Two further instances of the same root cause, both in _onSessionNeedsRefresh,
which is SERVER-triggered (it fires after SSE backpressure clears) so the user
has no gesture to blame the result on.
1. It ended in an unconditional scrollToBottom, so a user quietly reading
scrollback was dropped to the live output by a background event. It now
holds their place. The rewrite REPLACES the buffer, so an absolute viewportY
captured beforehand is meaningless afterwards; distance from the bottom is
the anchor that survives, via computeRewriteScrollLine().
2. It rebuilt the terminal from a 1MB TAIL. Measured end to end on a 900-line
shell pane: an 869-row buffer came back as 158 rows, so the refresh meant to
REPAIR the display was destroying most of the scrollback every time it ran.
It now asks for full history, and falls back to the tail only when
_replayWouldShrinkBuffer refuses the capture, which keeps repaint-mode panes
(tmux holds roughly one frame for them) exactly as they were.
Also records truncation state here, so the #258 banner stops describing the
pre-refresh buffer.
Verified in a real browser against a live session: baseY 869 -> 869 where it
used to be 869 -> 158, a reader 200 lines up stays 200 lines up, and a follower
stays pinned to the bottom.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Closes#259, closes#258. Both bottom out in the same gap: nothing tracked
whether the user was following live output or reading history.
#259 — the keyboard path forced the terminal to the bottom unconditionally
(onKeyboardShow/onKeyboardHide passed scrollToBottom:true, applied with no
check), so opening the keyboard while scrolled up yanked the user down. The
settle cycle now captures intent on its FIRST event, before any fit() has
reflowed the buffer, and returns to that anchor when the user was reading.
A later capture would read an already-moved viewportY, which is why the
capture point matters. The param is renamed restoreScroll to match.
Separately, flushPendingWrites gated viewport preservation on
_hasRecentUserScrollUp(), a 1500ms decay window, so a user who scrolled up and
then actually READ for longer lost protection mid-read. Being scrolled up IS
the intent however long ago it was expressed, so it now keys off position.
The recency window stays as a race guard on the sticky scroll-to-bottom.
The full-history repull already held the user's place and is unchanged.
#258 — truncation was reported by a grey line written INTO the terminal
("earlier output truncated"), which scrolls away with the output it describes,
cannot be acted on, and said the same thing whether the rest was one click away
or gone forever. The server set one `truncated` boolean at two sites meaning
opposite things, and the client discarded fullSize and source entirely.
The route now reports truncationReason ('tail' = intentional partial replay,
the rest is retained; 'capped' = the byte ceiling dropped it) plus
retainedBytes, and 'capped' is not downgraded by a later tail cut. The client
renders a dismissible banner outside terminal output with three honest states:
recoverable (offers Load full history), at-ceiling, and exhausted. The Load
button forces past the scroll cooldown but NOT past _replayWouldShrinkBuffer,
which still refuses a downgrade for repaint-mode panes.
The banner is an overlay, not a flex child: FitAddon derives rows/cols from the
terminal parent's computed height, so occupying real layout space would SIGWINCH
the CLI on every truncation-state change.
Verified in a real browser on the 7 skins: banner text and button clear 4.5:1
contrast on all of them, and terminal height is byte-identical with the banner
shown. The first cut used --bg-elevated and --accent-muted, which do not exist,
so light skins rendered a hardcoded dark bar under dark text; it now uses only
tokens every skin redefines.
test/terminal-scroll-intent.test.ts lives outside test/mobile/ deliberately —
that suite is excluded from test:ci, so a guard placed there is invisible to CI.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
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