diff --git a/lib/services/triage-note-format.test.ts b/lib/services/triage-note-format.test.ts
new file mode 100644
index 0000000..0ad5a73
--- /dev/null
+++ b/lib/services/triage-note-format.test.ts
@@ -0,0 +1,104 @@
+import { describe, it, expect } from 'vitest';
+import { formatTriageNote, type TriageNoteEvidence } from './triage-note-format';
+import type { BlastRadiusResult } from './mimecast-blast-radius';
+
+function baseEvidence(overrides: Partial<TriageNoteEvidence> = {}): TriageNoteEvidence {
+  return {
+    campaignId: 'campaign-1',
+    reportCount: 3,
+    companyName: 'Acme Corp',
+    subject: 'Your invoice is ready',
+    verdict: 'THREAT',
+    confidence: 0.85,
+    summary: 'Credential-harvesting link found in message body.',
+    reasons: ['Sender domain not in allowlist', 'URL matches known phishing indicator'],
+    recommendedActions: ['block_sender', 'purge_message'],
+    requiresApproval: true,
+    blastRadius: { status: 'unavailable', reason: 'not_configured' },
+    remediationActions: [],
+    urls: [],
+    ...overrides,
+  };
+}
+
+describe('formatTriageNote', () => {
+  it('includes the verdict label and confidence value', () => {
+    const output = formatTriageNote(baseEvidence());
+    expect(output).toContain('THREAT');
+    expect(output).toContain('0.85');
+  });
+
+  it('includes a Summary line and a Reasons section listing each reason', () => {
+    const output = formatTriageNote(baseEvidence());
+    expect(output).toContain('Credential-harvesting link found in message body.');
+    expect(output).toContain('Sender domain not in allowlist');
+    expect(output).toContain('URL matches known phishing indicator');
+  });
+
+  it('shows delivered/held/rejected/clicked counts when blast radius is ok', () => {
+    const ok: BlastRadiusResult = {
+      status: 'ok',
+      matched: 5,
+      delivered: 3,
+      held: 1,
+      rejected: 1,
+      clicked: 2,
+      perRecipient: [{ recipient: 'user@acme.example', status: 'delivered' }],
+      source: 'fan-out',
+    };
+    const output = formatTriageNote(baseEvidence({ blastRadius: ok }));
+    expect(output).toContain('3');
+    expect(output).toContain('1');
+    expect(output).toContain('2');
+  });
+
+  it('shows an explicit unavailable reason when blast radius is unavailable', () => {
+    const output = formatTriageNote(
+      baseEvidence({ blastRadius: { status: 'unavailable', reason: 'not_configured' } })
+    );
+    expect(output).toContain('unavailable');
+    expect(output).toContain('not_configured');
+  });
+
+  it('states no action taken when remediationActions is empty', () => {
+    const output = formatTriageNote(baseEvidence({ remediationActions: [] }));
+    expect(output.toLowerCase()).toMatch(/proposed|no action/);
+  });
+
+  it('lists each remediation action with status and approver when present', () => {
+    const output = formatTriageNote(
+      baseEvidence({
+        remediationActions: [
+          { actionType: 'block_sender', status: 'approved', approvedBy: 'operator@example.com', approvedAt: '2026-07-01T00:00:00Z' },
+          { actionType: 'purge_message', status: 'completed', approvedBy: 'operator@example.com', approvedAt: '2026-07-01T00:00:00Z' },
+        ],
+      })
+    );
+    expect(output).toContain('block_sender');
+    expect(output).toContain('approved');
+    expect(output).toContain('purge_message');
+    expect(output).toContain('completed');
+    expect(output).toContain('operator@example.com');
+  });
+
+  it('renders indicator URLs in sanitized form, dropping query strings', () => {
+    const output = formatTriageNote(baseEvidence({ urls: ['http://evil.example/p?token=leak'] }));
+    expect(output).not.toContain('token=leak');
+    expect(output).toContain('http://evil.example/p');
+  });
+
+  it('never leaks a secret embedded in free-text fields (sanitizeNoteText applied to whole output)', () => {
+    const output = formatTriageNote(
+      baseEvidence({ summary: 'Found link http://evil.example/x?access_token=SECRETVALUE in body' })
+    );
+    expect(output).not.toContain('access_token=SECRETVALUE');
+  });
+
+  it('handles null verdict/confidence gracefully without throwing', () => {
+    expect(() =>
+      formatTriageNote(baseEvidence({ verdict: null, confidence: null }))
+    ).not.toThrow();
+    const output = formatTriageNote(baseEvidence({ verdict: null, confidence: null }));
+    expect(output.toLowerCase()).toContain('not yet classified');
+  });
+});