diff --git a/lib/services/campaign-grouping-service.test.ts b/lib/services/campaign-grouping-service.test.ts
index bc92fbc..e0e5d21 100644
--- a/lib/services/campaign-grouping-service.test.ts
+++ b/lib/services/campaign-grouping-service.test.ts
@@ -1,4 +1,4 @@
-import { describe, it, expect, vi } from 'vitest';
+import { describe, it, expect, vi, beforeEach } from 'vitest';
 
 // Mock postgresClient BEFORE importing the module under test.
 const queryMock = vi.fn();
@@ -11,7 +11,7 @@ vi.mock('./postgres-client', () => ({
 }));
 
 // eslint-disable-next-line import/first -- imported after vi.mock hoisting
-import { normalizeSubject, extractUrlDomain } from './campaign-grouping-service';
+import { normalizeSubject, extractUrlDomain, groupReportIntoCampaign } from './campaign-grouping-service';
 
 describe('normalizeSubject', () => {
   it('strips a single Re: prefix, lowercases, trims', () => {
@@ -48,3 +48,289 @@ describe('extractUrlDomain', () => {
     expect(extractUrlDomain('http://another.example.net')).toBe('another.example.net');
   });
 });
+
+// =============================================================================
+// groupReportIntoCampaign — mocked-DB behavior (CAMP-01, CAMP-02, D-08)
+//
+// `transactionMock` invokes its callback with a fake `client` whose `query`
+// method routes to staged rows based on a distinguishing SQL substring for
+// each of the implementation's queries (own report / own message / tier 1 /
+// own indicators / tier 2 candidates / candidate indicators / tier 3 /
+// update campaigns / update reports / insert campaign). This mirrors
+// phishing-eml-service.test.ts's `callsContaining()` discipline but resolves
+// per-call instead of asserting only after the fact, since groupReportInto
+// Campaign's control flow branches on intermediate query results.
+// =============================================================================
+
+interface MockRows {
+  ownReport?: unknown[];
+  ownMessage?: unknown[];
+  tier1?: unknown[];
+  ownIndicators?: unknown[];
+  tier2Candidates?: unknown[];
+  candidateIndicators?: unknown[];
+  tier3?: unknown[];
+  insertCampaign?: unknown[];
+}
+
+/** Records every SQL call made through the fake transaction client. */
+let clientCalls: Array<{ sql: string; params: unknown[] }> = [];
+
+function makeClient(rows: MockRows) {
+  return {
+    query: vi.fn(async (sql: string, params?: unknown[]) => {
+      clientCalls.push({ sql, params: params ?? [] });
+
+      if (sql.includes('requester_contact_id, company_id, created_at')) {
+        return { rows: rows.ownReport ?? [], rowCount: rows.ownReport?.length ?? 0 };
+      }
+      if (sql.includes('FROM messages') && sql.includes('WHERE report_id = $1')) {
+        return { rows: rows.ownMessage ?? [], rowCount: rows.ownMessage?.length ?? 0 };
+      }
+      if (sql.includes('WHERE m.message_id = $1')) {
+        return { rows: rows.tier1 ?? [], rowCount: rows.tier1?.length ?? 0 };
+      }
+      if (sql.includes('FROM indicators') && sql.includes('WHERE message_id = $1')) {
+        return { rows: rows.ownIndicators ?? [], rowCount: rows.ownIndicators?.length ?? 0 };
+      }
+      if (sql.includes('BETWEEN $2::timestamptz')) {
+        return { rows: rows.tier2Candidates ?? [], rowCount: rows.tier2Candidates?.length ?? 0 };
+      }
+      if (sql.includes('message_id = ANY')) {
+        return { rows: rows.candidateIndicators ?? [], rowCount: rows.candidateIndicators?.length ?? 0 };
+      }
+      if (sql.includes('BETWEEN $4::timestamptz')) {
+        return { rows: rows.tier3 ?? [], rowCount: rows.tier3?.length ?? 0 };
+      }
+      if (sql.includes('UPDATE campaigns')) {
+        return { rows: [], rowCount: 1 };
