diff --git a/src/views/PeopleView.vue b/src/views/PeopleView.vue
index bb3e632..8c748c6 100644
--- a/src/views/PeopleView.vue
+++ b/src/views/PeopleView.vue
@@ -1097,7 +1097,14 @@ const faceMoveTarget = ref('')
 const faceMoveNewGroupName = ref('')
 
 // Cluster results (synced with store for cross-navigation persistence)
-const clusterResults = computed(() => clusterResultsCache.value[selectedFileUuid.value] || [])
+const clusterResults = computed(() => {
+  const results = clusterResultsCache.value[selectedFileUuid.value] || []
+  console.log('[clusterResults] cache for', selectedFileUuid.value, ':', results.length, 'groups')
+  if (results.length > 0) {
+    console.log('[clusterResults] first group:', JSON.stringify(results[0], null, 2))
+  }
+  return results
+})
 const clusterTracesMap = ref<Record<string, any>>({})
 const clusterRunning = computed(() => isClusterRunning(selectedFileUuid.value))
 
@@ -1131,6 +1138,10 @@ const faceGroups = computed(() => {
     }
     const defaultName = `group ${String(idx + 1).padStart(2, '0')}`
     if (!c.name) c.name = defaultName
+    // Convert Person_X to Group_X for display
+    if (c.name && c.name.startsWith('Person_')) {
+      c.name = 'Group_' + c.name.substring(7)
+    }
     const visibleTraceIds = ffFilterActive.value
       ? traceIds.filter(tid => !ffHiddenTraces.value.has(tid))
       : traceIds
@@ -1176,11 +1187,19 @@ const clusterDetailCluster = computed(() => {
 // Map trace_id → group name for Faces section
 const traceGroupMap = computed(() => {
   const map: Record<string, string> = {}
+  console.log('[traceGroupMap] clusterResults:', clusterResults.value.length, 'groups')
   for (const c of clusterResults.value) {
+    let name = c.name || ''
+    // Convert Person_X to Group_X for display
+    if (name.startsWith('Person_')) {
+      name = 'Group_' + name.substring(7)
+    }
+    console.log('[traceGroupMap] cluster:', c.cluster_id, 'name:', name, 'trace_ids:', c.trace_ids)
     for (const tid of c.trace_ids || []) {
-      map[String(tid)] = c.name
+      map[String(tid)] = name
     }
   }
+  console.log('[traceGroupMap] final map:', map)
   return map
 })
 
@@ -1218,7 +1237,25 @@ const facesTotalPages = computed(() => {
 })
 
 function traceLabel(tr: any): string {
-  const n = tr?.name || traceGroupMap.value[String(tr.trace_id)]
+  // Prefer cluster name from clusterResultsCache
+  const clusters = clusterResultsCache.value[selectedFileUuid.value] || []
+  console.log('[traceLabel] trace_id:', tr.trace_id, 'clusters in cache:', clusters.length)
+  if (clusters.length > 0) {
+    console.log('[traceLabel] first cluster:', clusters[0])
+  }
+  for (const c of clusters) {
+    if (c.trace_ids && c.trace_ids.includes(tr.trace_id)) {
+      let name = c.name || ''
+      // Convert Person_X to Group_X for display
+      if (name.startsWith('Person_')) {
+        name = 'Group_' + name.substring(7)
+      }
+      console.log('[traceLabel] Found cluster name:', name)
+      return name
+    }
+  }
+  const n = tr?.name
+  console.log('[traceLabel] Fallback to:', n || t('people.section.unassigned'))
   return n || t('people.section.unassigned')
 }
 
@@ -2028,6 +2065,11 @@ async function loadClusterResults() {
     }
     const groups = results?.face_groups || results?.clusters || []
     const frames = results?.frames || []
+    console.log('[loadClusterResults] groups:', groups.length, 'frames:', frames.length)
+    if (frames.length > 0) {
+      console.log('[loadClusterResults] first frame faces:', frames[0].faces)
+      console.log('[loadClusterResults] first group:', groups[0])
+    }
     // 統一 group_id → cluster_id, 並添加 group_uuid
     for (const g of groups) {
       if (g.group_id !== undefined && g.cluster_id === undefined) {
@@ -2069,6 +2111,7 @@ async function loadClusterResults() {
       const cid = c.cluster_id || c.group_id
       c.member_faces = clusterFacesMap[cid] || []
       c.face_count = c.member_faces.length
+      console.log(`[loadClusterResults] group ${c.name} (cid=${cid}): member_faces=${c.member_faces.length}`)
       c.trace_ids = Array.from(clusterTraceIdsMap[cid] || [])
       // Set representative_trace from representative_face
       if (c.representative_face?.face_id) {
@@ -2083,7 +2126,10 @@ async function loadClusterResults() {
       }
     }
     if (groups.length) {
+      console.log('[loadClusterResults] Calling setClusterResults with', groups.length, 'groups')
+      console.log('[loadClusterResults] First group trace_ids:', groups[0]?.trace_ids)
       setClusterResults(fileUuid, groups)
+      console.log('[loadClusterResults] After setClusterResults, cache:', clusterResultsCache.value[fileUuid]?.length)
 
       // Load trace profiles for names in background (non-blocking)
       loadClusterNames(fileUuid, groups).catch(() => {})
@@ -2749,7 +2795,7 @@ function closeClusterCtxMenu(e?: MouseEvent) {
   clusterCtxMenu.value.show = false
 }
 
