feat(web): show source provider freshness on alerts

apps/web/messages/en.json

@@ -747,8 +747,13 @@
     "sourceCoverageSentry": "Sentry refs",
     "sourceCoverageSigNoz": "SigNoz refs",
     "sourceCoverageRatio": "source refs coverage {ratio} / total {total}",
-    "sourceCoverageProvider": "{provider}: total {total}, missing {missing}, Sentry {sentry}, SigNoz {signoz}",
-    "sourceCoverageProviderWindow": "{provider} window: total {total}, with refs {withRefs}, missing {missing}"
+    "sourceCoverageProvider": "{provider}: total {total}, missing {missing}, Sentry {sentry}, SigNoz {signoz}, latest {latest} ({age})",
+    "sourceCoverageProviderWindow": "{provider} window: total {total}, with refs {withRefs}, missing {missing}, latest {latest} ({age})",
+    "sourceCoverageFreshness": "{provider} latest {latest} ({age})",
+    "sourceCoverageFresh": "fresh",
+    "sourceCoverageStaleHours": "stale {hours}h",
+    "sourceCoverageStaleDays": "stale {days}d",
+    "sourceCoverageNoEvents": "no events"
   },
   "navSection": {
     "aiCore": "AI Core",

apps/web/messages/zh-TW.json

@@ -748,8 +748,13 @@
     "sourceCoverageSentry": "Sentry refs",
     "sourceCoverageSigNoz": "SigNoz refs",
     "sourceCoverageRatio": "source refs 覆蓋率 {ratio} / total {total}",
-    "sourceCoverageProvider": "{provider}: total {total}, missing {missing}, Sentry {sentry}, SigNoz {signoz}",
-    "sourceCoverageProviderWindow": "{provider} window: total {total}, with refs {withRefs}, missing {missing}"
+    "sourceCoverageProvider": "{provider}: total {total}, missing {missing}, Sentry {sentry}, SigNoz {signoz}, latest {latest} ({age})",
+    "sourceCoverageProviderWindow": "{provider} window: total {total}, with refs {withRefs}, missing {missing}, latest {latest} ({age})",
+    "sourceCoverageFreshness": "{provider} latest {latest} ({age})",
+    "sourceCoverageFresh": "fresh",
+    "sourceCoverageStaleHours": "stale {hours}h",
+    "sourceCoverageStaleDays": "stale {days}d",
+    "sourceCoverageNoEvents": "no events"
   },
   "navSection": {
     "aiCore": "AI 核心",

apps/web/src/app/[locale]/alerts/page.tsx

@@ -26,6 +26,7 @@ import { Bell, BellOff, RefreshCw, AlertTriangle, AlertCircle, Info, ChevronLeft
 const SEVERITY_ORDER: Record<string, number> = { P0: 0, P1: 1, P2: 2, P3: 3 }
 const ALERTS_PAGE_SIZE = 50
 const SOURCE_COVERAGE_LIMIT = 100
+const SOURCE_FRESHNESS_STALE_HOURS = 24
 
 const SEVERITY_STYLE: Record<string, { bg: string; text: string }> = {
   P0: { bg: 'bg-status-critical/10', text: 'text-status-critical' },
@@ -91,6 +92,7 @@ interface SourceCoverageProvider {
   sentry_ref_total: number
   signoz_ref_total: number
   alert_ref_total: number
+  latest_received_at?: string | null
 }
 
 interface SourceCoverageResponse {
@@ -103,6 +105,38 @@ function percentLabel(value: number, total: number) {
   return `${Math.round((value / total) * 100)}%`
 }
 
