diff --git a/apps/api/tests/broker/expand.test.ts b/apps/api/tests/broker/expand.test.ts
index 1495fe3..8a05578 100644
--- a/apps/api/tests/broker/expand.test.ts
+++ b/apps/api/tests/broker/expand.test.ts
@@ -350,3 +350,144 @@ describe('expandOccurrences', () => {
     });
   });
 });
+
+// ─── Phase 11 Plan 03 Task 3: reminderLeadMinutes on CalendarOccurrence ─────────
+// D-06/D-10: reminderLeadMinutes is a series-level property — all occurrences of a
+// recurring master inherit the master's lead. NULL-vs-0-vs-positive must survive
+// through expansion.
+
+describe('expandOccurrences — reminderLeadMinutes propagation (Phase 11 Plan 03 Task 3)', () => {
+  // Helper: minimal VCALENDAR/VEVENT string for tests
+  function makeVevent(overrides: {
+    uid?: string;
+    allDay?: boolean;
+    reminderMinutes?: number | 'absolute' | 'none';
+    rrule?: string;
+  }): string {
+    const uid = overrides.uid ?? 'test-uid@test';
+    const lines: string[] = ['BEGIN:VCALENDAR', 'VERSION:2.0'];
+
+    if (!overrides.allDay) {
+      lines.push('BEGIN:VEVENT');
+      lines.push(`UID:${uid}`);
+      lines.push('SUMMARY:Test event');
+      lines.push('DTSTART:20260615T140000Z');
+      lines.push('DTEND:20260615T150000Z');
+    } else {
+      lines.push('BEGIN:VEVENT');
+      lines.push(`UID:${uid}`);
+      lines.push('SUMMARY:All-day test');
+      lines.push('DTSTART;VALUE=DATE:20260615');
+      lines.push('DTEND;VALUE=DATE:20260616');
+    }
+
+    if (overrides.rrule) {
+      lines.push(`RRULE:${overrides.rrule}`);
+    }
+
+    if (overrides.reminderMinutes === 'absolute') {
+      lines.push('BEGIN:VALARM');
+      lines.push('ACTION:DISPLAY');
+      lines.push('DESCRIPTION:Reminder');
+      lines.push('TRIGGER;VALUE=DATE-TIME:20260615T120000Z');
+      lines.push('END:VALARM');
+    } else if (overrides.reminderMinutes !== 'none' && overrides.reminderMinutes !== undefined) {
+      lines.push('BEGIN:VALARM');
+      lines.push('ACTION:DISPLAY');
+      lines.push('DESCRIPTION:Reminder');
+      lines.push(`TRIGGER:-PT${overrides.reminderMinutes}M`);
+      lines.push('END:VALARM');
+    }
+
+    lines.push('END:VEVENT');
+    lines.push('END:VCALENDAR');
+    return lines.join('\r\n');
+  }
+
+  const WINDOW_START = new Date('2026-06-01T00:00:00Z');
+  const WINDOW_END = new Date('2026-07-01T00:00:00Z');
+
+  // Non-recurring event with reminderLeadMinutes=30 → occurrence carries 30
+  it('non-recurring event: occurrence carries reminderLeadMinutes from master (30 minutes)', () => {
+    const raw = makeVevent({ reminderMinutes: 30 });
+
+    const occurrences = expandOccurrences(
+      raw,
+      WINDOW_START,
+      WINDOW_END,
+      1,
+      'My Calendar',
+      1,
+      null,
+      '#4A90D9',
+      false,
+    );
+
+    expect(occurrences).toHaveLength(1);
+    expect(occurrences[0].reminderLeadMinutes).toBe(30);
+  });
+
+  // NULL-vs-0: master with 0-minute all-day lead → occurrence carries 0, not null
+  it('non-recurring all-day event: occurrence carries reminderLeadMinutes=0 (same-day, D-06 NULL-vs-0)', () => {
+    // Use a 0-minute trigger (same-day all-day)
+    const raw = makeVevent({ allDay: true, reminderMinutes: 0 });
+
+    const occurrences = expandOccurrences(
+      raw,
+      new Date('2026-06-01T00:00:00Z'),
+      new Date('2026-07-01T00:00:00Z'),
+      1,
+      'My Calendar',
+      1,
+      null,
+      '#4A90D9',
+      false,
+    );
+
+    expect(occurrences).toHaveLength(1);
+    // 0-minute all-day trigger → preset 0 → reminderLeadMinutes=0 (not null)
+    expect(occurrences[0].reminderLeadMinutes).toBe(0);
+  });
+
+  // NULL: no VALARM in master → occurrence carries null
+  it('non-recurring event with no VALARM: occurrence carries reminderLeadMinutes=null', () => {
+    const raw = makeVevent({ reminderMinutes: 'none' });
+
+    const occurrences = expandOccurrences(
+      raw,
+      WINDOW_START,
+      WINDOW_END,
+      1,
+      'My Calendar',
+      1,
+      null,
+      '#4A90D9',
+      false,
+    );
+
+    expect(occurrences).toHaveLength(1);
+    expect(occurrences[0].reminderLeadMinutes).toBeNull();
+  });
+
+  // D-10 series-level: recurring event with reminderLeadMinutes=60 → all occurrences carry 60
+  it('D-10 series-level: all recurring occurrences inherit the master reminderLeadMinutes=60', () => {
+    const raw = makeVevent({ reminderMinutes: 60, rrule: 'FREQ=WEEKLY;COUNT=3' });
+
+    const occurrences = expandOccurrences(
+      raw,
+      WINDOW_START,
+      WINDOW_END,
+      1,
+      'My Calendar',
+      1,
+      null,
+      '#4A90D9',
+      false,
+    );
+
+    expect(occurrences.length).toBeGreaterThan(0);
+    for (const occ of occurrences) {
+      expect(occ.reminderLeadMinutes).toBe(60);
+    }
+  });
+});