framework tools/tmux: agent-send socket default resolution + ambiguity guard (B1) (#1466)

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

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

@@ -35,6 +35,9 @@
 #
 # OPTIONS
 #   -L NAME         tmux socket name passed to `tmux -L NAME` on the target host
+#
+# Exit 4: local target session exists on multiple socket servers and no
+#         -L / MOSAIC_TMUX_SOCKET disambiguated it (B1 stale-twin guard).
 #   -s DST_SESSION  target tmux session (or session:window.pane)   [required]
 #   -H SSH_TARGET   ssh target (user@host) for a remote pane; omit for local
 #   -n DST_HOST     hostname to show in the preamble for the target.
@@ -63,8 +66,10 @@
 #     group 1 = src label   group 2 = dst host:session
 #     group 3 = class (absent => actionable)   group 4 = message body
 #
-# EXIT CODES  (passed through from send-message.sh)
+# EXIT CODES  (passed through from send-message.sh, except 4)
 #   0 delivered/queued · 1 target not found · 2 still draft · 3 usage error
+#   4 agent-send refusal: local target session exists on multiple socket
+#     servers and no -L / MOSAIC_TMUX_SOCKET disambiguated it (B1)
 set -uo pipefail
 
 SELF_DIR=$(cd -- "$(dirname -- "$0")" && pwd)
@@ -154,6 +159,61 @@ FULL="${PREAMBLE} ${MSG}"
 B64=$(printf '%s' "$FULL" | base64 -w0)
 
 vflag=""; [ "$VERBOSE" = 1 ] && vflag="-v"
+
+# Exact session matching for the sender target (codex PR #1466): without
+# '=', tmux target syntax accepts an unambiguous PREFIX, so a delivery
+# aimed at session X can land in X-old. Compound targets (session:win.pane)
+# and already-exact ('=...') forms pass through untouched. Computed BEFORE
+# socket discovery so the discovery probes use the same target semantics
+# (probing '==name' for an already-exact input was a false-negative hit).
+DST_TARGET="$DST_SESSION"
+case "$DST_SESSION" in
+  =*) ;;
+  *:*)
+    # Compound target (session:win.pane): pin the SESSION component exact
+    # (=session:win.pane); unpinned, the session part still prefix-matches
+    # (codex PR #1466: 'agent:0.0' can resolve into 'agent-old').
+    DST_TARGET="=${DST_SESSION%%:*}:${DST_SESSION#*:}"
+    ;;
+  *) DST_TARGET="=$DST_SESSION" ;;
+esac
+
+# Socket default resolution (B1, 2026-08-29). Precedence: explicit -L >
+# launcher-exported MOSAIC_TMUX_SOCKET > unique socket hit > refusal on
+# ambiguity > tmux default socket. The ambiguity refusal fires ONLY when
+# no explicit or env choice exists and the session name lives on multiple
+# servers (measured 2026-08-28/29: tasking sends landed in a stale
+# default-socket twin; rc 0 reported honest delivery to the wrong pane).
+# Socket discovery scans tmux's own socket dir, ${TMUX_TMPDIR:-/tmp}/tmux-UID
+# (codex PR #1466: TMPDIR is not where tmux keeps -L sockets).
+# MOSAIC_TMUX_SOCKET is LOCAL-host state (launcher-exported): it must not
+# leak into remote sends, where -L would target a socket on the remote
+# host (codex PR #1466).
+if [ -z "$SOCKET_NAME" ] && [ -z "$SSH_TARGET" ] && [ -n "${MOSAIC_TMUX_SOCKET:-}" ]; then
+  SOCKET_NAME="$MOSAIC_TMUX_SOCKET"
+fi
+if [ -z "$SOCKET_NAME" ] && [ -z "$SSH_TARGET" ]; then
+  socket_dir="${TMUX_TMPDIR:-/tmp}/tmux-$(id -u)"
+  hits=""
+  for sf in "$socket_dir"/*; do
+    [ -S "$sf" ] || continue
+    sname="${sf##*/}"
+    # '=' forces exact session-name matching: tmux target syntax otherwise
+    # accepts an unambiguous PREFIX, so a session named X-old on a socket
+    # would count as a false hit for target X (codex PR #1466).
+    tmux -L "$sname" has-session -t "$DST_TARGET" 2>/dev/null && hits="$hits$sname"$'\n'
+  done
+  hit_count=$(printf '%s' "$hits" | grep -c . || true)
+  if [ "$hit_count" -gt 1 ]; then
+    echo "agent-send.sh: REFUSING - session '$DST_SESSION' exists on multiple sockets:" >&2
+    printf '  %s\n' $hits >&2
+    echo "  Pass -L <socket> explicitly (or export MOSAIC_TMUX_SOCKET to disambiguate)." >&2
+    exit 4
+  elif [ "$hit_count" -eq 1 ]; then
+    SOCKET_NAME="$(printf '%s' "$hits")"
+  fi
+fi
+
 socket_args=()
 if [ -n "$SOCKET_NAME" ]; then
   socket_args=(-L "$SOCKET_NAME")
@@ -161,9 +221,9 @@ fi
 
 if [ -z "$SSH_TARGET" ]; then
   # Local pane: call the canonical sender directly.
-  exec "$SENDER" "${socket_args[@]}" -t "$DST_SESSION" -b "$B64" -r "$RETRIES" $vflag
+  exec "$SENDER" "${socket_args[@]}" -t "$DST_TARGET" -b "$B64" -r "$RETRIES" $vflag
 else
   # Remote pane: ship the sender over ssh and run it local to the target.
   ssh -o ConnectTimeout=10 "$SSH_TARGET" \
-      "bash -s -- ${socket_args[*]@Q} -t '$DST_SESSION' -b '$B64' -r '$RETRIES' $vflag" < "$SENDER"
+      "bash -s -- ${socket_args[*]@Q} -t '$DST_TARGET' -b '$B64' -r '$RETRIES' $vflag" < "$SENDER"
 fi