+function parseApiTimestamp(value?: string | null) {
+  if (!value) return null
+  const normalized = /(?:z|[+-]\d{2}:?\d{2})$/i.test(value) ? value : `${value}Z`
+  const date = new Date(normalized)
+  return Number.isNaN(date.getTime()) ? null : date
+}
+
+function formatTimestamp(value: string | null | undefined, locale: string, emptyLabel: string) {
+  const date = parseApiTimestamp(value)
+  if (!date) return emptyLabel
+  return new Intl.DateTimeFormat(locale, {
+    month: '2-digit',
+    day: '2-digit',
+    hour: '2-digit',
+    minute: '2-digit',
+    hour12: false,
+  }).format(date)
+}
+
+function freshnessAgeHours(value?: string | null) {
+  const date = parseApiTimestamp(value)
+  if (!date) return null
+  return Math.max(0, (Date.now() - date.getTime()) / 3_600_000)
+}
+
+function freshnessToneClass(ageHours: number | null) {
+  if (ageHours === null || ageHours > SOURCE_FRESHNESS_STALE_HOURS) {
+    return 'border-status-warning/30 bg-status-warning/5 text-status-warning'
+  }
+  return 'border-status-healthy/30 bg-status-healthy/5 text-status-healthy'
+}
+
 // =============================================================================
 // Page
 // =============================================================================
@@ -206,6 +240,17 @@ export default function AlertsPage({ params }: { params: { locale: string } }) {
   const topCoverageProviders = sourceCoverage?.providers?.slice(0, 3) ?? []
   const sentryCoverageSummary = providerCoverage.sentry?.summary
   const signozCoverageSummary = providerCoverage.signoz?.summary
+  const emptyFreshnessLabel = tAlerts('sourceCoverageNoEvents')
+  const formatFreshnessAge = (value?: string | null) => {
+    const ageHours = freshnessAgeHours(value)
+    if (ageHours === null) return emptyFreshnessLabel
+    if (ageHours <= SOURCE_FRESHNESS_STALE_HOURS) return tAlerts('sourceCoverageFresh')
+    if (ageHours < 48) return tAlerts('sourceCoverageStaleHours', { hours: Math.floor(ageHours) })
+    return tAlerts('sourceCoverageStaleDays', { days: Math.floor(ageHours / 24) })
+  }
+  const coverageFreshnessAge = freshnessAgeHours(coverageSummary?.latest_received_at)
+  const sentryFreshnessAge = freshnessAgeHours(sentryCoverageSummary?.latest_received_at)
+  const signozFreshnessAge = freshnessAgeHours(signozCoverageSummary?.latest_received_at)
 
   return (
     <AppLayout locale={params.locale}>
@@ -289,10 +334,23 @@ export default function AlertsPage({ params }: { params: { locale: string } }) {
               total: coverageSummary?.source_count ?? 0,
             })}
           </span>
+          <span className={cn(
+            'rounded border px-2 py-1',
+            freshnessToneClass(coverageFreshnessAge)
+          )}>
+            {tAlerts('sourceCoverageFreshness', {
+              provider: 'overall',
+              latest: formatTimestamp(coverageSummary?.latest_received_at, params.locale, emptyFreshnessLabel),
+              age: formatFreshnessAge(coverageSummary?.latest_received_at),
+            })}
+          </span>
           {topCoverageProviders.map(provider => (
             <span
               key={provider.provider}
-              className="rounded border border-nothing-gray-200 bg-nothing-gray-50 px-2 py-1"
+              className={cn(
+                'rounded border px-2 py-1',
+                freshnessToneClass(freshnessAgeHours(provider.latest_received_at))
+              )}
             >
               {tAlerts('sourceCoverageProvider', {
                 provider: provider.provider,
@@ -300,23 +358,35 @@ export default function AlertsPage({ params }: { params: { locale: string } }) {
                 missing: provider.missing_source_refs_total,
                 sentry: provider.sentry_ref_total,
                 signoz: provider.signoz_ref_total,
+                latest: formatTimestamp(provider.latest_received_at, params.locale, emptyFreshnessLabel),
+                age: formatFreshnessAge(provider.latest_received_at),
               })}
             </span>
           ))}
-          <span className="rounded border border-nothing-gray-200 bg-nothing-gray-50 px-2 py-1">
+          <span className={cn(
+            'rounded border px-2 py-1',
+            freshnessToneClass(sentryFreshnessAge)
+          )}>
             {tAlerts('sourceCoverageProviderWindow', {
               provider: 'sentry',
               total: sentryCoverageSummary?.source_count ?? 0,
               withRefs: sentryCoverageSummary?.with_source_refs_total ?? 0,
               missing: sentryCoverageSummary?.missing_source_refs_total ?? 0,
+              latest: formatTimestamp(sentryCoverageSummary?.latest_received_at, params.locale, emptyFreshnessLabel),
+              age: formatFreshnessAge(sentryCoverageSummary?.latest_received_at),
             })}
           </span>
-          <span className="rounded border border-nothing-gray-200 bg-nothing-gray-50 px-2 py-1">
+          <span className={cn(
+            'rounded border px-2 py-1',
+            freshnessToneClass(signozFreshnessAge)
+          )}>
             {tAlerts('sourceCoverageProviderWindow', {
               provider: 'signoz',
               total: signozCoverageSummary?.source_count ?? 0,
               withRefs: signozCoverageSummary?.with_source_refs_total ?? 0,
               missing: signozCoverageSummary?.missing_source_refs_total ?? 0,
+              latest: formatTimestamp(signozCoverageSummary?.latest_received_at, params.locale, emptyFreshnessLabel),
+              age: formatFreshnessAge(signozCoverageSummary?.latest_received_at),
             })}
           </span>
         </div>