diff --git a/client/src/components/Trips/TripFormModal.test.tsx b/client/src/components/Trips/TripFormModal.test.tsx
index a75f301fc..cbe045694 100644
--- a/client/src/components/Trips/TripFormModal.test.tsx
+++ b/client/src/components/Trips/TripFormModal.test.tsx
@@ -11,6 +11,7 @@ import { resetAllStores, seedStore } from '../../../tests/helpers/store';
 import { buildUser, buildTrip } from '../../../tests/helpers/factories';
 import { server } from '../../../tests/helpers/msw/server';
 import type { Trip } from '../../types';
+import { MAX_TRIP_DAYS } from '@trek/shared';
 import TripFormModal from './TripFormModal';
 
 const defaultProps = {
@@ -321,7 +322,7 @@ describe('TripFormModal', () => {
 
   it('FE-COMP-TRIPFORM-029: clearing the day count leaves the field empty (no snap to 1)', () => {
     render(<TripFormModal {...defaultProps} trip={null} />);
-    const dayInput = document.querySelector('input[max="365"]') as HTMLInputElement;
+    const dayInput = document.querySelector(`input[max="${MAX_TRIP_DAYS}"]`) as HTMLInputElement;
     expect(dayInput).toBeInTheDocument();
     expect(dayInput.value).toBe('7');
     fireEvent.change(dayInput, { target: { value: '' } });
@@ -333,7 +334,7 @@ describe('TripFormModal', () => {
     const onSave = vi.fn();
     render(<TripFormModal {...defaultProps} trip={null} onSave={onSave} />);
     await user.type(screen.getByPlaceholderText(/Summer in Japan/i), 'No-date Trip');
-    const dayInput = document.querySelector('input[max="365"]') as HTMLInputElement;
+    const dayInput = document.querySelector(`input[max="${MAX_TRIP_DAYS}"]`) as HTMLInputElement;
     fireEvent.change(dayInput, { target: { value: '' } });
     const submitBtn = screen.getAllByText('Create New Trip').find(el => el.closest('button'))!;
     await user.click(submitBtn.closest('button')!);
@@ -534,7 +535,7 @@ describe('TripFormModal', () => {
     expect(screen.getByPlaceholderText(/Summer in Japan/i)).toHaveValue('');
     expect(screen.getByText(/^EUR/)).toBeInTheDocument();
     // No dates -> the day-count field appears and falls back to 7.
-    expect(document.querySelector('input[max="365"]')).toHaveValue('7');
+    expect(document.querySelector(`input[max="${MAX_TRIP_DAYS}"]`)).toHaveValue('7');
   });
 
   // ── Create follow-ups: members and cover ──────────────────────────────────
@@ -921,7 +922,7 @@ describe('TripFormModal', () => {
     fireEvent.keyDown(input, { key: 'Enter' });
 
     // The day-count field disappears once the trip is dated.
-    await waitFor(() => expect(document.querySelector('input[max="365"]')).toBeNull());
+    await waitFor(() => expect(document.querySelector(`input[max="${MAX_TRIP_DAYS}"]`)).toBeNull());
     await submitNewTrip(user);
     await waitFor(() => expect(onSave).toHaveBeenCalledWith(
       expect.objectContaining({ start_date: '2026-04-10', end_date: '2026-04-10' })
@@ -951,18 +952,18 @@ describe('TripFormModal', () => {
     ));
   });
 
-  it('FE-COMP-TRIPFORM-067: the day count is clamped to the 1..365 range', async () => {
+  it('FE-COMP-TRIPFORM-067: the day count is clamped to the 1..MAX_TRIP_DAYS range', async () => {
     const user = userEvent.setup();
     const onSave = vi.fn().mockResolvedValue({});
     render(<TripFormModal {...defaultProps} trip={null} onSave={onSave} />);
 
