[Bug]: Integrated terminal renders stale and garbled output that diverges from the shell

Before submitting

• I searched existing issues and did not find a duplicate.
• I included enough detail to reproduce or investigate the problem.

Area

apps/web

Steps to reproduce

1. Open the integrated terminal (Cmd+J).
2. Reproduce one of two ways:
   • With zsh-autosuggestions on, type at the shell. In a terminal that has already been used, leftover characters appear almost immediately.
   • Or run lazygit and leave it open. Within about a minute, once it does background refreshes I think, it starts dropping lines and garbling the header.

Expected behavior

The terminal renders what the shell actually holds. Old content clears when it should, and the screen stays consistent with the real terminal.

Actual behavior

The rendered screen drifts out of sync with the real terminal. Two forms I hit:

• lazygit drops rendered lines and leaves fragments of earlier output stuck at the top, overlapping the panel borders (see screenshot).
• zsh-autosuggestions leaves a stray character or space on screen that is not in the command buffer, so a command runs differently from what is shown. I have seen pypython script.py and a trailing 64 I never typed.

Both are the same problem: the drawn grid no longer matches the real terminal contents.

e.g. in lazygit, within a minute or so, you get garbled rendering like this (see the top header colliding with text that's not supposed to be there + lazygit separator lines missing)

when lazygit is supposed to look like (screenshotted in the ghostty app terminal window):

Impact

Major degradation or frequent failure

Version or commit

main @ 3b72d17cbca691f0b64e6d4a10c9e349f42873a5 (v0.0.33 tag)

Environment

macOS 26.5.2 Desktop App

Logs or stack traces

Screenshots, recordings, or supporting files

See "Actual behavior" section

Workaround

I am running a build with a patch for this on my fork and watching how it holds: https://github.com/kyleawayan/t3code/commit/95cd5c235e649af49ea1b3a73c0f46e53b8d4cdc. If it holds up after a few days I plan to open a PR.

Start in the apps/web area and reproduce both reported cases: zsh-autosuggestions in a previously used terminal and lazygit during background refreshes. Compare the rendered terminal with the shell’s actual contents, using the linked fork patch as investigation context; done means stale characters, dropped lines, and garbled borders no longer appear in either scenario.