A shell's automatic loads (tab select, dropped-output recovery, clear
terminal, a split/grid tile's load) replayed `session.terminalBuffer`,
the raw PTY recording, ahead of the visible frame. That recording holds
full-screen repaints (an ssh'd tmux, less, any TUI: cursor home, then the
rows joined by newlines, prompt on the last row) drawn for the pane
height of the moment. Replayed into a terminal with fewer rows, each
repaint's last newline scrolls and pushes its top row into scrollback,
so one line tmux holds once shows up dozens of times (26 copies in the
case that found this, after the pane went from 24 to 23 rows). Remote
SSH shell sessions hit it constantly: their inner tmux repaints often.
Shells now load a bounded window of tmux's rendered history instead
(`SHELL_LOAD_QUERY`: full=1&tail=1MiB&lines=10000), the same source the
scroll-to-top pull already used. `lines=10000` bounds the synchronous
capture-pane, measured at ~8 ms per 1000 lines (~0.1 s here vs ~0.8 s
for a 100k-line history). Because that bound is shallower than xterm's
scrollback, the server now reports a cut: the capture's existing
display-message query also reads `#{history_size}`
(`PaneCaptureOptions.capturedHistorySize`), and the route marks a full
capture `truncated` / 'tail' when tmux holds more than it read, so the
banner keeps offering Load full history and scroll-to-top keeps pulling
older lines. The byte cap still reports 'capped'. The banner no longer
names an amount it cannot know ("less than 1 KB more") for such a cut.
Agent sessions are unchanged.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
