diff --git a/app/build.gradle.kts b/app/build.gradle.kts
index 5641752..1b4852e 100644
--- a/app/build.gradle.kts
+++ b/app/build.gradle.kts
@@ -12,8 +12,8 @@ android {
         applicationId = "org.noxylva.lbjconsole"
         minSdk = 29
         targetSdk = 35
-        versionCode = 7
-        versionName = "0.0.7"
+        versionCode = 8
+        versionName = "0.0.8"
 
         testInstrumentationRunner = "androidx.test.runner.AndroidJUnitRunner"
     }
diff --git a/app/src/main/java/org/noxylva/lbjconsole/MainActivity.kt b/app/src/main/java/org/noxylva/lbjconsole/MainActivity.kt
index 7cd7228..8527e73 100644
--- a/app/src/main/java/org/noxylva/lbjconsole/MainActivity.kt
+++ b/app/src/main/java/org/noxylva/lbjconsole/MainActivity.kt
@@ -52,6 +52,7 @@ import androidx.core.content.ContextCompat
 import androidx.core.content.FileProvider
 import kotlinx.coroutines.delay
 import kotlinx.coroutines.launch
+import kotlinx.coroutines.Dispatchers
 import org.json.JSONObject
 import org.osmdroid.config.Configuration
 import org.noxylva.lbjconsole.model.TrainRecord
@@ -418,9 +419,11 @@ class MainActivity : ComponentActivity() {
                         deviceName = settingsDeviceName,
                         onDeviceNameChange = { newName -> settingsDeviceName = newName },
                         onApplySettings = {
-                            saveSettings()
-                            targetDeviceName = settingsDeviceName
-                            Log.d(TAG, "Applied settings deviceName=${settingsDeviceName}")
+                            if (targetDeviceName != settingsDeviceName) {
+                                targetDeviceName = settingsDeviceName
+                                Log.d(TAG, "Applied settings deviceName=${settingsDeviceName}")
+                                saveSettings()
+                            }
                         },
                         appVersion = getAppVersion(),
                         locoInfoUtil = locoInfoUtil,
@@ -795,28 +798,30 @@ class MainActivity : ComponentActivity() {
     
     
     private fun saveSettings() {
-        val editor = settingsPrefs.edit()
-            .putString("device_name", settingsDeviceName)
-            .putInt("current_tab", currentTab)
-            .putBoolean("history_edit_mode", historyEditMode)
-            .putString("history_selected_records", historySelectedRecords.joinToString(","))
-            .putString("history_expanded_states", historyExpandedStates.map { "${it.key}:${it.value}" }.joinToString(";"))
-            .putInt("history_scroll_position", historyScrollPosition)
-            .putInt("history_scroll_offset", historyScrollOffset)
-            .putInt("settings_scroll_position", settingsScrollPosition)
-            .putFloat("map_zoom_level", mapZoomLevel.toFloat())
-            .putBoolean("map_railway_visible", mapRailwayLayerVisible)
-            .putString("specified_device_address", specifiedDeviceAddress)
-            .putString("search_order_list", searchOrderList.joinToString(","))
-            .putBoolean("auto_connect_enabled", autoConnectEnabled)
+        lifecycleScope.launch(Dispatchers.IO) {
+            val editor = settingsPrefs.edit()
+                .putString("device_name", settingsDeviceName)
+                .putInt("current_tab", currentTab)
+                .putBoolean("history_edit_mode", historyEditMode)
+                .putString("history_selected_records", historySelectedRecords.joinToString(","))
+                .putString("history_expanded_states", historyExpandedStates.map { "${it.key}:${it.value}" }.joinToString(";"))
+                .putInt("history_scroll_position", historyScrollPosition)
+                .putInt("history_scroll_offset", historyScrollOffset)
+                .putInt("settings_scroll_position", settingsScrollPosition)
+                .putFloat("map_zoom_level", mapZoomLevel.toFloat())
+                .putBoolean("map_railway_visible", mapRailwayLayerVisible)
+                .putString("specified_device_address", specifiedDeviceAddress)
+                .putString("search_order_list", searchOrderList.joinToString(","))
+                .putBoolean("auto_connect_enabled", autoConnectEnabled)
+                
+            mapCenterPosition?.let { (lat, lon) ->
+                editor.putFloat("map_center_lat", lat.toFloat())
+                editor.putFloat("map_center_lon", lon.toFloat())
+            }
             
