From 641711322ec4ed3adacba8871503bda545383e52 Mon Sep 17 00:00:00 2001
From: Maurice <mauriceboe@icloud.com>
Date: Tue, 30 Jun 2026 13:55:17 +0200
Subject: [PATCH] feat(trips): transfer trip ownership to a member (#973)

Add POST /api/trips/:id/transfer so the owner can hand a trip to one of its
existing members. The swap runs in a transaction: the new owner takes
trips.user_id and the former owner is kept on as a regular member, so nobody
loses access. The endpoint is owner-only, writes a trip.transfer_ownership
audit entry and broadcasts the refreshed trip. The members modal gains a
"Make owner" action, shown only to the current owner.
---
 client/src/api/client.ts                      |  3 +-
 .../src/components/Trips/TripMembersModal.tsx | 28 +++++++++++
 server/src/nest/trips/trips.controller.ts     | 35 ++++++++++++++
 server/src/nest/trips/trips.service.ts        |  4 ++
 server/src/services/tripService.ts            | 42 ++++++++++++++++
 server/tests/integration/trips.test.ts        | 48 +++++++++++++++++++
 .../tests/unit/nest/trips.controller.test.ts  | 35 ++++++++++++++
 server/tests/unit/nest/trips.service.test.ts  |  2 +
 .../tests/unit/services/tripService.test.ts   | 46 +++++++++++++++++-
 shared/src/i18n/ar/members.ts                 |  3 ++
 shared/src/i18n/br/members.ts                 |  3 ++
 shared/src/i18n/cs/members.ts                 |  3 ++
 shared/src/i18n/de/members.ts                 |  3 ++
 shared/src/i18n/en/members.ts                 |  3 ++
 shared/src/i18n/es/members.ts                 |  3 ++
 shared/src/i18n/fr/members.ts                 |  3 ++
 shared/src/i18n/gr/members.ts                 |  3 ++
 shared/src/i18n/hu/members.ts                 |  3 ++
 shared/src/i18n/id/members.ts                 |  3 ++
 shared/src/i18n/it/members.ts                 |  3 ++
 shared/src/i18n/ja/members.ts                 |  3 ++
 shared/src/i18n/ko/members.ts                 |  3 ++
 shared/src/i18n/nl/members.ts                 |  3 ++
 shared/src/i18n/pl/members.ts                 |  3 ++
 shared/src/i18n/ru/members.ts                 |  3 ++
 shared/src/i18n/sv/members.ts                 |  3 ++
 shared/src/i18n/tr/members.ts                 |  3 ++
 shared/src/i18n/uk/members.ts                 |  3 ++
 shared/src/i18n/vi/members.ts                 |  3 ++
 shared/src/i18n/zh-TW/members.ts              |  3 ++
 shared/src/i18n/zh/members.ts                 |  3 ++
 shared/src/trip/trip.schema.ts                |  6 +++
 32 files changed, 312 insertions(+), 3 deletions(-)

diff --git a/client/src/api/client.ts b/client/src/api/client.ts
index 2b98c6f2a..f72fad943 100644
--- a/client/src/api/client.ts
+++ b/client/src/api/client.ts
@@ -15,7 +15,7 @@ import {
   type RegisterRequest, type LoginRequest, type ForgotPasswordRequest,
   type ResetPasswordRequest, type ChangePasswordRequest,
   type MfaVerifyLoginRequest, type MfaEnableRequest, type McpTokenCreateRequest,
-  type TripAddMemberRequest, type AssignmentReorderRequest,
+  type TripAddMemberRequest, type TripTransferOwnershipRequest, type AssignmentReorderRequest,
   type PackingReorderRequest, type PackingCreateBagRequest, type TodoReorderRequest,
   type TripCreateRequest, type TripUpdateRequest, type TripCopyRequest,
   type DayCreateRequest, type DayUpdateRequest, type DayReorderRequest,
@@ -340,6 +340,7 @@ export const tripsApi = {
   getMembers: (id: number | string) => apiClient.get(`/trips/${id}/members`).then(r => r.data),
   addMember: (id: number | string, identifier: string) => apiClient.post(`/trips/${id}/members`, { identifier } satisfies TripAddMemberRequest).then(r => r.data),
   removeMember: (id: number | string, userId: number) => apiClient.delete(`/trips/${id}/members/${userId}`).then(r => r.data),
+  transferOwnership: (id: number | string, newOwnerId: number) => apiClient.post(`/trips/${id}/transfer`, { newOwnerId } satisfies TripTransferOwnershipRequest).then(r => r.data),
   copy: (id: number | string, data?: TripCopyRequest) => apiClient.post(`/trips/${id}/copy`, data || {}).then(r => r.data),
   bundle: (id: number | string) => apiClient.get(`/trips/${id}/bundle`).then(r => r.data),
 }
diff --git a/client/src/components/Trips/TripMembersModal.tsx b/client/src/components/Trips/TripMembersModal.tsx
index 2862a548f..a167baa96 100644
--- a/client/src/components/Trips/TripMembersModal.tsx
+++ b/client/src/components/Trips/TripMembersModal.tsx
@@ -177,6 +177,7 @@ export default function TripMembersModal({ isOpen, onClose, tripId, tripTitle }:
   const [selectedUserId, setSelectedUserId] = useState('')
   const [adding, setAdding] = useState(false)
   const [removingId, setRemovingId] = useState(null)
+  const [transferringId, setTransferringId] = useState(null)
   const toast = useToast()
   const { user } = useAuthStore()
   const { t } = useTranslation()
@@ -227,6 +228,21 @@ export default function TripMembersModal({ isOpen, onClose, tripId, tripTitle }:
     }
   }
 
+  const handleTransfer = async (newOwnerId, username) => {
+    if (!confirm(t('members.confirmTransfer', { name: username }))) return
+    setTransferringId(newOwnerId)
+    try {
+      await tripsApi.transferOwnership(tripId, newOwnerId)
+      // The current user just dropped from owner to member — reload so the trip
+      // state and permissions everywhere reflect the new ownership.
