diff --git a/modules/ANSFR/ANSFR.cpp b/modules/ANSFR/ANSFR.cpp
index 6e2d049..34a03b3 100644
--- a/modules/ANSFR/ANSFR.cpp
+++ b/modules/ANSFR/ANSFR.cpp
@@ -1814,10 +1814,12 @@ namespace ANSCENTER {
                 }
             }
 
+            // No faces is a valid state (user just created or faces already removed)
             if (faceIds.empty()) {
                 LogThreadSafe("ANSFacialRecognition::DeleteFacesByUser",
-                    "No faces found for user ID " + std::to_string(userId));
-                return 0;
+                    "No faces found for user ID " + std::to_string(userId) + " — skipping",
+                    LogLevel::Debug);
+                return 1;
             }
 
             // Delete each face from database (lock per deletion)
diff --git a/modules/ANSFR/ANSFRCommon.cpp b/modules/ANSFR/ANSFRCommon.cpp
index e5e692c..fcf97b4 100644
--- a/modules/ANSFR/ANSFRCommon.cpp
+++ b/modules/ANSFR/ANSFRCommon.cpp
@@ -5,6 +5,7 @@
 #include <opencv2/dnn/dnn.hpp>
 #include <opencv2/highgui.hpp>
 #include <utils/ocv_common.hpp>
+#include <json.hpp>
 namespace ANSCENTER {
     constexpr size_t ndetections = 200;
     template <typename T> T GetData(const boost::property_tree::ptree& pt, const std::string& key)
@@ -684,46 +685,77 @@ namespace ANSCENTER {
         return faceResult;
     }
 
