diff --git a/internal/core/src/common/Utils.h b/internal/core/src/common/Utils.h
index 98f99451e4..68f1004f2f 100644
--- a/internal/core/src/common/Utils.h
+++ b/internal/core/src/common/Utils.h
@@ -228,6 +228,22 @@ GetCommonPrefix(const std::string& str1, const std::string& str2) {
     return str1.substr(0, i);
 }
 
+// Escape braces in the input string,
+// used for fmt::format json string
+inline std::string
+EscapeBraces(const std::string& input) {
+    std::string result;
+    for (char ch : input) {
+        if (ch == '{')
+            result += "{{";
+        else if (ch == '}')
+            result += "}}";
+        else
+            result += ch;
+    }
+    return result;
+}
+
 inline knowhere::sparse::SparseRow<float>
 CopyAndWrapSparseRow(const void* data,
                      size_t size,
diff --git a/internal/core/src/exec/Driver.cpp b/internal/core/src/exec/Driver.cpp
index 39ef70d14d..b6b62179a6 100644
--- a/internal/core/src/exec/Driver.cpp
+++ b/internal/core/src/exec/Driver.cpp
@@ -180,7 +180,7 @@ Driver::Next(std::shared_ptr<BlockingState>& blocking_state) {
             "Operator::{} failed for [Operator:{}, plan node id: "             \
             "{}] : {}",                                                        \
             method_name,                                                       \
-            operator->get_operator_type(),                                     \
+            operator->ToString(),                                              \
             operator->get_plannode_id(),                                       \
             e.what());                                                         \
         LOG_ERROR(err_msg);                                                    \
diff --git a/internal/core/src/index/VectorMemIndex.cpp b/internal/core/src/index/VectorMemIndex.cpp
index d133036718..454efc5f2f 100644
--- a/internal/core/src/index/VectorMemIndex.cpp
+++ b/internal/core/src/index/VectorMemIndex.cpp
@@ -25,6 +25,7 @@
 #include <unordered_map>
 #include <unordered_set>
 
+#include "common/Common.h"
 #include "common/Tracer.h"
 #include "common/Types.h"
 #include "common/type_c.h"
@@ -439,8 +440,8 @@ VectorMemIndex<T>::Query(const DatasetPtr dataset,
                 PanicInfo(
                     ErrorCode::UnexpectedError,
                     // escape json brace in case of using message as format
-                    "failed to search: config={{{}}} {}: {}",
-                    search_conf.dump(),
+                    "failed to search: config={} {}: {}",
+                    milvus::EscapeBraces(search_conf.dump()),
                     KnowhereStatusString(res.error()),
                     res.what());
             }
diff --git a/internal/core/unittest/test_sealed.cpp b/internal/core/unittest/test_sealed.cpp
index 15e7f50b8a..3c01681a04 100644
--- a/internal/core/unittest/test_sealed.cpp
+++ b/internal/core/unittest/test_sealed.cpp
@@ -151,6 +151,88 @@ TEST(Sealed, without_predicate) {
     EXPECT_EQ(sr->get_total_result_count(), 0);
 }
 
