diff --git a/apps/api/tests/routes/events.test.ts b/apps/api/tests/routes/events.test.ts
index 9284754..89b7847 100644
--- a/apps/api/tests/routes/events.test.ts
+++ b/apps/api/tests/routes/events.test.ts
@@ -446,6 +446,85 @@ describe('GET /api/events/sync-status', () => {
   })
 })
 
+// ---------------------------------------------------------------------------
+// CR-01 contract tests — canonical client payload shape (title/start/end)
+//
+// The PWA sends {title, start, end, allDay, recurrence} — the exact
+// CreateEventPayload shape from apps/pwa/src/api/client.ts:119-128.
+// These tests assert the server schema accepts that shape (202), NOT 400.
+// RED before Task 1 schema rename; GREEN after.
+// ---------------------------------------------------------------------------
+describe('CR-01: canonical client payload (title/start/end) accepted by server', () => {
+  beforeEach(() => {
+    // Seed a calendar row for calendar ownership check in create
+    mockDbRows = [
+      {
+        id: 1,
+        url: 'https://caldav.fastmail.com/dav/calendars/user/test@fm.com/Default/',
+        displayName: 'Default',
+        color: '#4A90D9',
+        userId: 1,
+        isShared: false,
+      },
+    ]
+    const mockSimpleWhere = vi.fn().mockImplementation(() => Promise.resolve(mockDbRows))
+    mockFromFn.mockReturnValue({ where: mockSimpleWhere })
+    mockSelectFn.mockReturnValue({ from: mockFromFn })
+  })
+
+  it('POST /create with exact CreateEventPayload shape {title,start,end,allDay,recurrence} returns 202 not 400', async () => {
+    // This mirrors the exact payload apps/pwa/src/api/client.ts CreateEventPayload sends
+    const { app } = await import('../../src/index.js')
+    const res = await app.request('/api/events/create', {
+      method: 'POST',
+      headers: { 'Content-Type': 'application/json' },
+      body: JSON.stringify({
+        title: 'Team standup',
+        allDay: false,
+        start: '2026-06-15T10:00:00Z',
+        end: '2026-06-15T10:30:00Z',
+        recurrence: 'none',
+        calendarUrl: 'https://caldav.fastmail.com/dav/calendars/user/test@fm.com/Default/',
+      }),
+    })
+    expect(res.status).toBe(202)
+    const body = await res.json() as { uid: string }
+    expect(body).toHaveProperty('uid')
+  })
+
+  it('PATCH /:uid/edit with exact CreateEventPayload shape {title,start,end,allDay,recurrence} returns 202 not 400', async () => {
+    // Seed an event row for edit lookup
+    mockDbRows = [
+      {
+        uid: 'uid-cr01@familysync',
+        etag: '"etag-cr01"',
+        objectUrl: 'https://caldav.fastmail.com/dav/calendars/user/test@fm.com/Default/uid-cr01.ics',
+        calendarId: 1,
+        calendarUrl: 'https://caldav.fastmail.com/dav/calendars/user/test@fm.com/Default/',
+        userId: 1,
+      },
+    ]
+    const mockSimpleWhere = vi.fn().mockImplementation(() => Promise.resolve(mockDbRows))
+    mockFromFn.mockReturnValue({ where: mockSimpleWhere })
+    mockSelectFn.mockReturnValue({ from: mockFromFn })
+
+    const { app } = await import('../../src/index.js')
+    const res = await app.request('/api/events/uid-cr01%40familysync/edit', {
+      method: 'PATCH',
+      headers: { 'Content-Type': 'application/json' },
+      body: JSON.stringify({
+        title: 'Updated standup',
+        allDay: false,
+        start: '2026-06-15T10:00:00Z',
+        end: '2026-06-15T10:30:00Z',
+        recurrence: 'weekly',
+        calendarUrl: 'https://caldav.fastmail.com/dav/calendars/user/test@fm.com/Default/',
+      }),
+    })
+    expect(res.status).toBe(202)
+  })
+})
+
 // ---------------------------------------------------------------------------
 // GET /api/events/writable-calendars
 // ---------------------------------------------------------------------------