send-message.sh located the REPL input box with grep -E '❯|^>|│ >'. That set is
Claude Code's box. A pi seat renders a bare U+2500 rule with no glyph, so on every
idle pi seat the capture succeeded, the grep matched nothing, status stayed
"unconfirmed", and the tool exited 2 "may be UNDELIVERED" with the paste and the
Enter both landed. The stderr tells the operator to retry, and that retry is the
duplicate delivery reported against the same tool.
Confirmation is now runtime-agnostic: our message tail sits on the input line
(located by cursor row, no glyph) before Enter and has left it after. That
transition is positive proof of submission.
Absence still proves nothing, which is the guard the 2026-08 fix was reaching for
and got backwards. Two positive checks keep it:
- a prompt box that IS locatable and still carries our tail => draft, exit 2.
This covers the cursor-row blind spot: a cooked pane whose foreground process
never reads stdin echoes the paste through the kernel line discipline and
moves the cursor off it on Enter, which by cursor row alone is indistinguishable
from a real submit.
- no draft ever observed on the input line => unconfirmed, non-zero.
Tests, both red-first against the shipping blob d397907:
test-send-message-glyph-agnostic.sh (new, 6 fixtures) 4/6 -> 6/6
test-send-message-verdict.sh (fixture 2 reshaped, 2b added) 3/4 -> 4/4
Fixture 2 of the verdict suite asserted exit 2 for a glyphless pane that submits
and was labelled "false-positive FIXED". A pi seat is that fixture, so the suite
was locking the bug in. It is reshaped deliberately, and the guard it was credited
with moves to new fixture 2b (glyphless AND non-submitting, raw/no-echo) so the
"never infer delivered from absence" property is tested positively rather than as
a side effect.
Measured on tmux 3.7b (sb-it-1-dt), 3.5a (fomo-lin), and dragon-lin.
Co-authored-by: scooby <[email protected]>
fredandscooby
jason.woltjeandMos