+      onClose()
+      window.location.reload()
+    } catch (err: unknown) {
+      toast.error(getApiErrorMessage(err, t('members.transferError')))
+      setTransferringId(null)
+    }
+  }
+
   const handleRemove = async (userId, isSelf) => {
     const msg = isSelf
       ? t('members.confirmLeave')
@@ -347,6 +363,18 @@ export default function TripMembersModal({ isOpen, onClose, tripId, tripTitle }:
                         )}
                       </div>
                     </div>
+                    {isCurrentOwner && member.role !== 'owner' && (
+                      <button
+                        onClick={() => handleTransfer(member.id, member.username)}
+                        disabled={transferringId === member.id}
+                        title={t('members.makeOwner')}
+                        style={{ background: 'none', border: 'none', cursor: 'pointer', padding: '4px', borderRadius: 6, display: 'flex', color: 'var(--text-faint)', opacity: transferringId === member.id ? 0.4 : 1 }}
+                        onMouseEnter={e => e.currentTarget.style.color = '#d97706'}
+                        onMouseLeave={e => e.currentTarget.style.color = '#9ca3af'}
+                      >
+                        <Crown size={14} />
+                      </button>
+                    )}
                     {canRemove && (
                       <button
                         onClick={() => handleRemove(member.id, isSelf)}
diff --git a/server/src/nest/trips/trips.controller.ts b/server/src/nest/trips/trips.controller.ts
index ca4ecc7db..bc64e5b63 100644
--- a/server/src/nest/trips/trips.controller.ts
+++ b/server/src/nest/trips/trips.controller.ts
@@ -279,6 +279,41 @@ export class TripsController {
     return { success: true };
   }
 
+  @Post(':id/transfer')
+  transferOwnership(
+    @CurrentUser() user: User,
+    @Param('id') id: string,
+    @Body('newOwnerId') newOwnerId: unknown,
+    @Req() req: Request,
+    @Headers('x-socket-id') socketId?: string,
+  ) {
+    const access = this.trips.canAccessTrip(id, user.id);
+    if (!access) {
+      throw new HttpException({ error: 'Trip not found' }, 404);
+    }
+    // Owner-only: handing over a trip is reserved for its actual owner, not just
+    // anyone who can manage members.
+    if (access.user_id !== user.id) {
+      throw new HttpException({ error: 'Only the owner can transfer ownership' }, 403);
+    }
+    if (typeof newOwnerId !== 'number') {
+      throw new HttpException({ error: 'newOwnerId is required' }, 400);
+    }
+    try {
+      const result = this.trips.transferOwnership(id, newOwnerId, user.id);
+      writeAudit({ userId: user.id, action: 'trip.transfer_ownership', ip: getClientIp(req), details: { tripId: Number(id), trip: result.tripTitle, from: result.fromEmail, to: result.toEmail } });
+      // Nudge everyone viewing the trip to re-read it so the new ownership and the
+      // recomputed permissions take effect live.
+      const updatedTrip = this.trips.get(id, user.id);
+      this.trips.broadcast(id, 'trip:updated', { trip: updatedTrip }, socketId);
+      return { success: true };
+    } catch (e: unknown) {
+      if (e instanceof NotFoundError) throw new HttpException({ error: e.message }, 404);
+      if (e instanceof ValidationError) throw new HttpException({ error: e.message }, 400);
+      throw e;
+    }
+  }
+
   @Get(':id/bundle')
   bundle(@CurrentUser() user: User, @Param('id') id: string) {
     const trip = this.trips.get(id, user.id) as { user_id: number } | undefined;
diff --git a/server/src/nest/trips/trips.service.ts b/server/src/nest/trips/trips.service.ts
index 9526e0061..2a04b048b 100644
--- a/server/src/nest/trips/trips.service.ts
+++ b/server/src/nest/trips/trips.service.ts
@@ -95,6 +95,10 @@ export class TripsService {
     tripSvc.removeMember(tripId, targetId);
   }
 
+  transferOwnership(tripId: string, newOwnerId: number, currentOwnerId: number) {
+    return tripSvc.transferOwnership(tripId, newOwnerId, currentOwnerId);
+  }
+
   exportICS(tripId: string) {
     return tripSvc.exportICS(tripId);
   }
diff --git a/server/src/services/tripService.ts b/server/src/services/tripService.ts
index 4aacb5f17..058cdf262 100644
--- a/server/src/services/tripService.ts
+++ b/server/src/services/tripService.ts
@@ -403,6 +403,48 @@ export function removeMember(tripId: string | number, targetUserId: number) {
   db.prepare('DELETE FROM trip_members WHERE trip_id = ? AND user_id = ?').run(tripId, targetUserId);
 }
 
+export interface TransferOwnershipResult {
+  tripTitle: string;
+  fromEmail: string;
+  toEmail: string;
+}
+
+/**
+ * Hand a trip over to one of its existing members (#973). The new owner must
+ * already be a member; afterwards they hold `trips.user_id` and the former owner
+ * becomes a regular member, so nobody loses access. Runs in a transaction so the
+ * owner pointer and the membership rows never diverge.