+      }
+      if (sql.includes('UPDATE reports SET campaign_id')) {
+        return { rows: [], rowCount: 1 };
+      }
+      if (sql.includes('INSERT INTO campaigns')) {
+        return { rows: rows.insertCampaign ?? [{ id: 'unstaged-campaign-id' }], rowCount: 1 };
+      }
+      throw new Error(`Unstaged query in test mock: ${sql}`);
+    }),
+  };
+}
+
+function callsContaining(needle: string) {
+  return clientCalls.filter((c) => c.sql.includes(needle));
+}
+
+describe('groupReportIntoCampaign', () => {
+  beforeEach(() => {
+    queryMock.mockReset();
+    transactionMock.mockReset();
+    clientCalls = [];
+  });
+
+  function stage(rows: MockRows) {
+    transactionMock.mockImplementation(async (callback: (client: unknown) => Promise<unknown>) =>
+      callback(makeClient(rows))
+    );
+  }
+
+  const REPORT_ROW = {
+    title: 'Re: Invoice Alert',
+    requester_contact_id: 5,
+    company_id: 10,
+    created_at: '2026-07-15T10:00:00Z',
+  };
+
+  it('Tier 3 match increments existing campaign report_count, updates last_seen_at, links campaign_id, and never creates a second campaign', async () => {
+    stage({
+      ownReport: [REPORT_ROW],
+      ownMessage: [],
+      tier3: [{ campaign_id: 'campaign-1', title: 'Invoice Alert' }],
+    });
+
+    const result = await groupReportIntoCampaign('report-2');
+
+    expect(result).toEqual({
+      campaignId: 'campaign-1',
+      groupMethod: 'sender_subject_client',
+      created: false,
+    });
+
+    const updateCampaignCalls = callsContaining('UPDATE campaigns');
+    expect(updateCampaignCalls).toHaveLength(1);
+    expect(updateCampaignCalls[0].sql).toContain('report_count = report_count + 1');
+    expect(updateCampaignCalls[0].sql).toContain('last_seen_at = NOW()');
+    expect(updateCampaignCalls[0].params).toEqual(['campaign-1']);
+
+    const updateReportCalls = callsContaining('UPDATE reports SET campaign_id');
+    expect(updateReportCalls).toHaveLength(1);
+    expect(updateReportCalls[0].params).toEqual(['campaign-1', 'report-2']);
+
+    expect(callsContaining('INSERT INTO campaigns')).toHaveLength(0);
+  });
+
+  it('creates exactly one new campaign when no tier matches anything', async () => {
+    stage({
+      ownReport: [REPORT_ROW],
+      ownMessage: [],
+      tier3: [],
+      insertCampaign: [{ id: 'new-campaign-id' }],
+    });
+
+    const result = await groupReportIntoCampaign('report-3');
+
+    expect(result).toEqual({
+      campaignId: 'new-campaign-id',
+      groupMethod: 'sender_subject_client',
+      created: true,
+    });
+
+    const insertCalls = callsContaining('INSERT INTO campaigns');
+    expect(insertCalls).toHaveLength(1);
+    expect(insertCalls[0].params).toEqual([
+      'sender_subject_client:5:invoice alert:10',
+      'sender_subject_client',
+    ]);
+    expect(callsContaining('UPDATE campaigns')).toHaveLength(0);
+  });
+
+  it('skipIfAlreadyGrouped:true returns null when the pre-check SELECT reports a non-null campaign_id (D-08)', async () => {
+    queryMock.mockResolvedValueOnce({ rows: [{ campaign_id: 'already-grouped' }], rowCount: 1 });
+
+    const result = await groupReportIntoCampaign('report-4', { skipIfAlreadyGrouped: true });
+
+    expect(result).toBeNull();
+    expect(transactionMock).not.toHaveBeenCalled();
+  });
+
+  it('skipIfAlreadyGrouped:true proceeds to full matching when campaign_id is null', async () => {
+    queryMock.mockResolvedValueOnce({ rows: [{ campaign_id: null }], rowCount: 1 });
+    stage({
+      ownReport: [REPORT_ROW],
+      ownMessage: [],
+      tier3: [{ campaign_id: 'campaign-9', title: 'Invoice Alert' }],
+    });
+
+    const result = await groupReportIntoCampaign('report-5', { skipIfAlreadyGrouped: true });