-        mapCenterPosition?.let { (lat, lon) ->
-            editor.putFloat("map_center_lat", lat.toFloat())
-            editor.putFloat("map_center_lon", lon.toFloat())
+            editor.apply()
+            Log.d(TAG, "Saved settings deviceName=${settingsDeviceName} tab=${currentTab} mapCenter=${mapCenterPosition} zoom=${mapZoomLevel}")
         }
-        
-        editor.apply()
-        Log.d(TAG, "Saved settings deviceName=${settingsDeviceName} tab=${currentTab} mapCenter=${mapCenterPosition} zoom=${mapZoomLevel}")
     }
     
     override fun onResume() {
diff --git a/app/src/main/java/org/noxylva/lbjconsole/model/MergeSettings.kt b/app/src/main/java/org/noxylva/lbjconsole/model/MergeSettings.kt
index 65d9d44..ea50b17 100644
--- a/app/src/main/java/org/noxylva/lbjconsole/model/MergeSettings.kt
+++ b/app/src/main/java/org/noxylva/lbjconsole/model/MergeSettings.kt
@@ -7,9 +7,10 @@ data class MergeSettings(
 )
 
 enum class GroupBy(val displayName: String) {
-    TRAIN_AND_LOCO("车次号+机车号"),
-    TRAIN_ONLY("仅车次号"),
-    LOCO_ONLY("仅机车号")
+    TRAIN_ONLY("车次号"),
+    LOCO_ONLY("机车号"),
+    TRAIN_OR_LOCO("车次号或机车号"),
+    TRAIN_AND_LOCO("车次号与机车号")
 }
 
 enum class TimeWindow(val displayName: String, val seconds: Long?) {
@@ -23,14 +24,6 @@ enum class TimeWindow(val displayName: String, val seconds: Long?) {
 
 fun generateGroupKey(record: TrainRecord, groupBy: GroupBy): String? {
     return when (groupBy) {
-        GroupBy.TRAIN_AND_LOCO -> {
-            val train = record.train.trim()
-            val loco = record.loco.trim()
-            if (train.isNotEmpty() && train != "<NUL>" && 
-                loco.isNotEmpty() && loco != "<NUL>") {
-                "${train}_${loco}"
-            } else null
-        }
         GroupBy.TRAIN_ONLY -> {
             val train = record.train.trim()
             if (train.isNotEmpty() && train != "<NUL>") train else null
@@ -39,5 +32,22 @@ fun generateGroupKey(record: TrainRecord, groupBy: GroupBy): String? {
             val loco = record.loco.trim()
             if (loco.isNotEmpty() && loco != "<NUL>") loco else null
         }
+        GroupBy.TRAIN_OR_LOCO -> {
+            val train = record.train.trim()
+            val loco = record.loco.trim()
+            when {
+                train.isNotEmpty() && train != "<NUL>" -> train
+                loco.isNotEmpty() && loco != "<NUL>" -> loco
+                else -> null
+            }
+        }
+        GroupBy.TRAIN_AND_LOCO -> {
+            val train = record.train.trim()
+            val loco = record.loco.trim()
+            if (train.isNotEmpty() && train != "<NUL>" && 
+                loco.isNotEmpty() && loco != "<NUL>") {
+                "${train}_${loco}"
+            } else null
+        }
     }
 }
\ No newline at end of file
diff --git a/app/src/main/java/org/noxylva/lbjconsole/model/TrainRecordManager.kt b/app/src/main/java/org/noxylva/lbjconsole/model/TrainRecordManager.kt
index 5eb65ed..89dca85 100644
--- a/app/src/main/java/org/noxylva/lbjconsole/model/TrainRecordManager.kt
+++ b/app/src/main/java/org/noxylva/lbjconsole/model/TrainRecordManager.kt
@@ -234,26 +234,79 @@ class TrainRecordManager(private val context: Context) {
     }
     
