fix(loop): resolve O-2 atomic race-free lock and marker ownership release guard (22/22 PASS)

.agents/skills/multi-agent-mux-loop/scripts/run_loop.sh

@@ -12,6 +12,8 @@ REPO_ROOT="$(cd "$SCRIPT_DIR/../../../.." && pwd)"
 source "$REPO_ROOT/.agents/skills/lib.sh"
 # shellcheck disable=SC1091
 source "$REPO_ROOT/.agents/skills/multi-agent-mux-loop/scripts/diff_collect.sh"
+# shellcheck disable=SC1091
+source "$REPO_ROOT/.agents/skills/multi-agent-mux-loop/scripts/loop_lock.sh"
 
 # Default configuration parameters
 PLAN_MODE=false
@@ -82,13 +84,8 @@ if [ -z "$TARGET_AGENT" ] || [ -z "$TASK" ]; then
   usage
 fi
 
-MAM_LOOP_MARKER="$REPO_ROOT/.mam/loop-guard-active"
-mkdir -p "$(dirname "$MAM_LOOP_MARKER")"
-_mam_lstart() { ps -p "$1" -o lstart= 2>/dev/null | tr -s ' ' | sed 's/^ *//;s/ *$//'; }
-printf 'pid=%s\nlstart=%s\nstarted=%s\n' \
-  "$$" "$(_mam_lstart $$)" "$(date -u +%Y-%m-%dT%H:%M:%SZ)" > "$MAM_LOOP_MARKER"
-_mam_release_guard() { rm -f "$MAM_LOOP_MARKER"; }
-trap _mam_release_guard EXIT INT TERM HUP
+MAM_LOOP_MARKER="${MAM_LOOP_MARKER:-$REPO_ROOT/.mam/loop-guard-active}"
+_mam_release_guard() { mam_release_loop_lock "$MAM_LOOP_MARKER" || true; }
 
 delegate_job_safe() {
   local orig_script="$REPO_ROOT/.agents/skills/multi-agent-mux-delegate-job/multi-agent-mux-delegate-job"
@@ -119,6 +116,25 @@ log_error() {
   echo -e "\033[1;31m[✗]\033[0m $1"
 }
 
+_mam_acquire_rc=0
+mam_acquire_loop_lock "$MAM_LOOP_MARKER" || _mam_acquire_rc=$?
+case "$_mam_acquire_rc" in
+  0) ;;
+  3)
+    _holder_pid=$(_mam_lock_field "$MAM_LOOP_MARKER" "pid" 2>/dev/null || echo "unknown")
+    log_error "Another multi-agent-mux-loop is already running in this workspace."
+    log_error "  holder PID: $_holder_pid"
+    log_error "  refusing to start a second loop (SQLite/YAML would race)."
+    exit 1
+    ;;
+  *)
+    log_error "Cannot determine whether another loop is running (ps unavailable?)."
+    log_error "  refusing to start rather than risk two loops writing the registry."
+    exit 1
+    ;;
+esac
+trap _mam_release_guard EXIT INT TERM HUP
+
 # --all-reviewer silently takes precedence over an explicit --reviewer list;
 # warn so the discarded list isn't mistaken for having been honored (P2-1).
 if [ "$ALL_REVIEWERS" = true ] && [ -n "$REVIEWER_LIST" ]; then