+ */
+export function transferOwnership(
+  tripId: string | number,
+  newOwnerId: number,
+  currentOwnerId: number,
+): TransferOwnershipResult {
+  const trip = db.prepare('SELECT id, title, user_id FROM trips WHERE id = ?').get(tripId) as { id: number; title: string; user_id: number } | undefined;
+  if (!trip) throw new NotFoundError('Trip not found');
+  if (trip.user_id !== currentOwnerId) throw new ValidationError('Only the owner can transfer ownership');
+  if (newOwnerId === currentOwnerId) throw new ValidationError('You already own this trip');
+
+  const newOwner = db.prepare('SELECT id, email FROM users WHERE id = ?').get(newOwnerId) as { id: number; email: string } | undefined;
+  if (!newOwner) throw new NotFoundError('User not found');
+
+  const isMember = db.prepare('SELECT id FROM trip_members WHERE trip_id = ? AND user_id = ?').get(tripId, newOwnerId);
+  if (!isMember) throw new ValidationError('New owner must be a trip member');
+
+  const fromEmail = (db.prepare('SELECT email FROM users WHERE id = ?').get(currentOwnerId) as { email: string } | undefined)?.email || '';
+
+  const run = db.transaction(() => {
+    db.prepare('UPDATE trips SET user_id = ? WHERE id = ?').run(newOwnerId, tripId);
+    // The new owner is no longer a plain member…
+    db.prepare('DELETE FROM trip_members WHERE trip_id = ? AND user_id = ?').run(tripId, newOwnerId);
+    // …and the former owner keeps access as a member.
+    db.prepare('INSERT OR IGNORE INTO trip_members (trip_id, user_id, invited_by) VALUES (?, ?, ?)').run(tripId, currentOwnerId, newOwnerId);
+  });
+  run();
+
+  return { tripTitle: trip.title, fromEmail, toEmail: newOwner.email };
+}
+
 // ── ICS export ────────────────────────────────────────────────────────────
 
 // RFC 5545 §3.1: content lines longer than 75 octets must be folded with a CRLF
diff --git a/server/tests/integration/trips.test.ts b/server/tests/integration/trips.test.ts
index 32694b716..1646cd0a6 100644
--- a/server/tests/integration/trips.test.ts
+++ b/server/tests/integration/trips.test.ts
@@ -736,6 +736,54 @@ describe('Trip members', () => {
     expect(res.body.success).toBe(true);
   });
 
+  it('TRIP-TRANSFER-001 — owner hands the trip to a member; roles swap (#973)', async () => {
+    const { user: owner } = createUser(testDb);
+    const { user: member } = createUser(testDb);
+    const trip = createTrip(testDb, owner.id, { title: 'Team Trip' });
+    addTripMember(testDb, trip.id, member.id);
+
+    const res = await request(app)
+      .post(`/api/trips/${trip.id}/transfer`)
+      .set('Cookie', authCookie(owner.id))
+      .send({ newOwnerId: member.id });
+
+    expect(res.status).toBe(201);
+    expect(res.body.success).toBe(true);
+
+    const row = testDb.prepare('SELECT user_id FROM trips WHERE id = ?').get(trip.id) as { user_id: number };
+    expect(row.user_id).toBe(member.id);
+    const memberRows = (testDb.prepare('SELECT user_id FROM trip_members WHERE trip_id = ?').all(trip.id) as { user_id: number }[]).map(r => r.user_id);
+    expect(memberRows).toContain(owner.id);
+    expect(memberRows).not.toContain(member.id);
+  });
+
+  it('TRIP-TRANSFER-002 — a non-owner cannot transfer ownership → 403', async () => {
+    const { user: owner } = createUser(testDb);
+    const { user: member } = createUser(testDb);
+    const trip = createTrip(testDb, owner.id, { title: 'Team Trip' });
+    addTripMember(testDb, trip.id, member.id);
+
+    const res = await request(app)
+      .post(`/api/trips/${trip.id}/transfer`)
+      .set('Cookie', authCookie(member.id))
+      .send({ newOwnerId: member.id });
+
+    expect(res.status).toBe(403);
+  });
+
+  it('TRIP-TRANSFER-003 — cannot transfer to a non-member → 400', async () => {
+    const { user: owner } = createUser(testDb);
+    const { user: stranger } = createUser(testDb);
+    const trip = createTrip(testDb, owner.id, { title: 'Team Trip' });
+
+    const res = await request(app)
+      .post(`/api/trips/${trip.id}/transfer`)
+      .set('Cookie', authCookie(owner.id))
+      .send({ newOwnerId: stranger.id });
+
+    expect(res.status).toBe(400);
+  });
+
   it('TRIP-013 — Non-owner member cannot add other members when member_manage is trip_owner', async () => {
