The overview showed the same session twice, one frame above another, after
switching sessions (reported from the beta with a screenshot).
Claude repaints by ABSOLUTE CURSOR POSITIONING, not by clearing: a 198KB pane
tail carries 1142 `CSI r;c H` and exactly one `CSI 2J`. The replay honoured the
COLUMN of those sequences and ignored the ROW, so a repaint could never
overwrite what came before and was appended instead. That same tail replayed as
FIFTY stacked copies of one frame. The preview shows the last N lines, so on a
short terminal you saw the newest frame by luck and on a tall one you saw the
end of the previous frame above it.
A cursor HOME now starts the buffer over. That is not a heuristic but the
line-based equivalent of what a home means: a full-screen app announcing it is
repainting from the top, with everything on screen about to be overwritten in
place. Only row 1 column 1 counts — any other address is a write position
inside the frame being painted, and resetting on those would erase live
content.
Measured on the real tail that produced the screenshot: 198599 bytes and 50
copies of the welcome frame collapse to 40 lines carrying exactly one.
The old test pinned the append behaviour, including a spurious leading empty
line that the initial CUP produced; both are gone.
A beta tester photographed claude's `❯` prompt and its `⏵⏵` bypass-permissions
marker rendering as empty boxes in the preview pane. Their font has no coverage
for those codepoints while drawing `·`, `─`, `│` and `▶` perfectly.
The glyph TIER cannot help here. It answers "can this terminal do Unicode at
all", which is a locale question, and it correctly says yes for exactly the
terminals this affects. Coverage is per-glyph and undetectable from inside the
process, so the handful of rare glyphs CLIs use as chrome are folded to the
ASCII arrows they already look like, and everything a plain font does render is
left alone.
Scoped tightly: the preview only, never the TUI's own chrome, and skipped
entirely at the `nerd` tier where the user has declared a font that can draw
anything. The table is short and every entry was seen as tofu in a real
terminal rather than guessed at. The fold is length-preserving, so the preview
pane's column arithmetic is unaffected.
Measured against a live Claude pane: an Ink TUI paints by ROW and emits
almost no newlines, so dropping cursor-position sequences collapsed a whole
screen into one unreadable line, and a tail cut mid-sequence printed the
remains of it (";1H") as text. Now a jump to column 1 starts a display line,
a jump inside a row moves the write position (capped, since a stream may
address a column no terminal has), and a severed CSI head is dropped before
parsing.
The preview is readable against a real session as a result: tool calls, the
working line and the composer all land where they belong.
Also drop the repeated session name from a search row, whose snippet opens
with the name the row already shows in its first column.
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
The preview pane shows a session's raw terminal stream, so it needs the tail
reconstructed rather than emulated: SGR survives, cursor steering and OSC do
not, and a carriage return returns to column 0 so a spinner that repaints its
line 200 times contributes one line instead of 200.
Widths count East Asian Wide characters as two columns, which the clip and pad
helpers rely on to never cut a wide character, a code point or an escape
sequence in half.
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Codeman maintainer