diff --git a/apps/pwa/src/components/EventForm.test.tsx b/apps/pwa/src/components/EventForm.test.tsx
index b65033d..d5f326d 100644
--- a/apps/pwa/src/components/EventForm.test.tsx
+++ b/apps/pwa/src/components/EventForm.test.tsx
@@ -239,7 +239,10 @@ describe('EventForm', () => {
 
   it('renders recurrence options: None, Daily, Weekly, Monthly, Yearly', () => {
     renderForm();
-    expect(screen.getByText('None')).toBeDefined();
+    // Use getAllByText since "None" now appears in both the recurrence picker and the
+    // reminder picker (Phase 11 — two <select> elements both have a "None" option).
+    const noneOptions = screen.getAllByText('None');
+    expect(noneOptions.length).toBeGreaterThanOrEqual(1);
     expect(screen.getByText('Daily')).toBeDefined();
     expect(screen.getByText('Weekly')).toBeDefined();
     expect(screen.getByText('Monthly')).toBeDefined();
@@ -986,3 +989,245 @@ describe('EventForm — Plan 06-06 end-tracking + recurrence-bound', () => {
     });
   });
 });
+
+// ── Phase 11 Plan 04: Reminder picker tests ───────────────────────────────────
+
+/**
+ * Fixture: edit occurrence with timed reminder (30 minutes before).
+ */
+const TIMED_REMINDER_OCCURRENCE: CalendarOccurrence = {
+  id: 'reminder-uid-001::2026-06-15T10:00:00',
+  uid: 'reminder-uid-001',
+  calendarId: 1,
+  calendarName: 'My Calendar',
+  ownerUserId: 1,
+  ownerName: 'Alice',
+  color: '#4A90D9',
+  isShared: false,
+  title: 'Meeting with reminder',
+  start: '2026-06-15T10:00:00-04:00',
+  end: '2026-06-15T11:00:00-04:00',
+  allDay: false,
+  location: null,
+  description: null,
+  hasRrule: false,
+  reminderLeadMinutes: 30,
+};
+
+/**
+ * Fixture: edit occurrence with all-day reminder (1440 min = 1 day before).
+ */
+const ALLDAY_REMINDER_OCCURRENCE: CalendarOccurrence = {
+  id: 'reminder-uid-002::2026-06-15',
+  uid: 'reminder-uid-002',
+  calendarId: 1,
+  calendarName: 'My Calendar',
+  ownerUserId: 1,
+  ownerName: 'Alice',
+  color: '#4A90D9',
+  isShared: false,
+  title: 'All-day event with reminder',
+  start: '2026-06-15',
+  end: '2026-06-16',
+  allDay: true,
+  location: null,
+  description: null,
+  hasRrule: false,
+  reminderLeadMinutes: 1440,
+};
+
+/**
+ * Fixture: edit occurrence with off-list timed reminder (45 min).
+ */
+const OFFLIST_REMINDER_OCCURRENCE: CalendarOccurrence = {
+  id: 'reminder-uid-003::2026-06-15T10:00:00',
+  uid: 'reminder-uid-003',
+  calendarId: 1,
+  calendarName: 'My Calendar',
+  ownerUserId: 1,
+  ownerName: 'Alice',
+  color: '#4A90D9',
+  isShared: false,
+  title: 'Meeting with off-list reminder',
+  start: '2026-06-15T10:00:00-04:00',
+  end: '2026-06-15T11:00:00-04:00',
+  allDay: false,
+  location: null,
+  description: null,
+  hasRrule: false,
+  reminderLeadMinutes: 45,
+};
+
+describe('EventForm — Phase 11 reminder picker (Plan 04)', () => {
+  beforeEach(() => {
+    vi.clearAllMocks();
+    mockEventFormOpen = true;
+    mockEventFormMode = 'create';
+    mockEventFormUid = null;
+  });
+
+  // ── D-01: default None in create mode ─────────────────────────────────────
+
+  it('D-01: reminder picker present with id=event-reminder and defaults to None in create mode', () => {
+    renderForm({ mode: 'create' });
+    const reminderSelect = document.querySelector('#event-reminder') as HTMLSelectElement;
+    expect(reminderSelect).not.toBeNull();
+    expect(reminderSelect.value).toBe('__none__');
+  });
+
+  it('D-01: timed preset labels visible in create mode (allDay=false)', () => {
+    renderForm({ mode: 'create' });
+    // Timed preset labels should be present
+    expect(screen.getByText('30 minutes before')).toBeDefined();
+    expect(screen.getByText('1 hour before')).toBeDefined();
+    expect(screen.getByText('1 day before')).toBeDefined();
+  });
+