     const { user: owner } = createUser(testDb);
     const { user: member } = createUser(testDb);
diff --git a/server/tests/unit/nest/trips.controller.test.ts b/server/tests/unit/nest/trips.controller.test.ts
index 5f4ded3e1..7a44c2b27 100644
--- a/server/tests/unit/nest/trips.controller.test.ts
+++ b/server/tests/unit/nest/trips.controller.test.ts
@@ -256,6 +256,41 @@ describe('TripsController (parity with the legacy /api/trips route)', () => {
     });
   });
 
+  describe('POST /:id/transfer (#973)', () => {
+    it('404 without trip access', () => {
+      const s = svc({ canAccessTrip: vi.fn().mockReturnValue(undefined) });
+      expect(thrown(() => new TripsController(s).transferOwnership(user, '9', 2, req))).toEqual({ status: 404, body: { error: 'Trip not found' } });
+    });
+
+    it('403 when the requester is not the owner', () => {
+      // access.user_id (5) differs from the requesting user (1)
+      const s = svc({ canAccessTrip: vi.fn().mockReturnValue({ user_id: 5 }) });
+      expect(thrown(() => new TripsController(s).transferOwnership(user, '9', 2, req))).toEqual({ status: 403, body: { error: 'Only the owner can transfer ownership' } });
+    });
+
+    it('400 when newOwnerId is not a number', () => {
+      const s = svc();
+      expect(thrown(() => new TripsController(s).transferOwnership(user, '9', 'nope' as unknown as number, req))).toEqual({ status: 400, body: { error: 'newOwnerId is required' } });
+    });
+
+    it('transfers, audits and broadcasts the refreshed trip', () => {
+      const transferOwnership = vi.fn().mockReturnValue({ tripTitle: 'Roadtrip', fromEmail: 'a@x.y', toEmail: 'b@x.y' });
+      const get = vi.fn().mockReturnValue({ id: 9, user_id: 2 });
+      const broadcast = vi.fn();
+      const s = svc({ transferOwnership, get, broadcast } as Partial<TripsService>);
+      expect(new TripsController(s).transferOwnership(user, '9', 2, req, 'sock')).toEqual({ success: true });
+      expect(transferOwnership).toHaveBeenCalledWith('9', 2, user.id);
+      expect(broadcast).toHaveBeenCalledWith('9', 'trip:updated', { trip: { id: 9, user_id: 2 } }, 'sock');
+    });
+
+    it('maps NotFoundError to 404 and ValidationError to 400', () => {
+      const nf = svc({ transferOwnership: vi.fn().mockImplementation(() => { throw new NotFoundError('User not found'); }) } as Partial<TripsService>);
+      expect(thrown(() => new TripsController(nf).transferOwnership(user, '9', 2, req))).toEqual({ status: 404, body: { error: 'User not found' } });
+      const ve = svc({ transferOwnership: vi.fn().mockImplementation(() => { throw new ValidationError('New owner must be a trip member'); }) } as Partial<TripsService>);
+      expect(thrown(() => new TripsController(ve).transferOwnership(user, '9', 2, req))).toEqual({ status: 400, body: { error: 'New owner must be a trip member' } });
+    });
+  });
+
   it('GET /:id/bundle 404 then aggregates', () => {
     expect(thrown(() => new TripsController(svc({ get: vi.fn().mockReturnValue(undefined) } as Partial<TripsService>)).bundle(user, '9'))).toEqual({ status: 404, body: { error: 'Trip not found' } });
     const bundle = vi.fn().mockReturnValue({ trip: { id: 9 }, days: [] });
diff --git a/server/tests/unit/nest/trips.service.test.ts b/server/tests/unit/nest/trips.service.test.ts
index b0daaa9a1..296a124ae 100644
--- a/server/tests/unit/nest/trips.service.test.ts
+++ b/server/tests/unit/nest/trips.service.test.ts
@@ -17,6 +17,7 @@ const { tripSvc } = vi.hoisted(() => ({
     listTrips: vi.fn(), createTrip: vi.fn(), getTrip: vi.fn(), updateTrip: vi.fn(), deleteTrip: vi.fn(),
     getTripRaw: vi.fn(), getTripOwner: vi.fn(), deleteOldCover: vi.fn(), updateCoverImage: vi.fn(),
     listMembers: vi.fn(() => ({ owner: { id: 1 }, members: [] })), addMember: vi.fn(), removeMember: vi.fn(),
+    transferOwnership: vi.fn(),
     exportICS: vi.fn(), copyTripById: vi.fn(), TRIP_SELECT: 'SELECT * FROM trips t',
   },
 }));
@@ -50,6 +51,7 @@ describe('TripsService (wrapper delegation + bundle/copy/notify helpers)', () =>
     s.listMembers('9', 1); expect(tripSvc.listMembers).toHaveBeenCalledWith('9', 1);
     s.addMember('9', 'b@x.y', 1, 1); expect(tripSvc.addMember).toHaveBeenCalledWith('9', 'b@x.y', 1, 1);