     private fun processRecordsForMerging(records: List<TrainRecord>, settings: MergeSettings): List<MergedTrainRecord> {
-        val groupedRecords = mutableMapOf<String, MutableList<TrainRecord>>()
         val currentTime = Date()
+        val validRecords = records.filter { record ->
+            settings.timeWindow.seconds?.let { windowSeconds ->
+                (currentTime.time - record.timestamp.time) / 1000 <= windowSeconds
+            } ?: true
+        }
+        
+        return when (settings.groupBy) {
+            GroupBy.TRAIN_OR_LOCO -> processTrainOrLocoMerging(validRecords)
+            else -> {
+                val groupedRecords = mutableMapOf<String, MutableList<TrainRecord>>()
+                validRecords.forEach { record ->
+                    val groupKey = generateGroupKey(record, settings.groupBy)
+                    if (groupKey != null) {
+                        groupedRecords.getOrPut(groupKey) { mutableListOf() }.add(record)
+                    }
+                }
+                
+                groupedRecords.mapNotNull { (groupKey, groupRecords) ->
+                    if (groupRecords.size >= 2) {
+                        val sortedRecords = groupRecords.sortedBy { it.timestamp }
+                        val latestRecord = sortedRecords.maxByOrNull { it.timestamp }!!
+                        MergedTrainRecord(
+                            groupKey = groupKey,
+                            records = sortedRecords,
+                            latestRecord = latestRecord
+                        )
+                    } else null
+                }.sortedByDescending { it.latestRecord.timestamp }
+            }
+        }
+    }
+    
+    private fun processTrainOrLocoMerging(records: List<TrainRecord>): List<MergedTrainRecord> {
+        val groups = mutableListOf<MutableList<TrainRecord>>()
         
         records.forEach { record ->
-            val groupKey = generateGroupKey(record, settings.groupBy)
-            if (groupKey != null) {
-                val withinTimeWindow = settings.timeWindow.seconds?.let { windowSeconds ->
-                    (currentTime.time - record.timestamp.time) / 1000 <= windowSeconds
-                } ?: true
-                
-                if (withinTimeWindow) {
-                    groupedRecords.getOrPut(groupKey) { mutableListOf() }.add(record)
+            val train = record.train.trim()
+            val loco = record.loco.trim()
+            
+            if ((train.isEmpty() || train == "<NUL>") && (loco.isEmpty() || loco == "<NUL>")) {
+                return@forEach
+            }
+            
+            var foundGroup: MutableList<TrainRecord>? = null
+            
+            for (group in groups) {
+                val shouldMerge = group.any { existingRecord ->
+                    val existingTrain = existingRecord.train.trim()
+                    val existingLoco = existingRecord.loco.trim()
+                    
+                    (train.isNotEmpty() && train != "<NUL>" && train == existingTrain) ||
+                    (loco.isNotEmpty() && loco != "<NUL>" && loco == existingLoco)
                 }
+                
+                if (shouldMerge) {
+                    foundGroup = group
+                    break
+                }
+            }
+            
+            if (foundGroup != null) {
+                foundGroup.add(record)
+            } else {
+                groups.add(mutableListOf(record))
             }
         }
         
-        return groupedRecords.mapNotNull { (groupKey, groupRecords) ->
+        return groups.mapNotNull { groupRecords ->
             if (groupRecords.size >= 2) {
                 val sortedRecords = groupRecords.sortedBy { it.timestamp }
                 val latestRecord = sortedRecords.maxByOrNull { it.timestamp }!!
+                val groupKey = "${latestRecord.train}_OR_${latestRecord.loco}"
                 MergedTrainRecord(
                     groupKey = groupKey,
                     records = sortedRecords,
diff --git a/app/src/main/java/org/noxylva/lbjconsole/ui/screens/HistoryScreen.kt b/app/src/main/java/org/noxylva/lbjconsole/ui/screens/HistoryScreen.kt
index fe712a1..eeb60bc 100644
--- a/app/src/main/java/org/noxylva/lbjconsole/ui/screens/HistoryScreen.kt
+++ b/app/src/main/java/org/noxylva/lbjconsole/ui/screens/HistoryScreen.kt
@@ -1,5 +1,6 @@
 package org.noxylva.lbjconsole.ui.screens
 