+  // ── D-02/D-03: allDay toggle swaps preset set and resets to None ──────────
+
+  it('D-02/D-03: toggling All-day swaps picker to day-granularity labels', () => {
+    renderForm({ mode: 'create' });
+
+    // Before toggle: timed preset
+    expect(screen.getByText('30 minutes before')).toBeDefined();
+
+    // Toggle all-day ON
+    const allDaySwitch = screen.getByRole('switch');
+    fireEvent.click(allDaySwitch);
+
+    // After toggle: all-day presets present
+    expect(screen.getByText('Same day (9 AM)')).toBeDefined();
+    expect(screen.getByText('1 day before (9 AM)')).toBeDefined();
+    expect(screen.getByText('1 week before (9 AM)')).toBeDefined();
+  });
+
+  it('D-03: toggling All-day resets picker selection to None (no carry-over)', () => {
+    renderForm({ mode: 'create' });
+
+    // Select a timed preset
+    const reminderSelect = document.querySelector('#event-reminder') as HTMLSelectElement;
+    fireEvent.change(reminderSelect, { target: { value: '30' } });
+    expect(reminderSelect.value).toBe('30');
+
+    // Toggle all-day ON — picker must reset to None
+    const allDaySwitch = screen.getByRole('switch');
+    fireEvent.click(allDaySwitch);
+
+    const reminderSelectAfter = document.querySelector('#event-reminder') as HTMLSelectElement;
+    expect(reminderSelectAfter.value).toBe('__none__');
+  });
+
+  // ── Edit-mode pre-population ───────────────────────────────────────────────
+
+  it('edit mode: reminderLeadMinutes=30 (timed) pre-selects "30 minutes before"', () => {
+    renderForm({
+      mode: 'edit',
+      uid: 'reminder-uid-001',
+      eventOccurrence: TIMED_REMINDER_OCCURRENCE,
+    });
+    const reminderSelect = document.querySelector('#event-reminder') as HTMLSelectElement;
+    expect(reminderSelect).not.toBeNull();
+    expect(reminderSelect.value).toBe('30');
+    // Option label should be "30 minutes before"
+    const selectedOption = reminderSelect.options[reminderSelect.selectedIndex];
+    expect(selectedOption.text).toBe('30 minutes before');
+  });
+
+  it('edit mode: reminderLeadMinutes=1440 all-day pre-selects "1 day before (9 AM)"', () => {
+    renderForm({
+      mode: 'edit',
+      uid: 'reminder-uid-002',
+      eventOccurrence: ALLDAY_REMINDER_OCCURRENCE,
+    });
+    const reminderSelect = document.querySelector('#event-reminder') as HTMLSelectElement;
+    expect(reminderSelect).not.toBeNull();
+    expect(reminderSelect.value).toBe('1440');
+    const selectedOption = reminderSelect.options[reminderSelect.selectedIndex];
+    expect(selectedOption.text).toBe('1 day before (9 AM)');
+  });
+
+  it('edit mode: reminderLeadMinutes=45 (off-list) shows synthetic "45 min before" option', () => {
+    renderForm({
+      mode: 'edit',
+      uid: 'reminder-uid-003',
+      eventOccurrence: OFFLIST_REMINDER_OCCURRENCE,
+    });
+    const reminderSelect = document.querySelector('#event-reminder') as HTMLSelectElement;
+    expect(reminderSelect).not.toBeNull();
+    expect(reminderSelect.value).toBe('45');
+    const selectedOption = reminderSelect.options[reminderSelect.selectedIndex];
+    expect(selectedOption.text).toBe('45 min before');
+  });
+
+  // ── Payload mapping ────────────────────────────────────────────────────────
+
+  it('payload mapping: None selection → reminderLeadMinutes: null', async () => {
+    renderForm({ mode: 'create' });
+    fireEvent.change(screen.getByPlaceholderText('Event title'), {
+      target: { value: 'Test Event' },
+    });
+    // Picker already at None (default)
+    const reminderSelect = document.querySelector('#event-reminder') as HTMLSelectElement;
+    expect(reminderSelect.value).toBe('__none__');
+
+    fireEvent.click(screen.getByText('Create Event'));
+
+    await waitFor(() => {
+      expect(mockCreateEvent).toHaveBeenCalledWith(