     s.removeMember('9', 2); expect(tripSvc.removeMember).toHaveBeenCalledWith('9', 2);
+    s.transferOwnership('9', 2, 1); expect(tripSvc.transferOwnership).toHaveBeenCalledWith('9', 2, 1);
     s.exportICS('9'); expect(tripSvc.exportICS).toHaveBeenCalledWith('9');
   });
 
diff --git a/server/tests/unit/services/tripService.test.ts b/server/tests/unit/services/tripService.test.ts
index 06afba637..4425aca9e 100644
--- a/server/tests/unit/services/tripService.test.ts
+++ b/server/tests/unit/services/tripService.test.ts
@@ -33,8 +33,8 @@ vi.mock('../../../src/config', () => ({
 import { createTables } from '../../../src/db/schema';
 import { runMigrations } from '../../../src/db/migrations';
 import { resetTestDb } from '../../helpers/test-db';
-import { createUser, createTrip, createReservation, createPlace, createDay, createDayAssignment, createDayNote } from '../../helpers/factories';
-import { exportICS, generateDays, deleteOldCover, updateTrip } from '../../../src/services/tripService';
+import { createUser, createTrip, createReservation, createPlace, createDay, createDayAssignment, createDayNote, addTripMember } from '../../helpers/factories';
+import { exportICS, generateDays, deleteOldCover, updateTrip, transferOwnership } from '../../../src/services/tripService';
 import fs from 'fs';
 
 beforeAll(() => {
@@ -507,3 +507,45 @@ describe('resyncReservationDays (#1288)', () => {
     expect(res.day_id).toBe(origDayId);
   });
 });
+
+describe('transferOwnership (#973)', () => {
+  it('TRIP-SVC-020: hands the trip to a member and demotes the former owner to a member', () => {
+    const { user: owner } = createUser(testDb);
+    const { user: member } = createUser(testDb);
+    const trip = createTrip(testDb, owner.id);
+    addTripMember(testDb, trip.id, member.id);
+
+    const result = transferOwnership(trip.id, member.id, owner.id);
+    expect(result.toEmail).toBe(member.email);
+
+    const updated = testDb.prepare('SELECT user_id FROM trips WHERE id = ?').get(trip.id) as { user_id: number };
+    expect(updated.user_id).toBe(member.id);
+
+    // New owner no longer sits in trip_members, former owner now does.
+    const memberIds = (testDb.prepare('SELECT user_id FROM trip_members WHERE trip_id = ?').all(trip.id) as { user_id: number }[]).map(r => r.user_id);
+    expect(memberIds).toContain(owner.id);
+    expect(memberIds).not.toContain(member.id);
+  });
+
+  it('TRIP-SVC-021: rejects a transfer from a non-owner', () => {
+    const { user: owner } = createUser(testDb);
+    const { user: member } = createUser(testDb);
+    const trip = createTrip(testDb, owner.id);
+    addTripMember(testDb, trip.id, member.id);
+    // member (not the owner) attempts the transfer
+    expect(() => transferOwnership(trip.id, member.id, member.id)).toThrow();
+  });
+
+  it('TRIP-SVC-022: rejects a transfer to someone who is not a member', () => {
+    const { user: owner } = createUser(testDb);
+    const { user: stranger } = createUser(testDb);
+    const trip = createTrip(testDb, owner.id);
+    expect(() => transferOwnership(trip.id, stranger.id, owner.id)).toThrow('New owner must be a trip member');
+  });
+
+  it('TRIP-SVC-023: rejects transferring to yourself', () => {
+    const { user: owner } = createUser(testDb);
+    const trip = createTrip(testDb, owner.id);
+    expect(() => transferOwnership(trip.id, owner.id, owner.id)).toThrow('You already own this trip');
+  });
+});
diff --git a/shared/src/i18n/ar/members.ts b/shared/src/i18n/ar/members.ts
index 4048da13c..95e92fa9c 100644
--- a/shared/src/i18n/ar/members.ts
+++ b/shared/src/i18n/ar/members.ts
@@ -20,5 +20,8 @@ const members: TranslationStrings = {
   'members.addError': 'فشلت الإضافة',
   'members.removed': 'تمت إزالة العضو',
   'members.removeError': 'فشلت الإزالة',
+  'members.makeOwner': 'تعيين كمالك',
+  'members.confirmTransfer': 'نقل الملكية إلى {name}؟ ستصبح عضوًا عاديًا.',
+  'members.transferError': 'فشل نقل الملكية',
 };
 export default members;
diff --git a/shared/src/i18n/br/members.ts b/shared/src/i18n/br/members.ts
index a735d1322..521c5aea6 100644
--- a/shared/src/i18n/br/members.ts
+++ b/shared/src/i18n/br/members.ts
@@ -20,5 +20,8 @@ const members: TranslationStrings = {
   'members.addError': 'Falha ao adicionar',
