fix(tmux): locate the REPL input box by shape, not by a Claude-only glyph (#1363)

Co-authored-by: veronica <[email protected]>

packages/mosaic/framework/tools/tmux/send-message.sh

@@ -32,7 +32,9 @@
 #   0  delivered (submitted) or queued (agent busy; will process when free)
 #   1  tmux target not found
 #   2  submission NOT confirmed — either still an unsubmitted draft, or the REPL
-#      input prompt could not be located to confirm the message actually landed.
+#      input box could not be located to confirm the message actually landed.
+#      Locating the box is runtime-specific; see locate_input_box() below, and
+#      add a shape there before pointing this tool at a new runtime.
 #      Delivery is NEVER inferred from absence of evidence: if we cannot positively
 #      see the input box clear of the message (or the queued banner), we fail loud
 #      so the sender learns immediately instead of a silent worker->lead stall.
@@ -97,10 +99,50 @@ printf '%s' "$MSG" | "${tmux_cmd[@]}" load-buffer -b "$BUF" -
 #   would otherwise accumulate forever.
 sleep 0.5
 
+# Locate the REPL input box in a captured pane. Prints the box's contents on
+# stdout and returns 0 when the box was FOUND; returns 1 when it could not be
+# located at all. Found-but-empty is a real, distinct answer (an empty input box
+# is what a submitted message leaves behind), so the caller must branch on the
+# return code, never on whether the output is empty.
+#
+# Two REPL shapes are recognised:
+#   * a prompt-glyph line — `❯`, a leading `>`, or `│ >`. Claude Code and most
+#     readline REPLs.
+#   * a box drawn as two horizontal `─` rules with the input between them and NO
+#     prompt glyph anywhere. pi renders this. Anchoring on the LAST rule pair is
+#     what makes it safe: agent output can contain its own rules, but nothing is
+#     drawn below the input box except the status line.
+#
+# Adding a runtime means adding its shape HERE. A shape that is missing does not
+# degrade gracefully: it turns every send to that runtime into a false
+# "may be UNDELIVERED", which is what #1362 measured on pi and #1257 on another
+# arm of the same probe.
+locate_input_box() {
+  local pane=$1 glyph_line rule_lines top bottom
+  glyph_line=$(printf '%s\n' "$pane" | grep -E '❯|^>|│ >' | tail -1)
+  if [ -n "$glyph_line" ]; then printf '%s\n' "$glyph_line"; return 0; fi
+  rule_lines=$(printf '%s\n' "$pane" | grep -nE '^[[:space:]]*─{4,}[[:space:]]*$' | cut -d: -f1 | tail -2)
+  [ -n "$rule_lines" ] || return 1
+  # Split the (at most two) captured line numbers with parameter expansion. Not
+  # `head -1`: piping into an early-exiting consumer SIGPIPEs the producer, which
+  # under `set -euo pipefail` aborts the caller with rc=141 and no output. The
+  # scripts/pipefail-early-exit.test.mjs guard reds on that shape, correctly.
+  # With one rule captured both halves resolve to the same value and the
+  # ordering test below rejects it, which is the answer we want anyway.
+  top=${rule_lines%%$'\n'*}
+  bottom=${rule_lines##*$'\n'}
+  [ "$top" != "$bottom" ] || return 1
+  [ "$bottom" -gt "$top" ] || return 1
+  # An empty range (adjacent rules) prints nothing and still returns 0: found,
+  # empty, which is the delivered shape.
+  printf '%s\n' "$pane" | sed -n "$((top + 1)),$((bottom - 1))p"
+  return 0
+}
+
 # 2) Submit, then POSITIVELY confirm submission; flush with another Enter if it is
 #    still a draft. Success requires positive evidence — the queued banner, OR the
 #    REPL input box located AND clear of our message tail. The historical bug was
-#    treating ABSENCE of a draft as delivery: if the prompt glyph was never matched
+#    treating ABSENCE of a draft as delivery: if the input box was never located
 #    (wrong pane / prompt-glyph drift), an unsubmitted message read as "delivered"
 #    and worker->lead relays stalled silently. We now default to UNCONFIRMED and only
 #    upgrade to delivered on positive evidence; anything we cannot confirm fails loud.
@@ -113,15 +155,14 @@ for attempt in $(seq 1 $((RETRIES + 1))); do
   if grep -qF "$QUEUED_RE" <<<"$pane"; then
     status="queued"; break
   fi
-  # Locate the REPL input box (prompt glyph). If we cannot see it, we have NO
-  # evidence of submission state — stay UNCONFIRMED and retry; never infer delivery.
-  promptline=$(printf '%s' "$pane" | grep -E '❯|^>|│ >' | tail -1)
-  if [ -z "$promptline" ]; then
+  # If we cannot see the input box, we have NO evidence of submission state —
+  # stay UNCONFIRMED and retry; never infer delivery.
+  if ! inputbox=$(locate_input_box "$pane"); then
     status="unconfirmed"; continue
   fi
   # Input box located AND still carrying our tail => unsubmitted draft. Flush + retry.
-  # (Submitted messages scroll up into history; a draft stays on the ❯ line.)
-  if [ -n "$snippet" ] && grep -qF "$snippet" <<<"$promptline"; then
+  # (Submitted messages scroll up into history; a draft stays in the box.)
+  if [ -n "$snippet" ] && grep -qF "$snippet" <<<"$inputbox"; then
     status="draft"; continue
   fi
   # Input box located AND clear of our tail => positively submitted. This is the
@@ -135,6 +176,6 @@ case "$status" in
   delivered)   echo "✓ delivered to $TARGET"; exit 0 ;;
   queued)      echo "✓ queued to $TARGET (agent busy — will process when it returns to prompt)"; exit 0 ;;
   draft)       echo "✗ still an unsubmitted draft on $TARGET after $RETRIES flush attempts" >&2; exit 2 ;;
-  unconfirmed) echo "✗ could not confirm submission on $TARGET: REPL input prompt not locatable after $((RETRIES + 1)) attempts — message may be UNDELIVERED (check target/pane, retry, or escalate)" >&2; exit 2 ;;
+  unconfirmed) echo "✗ could not confirm submission on $TARGET: REPL input box not locatable after $((RETRIES + 1)) attempts — message may be UNDELIVERED (check target/pane, retry, or escalate)" >&2; exit 2 ;;
   *)           echo "✗ could not confirm submission on $TARGET (unexpected state '$status')" >&2; exit 2 ;;
 esac