diff --git a/lib/services/remediation-service.test.ts b/lib/services/remediation-service.test.ts
index ca81a56..c21b5d9 100644
--- a/lib/services/remediation-service.test.ts
+++ b/lib/services/remediation-service.test.ts
@@ -16,8 +16,10 @@ vi.mock('./phishing-audit', () => ({
 }));
 
 const generateAndPostAcknowledgmentMock = vi.fn();
+const generateAndPostAccidentalReportNoteMock = vi.fn();
 vi.mock('./triage-note-service', () => ({
   generateAndPostAcknowledgment: (...args: unknown[]) => generateAndPostAcknowledgmentMock(...args),
+  generateAndPostAccidentalReportNote: (...args: unknown[]) => generateAndPostAccidentalReportNoteMock(...args),
 }));
 
 // eslint-disable-next-line import/first -- imported after vi.mock hoisting
@@ -25,6 +27,7 @@ import {
   approveRemediationActions,
   remediateApprovedActions,
   markCampaignFalsePositive,
+  markCampaignAccidentalReport,
   autoPostAcknowledgment,
   RemediationValidationError,
   RemediationConflictError,
@@ -97,6 +100,8 @@ beforeEach(() => {
   writeAuditEventMock.mockResolvedValue('audit-id');
   generateAndPostAcknowledgmentMock.mockReset();
   generateAndPostAcknowledgmentMock.mockResolvedValue({ noteText: 'thanks', tickets: [] });
+  generateAndPostAccidentalReportNoteMock.mockReset();
+  generateAndPostAccidentalReportNoteMock.mockResolvedValue({ noteText: 'no action needed', tickets: [] });
   clientCalls = [];
 });
 
@@ -346,6 +351,79 @@ describe('markCampaignFalsePositive', () => {
   });
 });
 
+// =============================================================================
+// markCampaignAccidentalReport (D-04 guard, quick task 260717-v6c)
+// =============================================================================
+
+describe('markCampaignAccidentalReport', () => {
+  it('throws RemediationConflictError when any remediation_actions row has status approved/completed', async () => {
+    stage({
+      guardRows: [{ id: 'action-1' }],
+    });
+
+    await expect(
+      markCampaignAccidentalReport('campaign-1', 'operator@example.com')
+    ).rejects.toThrow(RemediationConflictError);
+    expect(callsContaining('UPDATE campaigns SET status')).toHaveLength(0);
+    expect(generateAndPostAccidentalReportNoteMock).not.toHaveBeenCalled();
+  });
+
+  it('sets campaigns.status to accidental_report and writes one audit row when there are no approved/completed rows', async () => {
+    stage({
+      guardRows: [],
+      campaign: [{ status: 'open' }],
+    });
+
+    const result = await markCampaignAccidentalReport('campaign-1', 'operator@example.com', 'reported by mistake');
+
+    expect(callsContaining('UPDATE campaigns SET status')).toHaveLength(1);
+    expect(writeAuditEventMock).toHaveBeenCalledTimes(1);
+    const [auditArgs] = writeAuditEventMock.mock.calls[0];
+    expect(auditArgs).toMatchObject({
+      campaignId: 'campaign-1',
+      eventType: 'campaign_marked_accidental_report',
+      payload: { previousStatus: 'open', reason: 'reported by mistake' },
+    });
+    expect(result).toMatchObject({
+      campaignId: 'campaign-1',
+      status: 'accidental_report',
+      notePosted: true,
+    });
+    expect(generateAndPostAccidentalReportNoteMock).toHaveBeenCalledTimes(1);
+    expect(generateAndPostAccidentalReportNoteMock).toHaveBeenCalledWith('campaign-1');
+  });
+
+  it('throws RemediationValidationError when the campaign does not exist', async () => {
+    stage({
+      guardRows: [],
+      campaign: [],
+    });
+
+    await expect(
+      markCampaignAccidentalReport('campaign-missing', 'operator@example.com')
+    ).rejects.toThrow(RemediationValidationError);
+    expect(generateAndPostAccidentalReportNoteMock).not.toHaveBeenCalled();
+  });
+
+  it('still returns the committed status change with notePosted:false and noteError set when the note post fails', async () => {
+    stage({
+      guardRows: [],
+      campaign: [{ status: 'open' }],
+    });
+    generateAndPostAccidentalReportNoteMock.mockRejectedValueOnce(new Error('Autotask unavailable'));
+
+    const result = await markCampaignAccidentalReport('campaign-1', 'operator@example.com');
+
+    expect(callsContaining('UPDATE campaigns SET status')).toHaveLength(1);
+    expect(result).toMatchObject({
+      campaignId: 'campaign-1',
+      status: 'accidental_report',
+      notePosted: false,
+      noteError: 'Autotask unavailable',
+    });
+  });
+});
+
 // =============================================================================
 // autoPostAcknowledgment (AUTOGATE-03 gap closure — CR-01 / WR-01)
 // =============================================================================
diff --git a/lib/services/triage-note-service.test.ts b/lib/services/triage-note-service.test.ts
index ee809c3..ef673da 100644
--- a/lib/services/triage-note-service.test.ts
+++ b/lib/services/triage-note-service.test.ts
@@ -36,7 +36,11 @@ vi.mock('./triage-note-format', async (importOriginal) => {
 });
 
