diff --git a/server/utils/adminAlerts.js b/server/utils/adminAlerts.js
new file mode 100644
index 0000000..8b5cb17
--- /dev/null
+++ b/server/utils/adminAlerts.js
@@ -0,0 +1,39 @@
+import { createHash } from 'node:crypto'
+import Member from '../models/member.js'
+import Event from '../models/event.js'
+import PreRegistration from '../models/preRegistration.js'
+import TagSuggestion from '../models/tagSuggestion.js'
+import AdminAlertDismissal, { ADMIN_ALERT_TYPES } from '../models/adminAlertDismissal.js'
+import { connectDB } from './mongoose.js'
+
+export const ALERT_THRESHOLDS = {
+  NO_SLACK_DAYS: 7,
+  STUCK_PAYMENT_DAYS: 7,
+  PREREG_SELECTED_DAYS: 3,
+  DRAFT_IMMINENT_DAYS: 14,
+  NEAR_CAPACITY_RATIO: 0.8
+}
+
+const DAY_MS = 24 * 60 * 60 * 1000
+
+function daysAgo(days) {
+  return new Date(Date.now() - days * DAY_MS)
+}
+
+function daysSince(date) {
+  if (!date) return null
+  return Math.floor((Date.now() - new Date(date).getTime()) / DAY_MS)
+}
+
+export function computeSignature(ids) {
+  const normalized = ids
+    .map((id) => (id == null ? '' : String(id)))
+    .sort()
+  const hash = createHash('sha1')
+  hash.update(JSON.stringify(normalized))
+  return hash.digest('hex')
+}
+
+// Alert functions land here in tasks 4–7.
+
+// Aggregator lands in task 8.
diff --git a/tests/server/utils/adminAlerts.test.js b/tests/server/utils/adminAlerts.test.js
new file mode 100644
index 0000000..bbcea8c
--- /dev/null
+++ b/tests/server/utils/adminAlerts.test.js
@@ -0,0 +1,86 @@
+import { describe, it, expect, vi, beforeEach } from 'vitest'
+
+vi.mock('../../../server/utils/mongoose.js', () => ({
+  connectDB: vi.fn()
+}))
+
+vi.mock('../../../server/models/member.js', () => ({
+  default: {
+    find: vi.fn(),
+    countDocuments: vi.fn()
+  }
+}))
+
+vi.mock('../../../server/models/event.js', () => ({
+  default: {
+    find: vi.fn()
+  }
+}))
+
+vi.mock('../../../server/models/preRegistration.js', () => ({
+  default: {
+    find: vi.fn()
+  }
+}))
+
+vi.mock('../../../server/models/tagSuggestion.js', () => ({
+  default: {
+    find: vi.fn()
+  }
+}))
+
+vi.mock('../../../server/models/adminAlertDismissal.js', () => ({
+  default: {
+    find: vi.fn()
+  },
+  ADMIN_ALERT_TYPES: [
+    'slack_invite_failed',
+    'no_slack_handle_week',
+    'stuck_pending_payment',
+    'member_suspended',
+    'preregistrant_selected_not_invited',
+    'preregistrant_expired',
+    'event_draft_imminent',
+    'event_near_capacity',
+    'tag_suggestions_pending'
+  ]
+}))
+
+import { ALERT_THRESHOLDS, computeSignature } from '../../../server/utils/adminAlerts.js'
+
+describe('adminAlerts module shell', () => {
+  describe('ALERT_THRESHOLDS', () => {
+    it('exposes the four documented thresholds', () => {
+      expect(ALERT_THRESHOLDS.NO_SLACK_DAYS).toBe(7)
+      expect(ALERT_THRESHOLDS.STUCK_PAYMENT_DAYS).toBe(7)
+      expect(ALERT_THRESHOLDS.PREREG_SELECTED_DAYS).toBe(3)
+      expect(ALERT_THRESHOLDS.DRAFT_IMMINENT_DAYS).toBe(14)
+      expect(ALERT_THRESHOLDS.NEAR_CAPACITY_RATIO).toBe(0.8)
+    })
+  })
+
+  describe('computeSignature', () => {
+    it('returns a hex string', () => {
+      const sig = computeSignature(['a', 'b', 'c'])
+      expect(typeof sig).toBe('string')
+      expect(sig).toMatch(/^[a-f0-9]+$/)
+    })
+
+    it('is order-independent', () => {
+      expect(computeSignature(['a', 'b', 'c'])).toBe(computeSignature(['c', 'a', 'b']))
+    })
+
+    it('changes when membership changes', () => {
+      expect(computeSignature(['a', 'b'])).not.toBe(computeSignature(['a', 'b', 'c']))
+    })
+
+    it('returns a stable empty-set signature', () => {
+      expect(computeSignature([])).toBe(computeSignature([]))
+    })
+
+    it('coerces non-string ids to strings', () => {
+      expect(computeSignature([{ toString: () => 'x' }, 'y']))
+        .toBe(computeSignature(['x', 'y']))
+    })
+  })
+})