diff --git a/src/genesis/rag/store.py b/src/genesis/rag/store.py
index 2a05a72..4c4ac09 100644
--- a/src/genesis/rag/store.py
+++ b/src/genesis/rag/store.py
@@ -31,7 +31,9 @@ class RagStore:
             self.conn.commit()
 
     def add(self, scope: str, chunks: List[str], embeddings: List[List[float]]) -> None:
-        # 先清后写（增量索引），整段加锁串行化
+        # 按 scope 全量替换（先清后写），非追加；整段加锁串行化
+        if len(chunks) != len(embeddings):
+            raise ValueError("chunks 与 embeddings 长度不一致")
         with self._lock:
             self.conn.execute("DELETE FROM rag_chunks WHERE scope=?", (scope,))
             self.conn.executemany(
@@ -41,6 +43,10 @@ class RagStore:
             self.conn.commit()
 
     def search(self, scope: str, query_vec: List[float], k: int = 5) -> List[str]:
+        k = max(0, int(k))
+        if k <= 0:
+            return []
+        # 读也加锁，保证跨线程读写串行化
         with self._lock:
             rows = self.conn.execute(
                 "SELECT chunk, embedding FROM rag_chunks WHERE scope=?", (scope,)
@@ -50,3 +56,6 @@ class RagStore:
             scored.append((_cosine(query_vec, json.loads(emb)), chunk))
         scored.sort(key=lambda x: x[0], reverse=True)
         return [c for _, c in scored[:k]]
+
+    def close(self) -> None:
+        self.conn.close()
diff --git a/tests/test_rag_store.py b/tests/test_rag_store.py
index c96315d..e350888 100644
--- a/tests/test_rag_store.py
+++ b/tests/test_rag_store.py
@@ -16,6 +16,9 @@ def test_search_returns_most_similar_chunk():
     s.add("p1", ["订单模块处理创建", "用户认证登录"], [_vec(0, 1), _vec(4, 5)])
     res = s.search("p1", _vec(0, 1), k=1)
     assert res == ["订单模块处理创建"]
+    # k<=0 健壮性
+    assert s.search("p1", _vec(0, 1), k=0) == []
+    s.close()
 
 
 def test_reset_scope_clears():
@@ -24,6 +27,13 @@ def test_reset_scope_clears():
     s.add("p1", ["a"], [_vec(0)])
     s.reset_scope("p1")
     assert s.search("p1", _vec(0), k=3) == []
+    # chunks 与 embeddings 长度不一致应抛 ValueError
+    try:
+        import pytest
+        with pytest.raises(ValueError):
+            s.add("p1", ["a", "b"], [_vec(0)])
+    finally:
+        s.close()
 
 
 def test_concurrent_add_and_search_no_crash():
@@ -32,13 +42,20 @@ def test_concurrent_add_and_search_no_crash():
     s.reset_scope("p1")
 
     def worker(i):
-        s.add("p1", [f"chunk-{i}"], [_vec(i % 8)])
+        # 每个 worker 线程内交替执行 add 与 search，让读写真正并发跨线程运行
+        for j in range(5):
+            s.add("p1", [f"chunk-{i}-{j}"], [_vec(i % 8)])
+            res = s.search("p1", _vec(i % 8), k=3)
+            assert all(isinstance(r, str) for r in res)
 
-    threads = [threading.Thread(target=worker, args=(i,)) for i in range(8)]
-    for t in threads:
-        t.start()
-    for t in threads:
-        t.join()
-    res = s.search("p1", _vec(0), k=3)
-    assert len(res) <= 3
-    assert all(isinstance(r, str) for r in res)
+    try:
+        threads = [threading.Thread(target=worker, args=(i,)) for i in range(8)]
+        for t in threads:
+            t.start()
+        for t in threads:
+            t.join()
+        res = s.search("p1", _vec(0), k=3)
+        assert len(res) <= 3
+        assert all(isinstance(r, str) for r in res)
+    finally:
+        s.close()