+        expect.objectContaining({ reminderLeadMinutes: null }),
+      );
+    });
+  });
+
+  it('payload mapping: preset selection (30) → reminderLeadMinutes: 30', async () => {
+    renderForm({ mode: 'create' });
+    fireEvent.change(screen.getByPlaceholderText('Event title'), {
+      target: { value: 'Test Event' },
+    });
+
+    const reminderSelect = document.querySelector('#event-reminder') as HTMLSelectElement;
+    fireEvent.change(reminderSelect, { target: { value: '30' } });
+
+    fireEvent.click(screen.getByText('Create Event'));
+
+    await waitFor(() => {
+      expect(mockCreateEvent).toHaveBeenCalledWith(
+        expect.objectContaining({ reminderLeadMinutes: 30 }),
+      );
+    });
+  });
+
+  it('payload mapping: Custom (kept) selection → reminderLeadMinutes field omitted (D-08)', async () => {
+    // We cannot reach __custom__ via occurrence (occurrence only has number|null),
+    // but we can set it directly via the state simulation — programmatically
+    // select __custom__ via a forced renderForm with custom occurrence scenario.
+    // The plan notes: with only number|null, __custom__ is unreachable from occurrence;
+    // we test the omit-behavior by directly firing a change to __custom__ value.
+    renderForm({
+      mode: 'edit',
+      uid: 'reminder-uid-001',
+      eventOccurrence: TIMED_REMINDER_OCCURRENCE,
+    });
+    fireEvent.change(screen.getByPlaceholderText('Event title'), {
+      target: { value: 'Meeting with reminder' },
+    });
+
+    // Force the select to __custom__ sentinel (simulates a custom alarm preserved state)
+    const reminderSelect = document.querySelector('#event-reminder') as HTMLSelectElement;
+    // We need to inject the __custom__ option and select it
+    const customOption = document.createElement('option');
+    customOption.value = '__custom__';
+    customOption.text = 'Custom (kept)';
+    reminderSelect.appendChild(customOption);
+    fireEvent.change(reminderSelect, { target: { value: '__custom__' } });
+
+    fireEvent.click(screen.getByText('Save Changes'));
+
+    await waitFor(() => {
+      expect(mockUpdateEvent).toHaveBeenCalled();
+      const callPayload = mockUpdateEvent.mock.calls[0][1] as Record<string, unknown>;
+      // D-08: field must be absent (not null, not 0 — truly missing)
+      expect(Object.prototype.hasOwnProperty.call(callPayload, 'reminderLeadMinutes')).toBe(false);
+    });
+  });
+});
diff --git a/apps/pwa/src/components/EventForm.tsx b/apps/pwa/src/components/EventForm.tsx
index aaa62b2..37a50eb 100644
--- a/apps/pwa/src/components/EventForm.tsx
+++ b/apps/pwa/src/components/EventForm.tsx
@@ -52,11 +52,45 @@ import { useFocusTrap } from '../hooks/useFocusTrap.js';
 
 const LAST_CALENDAR_KEY = 'eventForm.lastCalendarUrl';
 
+// Phase 11: reminder preset values (minutes) for each event type.
+// Used for edit-mode classification and rendering.
+const TIMED_REMINDER_PRESETS = new Set([5, 10, 15, 30, 60, 120, 1440, 2880]);
+const ALLDAY_REMINDER_PRESETS = new Set([0, 1440, 2880, 10080]);
+
 // IN-03: todayIso is now imported from calendarStore (single source of truth).
 // getDefaultStartDate/getDefaultEndDate collapsed to todayIso() calls at use sites.
 
 // ── Helpers ────────────────────────────────────────────────────────────────────
 
+/**
+ * Humanize an off-list reminder lead (minutes) for the synthetic picker option label.
+ * Per UI-SPEC Copywriting Contract thresholds:
+ *   < 60 min  → "N min before"
+ *   ≥ 60 min  → "N hours before"
+ */
+function humanizeReminderLead(minutes: number): string {
+  if (minutes < 60) return `${minutes} min before`;
+  const hours = minutes / 60;
+  return `${hours} hour${hours !== 1 ? 's' : ''} before`;
+}
+
+/**
+ * Derive the initial reminder picker value from an occurrence's reminderLeadMinutes.