+import android.util.Log
 import androidx.compose.foundation.ExperimentalFoundationApi
 import androidx.compose.foundation.combinedClickable
 import androidx.compose.foundation.background
@@ -862,6 +863,7 @@ fun HistoryScreen(
 ) {
 
     val refreshKey = latestRecord?.timestamp?.time ?: 0
+    var wasAtTopBeforeUpdate by remember { mutableStateOf(false) }
 
     var isInEditMode by remember(editMode) { mutableStateOf(editMode) }
     val selectedRecordsList = remember(selectedRecords) { 
@@ -941,6 +943,22 @@ fun HistoryScreen(
             onStateChange(false, emptySet(), expandedStatesMap.toMap(), listState.firstVisibleItemIndex, listState.firstVisibleItemScrollOffset)
         }
     }
+    
+    LaunchedEffect(listState.firstVisibleItemIndex, listState.firstVisibleItemScrollOffset) {
+        if (!isInEditMode && filteredRecords.isNotEmpty()) {
+            wasAtTopBeforeUpdate = listState.firstVisibleItemIndex == 0 && listState.firstVisibleItemScrollOffset <= 100
+        }
+    }
+
+    LaunchedEffect(refreshKey) {
+        if (refreshKey > 0 && !isInEditMode && filteredRecords.isNotEmpty() && wasAtTopBeforeUpdate) {
+            try {
+                listState.animateScrollToItem(0, 0)
+            } catch (e: Exception) {
+                listState.scrollToItem(0, 0)
+            }
+        }
+    }
 
     Box(modifier = Modifier.fillMaxSize()) {
         Column(modifier = Modifier.fillMaxSize()) {
diff --git a/app/src/main/java/org/noxylva/lbjconsole/ui/screens/SettingsScreen.kt b/app/src/main/java/org/noxylva/lbjconsole/ui/screens/SettingsScreen.kt
index 506cedc..8cb370a 100644
--- a/app/src/main/java/org/noxylva/lbjconsole/ui/screens/SettingsScreen.kt
+++ b/app/src/main/java/org/noxylva/lbjconsole/ui/screens/SettingsScreen.kt
@@ -15,6 +15,7 @@ import androidx.compose.ui.platform.LocalUriHandler
 import androidx.compose.ui.text.font.FontWeight
 import androidx.compose.ui.text.style.TextAlign
 import androidx.compose.ui.unit.dp
+import kotlinx.coroutines.delay
 import org.noxylva.lbjconsole.model.MergeSettings
 import org.noxylva.lbjconsole.model.GroupBy
 import org.noxylva.lbjconsole.model.TimeWindow
@@ -46,17 +47,16 @@ fun SettingsScreen(
     val scrollState = rememberScrollState()
     
     LaunchedEffect(scrollPosition) {
-        scrollState.scrollTo(scrollPosition)
+        if (scrollState.value != scrollPosition) {
+            scrollState.scrollTo(scrollPosition)
+        }
     }
     
     LaunchedEffect(scrollState.value) {
+        delay(50)
         onScrollPositionChange(scrollState.value)
     }
     
-    LaunchedEffect(deviceName) {
-        onApplySettings()
-    }
-    
     Column(
         modifier = Modifier
             .fillMaxSize()
@@ -198,12 +198,13 @@ fun SettingsScreen(
                 }
                 
                 val context = LocalContext.current
-                var backgroundServiceEnabled by remember {
+                val notificationService = remember(context) { NotificationService(context) }
+                
+                var backgroundServiceEnabled by remember(context) {
                     mutableStateOf(SettingsActivity.isBackgroundServiceEnabled(context))
                 }
                 
-                val notificationService = remember { NotificationService(context) }
-                var notificationEnabled by remember {
+                var notificationEnabled by remember(context, notificationService) {
                     mutableStateOf(notificationService.isNotificationEnabled())
                 }