   'members.removed': 'Membro removido',
   'members.removeError': 'Falha ao remover',
+  'members.makeOwner': 'Tornar proprietário',
+  'members.confirmTransfer': 'Transferir a propriedade para {name}? Você se tornará um membro comum.',
+  'members.transferError': 'Falha ao transferir a propriedade',
 };
 export default members;
diff --git a/shared/src/i18n/cs/members.ts b/shared/src/i18n/cs/members.ts
index 88300252c..bbbe3f5f5 100644
--- a/shared/src/i18n/cs/members.ts
+++ b/shared/src/i18n/cs/members.ts
@@ -20,5 +20,8 @@ const members: TranslationStrings = {
   'members.addError': 'Nepodařilo se přidat',
   'members.removed': 'Člen odebrán',
   'members.removeError': 'Nepodařilo se odebrat',
+  'members.makeOwner': 'Nastavit jako vlastníka',
+  'members.confirmTransfer': 'Převést vlastnictví na {name}? Stanete se běžným členem.',
+  'members.transferError': 'Převod vlastnictví se nezdařil',
 };
 export default members;
diff --git a/shared/src/i18n/de/members.ts b/shared/src/i18n/de/members.ts
index 85aaa8bf8..83dc9a705 100644
--- a/shared/src/i18n/de/members.ts
+++ b/shared/src/i18n/de/members.ts
@@ -20,5 +20,8 @@ const members: TranslationStrings = {
   'members.addError': 'Fehler beim Hinzufügen',
   'members.removed': 'Mitglied entfernt',
   'members.removeError': 'Fehler beim Entfernen',
+  'members.makeOwner': 'Zum Eigentümer machen',
+  'members.confirmTransfer': 'Eigentümerschaft an {name} übertragen? Du wirst zu einem normalen Mitglied.',
+  'members.transferError': 'Übertragung fehlgeschlagen',
 };
 export default members;
diff --git a/shared/src/i18n/en/members.ts b/shared/src/i18n/en/members.ts
index dc2319b26..4433ea141 100644
--- a/shared/src/i18n/en/members.ts
+++ b/shared/src/i18n/en/members.ts
@@ -20,5 +20,8 @@ const members: TranslationStrings = {
   'members.addError': 'Failed to add',
   'members.removed': 'Member removed',
   'members.removeError': 'Failed to remove',
+  'members.makeOwner': 'Make owner',
+  'members.confirmTransfer': 'Transfer ownership to {name}? You will become a regular member.',
+  'members.transferError': 'Failed to transfer ownership',
 };
 export default members;
diff --git a/shared/src/i18n/es/members.ts b/shared/src/i18n/es/members.ts
index fe21ea22e..f78926d7e 100644
--- a/shared/src/i18n/es/members.ts
+++ b/shared/src/i18n/es/members.ts
@@ -20,5 +20,8 @@ const members: TranslationStrings = {
   'members.addError': 'No se pudo añadir',
   'members.removed': 'Miembro eliminado',
   'members.removeError': 'No se pudo eliminar',
+  'members.makeOwner': 'Hacer propietario',
+  'members.confirmTransfer': '¿Transferir la propiedad a {name}? Pasarás a ser un miembro normal.',
+  'members.transferError': 'Error al transferir la propiedad',
 };
 export default members;
diff --git a/shared/src/i18n/fr/members.ts b/shared/src/i18n/fr/members.ts
index 46f1078c2..03cab09a4 100644
--- a/shared/src/i18n/fr/members.ts
+++ b/shared/src/i18n/fr/members.ts
@@ -20,5 +20,8 @@ const members: TranslationStrings = {
   'members.addError': "Échec de l'ajout",
   'members.removed': 'Membre retiré',
   'members.removeError': 'Échec de la suppression',
+  'members.makeOwner': 'Définir comme propriétaire',
+  'members.confirmTransfer': 'Transférer la propriété à {name} ? Vous deviendrez un membre ordinaire.',
+  'members.transferError': 'Échec du transfert de propriété',
 };
 export default members;
diff --git a/shared/src/i18n/gr/members.ts b/shared/src/i18n/gr/members.ts
index 759bda6b7..523aea9f8 100644
--- a/shared/src/i18n/gr/members.ts
+++ b/shared/src/i18n/gr/members.ts
@@ -20,5 +20,8 @@ const members: TranslationStrings = {
   'members.addError': 'Αποτυχία προσθήκης',
   'members.removed': 'Το μέλος αφαιρέθηκε',
   'members.removeError': 'Αποτυχία αφαίρεσης',
+  'members.makeOwner': 'Ορισμός ως κάτοχο',
+  'members.confirmTransfer': 'Μεταβίβαση ιδιοκτησίας στον/στην {name}; Θα γίνετε απλό μέλος.',
+  'members.transferError': 'Αποτυχία μεταβίβασης ιδιοκτησίας',
 };
 export default members;
diff --git a/shared/src/i18n/hu/members.ts b/shared/src/i18n/hu/members.ts
index bec59e8bd..cba646090 100644
--- a/shared/src/i18n/hu/members.ts
+++ b/shared/src/i18n/hu/members.ts
@@ -20,5 +20,8 @@ const members: TranslationStrings = {
   'members.addError': 'Nem sikerült hozzáadni',