 // eslint-disable-next-line import/first -- imported after vi.mock hoisting
-import { generateAndPostTriageNote, generateAndPostAcknowledgment } from './triage-note-service';
+import {
+  generateAndPostTriageNote,
+  generateAndPostAcknowledgment,
+  generateAndPostAccidentalReportNote,
+} from './triage-note-service';
 
 interface MockRows {
   reports?: unknown[];
@@ -323,3 +327,69 @@ describe('generateAndPostAcknowledgment', () => {
     expect(createEntityMock).not.toHaveBeenCalled();
   });
 });
+
+describe('generateAndPostAccidentalReportNote', () => {
+  it('posts a customer-visible (noteType 18, publish 1) reviewed-report note to every linked ticket', async () => {
+    stage({
+      reports: [
+        report({ id: 'r1', ticket_id: '1001' }),
+        report({ id: 'r2', ticket_id: '1002' }),
+      ],
+    });
+
+    const result = await generateAndPostAccidentalReportNote('campaign-1');
+
+    expect(createEntityMock).toHaveBeenCalledTimes(2);
+    for (const [entityName, data] of createEntityMock.mock.calls) {
+      expect(entityName).toBe('TicketNotes');
+      expect(data).toMatchObject({
+        description: result.noteText,
+        noteType: 18,
+        publish: 1,
+      });
+      expect(typeof (data as { ticketID: unknown }).ticketID).toBe('number');
+    }
+    expect(createEntityMock.mock.calls.map((c) => (c[1] as { ticketID: number }).ticketID)).toEqual([1001, 1002]);
+    expect(result.tickets).toEqual([
+      { ticketId: '1001', posted: true },
+      { ticketId: '1002', posted: true },
+    ]);
+    expect(result.noteText.length).toBeGreaterThan(0);
+    // Fixed template, zero evidence/URL/classification interpolation (T-23-01).
+    expect(result.noteText).not.toContain('Blast Radius');
+    expect(result.noteText).not.toContain('Recommended Actions');
+  });
+
+  it('isolates a single ticket write failure without aborting the remaining writes', async () => {
+    stage({
+      reports: [
+        report({ id: 'r1', ticket_id: '1001' }),
+        report({ id: 'r2', ticket_id: '1002' }),
+        report({ id: 'r3', ticket_id: '1003' }),
+      ],
+    });
+    createEntityMock
+      .mockResolvedValueOnce({ id: 1 })
+      .mockRejectedValueOnce(new Error('Autotask API unavailable'))
+      .mockResolvedValueOnce({ id: 3 });
+
+    const result = await generateAndPostAccidentalReportNote('campaign-1');
+
+    expect(createEntityMock).toHaveBeenCalledTimes(3);
+    expect(result.tickets[0]).toEqual({ ticketId: '1001', posted: true });
+    expect(result.tickets[1]).toMatchObject({ ticketId: '1002', posted: false });
+    expect(result.tickets[1].error).toBe('Autotask API unavailable');
+    expect(result.tickets[2]).toEqual({ ticketId: '1003', posted: true });
+  });
+
+  it('resolves { noteText, tickets: [] } for a campaign with zero linked reports, without throwing', async () => {
+    stage({ reports: [] });
+
+    const result = await generateAndPostAccidentalReportNote('campaign-empty');
+
+    expect(result.tickets).toEqual([]);
+    expect(typeof result.noteText).toBe('string');
+    expect(result.noteText.length).toBeGreaterThan(0);
+    expect(createEntityMock).not.toHaveBeenCalled();
+  });
+});