+
+    expect(result).toEqual({
+      campaignId: 'campaign-9',
+      groupMethod: 'sender_subject_client',
+      created: false,
+    });
+  });
+
+  it('Tier 1 (Message-ID) matches before Tier 2/3 are ever queried', async () => {
+    stage({
+      ownReport: [REPORT_ROW],
+      ownMessage: [{ id: 'own-msg-id', message_id: 'shared-message-id-123' }],
+      tier1: [{ campaign_id: 'campaign-t1' }],
+    });
+
+    const result = await groupReportIntoCampaign('report-6');
+
+    expect(result).toEqual({
+      campaignId: 'campaign-t1',
+      groupMethod: 'message_id',
+      created: false,
+    });
+    expect(callsContaining('FROM indicators')).toHaveLength(0);
+    expect(callsContaining('JOIN contacts c')).toHaveLength(0);
+  });
+
+  it('Tier 2 (attachment-hash/URL-domain + subject + sender + 24h) matches when Tier 1 finds nothing', async () => {
+    stage({
+      ownReport: [REPORT_ROW],
+      ownMessage: [{ id: 'own-msg-id', message_id: 'unique-message-id-no-other-match' }],
+      tier1: [], // own message_id matches no other already-grouped report
+      ownIndicators: [
+        { indicator_type: 'attachment_hash', value: 'hash123' },
+        { indicator_type: 'sender', value: 'attacker@evil.example.com' },
+      ],
+      tier2Candidates: [
+        {
+          report_id: 'other-report',
+          campaign_id: 'campaign-t2',
+          title: 'Invoice Alert',
+          message_id: 'other-msg-id',
+        },
+      ],
+      candidateIndicators: [
+        { message_id: 'other-msg-id', indicator_type: 'attachment_hash', value: 'hash123' },
+        { message_id: 'other-msg-id', indicator_type: 'sender', value: 'attacker@evil.example.com' },
+      ],
+    });
+
+    const result = await groupReportIntoCampaign('report-7');
+
+    expect(result).toEqual({
+      campaignId: 'campaign-t2',
+      groupMethod: 'attachment_or_url',
+      created: false,
+    });
+  });
+
+  it('extracts URL-domain (not raw URL string) when matching Tier 2 via url indicators', async () => {
+    stage({
+      ownReport: [REPORT_ROW],
+      ownMessage: [{ id: 'own-msg-id', message_id: 'unique-message-id-no-other-match-2' }],
+      tier1: [],
+      ownIndicators: [
+        { indicator_type: 'url', value: 'https://evil.example.com/phish?x=1' },
+        { indicator_type: 'sender', value: 'attacker@evil.example.com' },
+      ],
+      tier2Candidates: [
+        {
+          report_id: 'other-report',
+          campaign_id: 'campaign-t2-url',
+          title: 'Invoice Alert',
+          message_id: 'other-msg-id-2',
+        },
+      ],
+      candidateIndicators: [
+        // Different raw URL string, same domain — must match via extractUrlDomain, not exact string equality.
+        { message_id: 'other-msg-id-2', indicator_type: 'url', value: 'https://evil.example.com/different-path' },
+        { message_id: 'other-msg-id-2', indicator_type: 'sender', value: 'attacker@evil.example.com' },
+      ],
+    });
+
+    const result = await groupReportIntoCampaign('report-8');
+
+    expect(result).toEqual({
+      campaignId: 'campaign-t2-url',
+      groupMethod: 'attachment_or_url',
+      created: false,
+    });
+  });
+
+  it('re-running on an already-grouped report whose own messages/indicators would otherwise self-match does not increment report_count a second time (self-exclusion)', async () => {
+    // Own message_id and own indicators exist (this report has already been
+    // through parseAndStoreMessage), but NO other report shares them — the
+    // only thing that *could* match is this report's own row, which every
+    // tier query excludes via `r.id != <this report's id>`.