   'members.removed': 'Tag eltávolítva',
   'members.removeError': 'Nem sikerült eltávolítani',
+  'members.makeOwner': 'Tulajdonossá tétel',
+  'members.confirmTransfer': 'Átruházza a tulajdonjogot {name} részére? Ön normál taggá válik.',
+  'members.transferError': 'A tulajdonjog átruházása sikertelen',
 };
 export default members;
diff --git a/shared/src/i18n/id/members.ts b/shared/src/i18n/id/members.ts
index eebdb9f0a..b9c41442e 100644
--- a/shared/src/i18n/id/members.ts
+++ b/shared/src/i18n/id/members.ts
@@ -20,5 +20,8 @@ const members: TranslationStrings = {
   'members.addError': 'Gagal menambahkan',
   'members.removed': 'Anggota dihapus',
   'members.removeError': 'Gagal menghapus',
+  'members.makeOwner': 'Jadikan pemilik',
+  'members.confirmTransfer': 'Alihkan kepemilikan ke {name}? Anda akan menjadi anggota biasa.',
+  'members.transferError': 'Gagal mengalihkan kepemilikan',
 };
 export default members;
diff --git a/shared/src/i18n/it/members.ts b/shared/src/i18n/it/members.ts
index 1a05a7349..08c0a69cb 100644
--- a/shared/src/i18n/it/members.ts
+++ b/shared/src/i18n/it/members.ts
@@ -20,5 +20,8 @@ const members: TranslationStrings = {
   'members.addError': 'Impossibile aggiungere',
   'members.removed': 'Membro rimosso',
   'members.removeError': 'Impossibile rimuovere',
+  'members.makeOwner': 'Rendi proprietario',
+  'members.confirmTransfer': 'Trasferire la proprietà a {name}? Diventerai un membro normale.',
+  'members.transferError': 'Trasferimento della proprietà non riuscito',
 };
 export default members;
diff --git a/shared/src/i18n/ja/members.ts b/shared/src/i18n/ja/members.ts
index 3d749039d..9d5691d2b 100644
--- a/shared/src/i18n/ja/members.ts
+++ b/shared/src/i18n/ja/members.ts
@@ -20,5 +20,8 @@ const members: TranslationStrings = {
   'members.addError': '追加に失敗しました',
   'members.removed': 'メンバーを削除しました',
   'members.removeError': '削除に失敗しました',
+  'members.makeOwner': 'オーナーにする',
+  'members.confirmTransfer': '所有権を {name} に移譲しますか？あなたは通常のメンバーになります。',
+  'members.transferError': '所有権の移譲に失敗しました',
 };
 export default members;
diff --git a/shared/src/i18n/ko/members.ts b/shared/src/i18n/ko/members.ts
index 582435417..ab3afacd2 100644
--- a/shared/src/i18n/ko/members.ts
+++ b/shared/src/i18n/ko/members.ts
@@ -20,5 +20,8 @@ const members: TranslationStrings = {
   'members.addError': '추가 실패',
   'members.removed': '멤버가 제거되었습니다',
   'members.removeError': '제거 실패',
+  'members.makeOwner': '소유자로 지정',
+  'members.confirmTransfer': '{name}님에게 소유권을 이전하시겠습니까? 일반 멤버가 됩니다.',
+  'members.transferError': '소유권 이전 실패',
 };
 export default members;
diff --git a/shared/src/i18n/nl/members.ts b/shared/src/i18n/nl/members.ts
index 074c3b10a..92c6333e6 100644
--- a/shared/src/i18n/nl/members.ts
+++ b/shared/src/i18n/nl/members.ts
@@ -20,5 +20,8 @@ const members: TranslationStrings = {
   'members.addError': 'Toevoegen mislukt',
   'members.removed': 'Lid verwijderd',
   'members.removeError': 'Verwijderen mislukt',
+  'members.makeOwner': 'Eigenaar maken',
+  'members.confirmTransfer': 'Eigenaarschap overdragen aan {name}? Je wordt een gewoon lid.',
+  'members.transferError': 'Overdracht van eigenaarschap mislukt',
 };
 export default members;
diff --git a/shared/src/i18n/pl/members.ts b/shared/src/i18n/pl/members.ts
index 99f756ea4..b5c04bf82 100644
--- a/shared/src/i18n/pl/members.ts
+++ b/shared/src/i18n/pl/members.ts
@@ -20,5 +20,8 @@ const members: TranslationStrings = {
   'members.addError': 'Nie udało się dodać członka',
   'members.removed': 'Usunięto członka',
   'members.removeError': 'Nie udało się usunąć członka',
+  'members.makeOwner': 'Ustaw jako właściciela',
+  'members.confirmTransfer': 'Przekazać własność użytkownikowi {name}? Staniesz się zwykłym członkiem.',
+  'members.transferError': 'Nie udało się przekazać własności',
 };
 export default members;
diff --git a/shared/src/i18n/ru/members.ts b/shared/src/i18n/ru/members.ts
index 237d0556a..a0c4affb4 100644
--- a/shared/src/i18n/ru/members.ts
+++ b/shared/src/i18n/ru/members.ts
@@ -20,5 +20,8 @@ const members: TranslationStrings = {
   'members.addError': 'Ошибка добавления',
   'members.removed': 'Участник удалён',
   'members.removeError': 'Ошибка удаления',
+  'members.makeOwner': 'Назначить владельцем',