-    const dayInput = document.querySelector('input[max="365"]') as HTMLInputElement;
-    fireEvent.change(dayInput, { target: { value: '400' } });
-    expect(dayInput.value).toBe('365');
+    const dayInput = document.querySelector(`input[max="${MAX_TRIP_DAYS}"]`) as HTMLInputElement;
+    fireEvent.change(dayInput, { target: { value: String(MAX_TRIP_DAYS + 1) } });
+    expect(dayInput.value).toBe(String(MAX_TRIP_DAYS));
 
     await user.type(screen.getByPlaceholderText(/Summer in Japan/i), 'Long Trip');
     await submitNewTrip(user);
-    await waitFor(() => expect(onSave).toHaveBeenCalledWith(expect.objectContaining({ day_count: 365 })));
+    await waitFor(() => expect(onSave).toHaveBeenCalledWith(expect.objectContaining({ day_count: MAX_TRIP_DAYS })));
   });
 
   it('FE-COMP-TRIPFORM-068: a currency without a known symbol is labelled with its code', () => {
@@ -1249,4 +1250,44 @@ describe('TripFormModal', () => {
     await waitFor(() => expect(revokeObjectURL).toHaveBeenCalledWith('blob:first'));
     Object.defineProperty(URL, 'revokeObjectURL', { writable: true, configurable: true, value: original });
   });
+
+  it('FE-COMP-TRIPFORM-085: a trip longer than a year is saved with its full range (#2403)', async () => {
+    const user = userEvent.setup();
+    const onSave = vi.fn().mockResolvedValue({});
+    const trip = buildTrip({ id: 1, title: 'Gap year', start_date: '2025-01-26', end_date: '2026-01-28' });
+    render(<TripFormModal {...defaultProps} trip={trip} onSave={onSave} />);
+    await user.click(screen.getByRole('button', { name: /Update/i }));
+    await waitFor(() => expect(onSave).toHaveBeenCalledWith(
+      expect.objectContaining({ start_date: '2025-01-26', end_date: '2026-01-28' })
+    ));
+  });
+
+  it('FE-COMP-TRIPFORM-086: a range past MAX_TRIP_DAYS is refused before anything is sent', async () => {
+    const user = userEvent.setup();
+    const onSave = vi.fn();
+    const trip = buildTrip({ id: 1, title: 'Week', start_date: '2026-01-01', end_date: '2026-01-07' });
+    render(<TripFormModal {...defaultProps} trip={trip} onSave={onSave} />);
+
+    await user.click(screen.getAllByRole('button', { name: 'Enter date manually' })[1]);
+    const endInput = screen.getByPlaceholderText('DD.MM.YYYY');
+    fireEvent.change(endInput, { target: { value: '2036-01-01' } });
+    fireEvent.keyDown(endInput, { key: 'Enter' });
+
+    await user.click(screen.getByRole('button', { name: /Update/i }));
+    await screen.findByText(`A trip can span at most ${MAX_TRIP_DAYS} days`);
+    expect(onSave).not.toHaveBeenCalled();
+  });
+
+  it('FE-COMP-TRIPFORM-087: a trip stored with a longer range can still be renamed', async () => {
+    const user = userEvent.setup();
+    const onSave = vi.fn().mockResolvedValue({});
+    const trip = buildTrip({ id: 1, title: 'Legacy', start_date: '2020-01-01', end_date: '2030-01-01' });
+    render(<TripFormModal {...defaultProps} trip={trip} onSave={onSave} />);
+    await user.clear(screen.getByPlaceholderText(/Summer in Japan/i));
+    await user.type(screen.getByPlaceholderText(/Summer in Japan/i), 'Renamed');
+    await user.click(screen.getByRole('button', { name: /Update/i }));
+    await waitFor(() => expect(onSave).toHaveBeenCalledWith(
+      expect.objectContaining({ title: 'Renamed', start_date: '2020-01-01', end_date: '2030-01-01' })
+    ));
+  });
 });
diff --git a/client/src/components/Trips/TripFormModal.tsx b/client/src/components/Trips/TripFormModal.tsx
index 5b954eaa1..526e0f1e4 100644
--- a/client/src/components/Trips/TripFormModal.tsx
+++ b/client/src/components/Trips/TripFormModal.tsx
@@ -11,7 +11,7 @@ import { useTranslation } from '../../i18n'
 import { CustomDatePicker } from '../shared/CustomDateTimePicker'
 import { normalizeImageFile } from '../../utils/convertHeic'
 import { getApiErrorMessage, type Trip } from '../../types'
-import type { TripCreateRequest } from '@trek/shared'
+import { MAX_TRIP_DAYS, tripSpanDays, type TripCreateRequest } from '@trek/shared'
 import { NumericInput } from '../shared/NumericInput'
 import { currenciesWith, SYMBOLS } from '../Budget/BudgetPanel.constants'
 