-    std::string ANSFRHelper::UserRecordToJsonString(const UserRecord userRecord) {
-        boost::property_tree::ptree root;
-        boost::property_tree::ptree faceIds;
-        for (int i = 0; i < userRecord.FaceIds.size(); i++) {
-            boost::property_tree::ptree faceIdNode;
-            faceIdNode.put("", userRecord.FaceIds[i]);
-            faceIds.push_back(std::make_pair("", faceIdNode));
+    // Encode non-ASCII UTF-8 characters as double-escaped Unicode (\uXXXX) for JSON transport.
+    // Surrogate pairs are used for codepoints above U+FFFF.
+    static std::string DoubleEscapeUnicode(const std::string& utf8Str) {
+        bool hasNonAscii = false;
+        for (unsigned char c : utf8Str) {
+            if (c >= 0x80) { hasNonAscii = true; break; }
         }
-        root.put("user_id", userRecord.UserId);
-        root.put("user_code", userRecord.UserCode);
-        root.put("user_username", userRecord.UserName);
-        root.add_child("face_ids", faceIds);
-        std::ostringstream stream;
-        boost::property_tree::write_json(stream, root,false);
-        std::string userRecordResult = stream.str();
-        return userRecordResult;
+        if (!hasNonAscii) return utf8Str;
+        std::string result;
+        result.reserve(utf8Str.size() * 2);
+        size_t i = 0;
+        while (i < utf8Str.size()) {
+            unsigned char c = static_cast<unsigned char>(utf8Str[i]);
+            if (c < 0x80) { result += utf8Str[i++]; continue; }
+            uint32_t cp = 0;
+            if ((c & 0xE0) == 0xC0 && i + 1 < utf8Str.size()) {
+                cp = ((c & 0x1F) << 6) | (static_cast<unsigned char>(utf8Str[i + 1]) & 0x3F); i += 2;
+            } else if ((c & 0xF0) == 0xE0 && i + 2 < utf8Str.size()) {
+                cp = ((c & 0x0F) << 12) | ((static_cast<unsigned char>(utf8Str[i + 1]) & 0x3F) << 6) | (static_cast<unsigned char>(utf8Str[i + 2]) & 0x3F); i += 3;
+            } else if ((c & 0xF8) == 0xF0 && i + 3 < utf8Str.size()) {
+                cp = ((c & 0x07) << 18) | ((static_cast<unsigned char>(utf8Str[i + 1]) & 0x3F) << 12) | ((static_cast<unsigned char>(utf8Str[i + 2]) & 0x3F) << 6) | (static_cast<unsigned char>(utf8Str[i + 3]) & 0x3F); i += 4;
+            } else { i++; continue; }
+            if (cp <= 0xFFFF) { char buf[8]; snprintf(buf, sizeof(buf), "\\u%04x", cp); result += buf; }
+            else { cp -= 0x10000; char buf[16]; snprintf(buf, sizeof(buf), "\\u%04x\\u%04x", 0xD800 + (uint16_t)(cp >> 10), 0xDC00 + (uint16_t)(cp & 0x3FF)); result += buf; }
+        }
+        return result;
     }
-    std::string ANSFRHelper::UserRecordsToJsonString(const std::vector<UserRecord> userRecords) {
-        boost::property_tree::ptree root;
-        boost::property_tree::ptree userRecordNodes;
-        for (int i=0; i < userRecords.size(); i++) {
-            boost::property_tree::ptree userRecordNode;
-            boost::property_tree::ptree faceIds;
-            UserRecord userRecord = userRecords[i];
-            for (int j = 0; j < userRecord.FaceIds.size(); j++) {
-                boost::property_tree::ptree faceIdNode;
-                faceIdNode.put("", userRecord.FaceIds[j]);
-                faceIds.push_back(std::make_pair("", faceIdNode));
+
+    // Using nlohmann/json (consistent with FaceObjectsToJsonString)
+    std::string ANSFRHelper::UserRecordToJsonString(const UserRecord userRecord) {
+        try {
+            nlohmann::json faceIdArray = nlohmann::json::array();
+            for (const auto& faceId : userRecord.FaceIds) {
+                faceIdArray.push_back(faceId);
             }
-            userRecordNode.put("user_id", userRecord.UserId);
-            userRecordNode.put("user_code", userRecord.UserCode);
-            userRecordNode.put("user_username", userRecord.UserName);
-            userRecordNode.add_child("face_ids", faceIds);
-            userRecordNodes.push_back(std::make_pair("", userRecordNode));
+            nlohmann::json root = {
+                {"user_id", std::to_string(userRecord.UserId)},
+                {"user_code", userRecord.UserCode},
+                {"user_username", DoubleEscapeUnicode(userRecord.UserName)},
+                {"face_ids", faceIdArray}
+            };
+            return root.dump();
+        }
+        catch (const std::exception&) {
+            return R"({})";
+        }
+    }
+
+    // Using nlohmann/json (consistent with FaceObjectsToJsonString)
+    std::string ANSFRHelper::UserRecordsToJsonString(const std::vector<UserRecord> userRecords) {
+        try {
+            nlohmann::json root;
+            auto& records = root["user_records"] = nlohmann::json::array();
+
+            for (const auto& userRecord : userRecords) {
+                nlohmann::json faceIdArray = nlohmann::json::array();
+                for (const auto& faceId : userRecord.FaceIds) {
+                    faceIdArray.push_back(faceId);
+                }
+                records.push_back({
+                    {"user_id", std::to_string(userRecord.UserId)},
+                    {"user_code", userRecord.UserCode},
+                    {"user_username", DoubleEscapeUnicode(userRecord.UserName)},
+                    {"face_ids", faceIdArray}
+                });
+            }
+            return root.dump();
+        }
+        catch (const std::exception&) {
+            return R"({"user_records":[]})";
         }
-        root.add_child("user_records", userRecordNodes);
-        std::ostringstream stream;
-        boost::property_tree::write_json(stream, root,false);
-        std::string userRecordResult = stream.str();
-        return userRecordResult;
     }
     std::string ANSFRHelper::FaceRecordToJsonString(const FaceRecord faceRecord) {
         boost::property_tree::ptree root;
diff --git a/tests/ANSFR-UnitTest/CMakeLists.txt b/tests/ANSFR-UnitTest/CMakeLists.txt
index c553704..8e239d5 100644
--- a/tests/ANSFR-UnitTest/CMakeLists.txt
+++ b/tests/ANSFR-UnitTest/CMakeLists.txt
@@ -37,6 +37,7 @@ target_include_directories(ANSFR-UnitTest PRIVATE
     ${ANSLIBS_DIR}/faiss
     ${ANSLIBS_DIR}/TensorRT/include
     ${ANSLIBS_DIR}/fastdeploy_gpu/include
+    ${ANSLIBS_DIR}/nlohmann
 )
 
 target_link_libraries(ANSFR-UnitTest