diff --git a/frontend/src/api/channelMonitorV2.ts b/frontend/src/api/channelMonitorV2.ts
index 5dac6f6270..49433468c5 100644
--- a/frontend/src/api/channelMonitorV2.ts
+++ b/frontend/src/api/channelMonitorV2.ts
@@ -76,6 +76,14 @@ export interface MonitorHealth {
   }
 }
 
+/** First-upgrade historical fill for 90m/24h/7d/30d; omitted when complete. */
+export interface MonitorBootstrap {
+  active: boolean
+  progress_percent: number
+  covered_from?: string
+  target_start?: string
+}
+
 export interface MonitorCoverage {
   requested_start: string
   coverage_start: string
@@ -84,6 +92,8 @@ export interface MonitorCoverage {
   aggregation_lag_seconds: number
   coverage_complete: boolean
   bucket_seconds: number
+  /** Present while initial aggregation has not covered the 30d product window. */
+  bootstrap?: MonitorBootstrap | null
 }
 
 export interface MonitorConfig {
diff --git a/frontend/src/i18n/locales/en/channelMonitorV2.ts b/frontend/src/i18n/locales/en/channelMonitorV2.ts
index 95f8f32a79..9862d55547 100644
--- a/frontend/src/i18n/locales/en/channelMonitorV2.ts
+++ b/frontend/src/i18n/locales/en/channelMonitorV2.ts
@@ -5,6 +5,13 @@ export default {
     updating: 'Updating data',
     updatedTo: 'Updated to {time}',
     partialCoverage: 'Partial historical coverage',
+    bootstrap: {
+      title: 'Building historical monitor data',
+      description:
+        'On first enable, passive aggregation silently fills the 90m, 24h, 7d, and 30d windows in the background. All ranges become complete once this finishes.',
+      progress: '{percent}% complete',
+      working: 'Aggregating in the background…',
+    },
     timeRange: 'Time range',
     clearFilters: 'Reset',
     refreshingFilters: 'Filters changed; refreshing matrix, trend, and details…',
diff --git a/frontend/src/i18n/locales/zh/channelMonitorV2.ts b/frontend/src/i18n/locales/zh/channelMonitorV2.ts
index f974e753f7..ca4518bc02 100644
--- a/frontend/src/i18n/locales/zh/channelMonitorV2.ts
+++ b/frontend/src/i18n/locales/zh/channelMonitorV2.ts
@@ -5,6 +5,13 @@ export default {
     updating: '正在更新数据',
     updatedTo: '更新至 {time}',
     partialCoverage: '部分历史覆盖',
+    bootstrap: {
+      title: '正在补齐历史监控数据',
+      description:
+        '首次启用被动监控时，系统会在后台静默聚合 90 分钟、24 小时、7 天与 30 天窗口；完成后可切换全部时间范围。',
+      progress: '进度 {percent}%',
+      working: '后台聚合中…',
+    },
     timeRange: '时间范围',
     clearFilters: '重置',
     refreshingFilters: '筛选条件已变化，正在刷新矩阵、趋势和明细…',
diff --git a/frontend/src/views/user/ChannelStatusV2View.vue b/frontend/src/views/user/ChannelStatusV2View.vue
index 303b438b57..d97b14cb99 100644
--- a/frontend/src/views/user/ChannelStatusV2View.vue
+++ b/frontend/src/views/user/ChannelStatusV2View.vue
@@ -29,11 +29,18 @@
               </span>
               <span v-else class="text-gray-400">{{ t('common.loading') }}</span>
               <span
-                v-if="snapshot && !snapshot.coverage.coverage_complete"
+                v-if="snapshot && !snapshot.coverage.coverage_complete && !bootstrapActive"
                 class="badge badge-warning"
               >
                 {{ t('channelMonitorV2.partialCoverage') }}
               </span>
+              <span
+                v-if="bootstrapActive"
+                class="badge badge-primary inline-flex items-center gap-1"
+              >
+                <LoadingSpinner size="sm" />
+                {{ t('channelMonitorV2.bootstrap.progress', { percent: bootstrapPercent }) }}
+              </span>
             </div>
           </div>
           <button
@@ -47,6 +54,41 @@
           </button>
         </header>
 
