diff --git a/server/utils/adminAlerts.js b/server/utils/adminAlerts.js
index 90999f6..3a24113 100644
--- a/server/utils/adminAlerts.js
+++ b/server/utils/adminAlerts.js
@@ -257,4 +257,49 @@ export async function detectPendingTagSuggestions() {
   }
 }
 
-// Aggregator lands in task 8.
+const DETECTORS = [
+  detectSlackInviteFailed,
+  detectNoSlackHandleAfterWeek,
+  detectStuckPendingPayment,
+  detectSuspendedMembers,
+  detectPreRegistrantSelectedNotInvited,
+  detectPreRegistrantExpired,
+  detectDraftEventsImminent,
+  detectEventsNearCapacity,
+  detectPendingTagSuggestions
+]
+
+function signatureForAlert(alert) {
+  if (Array.isArray(alert.signatureIds)) {
+    return computeSignature(alert.signatureIds)
+  }
+  return computeSignature(alert.items.map((item) => item.id))
+}
+
+export async function computeAllAlerts(adminId) {
+  await connectDB()
+
+  const [rawAlerts, dismissals] = await Promise.all([
+    Promise.all(DETECTORS.map((fn) => fn())),
+    AdminAlertDismissal.find({ adminId }).lean()
+  ])
+
+  const dismissedByType = new Map()
+  for (const d of dismissals) {
+    dismissedByType.set(d.alertType, d.signature)
+  }
+
+  const result = []
+  for (const alert of rawAlerts) {
+    if (!alert.items || alert.items.length === 0) continue
+    const signature = signatureForAlert(alert)
+    if (dismissedByType.get(alert.type) === signature) continue
+    const { signatureIds, ...publicFields } = alert
+    result.push({
+      ...publicFields,
+      count: alert.items.length,
+      signature
+    })
+  }
+  return result
+}
diff --git a/tests/server/utils/adminAlerts.test.js b/tests/server/utils/adminAlerts.test.js
index 1462bc0..aae36e2 100644
--- a/tests/server/utils/adminAlerts.test.js
+++ b/tests/server/utils/adminAlerts.test.js
@@ -391,3 +391,107 @@ describe('adminAlerts module shell', () => {
     })
   })
 })
+
+import { computeAllAlerts } from '../../../server/utils/adminAlerts.js'
+import AdminAlertDismissal from '../../../server/models/adminAlertDismissal.js'
+
+describe('computeAllAlerts aggregator', () => {
+  beforeEach(() => {
+    vi.clearAllMocks()
+    // Default: every detector returns empty
+    Member.find.mockReturnValue({
+      select: vi.fn().mockReturnValue({ lean: vi.fn().mockResolvedValue([]) })
+    })
+    Event.find.mockReturnValue({
+      select: vi.fn().mockReturnValue({ lean: vi.fn().mockResolvedValue([]) })
+    })
+    PreRegistration.find.mockReturnValue({
+      select: vi.fn().mockReturnValue({ lean: vi.fn().mockResolvedValue([]) })
+    })
+    TagSuggestion.find.mockReturnValue({
+      select: vi.fn().mockReturnValue({ lean: vi.fn().mockResolvedValue([]) })
+    })
+    AdminAlertDismissal.find.mockReturnValue({
+      lean: vi.fn().mockResolvedValue([])
+    })
+  })
+
+  it('returns an empty list when nothing matches', async () => {
+    const alerts = await computeAllAlerts('admin-1')
+    expect(alerts).toEqual([])
+  })
+
+  it('returns alerts that have items and have not been dismissed', async () => {
+    Member.find.mockImplementation((query) => {
+      if (query.slackInviteStatus === 'failed') {
+        return { select: vi.fn().mockReturnValue({ lean: vi.fn().mockResolvedValue([
+          { _id: 'm1', name: 'Alex', email: 'alex@example.com' }
+        ]) }) }
+      }
+      return { select: vi.fn().mockReturnValue({ lean: vi.fn().mockResolvedValue([]) }) }
+    })
+
+    const alerts = await computeAllAlerts('admin-1')
+    expect(alerts).toHaveLength(1)
+    expect(alerts[0].type).toBe('slack_invite_failed')
+    expect(alerts[0].signature).toMatch(/^[a-f0-9]+$/)
+  })
+
+  it('hides alerts whose signature matches an existing dismissal', async () => {
+    Member.find.mockImplementation((query) => {
+      if (query.slackInviteStatus === 'failed') {
+        return { select: vi.fn().mockReturnValue({ lean: vi.fn().mockResolvedValue([
+          { _id: 'm1', name: 'Alex', email: 'alex@example.com' }
+        ]) }) }
+      }
+      return { select: vi.fn().mockReturnValue({ lean: vi.fn().mockResolvedValue([]) }) }
+    })
+
+    const sig = computeSignature(['m1'])
+    AdminAlertDismissal.find.mockReturnValue({
+      lean: vi.fn().mockResolvedValue([
+        { adminId: 'admin-1', alertType: 'slack_invite_failed', signature: sig }
+      ])
+    })
+
+    const alerts = await computeAllAlerts('admin-1')
+    expect(alerts).toEqual([])
+  })
+
+  it('shows an alert again when the underlying set changes', async () => {
+    Member.find.mockImplementation((query) => {
+      if (query.slackInviteStatus === 'failed') {
+        return { select: vi.fn().mockReturnValue({ lean: vi.fn().mockResolvedValue([
+          { _id: 'm1', name: 'Alex', email: 'alex@example.com' },
+          { _id: 'm2', name: 'Bea', email: 'bea@example.com' }
+        ]) }) }
+      }
+      return { select: vi.fn().mockReturnValue({ lean: vi.fn().mockResolvedValue([]) }) }
+    })
+
+    const staleSig = computeSignature(['m1']) // dismissal was for the old single-member state
+    AdminAlertDismissal.find.mockReturnValue({
+      lean: vi.fn().mockResolvedValue([
+        { adminId: 'admin-1', alertType: 'slack_invite_failed', signature: staleSig }
+      ])
+    })
+
+    const alerts = await computeAllAlerts('admin-1')
+    expect(alerts).toHaveLength(1)
+    expect(alerts[0].count).toBe(2)
+  })
+
+  it('uses signatureIds for tag_suggestions_pending', async () => {
+    TagSuggestion.find.mockReturnValue({
+      select: vi.fn().mockReturnValue({ lean: vi.fn().mockResolvedValue([
+        { _id: 't1' }, { _id: 't2' }
+      ]) })
+    })
+
+    const alerts = await computeAllAlerts('admin-1')
+    const tagAlert = alerts.find((a) => a.type === 'tag_suggestions_pending')
+    expect(tagAlert.signature).toBe(computeSignature(['t1', 't2']))
+    // The synthetic item id should not appear in the signature
+    expect(tagAlert.signature).not.toBe(computeSignature(['tag-suggestions']))
+  })
+})