+    stage({
+      ownReport: [REPORT_ROW],
+      ownMessage: [{ id: 'own-msg-id', message_id: 'self-message-id' }],
+      tier1: [], // self-exclusion means the report's own linked campaign never surfaces here
+      ownIndicators: [
+        { indicator_type: 'attachment_hash', value: 'self-hash' },
+        { indicator_type: 'sender', value: 'attacker@evil.example.com' },
+      ],
+      tier2Candidates: [], // no other report in the 24h window
+      tier3: [], // no other report matches sender+subject+client either
+      insertCampaign: [{ id: 'fresh-campaign-id' }],
+    });
+
+    const result = await groupReportIntoCampaign('already-grouped-report');
+
+    // Tier 1's own message_id exists, so the new campaign is created with
+    // the strongest available key (message_id) — see computeTier1Key.
+    expect(result).toEqual({
+      campaignId: 'fresh-campaign-id',
+      groupMethod: 'message_id',
+      created: true,
+    });
+    // The critical assertion: no existing campaign's report_count is bumped
+    // a second time for this report re-run.
+    expect(callsContaining('UPDATE campaigns')).toHaveLength(0);
+  });
+});
diff --git a/lib/services/campaign-grouping-service.ts b/lib/services/campaign-grouping-service.ts
index 399d769..39ba1df 100644
--- a/lib/services/campaign-grouping-service.ts
+++ b/lib/services/campaign-grouping-service.ts
@@ -50,3 +50,340 @@ export function extractUrlDomain(url: string): string | null {
     return null;
   }
 }
+
+// =============================================================================
+// Orchestration — groupReportIntoCampaign (mirrors detectPhishingTicket)
+// =============================================================================
+
+export interface GroupReportResult {
+  campaignId: string;
+  groupMethod: 'message_id' | 'attachment_or_url' | 'sender_subject_client';
+  created: boolean;
+}
+
+interface OwnReportRow {
+  title: string | null;
+  requester_contact_id: number | null;
+  company_id: number | null;
+  created_at: string;
+}
+
+interface OwnMessageRow {
+  id: string;
+  message_id: string | null;
+}
+
+interface IndicatorRow {
+  indicator_type: string;
+  value: string;
+}
+
+interface CandidateIndicatorRow extends IndicatorRow {
+  message_id: string;
+}
+
+interface Tier2CandidateRow {
+  report_id: string;
+  campaign_id: string;
+  title: string | null;
+  message_id: string;
+}
+
+/** Builds a `message_id:...` key — the strongest available signal (Tier 1). */
+function computeTier1Key(messageId: string | null): string | null {
+  return messageId ? `message_id:${messageId}` : null;
+}
+
+/** Builds an `attachment_or_url:...` key from own indicators + subject + sender (Tier 2). */
+function computeTier2Key(
+  attachmentHashes: string[],
+  urlDomains: string[],
+  normalizedSubject: string,
+  senderValue: string | null
+): string | null {
+  if (!senderValue || !normalizedSubject) return null;
+  if (attachmentHashes.length === 0 && urlDomains.length === 0) return null;
+  const keyParts = [...attachmentHashes, ...urlDomains].sort();
+  return `attachment_or_url:${keyParts.join(',')}:${normalizedSubject}:${senderValue}`;
+}
+
+/** Builds a `sender_subject_client:...` key from sender + subject + company (Tier 3). */
+function computeTier3Key(
+  requesterContactId: number | null,
+  normalizedSubject: string,
+  companyId: number | null
+): string | null {
+  if (!requesterContactId || !normalizedSubject || !companyId) return null;
+  return `sender_subject_client:${requesterContactId}:${normalizedSubject}:${companyId}`;
+}
+
+/**
+ * Shared entry point called by the webhook path, the cron sweep, and the
+ * on-demand `/analyze` route. Looks up the report's own signal (message,
+ * indicators, requester/company), tries Tier 1 -> Tier 2 -> Tier 3 matching
+ * queries in order inside a single transaction (Pitfall 2 — `campaigns.