@@ -148,12 +148,17 @@ export default function TripFormModal({ isOpen, onClose, onSave, trip, onCoverUp
     e.preventDefault()
     setError('')
     if (!formData.title.trim()) { setError(t('dashboard.titleRequired')); return }
-    if (formData.start_date && formData.end_date && new Date(formData.end_date) < new Date(formData.start_date)) {
-      setError(t('dashboard.endDateError')); return
+    if (formData.start_date && formData.end_date) {
+      const span = tripSpanDays(formData.start_date, formData.end_date)
+      if (span < 1) { setError(t('dashboard.endDateError')); return }
+      // Only a range being set is held to the limit, as on the server: a trip that
+      // already carries a longer one can still be renamed.
+      const datesTouched = !trip || formData.start_date !== (trip.start_date || '') || formData.end_date !== (trip.end_date || '')
+      if (datesTouched && span > MAX_TRIP_DAYS) { setError(t('dashboard.tripTooLong', { days: MAX_TRIP_DAYS })); return }
     }
     if (!formData.start_date && !formData.end_date) {
       const dc = Number(formData.day_count)
-      if (formData.day_count === '' || !Number.isInteger(dc) || dc < 1 || dc > 365) {
+      if (formData.day_count === '' || !Number.isInteger(dc) || dc < 1 || dc > MAX_TRIP_DAYS) {
         setError(t('dashboard.dayCountRequired')); return
       }
     }
@@ -557,11 +562,11 @@ export default function TripFormModal({ isOpen, onClose, onSave, trip, onCoverUp
             <label className={labelCls}>
               {t('dashboard.dayCount')}
             </label>
-            <NumericInput min={1} max={365} value={formData.day_count}
+            <NumericInput min={1} max={MAX_TRIP_DAYS} value={formData.day_count}
               onValueChange={raw => {
                 if (raw === '') { update('day_count', ''); return }
                 const n = Math.floor(Number(raw))
-                if (Number.isFinite(n)) update('day_count', Math.min(365, Math.max(1, n)))
+                if (Number.isFinite(n)) update('day_count', Math.min(MAX_TRIP_DAYS, Math.max(1, n)))
               }}
               className={inputCls} />
             <p className="text-caption text-content-faint mt-1.5">{t('dashboard.dayCountHint')}</p>
diff --git a/client/src/mobile/screens/dashboard/MNewTripSheet.tsx b/client/src/mobile/screens/dashboard/MNewTripSheet.tsx
index e046b0a54..a2bc80c31 100644
--- a/client/src/mobile/screens/dashboard/MNewTripSheet.tsx
+++ b/client/src/mobile/screens/dashboard/MNewTripSheet.tsx
@@ -11,7 +11,7 @@ import { CustomDatePicker } from '../../../components/shared/CustomDateTimePicke
 import CustomSelect from '../../../components/shared/CustomSelect'
 import { currenciesWith, SYMBOLS } from '../../../components/Budget/BudgetPanel.constants'
 import type { DashboardTrip } from '../../../pages/dashboard/dashboardModel'
-import type { Trip, TripCreateRequest } from '@trek/shared'
+import { MAX_TRIP_DAYS, tripSpanDays, type Trip, type TripCreateRequest } from '@trek/shared'
 import MSheet from '../../components/MSheet'
 import MIconBtn from '../../components/MIconBtn'
 import MListRow from '../../components/MListRow'
@@ -112,8 +112,11 @@ export default function MNewTripSheet({ open, trip, onClose, onSave, onCoverUpda
   const handleSave = async () => {
     setError('')
     if (!title.trim()) { setError(t('dashboard.titleRequired')); return }
-    if (startDate && endDate && new Date(endDate) < new Date(startDate)) {
-      setError(t('dashboard.endDateError')); return
+    if (startDate && endDate) {
+      const span = tripSpanDays(startDate, endDate)
+      if (span < 1) { setError(t('dashboard.endDateError')); return }
+      const datesTouched = !trip || startDate !== (trip.start_date || '') || endDate !== (trip.end_date || '')
+      if (datesTouched && span > MAX_TRIP_DAYS) { setError(t('dashboard.tripTooLong', { days: MAX_TRIP_DAYS })); return }
     }
     setIsSaving(true)
     try {
diff --git a/client/tests/unit/mobile/dashboard/MNewTripSheet.test.tsx b/client/tests/unit/mobile/dashboard/MNewTripSheet.test.tsx
index 441519042..9520ce9c8 100644
--- a/client/tests/unit/mobile/dashboard/MNewTripSheet.test.tsx
+++ b/client/tests/unit/mobile/dashboard/MNewTripSheet.test.tsx
@@ -8,7 +8,7 @@ import { usePermissionsStore } from '../../../../src/store/permissionsStore';
 import { useSettingsStore } from '../../../../src/store/settingsStore';
 import { buildUser } from '../../../helpers/factories';
 import type { DashboardTrip } from '../../../../src/pages/dashboard/dashboardModel';
-import type { Trip, TripCreateRequest } from '@trek/shared';
+import { MAX_TRIP_DAYS, type Trip, type TripCreateRequest } from '@trek/shared';
 
