Resetting asciinema with Scroll Stacking

Your asciinema recording looks broken: newlines don’t work, old text gets overwritten, or the screen fills with garbage. This simple tutorial shows how to reset the terminal screen mid-recording using scroll stacking. Fix messy casts without starting over - just edit the file!

Why You Need This #

Newlines fail and text overwrites because terminals have scrollback limits and state corruption during long recordings. Commands like ls or cat print without proper line wrapping, leaving a cluttered screen that ruins playback. Scroll stacking resets the terminal to a clean state at any point (like 12.5 seconds) so your demo continues fresh.

Common problems this fixes:

• Lost newlines: Output stacks on one line instead of wrapping
• Scrollback overflow: Old commands stay visible when they shouldn’t
• State corruption: Colors, cursor position, or margins get messed up
• Multi-step demos: Want clean breaks between sections in one file

How Scroll Stacking Works #

Instead of clear (which only erases visible screen), ESC c (\u001bc) does a full terminal reset - clears screen, resets margins, cursor, colors, everything. The [12.5, “o”, “\u001bc”] event injects this at timestamp 12.5 seconds during playback.

Quick Fix Steps #

1. Backup your demo.cast file
2. Open in any text editor (VS Code, nano, etc.)
3. Find where mess starts (check timestamps)
4. Add this exact line on its own:

[12.5, "o", "\u001bc"]

5. Save and play: asciinema play -s=10 demo.cast (increase speed ten fold)

Before/After Example #

Broken cast (newlines lost, text overwritten):

[0.0, "o", "dir1/"]
[1.2, "o", "file1 file2 file3"]  // Should be new line!
[2.1, "o", "pwd"]               // Overwrites above

Fixed with reset:

[0.0, "o", "dir1/"]
[1.2, "o", "file1 file2 file3"]
[12.5, "o", "\u001bc"]         // ← Screen resets here
[13.0, "o", "pwd"]             // Fresh clean screen