+ * campaign_key` has no UNIQUE constraint), and either links the report to an
+ * existing campaign (bumping report_count/last_seen_at, CAMP-02) or inserts a
+ * new campaigns row.
+ *
+ * D-08: `opts.skipIfAlreadyGrouped` short-circuits (returns null) when the
+ * report is already linked — used by the automatic webhook/cron path to
+ * avoid redundant work on every re-fire/sweep pass. The `/analyze` route
+ * omits this option so it always re-runs full tiered matching (it may
+ * upgrade a Tier-3-only report to Tier 1 after `parseAndStoreMessage` has
+ * just populated `messages`/`indicators` for the first time).
+ *
+ * D-04: never merges campaigns — attaches to the first/best tiered match
+ * found, or creates a new campaign. Multi-campaign-merge logic is explicitly
+ * out of scope this phase.
+ */
+export async function groupReportIntoCampaign(
+  reportId: string,
+  opts?: { skipIfAlreadyGrouped?: boolean }
+): Promise<GroupReportResult | null> {
+  try {
+    if (opts?.skipIfAlreadyGrouped) {
+      const existing = await postgresClient.query<{ campaign_id: string | null }>(
+        `SELECT campaign_id::text AS campaign_id FROM reports WHERE id = $1`,
+        [reportId]
+      );
+      if (existing.rows[0]?.campaign_id) {
+        return null; // already grouped, short-circuit (D-08)
+      }
+    }
+
+    return await postgresClient.transaction(async (client) => {
+      const ownReportRes = await client.query<OwnReportRow>(
+        `SELECT title, requester_contact_id, company_id, created_at
+           FROM reports
+          WHERE id = $1`,
+        [reportId]
+      );
+      const ownReport = ownReportRes.rows[0];
+      if (!ownReport) {
+        throw new Error(`groupReportIntoCampaign: report ${reportId} not found`);
+      }
+
+      const normalizedSubject = normalizeSubject(ownReport.title);
+
+      // Own messages row, if `parseAndStoreMessage` has already run for this
+      // report (D-07 — not the case for the automatic webhook/cron path
+      // until an explicit /analyze call has happened at least once).
+      const ownMessageRes = await client.query<OwnMessageRow>(
+        `SELECT id::text AS id, message_id
+           FROM messages
+          WHERE report_id = $1
+          LIMIT 1`,
+        [reportId]
+      );
+      const ownMessage = ownMessageRes.rows[0] ?? null;
+
+      let matchCampaignId: string | null = null;
+      let matchGroupMethod: GroupReportResult['groupMethod'] | null = null;
+
+      // ---------------------------------------------------------------------
+      // Tier 1: Message-ID. Self-exclusion (`r.id != $2`) is REQUIRED — without
+      // it this query would trivially match the report's own messages row
+      // against itself, double-incrementing its own already-linked campaign
+      // on every re-run (plan-checker finding).
+      // ---------------------------------------------------------------------
+      if (ownMessage?.message_id) {
+        const tier1 = await client.query<{ campaign_id: string }>(
+          `SELECT r.campaign_id::text AS campaign_id
+             FROM messages m
+             JOIN reports r ON r.id = m.report_id
+            WHERE m.message_id = $1
+              AND r.campaign_id IS NOT NULL
+              AND r.id != $2
+            ORDER BY r.created_at ASC
+            LIMIT 1`,
+          [ownMessage.message_id, reportId]
+        );
+        if (tier1.rows[0]?.campaign_id) {
+          matchCampaignId = tier1.rows[0].campaign_id;
+          matchGroupMethod = 'message_id';
+        }
+      }
+
+      // ---------------------------------------------------------------------
+      // Tier 2: attachment-hash / URL-domain + normalized subject + sender,
+      // within a 24h window (D-02). Only reachable if the own report has its
+      // own indicators (i.e. parseAndStoreMessage already ran for it).
