diff --git a/workspace-server/src/__tests__/services/CalendarService.test.ts b/workspace-server/src/__tests__/services/CalendarService.test.ts
index 94fde5e..9a5b543 100644
--- a/workspace-server/src/__tests__/services/CalendarService.test.ts
+++ b/workspace-server/src/__tests__/services/CalendarService.test.ts
@@ -857,7 +857,7 @@ describe('CalendarService', () => {
         attendees: [{ email: 'new@example.com' }],
       };
 
-      mockCalendarAPI.events.update.mockResolvedValue({ data: updatedEvent });
+      mockCalendarAPI.events.patch.mockResolvedValue({ data: updatedEvent });
 
       const result = await calendarService.updateEvent({
         eventId: 'event123',
@@ -867,7 +867,7 @@ describe('CalendarService', () => {
         attendees: ['new@example.com'],
       });
 
-      expect(mockCalendarAPI.events.update).toHaveBeenCalledWith({
+      expect(mockCalendarAPI.events.patch).toHaveBeenCalledWith({
         calendarId: 'primary',
         eventId: 'event123',
         requestBody: {
@@ -889,14 +889,14 @@ describe('CalendarService', () => {
         description: 'New updated description',
       };
 
-      mockCalendarAPI.events.update.mockResolvedValue({ data: updatedEvent });
+      mockCalendarAPI.events.patch.mockResolvedValue({ data: updatedEvent });
 
       const result = await calendarService.updateEvent({
         eventId: 'event123',
         description: 'New updated description',
       });
 
-      expect(mockCalendarAPI.events.update).toHaveBeenCalledWith({
+      expect(mockCalendarAPI.events.patch).toHaveBeenCalledWith({
         calendarId: 'primary',
         eventId: 'event123',
         requestBody: {
@@ -910,7 +910,7 @@ describe('CalendarService', () => {
 
     it('should handle update errors', async () => {
       const apiError = new Error('Update failed');
-      mockCalendarAPI.events.update.mockRejectedValue(apiError);
+      mockCalendarAPI.events.patch.mockRejectedValue(apiError);
 
       const result = await calendarService.updateEvent({
         eventId: 'event123',
@@ -927,14 +927,14 @@ describe('CalendarService', () => {
         summary: 'Updated Meeting Only',
       };
 
-      mockCalendarAPI.events.update.mockResolvedValue({ data: updatedEvent });
+      mockCalendarAPI.events.patch.mockResolvedValue({ data: updatedEvent });
 
       await calendarService.updateEvent({
         eventId: 'event123',
         summary: 'Updated Meeting Only',
       });
 
-      expect(mockCalendarAPI.events.update).toHaveBeenCalledWith({
+      expect(mockCalendarAPI.events.patch).toHaveBeenCalledWith({
         calendarId: 'primary',
         eventId: 'event123',
         requestBody: {
@@ -942,6 +942,43 @@ describe('CalendarService', () => {
         },
       });
     });
+
+    it('should preserve Focus Time eventType on partial update', async () => {
+      const focusTimeEvent = {
+        id: 'focus123',
+        summary: 'Deep Work',
+        eventType: 'focusTime',
+        focusTimeProperties: { autoDeclineMode: 'declineNone' },
+        start: { dateTime: '2024-01-15T10:00:00Z' },
+        end: { dateTime: '2024-01-15T12:00:00Z' },
+      };
+
+      mockCalendarAPI.events.patch.mockResolvedValue({ data: focusTimeEvent });
+
+      const result = await calendarService.updateEvent({
+        eventId: 'focus123',
+        start: { dateTime: '2024-01-16T10:00:00Z' },
+        end: { dateTime: '2024-01-16T12:00:00Z' },
+      });
+
+      // Verify patch was called (not update) — patch preserves unspecified fields
+      expect(mockCalendarAPI.events.patch).toHaveBeenCalled();
+      expect(mockCalendarAPI.events.update).not.toHaveBeenCalled();
+
+      // Verify only the requested fields were sent (eventType is NOT in the body —
+      // it is preserved server-side by PATCH semantics)
+      expect(mockCalendarAPI.events.patch).toHaveBeenCalledWith(
+        expect.objectContaining({
+          requestBody: {
+            start: { dateTime: '2024-01-16T10:00:00Z' },
+            end: { dateTime: '2024-01-16T12:00:00Z' },
+          },
+        }),
+      );
+
+      const parsedResult = JSON.parse(result.content[0].text);
+      expect(parsedResult.eventType).toBe('focusTime');
+    });
   });
 
   describe('respondToEvent', () => {
@@ -1495,14 +1532,14 @@ describe('CalendarService', () => {
           },
         };
 
