diff --git a/run-fs-scraper-mac.sh b/run-fs-scraper-mac.sh
index 92bdd40..3fdab47 100755
--- a/run-fs-scraper-mac.sh
+++ b/run-fs-scraper-mac.sh
@@ -40,7 +40,22 @@ close_tunnel() {
 }
 
 # ── Main ──────────────────────────────────────────────────────────────────────
+LOCK_FILE="/tmp/tip-fs-scraper.lock"
+
 mkdir -p "$(dirname "$LOG")"
+
+# Prevent simultaneous runs (e.g. launchd fires during a still-running instance)
+if [ -f "$LOCK_FILE" ]; then
+  LOCK_PID=$(cat "$LOCK_FILE" 2>/dev/null || echo "")
+  if [ -n "$LOCK_PID" ] && kill -0 "$LOCK_PID" 2>/dev/null; then
+    echo "[$(date '+%Y-%m-%d %H:%M:%S')] Already running (PID $LOCK_PID) — skipping" >> "$LOG"
+    exit 0
+  fi
+  rm -f "$LOCK_FILE"
+fi
+echo $$ > "$LOCK_FILE"
+trap 'rm -f "$LOCK_FILE"' EXIT
+
 log "=== FS.com Mac Scraper starting ==="
 
 # Only close tunnel if we opened it (not if one was already running)