+TEST(Sealed, without_search_ef_less_than_limit) {
+    auto schema = std::make_shared<Schema>();
+    auto dim = 16;
+    auto topK = 5;
+    auto metric_type = knowhere::metric::L2;
+    auto fake_id = schema->AddDebugField(
+        "fakevec", DataType::VECTOR_FLOAT, dim, metric_type);
+    auto float_fid = schema->AddDebugField("age", DataType::FLOAT);
+    auto i64_fid = schema->AddDebugField("counter", DataType::INT64);
+    schema->set_primary_field_id(i64_fid);
+
+    const char* raw_plan = R"(vector_anns: <
+                                    field_id: 100
+                                    query_info: <
+                                      topk: 100
+                                      round_decimal: 3
+                                      metric_type: "L2"
+                                      search_params: "{\"ef\": 10}"
+                                    >
+                                    placeholder_tag: "$0"
+        >)";
+
+    auto N = ROW_COUNT;
+
+    auto dataset = DataGen(schema, N);
+    auto vec_col = dataset.get_col<float>(fake_id);
+    auto query_ptr = vec_col.data() + BIAS * dim;
+
+    auto plan_str = translate_text_plan_to_binary_plan(raw_plan);
+    auto plan =
+        CreateSearchPlanByExpr(*schema, plan_str.data(), plan_str.size());
+    auto num_queries = 5;
+    auto ph_group_raw =
+        CreatePlaceholderGroupFromBlob(num_queries, 16, query_ptr);
+    auto ph_group =
+        ParsePlaceholderGroup(plan.get(), ph_group_raw.SerializeAsString());
+    Timestamp timestamp = 1000000;
+
+    milvus::index::CreateIndexInfo create_index_info;
+    create_index_info.field_type = DataType::VECTOR_FLOAT;
+    create_index_info.metric_type = knowhere::metric::L2;
+    create_index_info.index_type = knowhere::IndexEnum::INDEX_HNSW;
+    create_index_info.index_engine_version =
+        knowhere::Version::GetCurrentVersion().VersionNumber();
+
+    auto indexing = milvus::index::IndexFactory::GetInstance().CreateIndex(
+        create_index_info, milvus::storage::FileManagerContext());
+
+    auto build_conf =
+        knowhere::Json{{knowhere::meta::METRIC_TYPE, knowhere::metric::L2},
+                       {knowhere::indexparam::M, "16"},
+                       {knowhere::indexparam::EF, "10"}};
+
+    auto database = knowhere::GenDataSet(N, dim, vec_col.data());
+    indexing->BuildWithDataset(database, build_conf);
+
+    LoadIndexInfo load_info;
+    load_info.field_id = fake_id.get();
+    load_info.index = std::move(indexing);
+    load_info.index_params["metric_type"] = "L2";
+
+    // load index for vec field, load raw data for scalar field
+    auto sealed_segment = SealedCreator(schema, dataset);
+    sealed_segment->DropFieldData(fake_id);
+    sealed_segment->LoadIndex(load_info);
+
+    // Test that search fails when ef parameter is less than top-k
+    // HNSW index requires ef to be larger than k for proper search
+    bool exception_thrown = false;
+    try {
+        auto sr = sealed_segment->Search(plan.get(), ph_group.get(), timestamp);
+        FAIL() << "Expected exception for invalid ef parameter";
+    } catch (const std::exception& e) {
+        exception_thrown = true;
+        std::string error_msg = e.what();
+        ASSERT_TRUE(error_msg.find("ef(10) should be larger than k(100)") !=
+                    std::string::npos)
+            << "Unexpected error message: " << error_msg;
+    }
+    ASSERT_TRUE(exception_thrown) << "Expected exception was not thrown";
+}
+
 TEST(Sealed, with_predicate) {
     auto schema = std::make_shared<Schema>();
     auto dim = 16;
diff --git a/scripts/core_build.sh b/scripts/core_build.sh
index 7169ce05c7..bbaef6befe 100755
--- a/scripts/core_build.sh
+++ b/scripts/core_build.sh
@@ -288,7 +288,7 @@ if [[ ${RUN_CPPLINT} == "ON" ]]; then
   echo "clang-format check passed!"
 else
   # compile and build
-  make -j ${jobs} install || exit 1
+  make -j 7 install || exit 1
 fi
 
 if command -v ccache &> /dev/null
diff --git a/tests/python_client/testcases/test_search.py b/tests/python_client/testcases/test_search.py
index 4962d9e61d..1bc9fe2c12 100644
--- a/tests/python_client/testcases/test_search.py
+++ b/tests/python_client/testcases/test_search.py
@@ -1249,6 +1249,30 @@ class TestCollectionSearchInvalid(TestcaseBase):
                                                "err_msg": f"metric type {metric} not found or not supported, "
                                                           "supported: [HAMMING JACCARD]"})
 
+    @pytest.mark.tags(CaseLabel.L2)
+    def test_search_ef_less_than_limit(self):
+        """
+        target: test the scenario which search with ef less than limit
+        method: 1. create collection
+                2. search with ef less than limit
+        expected: raise exception and report the error
+        """
+        collection_w = self.init_collection_general(prefix, True, 2000, 0, is_index=False)[0]
+        index_hnsw = {
+            "index_type": "HNSW",
+            "metric_type": "L2",
+            "params": {"M": 8, "efConstruction" : 256},
+        }
+        collection_w.create_index(ct.default_float_vec_field_name, index_params=index_hnsw)
+        collection_w.flush()
+        collection_w.load()
+        search_params = {"metric_type": "L2", "params": {"ef": 10}}
+        res = collection_w.search(vectors, ct.default_float_vec_field_name,
+                            search_params, limit=100,
+                            check_task=CheckTasks.err_res,
+                            check_items={"err_code": 65535,
+                                         "err_msg": "query failed: N6milvus21ExecOperatorExceptionE :Operator::GetOutput failed"})
+        
     @pytest.mark.tags(CaseLabel.L1)
     def test_search_dynamic_compare_two_fields(self):
         """