+      // Self-exclusion (`r.id != $1`) required for the same reason as Tier 1.
+      // ---------------------------------------------------------------------
+      let ownAttachmentHashes: string[] = [];
+      let ownUrlDomains: string[] = [];
+      let ownSenderValue: string | null = null;
+
+      if (!matchCampaignId && ownMessage) {
+        const ownIndicatorsRes = await client.query<IndicatorRow>(
+          `SELECT indicator_type, value
+             FROM indicators
+            WHERE message_id = $1`,
+          [ownMessage.id]
+        );
+        ownAttachmentHashes = ownIndicatorsRes.rows
+          .filter((i) => i.indicator_type === 'attachment_hash')
+          .map((i) => i.value);
+        ownUrlDomains = ownIndicatorsRes.rows
+          .filter((i) => i.indicator_type === 'url')
+          .map((i) => extractUrlDomain(i.value))
+          .filter((d): d is string => d !== null);
+        ownSenderValue =
+          ownIndicatorsRes.rows.find((i) => i.indicator_type === 'sender')?.value ?? null;
+
+        if (
+          (ownAttachmentHashes.length > 0 || ownUrlDomains.length > 0) &&
+          ownSenderValue &&
+          normalizedSubject
+        ) {
+          const tier2Candidates = await client.query<Tier2CandidateRow>(
+            `SELECT r.id::text AS report_id, r.campaign_id::text AS campaign_id, r.title,
+                    m.id::text AS message_id
+               FROM messages m
+               JOIN reports r ON r.id = m.report_id
+              WHERE r.campaign_id IS NOT NULL
+                AND r.id != $1
+                AND r.created_at BETWEEN $2::timestamptz - INTERVAL '24 hours'
+                                     AND $2::timestamptz + INTERVAL '24 hours'`,
+            [reportId, ownReport.created_at]
+          );
+
+          if (tier2Candidates.rows.length > 0) {
+            const candidateMessageIds = tier2Candidates.rows.map((c) => c.message_id);
+            const candidateIndicatorsRes = await client.query<CandidateIndicatorRow>(
+              `SELECT message_id::text AS message_id, indicator_type, value
+                 FROM indicators
+                WHERE message_id = ANY($1::uuid[])`,
+              [candidateMessageIds]
+            );
+            const indicatorsByMessage = new Map<string, CandidateIndicatorRow[]>();
+            for (const ind of candidateIndicatorsRes.rows) {
+              const arr = indicatorsByMessage.get(ind.message_id) ?? [];
+              arr.push(ind);
+              indicatorsByMessage.set(ind.message_id, arr);
+            }
+
+            for (const candidate of tier2Candidates.rows) {
+              if (normalizeSubject(candidate.title) !== normalizedSubject) continue;
+              const candidateIndicators = indicatorsByMessage.get(candidate.message_id) ?? [];
+              const candidateSender = candidateIndicators.find(
+                (i) => i.indicator_type === 'sender'
+              )?.value;
+              if (candidateSender !== ownSenderValue) continue;
+              const candidateHashes = candidateIndicators
+                .filter((i) => i.indicator_type === 'attachment_hash')
+                .map((i) => i.value);
+              const candidateDomains = candidateIndicators
+                .filter((i) => i.indicator_type === 'url')
+                .map((i) => extractUrlDomain(i.value))
+                .filter((d): d is string => d !== null);
+              const hashMatch = ownAttachmentHashes.some((h) => candidateHashes.includes(h));
+              const domainMatch = ownUrlDomains.some((d) => candidateDomains.includes(d));
+              if (hashMatch || domainMatch) {
+                matchCampaignId = candidate.campaign_id;
+                matchGroupMethod = 'attachment_or_url';
+                break;
+              }
+            }
+          }
+        }
+      }
+
+      // ---------------------------------------------------------------------
+      // Tier 3: sender + normalizeSubject(title) + client + 24h window
+      // (D-02). Joins reports.requester_contact_id -> contacts (Pitfall 5 —
+      // NOT `contact_id`). Self-exclusion (`r.id != $3`) required for the
+      // same reason as Tiers 1-2.