+  'members.confirmTransfer': 'Передать права владельца пользователю {name}? Вы станете обычным участником.',
+  'members.transferError': 'Не удалось передать права владельца',
 };
 export default members;
diff --git a/shared/src/i18n/sv/members.ts b/shared/src/i18n/sv/members.ts
index 0877937f1..0189e8942 100644
--- a/shared/src/i18n/sv/members.ts
+++ b/shared/src/i18n/sv/members.ts
@@ -20,5 +20,8 @@ const members: TranslationStrings = {
   'members.addError': 'Kunde inte lägga till',
   'members.removed': 'Medlem borttagen',
   'members.removeError': 'Kunde inte ta bort',
+  'members.makeOwner': 'Gör till ägare',
+  'members.confirmTransfer': 'Överför ägarskapet till {name}? Du blir en vanlig medlem.',
+  'members.transferError': 'Det gick inte att överföra ägarskapet',
 };
 export default members;
diff --git a/shared/src/i18n/tr/members.ts b/shared/src/i18n/tr/members.ts
index 224f0e0e6..bb39de84b 100644
--- a/shared/src/i18n/tr/members.ts
+++ b/shared/src/i18n/tr/members.ts
@@ -20,5 +20,8 @@ const members: TranslationStrings = {
   'members.addError': 'Eklenemedi',
   'members.removed': 'Üye kaldırıldı',
   'members.removeError': 'Kaldırılamadı',
+  'members.makeOwner': 'Sahip yap',
+  'members.confirmTransfer': 'Sahipliği {name} kullanıcısına devret? Normal bir üye olacaksınız.',
+  'members.transferError': 'Sahiplik devredilemedi',
 };
 export default members;
diff --git a/shared/src/i18n/uk/members.ts b/shared/src/i18n/uk/members.ts
index ac28a9fa0..f529f08e1 100644
--- a/shared/src/i18n/uk/members.ts
+++ b/shared/src/i18n/uk/members.ts
@@ -20,5 +20,8 @@ const members: TranslationStrings = {
   'members.addError': 'Помилка додавання',
   'members.removed': 'Учасник видалений',
   'members.removeError': 'Помилка видалення',
+  'members.makeOwner': 'Призначити власником',
+  'members.confirmTransfer': 'Передати право власності користувачу {name}? Ви станете звичайним учасником.',
+  'members.transferError': 'Не вдалося передати право власності',
 };
 export default members;
diff --git a/shared/src/i18n/vi/members.ts b/shared/src/i18n/vi/members.ts
index 33c3f45dd..bbfd775f0 100644
--- a/shared/src/i18n/vi/members.ts
+++ b/shared/src/i18n/vi/members.ts
@@ -20,5 +20,8 @@ const members: TranslationStrings = {
   'members.addError': 'Không thể thêm',
   'members.removed': 'Thành viên đã bị xóa',
   'members.removeError': 'Không thể xóa',
+  'members.makeOwner': 'Đặt làm chủ sở hữu',
+  'members.confirmTransfer': 'Chuyển quyền sở hữu cho {name}? Bạn sẽ trở thành thành viên thường.',
+  'members.transferError': 'Không thể chuyển quyền sở hữu',
 };
 export default members;
diff --git a/shared/src/i18n/zh-TW/members.ts b/shared/src/i18n/zh-TW/members.ts
index 17049fe3f..4f57aad16 100644
--- a/shared/src/i18n/zh-TW/members.ts
+++ b/shared/src/i18n/zh-TW/members.ts
@@ -20,5 +20,8 @@ const members: TranslationStrings = {
   'members.addError': '新增失敗',
   'members.removed': '成員已移除',
   'members.removeError': '移除失敗',
+  'members.makeOwner': '設為擁有者',
+  'members.confirmTransfer': '將擁有權轉移給 {name}？你將成為一般成員。',
+  'members.transferError': '轉移擁有權失敗',
 };
 export default members;
diff --git a/shared/src/i18n/zh/members.ts b/shared/src/i18n/zh/members.ts
index d2a62003e..9c45e7354 100644
--- a/shared/src/i18n/zh/members.ts
+++ b/shared/src/i18n/zh/members.ts
@@ -20,5 +20,8 @@ const members: TranslationStrings = {
   'members.addError': '添加失败',
   'members.removed': '成员已移除',
   'members.removeError': '移除失败',
+  'members.makeOwner': '设为所有者',
+  'members.confirmTransfer': '将所有权转移给 {name}？你将成为普通成员。',
+  'members.transferError': '转移所有权失败',
 };
 export default members;
diff --git a/shared/src/trip/trip.schema.ts b/shared/src/trip/trip.schema.ts
index 1e1db07da..c4bd36d66 100644
--- a/shared/src/trip/trip.schema.ts
+++ b/shared/src/trip/trip.schema.ts
@@ -92,3 +92,9 @@ export const tripAddMemberRequestSchema = z.object({
   identifier: z.string(),
 });
 export type TripAddMemberRequest = z.infer<typeof tripAddMemberRequestSchema>;
+
+// Hand the trip over to an existing member (#973).
+export const tripTransferOwnershipRequestSchema = z.object({
+  newOwnerId: z.number().int().positive(),
+});
+export type TripTransferOwnershipRequest = z.infer<typeof tripTransferOwnershipRequestSchema>;