Bottom toolbar git subprocess calls cause typing lag at normal prompt

Bottom toolbar git subprocess calls cause typing lag at normal prompt

Summary

During normal prompt typing (no active turn, no modal, no completion menu), the bottom toolbar's git branch/status subprocess calls cause noticeable keystroke lag. This was isolated via binary search: the lag disappears when _get_git_branch() and _get_git_status() are removed from _render_bottom_toolbar().

Diagnostic evidence

We tested incrementally by stripping _render_bottom_toolbar() down to return FormattedText([]) and restoring sections one by one:

The lag is present even when no turn is running and even with complete_while_typing=False, so it is purely a rendering/refresh overhead issue.

Likely root cause

_render_bottom_toolbar() calls _get_git_branch() and _get_git_status() on every UI redraw. Both use cached subprocesses (5s TTL for branch, 15s TTL for status), but on every redraw the code still:

1. Calls state.proc.poll() on the cached subprocess
2. If finished, calls state.proc.communicate() to read stdout
3. Re-computes _format_git_badge() and string widths

When combined with prompt_toolkit redrawing on every keystroke, this subprocess polling + string formatting overhead creates per-keystroke lag — especially noticeable in Ghostty on a large (5K) display where redraw frequency is high.

Suggested fixes

1. Throttle git status to the background refresh task instead of querying on every toolbar render. The bottom toolbar should read from a cached variable that the _refresh() loop updates at most every 1–5 seconds, rather than evaluating the subprocess state on every keystroke.

2. Move git metadata into the background refresh task alongside context usage and tip rotation, so _render_bottom_toolbar() becomes a pure formatter reading cached values.

3. Add memoization to _render_bottom_toolbar() — if terminal width, CWD, git branch, git status, and background task count haven't changed since the last render, return the previously computed FormattedText without re-evaluating subprocesses or re-allocating strings.

Related issues

• #2032 — Extreme typing latency in inline modal inputs (separate rendering bug, same symptom)

Start by tracing _render_bottom_toolbar() and its calls to _get_git_branch() and _get_git_status(), then inspect the _refresh() loop and how prompt_toolkit redraws on typing. Done means git metadata is refreshed without per-keystroke subprocess work, the toolbar still displays current branch and status, and normal prompt typing no longer lags.