 interface CoverSearchPhoto {
   id: string
@@ -136,6 +136,20 @@ describe('MNewTripSheet', () => {
     expect(onSave).not.toHaveBeenCalled();
   });
 
+  it('FE-MOB-NTSH-036: a range past MAX_TRIP_DAYS blocks the save (#2403)', () => {
+    const onSave = vi.fn(async () => undefined);
+    render(<MNewTripSheet open trip={null} onClose={() => {}} onSave={onSave} />);
+
+    fireEvent.change(screen.getByPlaceholderText('e.g. Summer in Japan'), { target: { value: 'Decade' } });
+    fireEvent.change(screen.getByLabelText('Start Date'), { target: { value: '2026-01-01' } });
+    fireEvent.change(screen.getByLabelText('End Date'), { target: { value: '2036-01-01' } });
+
+    fireEvent.click(screen.getByRole('button', { name: 'Create New Trip' }));
+
+    expect(screen.getByText(`A trip can span at most ${MAX_TRIP_DAYS} days`)).toBeInTheDocument();
+    expect(onSave).not.toHaveBeenCalled();
+  });
+
   it('FE-MOB-NTSH-005: a dateless create asks for the 7 default days and closes', async () => {
     const onSave = vi.fn(async (_data: TripCreateRequest) => undefined);
     const onClose = vi.fn();
diff --git a/server/src/mcp/tools/_shared.ts b/server/src/mcp/tools/_shared.ts
index d0a2b4b9a..9b6a7922f 100644
--- a/server/src/mcp/tools/_shared.ts
+++ b/server/src/mcp/tools/_shared.ts
@@ -17,8 +17,6 @@ export {
   TOOL_ANNOTATIONS_WRITE,
 } from '../../nest-mcp';
 
-export const MAX_MCP_TRIP_DAYS = 90;
-
 export function noAccess() {
   return errorResult('Trip not found or access denied.');
 }
diff --git a/server/src/nest/mcp-shared/mcp-tool-guards.service.ts b/server/src/nest/mcp-shared/mcp-tool-guards.service.ts
index 891056ce2..d8a9bfba4 100644
--- a/server/src/nest/mcp-shared/mcp-tool-guards.service.ts
+++ b/server/src/nest/mcp-shared/mcp-tool-guards.service.ts
@@ -8,7 +8,7 @@ import { RealtimeService } from '../realtime/realtime.service';
  * src/mcp/tools/_shared.ts, reaching the db Proxy, permissions.bridge and the
  * src/websocket stub as module globals. The @McpController domain classes are
  * ordinary Nest providers, so they inject this instead. The pure result
- * helpers (noAccess/permissionDenied/adminRequired/MAX_MCP_TRIP_DAYS and the
+ * helpers (noAccess/permissionDenied/adminRequired and the
  * src/nest-mcp re-exports) stay in _shared.ts — they carry no dependencies.
  */
 @Injectable()
diff --git a/server/src/nest/mcp-transport/mcp-transport.constants.ts b/server/src/nest/mcp-transport/mcp-transport.constants.ts
index a0396c0cd..dc687fcd7 100644
--- a/server/src/nest/mcp-transport/mcp-transport.constants.ts
+++ b/server/src/nest/mcp-transport/mcp-transport.constants.ts
@@ -44,7 +44,7 @@ You are connected to TREK, a travel planning application. Below is a compact ref
 - The authenticated user can only access trips they own or are a member of. Never guess at trip IDs.
 - Only the trip owner can delete the trip, add members, or remove members.
 - Deleting a place removes all of its day assignments as well — warn the user before doing this.
-- Trips created via MCP are capped at 90 days.
+- A trip can span at most 999 days, by date range or by day_count.
 