+ * Returns '__none__' for null, the matching preset string for a preset, or the numeric
+ * string for an off-list value (synthetic option will be rendered for this case).
+ * There is no '__custom__' path here — the occurrence only carries number|null.
+ */
+function deriveReminderValue(
+  leadMinutes: number | null,
+  isAllDay: boolean,
+): string {
+  if (leadMinutes === null) return '__none__';
+  const presets = isAllDay ? ALLDAY_REMINDER_PRESETS : TIMED_REMINDER_PRESETS;
+  if (presets.has(leadMinutes)) return String(leadMinutes);
+  // Off-list positive value — use the numeric string; a synthetic option will be rendered
+  return String(leadMinutes);
+}
+
 /** Determine if we're on phone breakpoint. */
 function isPhoneBreakpoint(): boolean {
   return typeof window !== 'undefined' && window.matchMedia('(max-width: 767px)').matches;
@@ -219,6 +253,11 @@ export function EventForm() {
   const [endDate, setEndDate] = useState(initEndDate);
   const [endTime, setEndTime] = useState(initEnd.time);
   const [recurrence, setRecurrence] = useState<RecurrencePreset>('none');
+  // Phase 11: reminder picker state. Sentinel values:
+  //   '__none__'   = None (no reminder)
+  //   '__custom__' = read-only "Custom (kept)" (absolute/multi VALARM, D-07/D-08)
+  //   numeric str  = preset or synthetic off-list lead in minutes
+  const [reminderValue, setReminderValue] = useState<string>('__none__');
   // D-06: recurrence bound state — "Ends" control
   const [recurrenceBound, setRecurrenceBound] = useState<'never' | 'until' | 'count'>('never');
   const [recurrenceUntil, setRecurrenceUntil] = useState('');
@@ -280,6 +319,9 @@ export function EventForm() {
       setRecurrenceCount(1);
       setLocation(occurrence?.location ?? '');
       setDescription(occurrence?.description ?? '');
+      // Phase 11: derive reminder picker value from occurrence (edit-mode pre-population, D-01/D-07)
+      const occAllDay = occurrence?.allDay ?? false;
+      setReminderValue(deriveReminderValue(occurrence?.reminderLeadMinutes ?? null, occAllDay));
     }
   }, [eventFormOpen, eventFormMode, eventFormUid, occurrence?.uid]); // eslint-disable-line react-hooks/exhaustive-deps
 
@@ -316,6 +358,8 @@ export function EventForm() {
   const handleAllDayToggle = () => {
     const next = !allDay;
     setAllDay(next);
+    // D-03 (Phase 11): reset reminder to None on allDay toggle — no carry-over between preset sets
+    setReminderValue('__none__');
     if (!next) {
       // Turning off all-day: restore default times
       setStartTime('09:00');
@@ -418,6 +462,23 @@ export function EventForm() {
     // outbox worker then preserves the stored RRULE (see outboxWorker.ts WR-01). On
     // CREATE the user explicitly chose a recurrence, so it is always sent.
     const isEdit = eventFormMode === 'edit' && !!eventFormUid;
+
+    // Phase 11: map reminder picker value to payload field (D-08).
+    //   '__none__'   → null  (explicit clear)
+    //   '__custom__' → omit  (unchanged custom alarm — server preserves original VALARM)
+    //   numeric str  → integer (preset or synthetic off-list lead)
+    let reminderPayload: { reminderLeadMinutes?: number | null } = {};
+    if (reminderValue === '__none__') {
+      reminderPayload = { reminderLeadMinutes: null };
+    } else if (reminderValue !== '__custom__') {
+      const parsed = parseInt(reminderValue, 10);
+      if (Number.isFinite(parsed) && parsed >= 0) {
+        reminderPayload = { reminderLeadMinutes: parsed };
+      }
+      // If parse fails (should not happen), omit field (safe default: no-change)
+    }
+    // __custom__ → reminderPayload stays {} (field absent = no-change, D-08)
+
     const payload: CreateEventPayload = {
       title: title.trim(),
       allDay,
@@ -433,6 +494,7 @@ export function EventForm() {
         : {}),
       ...(location.trim() ? { location: location.trim() } : {}),
       ...(description.trim() ? { description: description.trim() } : {}),
+      ...reminderPayload,
       ...(writableCalendars.length > 1 && calendarUrl ? { calendarUrl } : {}),
     };
 
@@ -884,6 +946,96 @@ export function EventForm() {
           )}
         </div>
 
+        {/* Phase 11: Reminder picker (allDay-aware swap, D-01/D-02/D-03/D-07/D-08).