+        <!-- First-upgrade silent backfill: show until 30d product window is covered -->
+        <div
+          v-if="bootstrapActive"
+          class="border-b border-blue-100 bg-blue-50/90 px-5 py-3 dark:border-blue-900/40 dark:bg-blue-950/40 sm:px-6"
+          role="status"
+          aria-live="polite"
+        >
+          <div class="flex flex-wrap items-start justify-between gap-3">
+            <div class="min-w-0 flex-1">
+              <p class="text-sm font-semibold text-blue-900 dark:text-blue-100">
+                {{ t('channelMonitorV2.bootstrap.title') }}
+              </p>
+              <p class="mt-0.5 text-xs text-blue-800/80 dark:text-blue-200/80">
+                {{ t('channelMonitorV2.bootstrap.description') }}
+              </p>
+            </div>
+            <span class="shrink-0 text-xs font-medium tabular-nums text-blue-700 dark:text-blue-300">
+              {{ t('channelMonitorV2.bootstrap.progress', { percent: bootstrapPercent }) }}
+            </span>
+          </div>
+          <div
+            class="mt-2.5 h-1.5 overflow-hidden rounded-full bg-blue-200/80 dark:bg-blue-900/60"
+            role="progressbar"
+            :aria-valuenow="bootstrapPercent"
+            aria-valuemin="0"
+            aria-valuemax="100"
+            :aria-label="t('channelMonitorV2.bootstrap.working')"
+          >
+            <div
+              class="h-full rounded-full bg-blue-500 transition-[width] duration-500 ease-out dark:bg-blue-400"
+              :style="{ width: `${bootstrapPercent}%` }"
+            />
+          </div>
+        </div>
+
         <!-- Single compact toolbar row: range · filters · view controls -->
         <div class="monitor-toolbar flex flex-nowrap items-center gap-1.5 overflow-x-auto px-4 py-3 sm:gap-2 sm:px-5">
           <div
@@ -394,8 +436,20 @@
 
           <div v-if="tabLoading" class="empty-state py-10 text-sm text-gray-400">{{ t('common.loading') }}</div>
           <div v-else-if="activeRowsEmpty" class="empty-state py-10">
-            <p class="empty-state-title text-base">{{ t('channelMonitorV2.empty.title') }}</p>
-            <p class="empty-state-description">{{ t('channelMonitorV2.empty.description') }}</p>
+            <p class="empty-state-title text-base">
+              {{
+                bootstrapActive
+                  ? t('channelMonitorV2.bootstrap.title')
+                  : t('channelMonitorV2.empty.title')
+              }}
+            </p>
+            <p class="empty-state-description">
+              {{
+                bootstrapActive
+                  ? t('channelMonitorV2.bootstrap.description')
+                  : t('channelMonitorV2.empty.description')
+              }}
+            </p>
           </div>
         </div>
       </section>
@@ -585,6 +639,13 @@ const activeRowsEmpty = computed(() =>
       ? errorRows.value.length === 0
       : userRows.value.length === 0
 )
+/** First-upgrade backfill toward 90m/24h/7d/30d; banner hides when backend omits bootstrap. */
+const bootstrapActive = computed(() => Boolean(snapshot.value?.coverage?.bootstrap?.active))
+const bootstrapPercent = computed(() => {
+  const raw = snapshot.value?.coverage?.bootstrap?.progress_percent
+  if (typeof raw !== 'number' || Number.isNaN(raw)) return 0
+  return Math.min(100, Math.max(0, Math.round(raw)))
+})
 const matrixRows = computed(() => {
   const items = matrix.value?.items || []
   // platform_group views should only show real groups, never bare platform placeholders.
@@ -740,12 +801,15 @@ function scheduleAutoRefresh() {
     window.clearInterval(autoRefreshTimer)
     autoRefreshTimer = null
   }
-  const seconds = snapshot.value?.config?.refresh_interval_seconds || 300
+  // Poll faster while first-upgrade bootstrap is filling 90m→30d so the progress bar moves.
+  const seconds = bootstrapActive.value
+    ? 10
+    : snapshot.value?.config?.refresh_interval_seconds || 300
   autoRefreshTimer = window.setInterval(() => {
     if (!loading.value && !refreshing.value) {
       void reload(true)
     }
-  }, Math.max(60, seconds) * 1000)
+  }, Math.max(bootstrapActive.value ? 10 : 60, seconds) * 1000)
 }
 function drillModel(row: MonitorModelRow) {
   filter.value.platforms = [row.platform]