diff --git a/deploy/profile-scripts/candidate_filter.py b/deploy/profile-scripts/candidate_filter.py
index fe8b981a..d5fc1a52 100644
--- a/deploy/profile-scripts/candidate_filter.py
+++ b/deploy/profile-scripts/candidate_filter.py
@@ -373,6 +373,15 @@ def stage5_fundamental(code, name, price):
 # ── 主流程 ──
 
 def main():
+    # ── 单例守卫（规范5.3，2026-08-10）──
+    import fcntl
+    lock_f = open("/tmp/candidate_filter.lock", "w")
+    try:
+        fcntl.flock(lock_f, fcntl.LOCK_EX | fcntl.LOCK_NB)
+    except OSError:
+        print("[FILTER] 已有实例在运行，退出")
+        return
+
     stage_filter = None
     single_code = None
     for i, arg in enumerate(sys.argv[1:]):