+            NOT disabled in edit mode — reminders are editable (unlike Repeat/WR-01). */}
+        <div style={fieldStyle}>
+          <label htmlFor="event-reminder" style={labelStyle}>
+            Reminder
+          </label>
+          <select
+            id="event-reminder"
+            value={reminderValue}
+            onChange={(e) => setReminderValue(e.target.value)}
+            style={{
+              ...inputStyle,
+              padding: '0 var(--space-3)',
+              cursor: 'pointer',
+            }}
+          >
+            {allDay ? (
+              // D-02: all-day presets (day-granularity)
+              <>
+                <option value="__none__">None</option>
+                <option value="0">Same day (9 AM)</option>
+                <option value="1440">1 day before (9 AM)</option>
+                <option value="2880">2 days before (9 AM)</option>
+                <option value="10080">1 week before (9 AM)</option>
+                {/* D-07: synthetic option for off-list all-day value */}
+                {reminderValue !== '__none__' &&
+                  reminderValue !== '__custom__' &&
+                  !ALLDAY_REMINDER_PRESETS.has(parseInt(reminderValue, 10)) &&
+                  Number.isFinite(parseInt(reminderValue, 10)) && (
+                    <option value={reminderValue}>
+                      {humanizeReminderLead(parseInt(reminderValue, 10))}
+                    </option>
+                  )}
+                {/* D-07: read-only Custom (kept) for absolute/multi alarm */}
+                {reminderValue === '__custom__' && (
+                  <option value="__custom__" disabled>
+                    Custom (kept)
+                  </option>
+                )}
+              </>
+            ) : (
+              // D-01: timed presets
+              <>
+                <option value="__none__">None</option>
+                <option value="5">5 minutes before</option>
+                <option value="10">10 minutes before</option>
+                <option value="15">15 minutes before</option>
+                <option value="30">30 minutes before</option>
+                <option value="60">1 hour before</option>
+                <option value="120">2 hours before</option>
+                <option value="1440">1 day before</option>
+                <option value="2880">2 days before</option>
+                {/* D-07: synthetic option for off-list timed value */}
+                {reminderValue !== '__none__' &&
+                  reminderValue !== '__custom__' &&
+                  !TIMED_REMINDER_PRESETS.has(parseInt(reminderValue, 10)) &&
+                  Number.isFinite(parseInt(reminderValue, 10)) && (
+                    <option value={reminderValue}>
+                      {humanizeReminderLead(parseInt(reminderValue, 10))}
+                    </option>
+                  )}
+                {/* D-07: read-only Custom (kept) for absolute/multi alarm */}
+                {reminderValue === '__custom__' && (
+                  <option value="__custom__" disabled>
+                    Custom (kept)
+                  </option>
+                )}
+              </>
+            )}
+          </select>
+          {/* Helper text: shown in edit mode when value is __custom__ or synthetic off-list (D-07) */}
+          {eventFormMode === 'edit' &&
+            (reminderValue === '__custom__' ||
+              (reminderValue !== '__none__' &&
+                !TIMED_REMINDER_PRESETS.has(parseInt(reminderValue, 10)) &&
+                !ALLDAY_REMINDER_PRESETS.has(parseInt(reminderValue, 10)) &&
+                Number.isFinite(parseInt(reminderValue, 10)))) && (
+              <div
+                style={{
+                  fontSize: 'var(--text-label-size)',
+                  color: 'var(--color-text-secondary)',
+                  marginTop: 'var(--space-1)',
+                }}
+              >
+                {/* Plain text — XSS guard (T-11-10 / T-03-15) */}
+                Custom reminder kept — select a preset to replace it.
+              </div>
+            )}
+        </div>
+
         {/* D-06: Recurrence bound control — shown only when recurrence ≠ 'none' in create mode */}
         {eventFormMode !== 'edit' && recurrence !== 'none' && (
           <div style={fieldStyle}>