleting a file, moving files around, or installing something. A file that only a command touched isn’t tracked, so rewinding can’t bring it back.

When Claude gets confused

• The rewind list doesn’t show the message you want. Each session has its own checkpoints. If you quit Claude Code and started a new session, resume the old one with claude --continue (or pick it with claude --resume), then rewind from there: checkpoints are saved with the conversation.
• You restored, but the browser still shows the new version. The browser is showing an old copy: refresh the tab.
• Some files came back but one didn’t. That file was probably changed by a command rather than Claude’s editing tool (see the catch above). Ask Claude: “Did you change any files using a terminal command?”

Did it work?

• You made a dramatic change and saw it in the browser
• You rewound with Esc Esc and your previous version came back
• You tried a different idea on top of the restored version
• You know checkpoints can’t undo changes made by terminal commands