Found while verifying Auto Copy in a browser: a plain left click in a
claude/codex/gemini pane sent a synthetic SGR mouse report into the PTY
whether or not the program in that pane had ever enabled mouse tracking.
When the pane holds a plain shell (the CLI exited, or a shell was started
inside a session of that mode) readline prints the report as literal text
and it garbles the next line typed:
$ [<0;88;20Mecho hello
bash: 0: No such file or directory
The cause is that the browser could not know. The full strip
(isAltScreenStripMode) removes the mouse DECSETs from the stream, so
xterm's modes.mouseTrackingMode is permanently 'none' for those modes and
_sendSyntheticSgrTap() hand-encodes reports to stand in for xterm's own
encoder. With no state to consult it had to do that on every click.
What the strip removes, the server now remembers.
_recordStrippedMouseMode() records each sequence as it is stripped,
toState() publishes it as cliMouseTracking, and the browser's
_shouldReportMouseToCli() (renamed from _sessionUsesServerMouseStrip)
requires it at all three report sites: the desktop click, the touchend
tap, and the mobile tap classifier.
Details that are easy to get wrong:
* Only the tracking modes count (1000/1001/1002/1003). 1005/1006 select
an encoding and 1007 is alt-scroll; a CLI that picks SGR encoding
without turning tracking on is not asking about clicks, and counting
those would put the stray reports straight back.
* Modes are held in a Set, so a TUI disabling a mode it never enabled
cannot clear the ones that are really on.
* The change broadcasts immediately instead of through
broadcastSessionStateDebounced: the flag flips when a dialog opens, and
the user can click that dialog well inside the 500ms debounce window.
* It fails toward silence. After a server restart the flag is false until
the CLI re-emits its DECSET, which tmux does at client attach.
Verified against a live claude 2.x session: the CLI holds a tracking mode
on continuously, so its clicks are still reported byte for byte as
before, while a bash prompt in the same stripped mode now reports
nothing and types cleanly. The flag also propagates live over SSE in both
directions, checked by toggling ?1002h/?1002l from inside the pane.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Four fixes for the scrollback reports in #205 (plus its follow-up comment).
1. tmux-backed shell/opencode/antigravity sessions were parked in xterm's
ALTERNATE buffer for their whole life. The tmux CLIENT emits smcup
(\x1b[?1049h) as its first bytes on attach, and the existing strip is gated
to claude/codex/gemini, so it reached the browser verbatim. In the alternate
buffer baseY is pinned at 0 (no scrollback, so touch scrolling is a no-op)
and xterm's own wheel handler translates the wheel into \x1bOA cursor keys,
which readline receives as shell history navigation. Both reported symptoms,
one sequence. isMuxAltScreenOnlyStripMode() now strips that toggle for those
modes, but ONLY under tmux (the direct-PTY fallback still needs a program's
own alt screen) and ONLY the alt-screen toggle: 3J from a user's `clear` and
the mouse DECSETs a pane's htop/vim rely on are left alone. Safe because tmux
never forwards a pane's alt-screen toggles to its client, it repaints;
captured from a real attach, vim/less/htop emit zero.
2. "Load more history" on scroll-to-top. xterm's buffer is only ever a window
onto tmux's history, and tmux repaints the pane rectangle instead of emitting
linefeeds whenever output outpaces its flush, OVERWRITING already-rendered
scrollback. Measured: a 60-line burst added 1 row and destroyed 34, while the
same 60 lines emitted slowly added all 60. Scrolling up at the top now
re-pulls the full tmux scrollback and holds the user's place. Verified
end to end: 42 rendered rows -> 213, recovering all 150+60 printed lines.
3. The full-scrollback replay was gated on a single "first load after page load"
flag, which whichever session auto-selected consumed, so every other tab
started with one visible frame. Now tracked per session.
4. _wheelScrollLines ignored ev.deltaMode, so Firefox (DOM_DELTA_LINE, deltaY 3
per notch) scrolled one line where Chrome scrolls four or five, and capped
the forwarded SGR report at one tick. Line and page deltas are now converted,
and a pure horizontal swipe no longer falls through to a phantom -1.
Analysis and measurements: docs/scrollback-issues-analysis.md
Terminal scroll-up intermittently broke for Claude sessions (most visible on
iPhone). Claude Code periodically emits alt-screen switches (?1049h/?47h/?1047h),
scrollback-erase (3J), and mouse-tracking enables for full-screen UIs, which move
xterm.js to the scrollback-less alt buffer / wipe saved lines / hijack the wheel.
Codeman stripped these but only for codex mode.
Share the strip via isAltScreenStripMode(mode) = codex || claude, applied at both
sites that were codex-only: the live PTY stream (Session._handleTerminalOutput,
incl. the chunk-boundary carry) and the /terminal buffer replay. shell stays
excluded (vim/less/htop need the alt screen); opencode unchanged.
Tests: test/claude-scrollback-strip.test.ts (8 new); codex strip tests unchanged.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Codeman maintainer