scrollback breaks after zoom/un-zoom a pane

[armyers]

Description

Zoom a pane that isn't full-width/full-height (cmd-shift-enter), then un-zoom, and the scrollback that was there comes back empty - the screen looks like it was just cleared, with the prompt at the top. New output works fine; only the pre-existing scrollback is gone.

• Only happens when the pane is both less than full height and less than full width
• Dragging the split dividers to resize the same pane (even drastically) does not cause it - only zoom does.
• Native Ghostty terminal does NOT have this problem.
• (edited) also, both cmux and supacode are built using libghostty-vt and they do not have this problem, just for reference :)

Steps to reproduce

1. Split into a 2x2 grid (so a pane is neither full width nor full height).
2. In one pane, run commands so that output lines exceed the current viewable area; ie, make use of the scrollback buffer.
3. Use mouse wheel to scroll back to verify that there are scrollback lines.
4. Zoom that pane (cmd-shift-enter)
5. Verify that scrollback is working
6. Un-zoom (cmd-shift-enter again).
7. Notice that it's as if the screen has cleared; basically, looks exactly like what you get from the clear command
8. Scroll up - the scrollback content is just empty lines.

Expected behavior

zoom/un-zoom should not clear the screen and scrollback lines should not be lost.

Macterm version

Version 1.18.1 (1.18.1)

macOS version

OS: macOS Tahoe 26.5.1 (25F80) arm64

Logs or screenshots

zoom-scrollback-problem.mov

BTW, excellent job on this terminal! :)

[thdxg]

@armyers Thanks for your feedback! I cannot reproduce this issue on the latest version (v1.19.0). Does the issue persist on your machine with the latest release?

[armyers]

Hi @thdxg yes, it still persists on my computer with 1.19.0. Any thoughts on what might be the problem on my system? The weird thing is that ghostty, cmux and supacode do not have this problem.

[thdxg]

Hmm. Does this happen every time you zoom or only sometimes?

[armyers]

yes, happens every time. It's not intermittent.