-        mockCalendarAPI.events.update.mockResolvedValue({ data: updatedEvent });
+        mockCalendarAPI.events.patch.mockResolvedValue({ data: updatedEvent });
 
         const result = await calendarService.updateEvent({
           eventId: 'event123',
           addGoogleMeet: true,
         });
 
-        const callArgs = mockCalendarAPI.events.update.mock.calls[0][0];
+        const callArgs = mockCalendarAPI.events.patch.mock.calls[0][0];
         expect(callArgs.conferenceDataVersion).toBe(1);
         expect(callArgs.requestBody.conferenceData).toBeDefined();
         expect(
@@ -1515,7 +1552,7 @@ describe('CalendarService', () => {
 
       it('should not include conferenceData when addGoogleMeet is false', async () => {
         const updatedEvent = { id: 'event123', summary: 'No Meet' };
-        mockCalendarAPI.events.update.mockResolvedValue({ data: updatedEvent });
+        mockCalendarAPI.events.patch.mockResolvedValue({ data: updatedEvent });
 
         await calendarService.updateEvent({
           eventId: 'event123',
@@ -1523,7 +1560,7 @@ describe('CalendarService', () => {
           addGoogleMeet: false,
         });
 
-        const callArgs = mockCalendarAPI.events.update.mock.calls[0][0];
+        const callArgs = mockCalendarAPI.events.patch.mock.calls[0][0];
         expect(callArgs.conferenceDataVersion).toBeUndefined();
         expect(callArgs.requestBody.conferenceData).toBeUndefined();
       });
@@ -1541,7 +1578,7 @@ describe('CalendarService', () => {
           ],
         };
 
-        mockCalendarAPI.events.update.mockResolvedValue({ data: updatedEvent });
+        mockCalendarAPI.events.patch.mockResolvedValue({ data: updatedEvent });
 
         const result = await calendarService.updateEvent({
           eventId: 'event123',
@@ -1553,7 +1590,7 @@ describe('CalendarService', () => {
           ],
         });
 
-        const callArgs = mockCalendarAPI.events.update.mock.calls[0][0];
+        const callArgs = mockCalendarAPI.events.patch.mock.calls[0][0];
         expect(callArgs.supportsAttachments).toBe(true);
         expect(callArgs.requestBody.attachments).toEqual([
           expect.objectContaining({
diff --git a/workspace-server/src/services/CalendarService.ts b/workspace-server/src/services/CalendarService.ts
index e67f3bb..a57db2a 100644
--- a/workspace-server/src/services/CalendarService.ts
+++ b/workspace-server/src/services/CalendarService.ts
@@ -724,7 +724,7 @@ export class CalendarService {
     try {
       const calendar = await this.getCalendar();
 
-      // Build request body with only the fields to update (patch semantics)
+      // Build request body with only the fields to update (true patch semantics)
       const requestBody: calendar_v3.Schema$Event = {};
       if (summary !== undefined) requestBody.summary = summary;
       if (description !== undefined) requestBody.description = description;
@@ -733,19 +733,24 @@ export class CalendarService {
       if (attendees)
         requestBody.attendees = attendees.map((email) => ({ email }));
 
-      const updateParams: calendar_v3.Params$Resource$Events$Update = {
+      const patchParams: calendar_v3.Params$Resource$Events$Patch = {
         calendarId: finalCalendarId,
         eventId,
         requestBody,
       };
       this.applyMeetAndAttachments(
         requestBody,
-        updateParams,
+        patchParams,
         addGoogleMeet,
         attachments,
       );
 
-      const res = await calendar.events.update(updateParams);
+      // Use events.patch (not events.update) so only specified fields are modified.
+      // events.update (PUT) replaces the entire event, which wipes unspecified fields
+      // like summary, description, reminders, colorId, visibility, and — critically —
+      // rejects non-default eventTypes (Focus Time, Out of Office, Working Location)
+      // with "Event type cannot be changed."
+      const res = await calendar.events.patch(patchParams);
 
       logToFile(`Successfully updated event: ${res.data.id}`);
       return {