 ## Dates and times
 
diff --git a/server/src/nest/reservation-import/reservation-import.mcp.ts b/server/src/nest/reservation-import/reservation-import.mcp.ts
index 3b67928e8..2f412fd69 100644
--- a/server/src/nest/reservation-import/reservation-import.mcp.ts
+++ b/server/src/nest/reservation-import/reservation-import.mcp.ts
@@ -20,8 +20,8 @@ const airtrailAddonOn = addonGate(ADDON_IDS.AIRTRAIL);
 /**
  * The picker sends whatever a human ticked; a model can name a hundred ids off
  * one hallucinated list, and each one becomes a reservation and a broadcast.
- * The same reasoning as MAX_MCP_TRIP_DAYS: the tool surface caps a bulk write
- * the REST route leaves open, and says how to continue.
+ * The tool surface caps a bulk write the REST route leaves open, and says how
+ * to continue.
  */
 const MAX_MCP_AIRTRAIL_FLIGHTS = 50;
 
diff --git a/server/src/nest/trips/trips.controller.ts b/server/src/nest/trips/trips.controller.ts
index eb940b8bb..91c4d36b0 100644
--- a/server/src/nest/trips/trips.controller.ts
+++ b/server/src/nest/trips/trips.controller.ts
@@ -23,7 +23,7 @@ import { RuntimeEnvService } from '../app-config/runtime-env.service';
 import type { Request, Response } from 'express';
 import type { Options } from 'multer';
 import path from 'path';
-import type { ActiveTripResponse } from '@trek/shared';
+import { MAX_TRIP_DAYS, type ActiveTripResponse } from '@trek/shared';
 import { StorageService } from '../storage/storage.service';
 import type { User } from '../../types';
 import { TripsService } from './trips.service';
@@ -116,11 +116,16 @@ export class TripsController {
     if (start_date && end_date && new Date(end_date) < new Date(start_date)) {
       throw new HttpException({ error: 'End date must be after start date' }, 400);
     }
-    const parsedDayCount = day_count ? Math.min(Math.max(Number(day_count) || 7, 1), 365) : undefined;
-    const { trip, tripId, reminderDays } = this.trips.create(user.id, { title, description, start_date, end_date, currency, reminder_days, day_count: parsedDayCount });
-    this.audit.writeAudit({ userId: user.id, action: 'trip.create', ip: getClientIp(req), details: { tripId, title, reminder_days: reminderDays === 0 ? 'none' : `${reminderDays} days` } });
-    if (reminderDays > 0) logInfo(`${user.email} set ${reminderDays}-day reminder for trip "${title}"`);
-    return { trip };
+    const parsedDayCount = day_count ? Math.min(Math.max(Number(day_count) || 7, 1), MAX_TRIP_DAYS) : undefined;
+    try {
+      const { trip, tripId, reminderDays } = this.trips.create(user.id, { title, description, start_date, end_date, currency, reminder_days, day_count: parsedDayCount });
+      this.audit.writeAudit({ userId: user.id, action: 'trip.create', ip: getClientIp(req), details: { tripId, title, reminder_days: reminderDays === 0 ? 'none' : `${reminderDays} days` } });
+      if (reminderDays > 0) logInfo(`${user.email} set ${reminderDays}-day reminder for trip "${title}"`);
+      return { trip };
+    } catch (e: unknown) {
+      if (e instanceof ValidationError) throw new HttpException({ error: e.message }, 400);
+      throw e;
+    }
   }
 
