diff --git a/apps/api/tests/broker/outboxWorker.test.ts b/apps/api/tests/broker/outboxWorker.test.ts
index 2ca3f62..bef65ae 100644
--- a/apps/api/tests/broker/outboxWorker.test.ts
+++ b/apps/api/tests/broker/outboxWorker.test.ts
@@ -73,6 +73,15 @@ vi.mock('../../src/broker/client.js', () => ({
   }),
 }))
 
+// Default payload is form JSON (the worker must build ICS from this — not pass raw JSON to CalDAV)
+const DEFAULT_FORM_PAYLOAD = JSON.stringify({
+  title: 'Lunch',
+  allDay: false,
+  start: '2026-06-10T12:00:00',
+  end: '2026-06-10T13:00:00',
+  recurrence: 'none',
+})
+
 const makeRow = (overrides: Record<string, unknown> = {}) => ({
   id: 1,
   userId: 42,
@@ -82,7 +91,7 @@ const makeRow = (overrides: Record<string, unknown> = {}) => ({
   calendarUrl: 'https://caldav.fastmail.com/dav/calendars/user/test@fm.com/Default/',
   calendarObjectUrl: null,
   etag: null,
-  payload: 'BEGIN:VCALENDAR\r\nEND:VCALENDAR',
+  payload: DEFAULT_FORM_PAYLOAD,
   attemptCount: 0,
   nextAttemptAt: new Date(Date.now() - 5000), // already due
   lastError: null,
@@ -175,6 +184,61 @@ describe('runOutboxDrain — state transitions', () => {
   })
 })
 
+describe('runOutboxDrain — ICS building from form JSON (CR-02)', () => {
+  beforeEach(() => {
+    vi.clearAllMocks()
+    mockPendingRows = []
+    mockUpdateSet.mockReturnValue({ where: vi.fn().mockResolvedValue(undefined) })
+    mockUpdate.mockReturnValue({ set: mockUpdateSet })
+    mockWherePending.mockImplementation(() => Promise.resolve(mockPendingRows))
+    mockFromFn.mockReturnValue({ where: mockWherePending })
+    mockSelectFn.mockReturnValue({ from: mockFromFn })
+  })
+
+  it('create row: icsString passed to createCalendarEvent starts with BEGIN:VCALENDAR and contains SUMMARY', async () => {
+    const { createCalendarEvent } = await import('../../src/broker/write.js')
+    let capturedIcsString: unknown = null
+    vi.mocked(createCalendarEvent).mockImplementation(async (_client, _cal, _uid, icsString) => {
+      capturedIcsString = icsString
+      return makeResponse(201)
+    })
+    mockPendingRows = [makeRow()]
+
+    await runOutboxDrain()
+
+    expect(typeof capturedIcsString).toBe('string')
+    expect((capturedIcsString as string).startsWith('BEGIN:VCALENDAR')).toBe(true)
+    expect(capturedIcsString).toContain('SUMMARY:Lunch')
+  })
+
+  it('update row: icsString passed to updateCalendarEvent starts with BEGIN:VCALENDAR', async () => {
+    const { updateCalendarEvent } = await import('../../src/broker/write.js')
+    let capturedIcsString: unknown = null
+    vi.mocked(updateCalendarEvent).mockImplementation(async (_client, _url, icsString, _etag) => {
+      capturedIcsString = icsString
+      return makeResponse(204)
+    })
+    mockPendingRows = [makeRow({
+      operation: 'update',
+      calendarObjectUrl: 'https://caldav.fastmail.com/dav/calendars/user/test/uid.ics',
+    })]
+
+    await runOutboxDrain()
+
+    expect(typeof capturedIcsString).toBe('string')
+    expect((capturedIcsString as string).startsWith('BEGIN:VCALENDAR')).toBe(true)
+  })
+
+  it('create row with unparseable payload marks the row failed (hard fail, no retry)', async () => {
+    mockPendingRows = [makeRow({ payload: 'NOT_VALID_JSON{{{' })]
+
+    await runOutboxDrain()
+
+    const setArg = mockUpdateSet.mock.calls[0]?.[0] as { status?: string }
+    expect(setArg?.status).toBe('failed')
+  })
+})
+
 describe('runOutboxDrain — edit-as-move ordering (D-04)', () => {
   beforeEach(() => {
     vi.clearAllMocks()
diff --git a/apps/api/tests/broker/vevent.test.ts b/apps/api/tests/broker/vevent.test.ts
index 81b85b9..52d608b 100644
--- a/apps/api/tests/broker/vevent.test.ts
+++ b/apps/api/tests/broker/vevent.test.ts
@@ -116,3 +116,46 @@ describe('buildVeventString', () => {
     expect(result.uid.length).toBeGreaterThan(10)
   })
 })
+
+describe('buildVeventString — D-13 form-parsed contract', () => {
+  it('timed event: produces BEGIN:VCALENDAR, SUMMARY, UID, timed DTSTART (Z suffix), and DTEND', () => {
+    // Simulates the field shape parsed by the worker from the stored form JSON
+    const result = buildVeventString({
+      uid: 'u1@familysync',
+      summary: 'Lunch',
+      allDay: false,
+      dtstart: new Date('2026-06-10T12:00:00Z'),
+      dtend: new Date('2026-06-10T13:00:00Z'),
+    })
+
+    expect(result.icsString).toContain('BEGIN:VCALENDAR')
+    expect(result.icsString).toContain('SUMMARY:Lunch')
+    expect(result.icsString).toContain('UID:u1@familysync')
+    // D-13 timed contract: DATETIME in UTC → 'Z' suffix, no TZID
+    expect(result.icsString).toMatch(/DTSTART:\d{8}T\d{6}Z/)
+    // DTEND must be present
+    expect(result.icsString).toMatch(/DTEND:\d{8}T\d{6}Z/)
+  })
+
+  it('single-day all-day event: DTSTART is DATE format and DTEND = DTSTART + 1 day (RFC-5545 exclusive end, WR-04)', () => {
+    // Simulates a single-day all-day event where start and end are the same calendar day.
+    // WR-04: the outbox worker passes the user-entered inclusive end; vevent.ts must advance it.
+    const result = buildVeventString({
+      summary: 'Birthday',
+      allDay: true,
+      dtstart: '2026-06-10',
+      dtend: '2026-06-10',
+    })
+
+    // DTSTART must be DATE format (no time component, no TZID) — D-13 all-day contract
+    expect(result.icsString).toMatch(/DTSTART[^:]*:20260610/)
+    expect(result.icsString).not.toMatch(/DTSTART[^:]*:20260610T/)
+
+    // WR-04: DTEND must be DTSTART + 1 day (RFC-5545 exclusive end)
+    expect(result.icsString).toMatch(/DTEND[^:]*:20260611/)
+    // DTEND date string must NOT equal DTSTART date string (owning-boundary assertion)
+    const dtendMatch = result.icsString.match(/DTEND[^:]*:(\d{8})/)
+    const dtstartMatch = result.icsString.match(/DTSTART[^:]*:(\d{8})/)
+    expect(dtendMatch?.[1]).not.toBe(dtstartMatch?.[1])
+  })
+})