+      // ---------------------------------------------------------------------
+      if (!matchCampaignId && ownReport.requester_contact_id && ownReport.company_id && normalizedSubject) {
+        const tier3 = await client.query<{ campaign_id: string; title: string | null }>(
+          `SELECT r.campaign_id::text AS campaign_id, r.title
+             FROM reports r
+             JOIN contacts c ON c.id = r.requester_contact_id
+            WHERE r.requester_contact_id = $1
+              AND r.company_id = $2
+              AND r.campaign_id IS NOT NULL
+              AND r.id != $3
+              AND r.created_at BETWEEN $4::timestamptz - INTERVAL '24 hours'
+                                   AND $4::timestamptz + INTERVAL '24 hours'
+            ORDER BY r.created_at ASC`,
+          [ownReport.requester_contact_id, ownReport.company_id, reportId, ownReport.created_at]
+        );
+        const match = tier3.rows.find((r) => normalizeSubject(r.title) === normalizedSubject);
+        if (match) {
+          matchCampaignId = match.campaign_id;
+          matchGroupMethod = 'sender_subject_client';
+        }
+      }
+
+      // ---------------------------------------------------------------------
+      // Find-or-create against `campaigns` (CAMP-02).
+      // ---------------------------------------------------------------------
+      if (matchCampaignId && matchGroupMethod) {
+        await client.query(
+          `UPDATE campaigns
+              SET report_count = report_count + 1, last_seen_at = NOW(), updated_at = NOW()
+            WHERE id = $1`,
+          [matchCampaignId]
+        );
+        await client.query(
+          `UPDATE reports SET campaign_id = $1, updated_at = NOW() WHERE id = $2`,
+          [matchCampaignId, reportId]
+        );
+        return { campaignId: matchCampaignId, groupMethod: matchGroupMethod, created: false };
+      }
+
+      // No match on any tier — create a new campaign. Prefer the strongest
+      // available key (Tier 1 > Tier 2 > Tier 3) so future duplicates of THIS
+      // report can match it; do NOT set/transition campaigns.status (leave
+      // migration default 'open' — Phase 19/20's concern).
+      const tier1Key = computeTier1Key(ownMessage?.message_id ?? null);
+      const tier2Key = computeTier2Key(
+        ownAttachmentHashes,
+        ownUrlDomains,
+        normalizedSubject,
+        ownSenderValue
+      );
+      const tier3Key = computeTier3Key(
+        ownReport.requester_contact_id,
+        normalizedSubject,
+        ownReport.company_id
+      );
+
+      let newCampaignKey: string;
+      let newGroupMethod: GroupReportResult['groupMethod'];
+      if (tier1Key) {
+        newCampaignKey = tier1Key;
+        newGroupMethod = 'message_id';
+      } else if (tier2Key) {
+        newCampaignKey = tier2Key;
+        newGroupMethod = 'attachment_or_url';
+      } else if (tier3Key) {
+        newCampaignKey = tier3Key;
+        newGroupMethod = 'sender_subject_client';
+      } else {
+        newCampaignKey = `report:${reportId}`;
+        newGroupMethod = 'sender_subject_client';
+      }
+
+      const newCampaign = await client.query<{ id: string }>(
+        `INSERT INTO campaigns (campaign_key, group_method, first_seen_at, last_seen_at, report_count)
+         VALUES ($1, $2, NOW(), NOW(), 1)
+         RETURNING id::text AS id`,
+        [newCampaignKey, newGroupMethod]
+      );
+      const newCampaignId = newCampaign.rows[0].id;
+
+      await client.query(
+        `UPDATE reports SET campaign_id = $1, updated_at = NOW() WHERE id = $2`,
+        [newCampaignId, reportId]
+      );
+
+      return { campaignId: newCampaignId, groupMethod: newGroupMethod, created: true };
+    });
+  } catch (error) {
+    console.error('[CAMPAIGN-GROUPING] Failed to group report into campaign', reportId, error);
+    throw error;
+  }
+}