-function clusterCtxAction(action: string) {
+async function clusterCtxAction(action: string) {
   const c = clusterCtxMenu.value.cluster
   if (!c) return
   clusterCtxMenu.value.show = false
@@ -2766,7 +2812,7 @@ function clusterCtxAction(action: string) {
       // Update trace profiles via API
       const traceIds = clusters[idx]?.trace_ids || []
       if (traceIds.length && selectedFileUuid.value) {
-        updateTraceProfileGroup(selectedFileUuid.value, traceIds, { name })
+        await updateTraceProfileGroup(selectedFileUuid.value, traceIds, { name })
       }
     }
   } else if (action === 'skip') {
@@ -3297,24 +3343,75 @@ async function executeMerge(targetGroupId: string) {
   const sourceGroupIds = groupIds.filter(id => id !== targetGroupId)
   const sourceGroups = faceGroups.value.filter((c: any) => sourceGroupIds.includes(c.group_uuid))
   
-  const sourceGroupNames = sourceGroups.map(g => g.name).filter(Boolean)
+  // Collect all trace_ids from source groups
+  const allTraceIds: number[] = []
+  for (const g of sourceGroups) {
+    if (g.trace_ids) {
+      allTraceIds.push(...g.trace_ids)
+    }
+  }
   
-  if (sourceGroupNames.length === 0) {
-    alert('No valid source groups to merge')
+  if (allTraceIds.length === 0) {
+    alert('No traces to merge')
     return
   }
   
-  if (!confirm(`Merge ${sourceGroupNames.length} group(s) into "${targetGroupName}"?`)) return
+  if (!confirm(`Merge ${sourceGroups.length} group(s) with ${allTraceIds.length} trace(s) into "${targetGroupName}"?`)) return
   
   operationLoading.value = true
-  operationMessage.value = `Merging ${sourceGroupNames.length} group(s)...`
+  operationMessage.value = `Merging ${sourceGroups.length} group(s)...`
   
   try {
-    const result = await apiCall('merge_groups', {
-      fileUuid: selectedFileUuid.value,
-      sourceGroups: sourceGroupNames,
-      targetGroupName: targetGroupName
-    })
+    // Update all source traces to target group name
+    console.log('[executeMerge] Updating trace_ids:', allTraceIds, 'to name:', targetGroupName)
+    
+    // 1. Update trace_profiles via API
+    const result = await updateTraceProfileGroup(selectedFileUuid.value, allTraceIds, { name: targetGroupName })
+    console.log('[executeMerge] API Result:', result)
+    
+    // 2. Update clusterResultsCache locally
+    const clusters = getClusterResults(selectedFileUuid.value)
+    
+    // Find target cluster
+    const targetCluster = clusters.find((c: any) => c.name === targetGroupName || c.cluster_id === targetGroup.cluster_id)
+    
+    if (targetCluster) {
+      // Add source trace_ids to target cluster (avoid duplicates)
+      if (!targetCluster.trace_ids) targetCluster.trace_ids = []
+      for (const tid of allTraceIds) {
+        if (!targetCluster.trace_ids.includes(tid)) {
+          targetCluster.trace_ids.push(tid)
+        }
+      }
+      targetCluster.trace_count = targetCluster.trace_ids.length
+    }
+    
+    // Remove trace_ids from source clusters
+    for (const sourceGroup of sourceGroups) {
+      const sourceCluster = clusters.find((c: any) => c.cluster_id === sourceGroup.cluster_id || c.group_id === sourceGroup.group_id)
+      if (sourceCluster && sourceCluster.trace_ids) {
+        sourceCluster.trace_ids = sourceCluster.trace_ids.filter((tid: number) => !allTraceIds.includes(tid))
+        sourceCluster.trace_count = sourceCluster.trace_ids.length
+      }
+    }
+    
+    // Remove empty source clusters
+    const nonEmptyClusters = clusters.filter((c: any) => !sourceGroups.some(sg => 
+      (c.cluster_id === sg.cluster_id || c.group_id === sg.group_id) && (!c.trace_ids || c.trace_ids.length === 0)
+    ))
+    
+    setClusterResults(selectedFileUuid.value, nonEmptyClusters)
+    console.log('[executeMerge] Updated cache')
+    
+    // Reload thumbnails for updated clusters
+    for (const c of nonEmptyClusters) {
+      if (c.trace_ids && c.trace_ids.length > 0) {
+        const repId = c.representative_trace || c.trace_ids[0]
+        if (repId) {
+          loadTraceThumb({ trace_id: repId, file_uuid: selectedFileUuid.value, best_face_id: 0 })
+        }
+      }
+    }
     
     
     if (result?.success) {
@@ -4121,7 +4218,7 @@ h1 { margin: 0; }
 
 /* Face detail side navigation arrows */
 .ms-fs-nav-arrow {
-  position: fixed; top: 50%; transform: translateY(-50%); z-index: 10010;
+  position: fixed; top: 50%; transform: translateY(-50%); z-index: 10100;
   width: 44px; height: 44px; border-radius: 50%; border: none;
   background: rgba(0,0,0,0.5); color: #fff; cursor: pointer;
   display: flex; align-items: center; justify-content: center;