   @Get(':id')
diff --git a/server/src/nest/trips/trips.mcp.ts b/server/src/nest/trips/trips.mcp.ts
index 483abc018..efb20d16f 100644
--- a/server/src/nest/trips/trips.mcp.ts
+++ b/server/src/nest/trips/trips.mcp.ts
@@ -12,9 +12,10 @@ import { CalendarService } from '../calendar/calendar.service';
 import { TripMembersService } from '../trip-members/trip-members.service';
 import { TripReadModelService } from '../trip-read-model/trip-read-model.service';
 import { ADDON_IDS } from '../../addons';
-import { MAX_MCP_TRIP_DAYS, noAccess, permissionDenied } from '../../mcp/tools/_shared';
+import { noAccess, permissionDenied } from '../../mcp/tools/_shared';
 import { canRead, canReadTrips, canDeleteTrips } from '../../mcp/scopes';
-import { TripsService, MAX_TRIP_DAYS, NotFoundError, ValidationError } from './trips.service';
+import { MAX_TRIP_DAYS } from '@trek/shared';
+import { TripsService, NotFoundError, ValidationError } from './trips.service';
 import { TodoService } from '../todo/todo.service';
 import { CollabService } from '../collab/collab.service';
 import { AddonsService } from '../addons/addons.service';
@@ -81,7 +82,7 @@ export class TripsMcp {
 
   @Tool({
     name: 'create_trip',
-    description: 'Create a new trip. Returns the created trip with its generated days.',
+    description: 'Create a new trip. Returns the created trip; its day_count is the number of days generated, one per day of the date range.',
     inputSchema: {
       title: z.string().min(1).max(200).describe('Trip title'),
       description: z.string().max(2000).optional().describe('Trip description'),
@@ -117,8 +118,13 @@ export class TripsMcp {
     if (start_date && end_date && new Date(end_date) < new Date(start_date)) {
       return { content: [{ type: 'text' as const, text: 'End date must be after start date.' }], isError: true };
     }
-    const { trip } = this.trips.create(ctx.userId, { title, description, start_date, end_date, currency, day_count, reminder_days }, MAX_MCP_TRIP_DAYS);
-    return ok({ trip });
+    try {
+      const { trip } = this.trips.create(ctx.userId, { title, description, start_date, end_date, currency, day_count, reminder_days });
+      return ok({ trip });
+    } catch (err) {
+      if (err instanceof ValidationError) return errorResult(err.message);
+      throw err;
+    }
   }
 
   @Tool({
@@ -177,9 +183,14 @@ export class TripsMcp {
       : { start_date, end_date };
     // update() re-anchors the budget before the trip row moves off the old
     // currency (#1543) and then runs the legacy updateTrip core.
-    const { updatedTrip } = await this.trips.update(tripId, ctx.userId, { title, description, ...dates, currency, is_archived, cover_image, day_count, reminder_days, date_shift_mode }, 'user');
-    this.guards.safeBroadcast(tripId, 'trip:updated', { trip: updatedTrip });
-    return ok({ trip: updatedTrip });
+    try {
+      const { updatedTrip } = await this.trips.update(tripId, ctx.userId, { title, description, ...dates, currency, is_archived, cover_image, day_count, reminder_days, date_shift_mode }, 'user');
+      this.guards.safeBroadcast(tripId, 'trip:updated', { trip: updatedTrip });
+      return ok({ trip: updatedTrip });
+    } catch (err) {
+      if (err instanceof ValidationError) return errorResult(err.message);
+      throw err;
+    }
   }
 
   @Tool({
diff --git a/server/src/nest/trips/trips.service.ts b/server/src/nest/trips/trips.service.ts
index ae2ed81c0..f500def9d 100644
--- a/server/src/nest/trips/trips.service.ts
+++ b/server/src/nest/trips/trips.service.ts
@@ -1,7 +1,7 @@
 import { Injectable } from '@nestjs/common';
 import path from 'path';
 import { DatabaseService } from '../database/database.service';
-import type { ActiveTrip, TrekWsPayload, TrekWsTripEventName } from '@trek/shared';
+import { MAX_TRIP_DAYS, tripSpanDays, type ActiveTrip, type TrekWsPayload, type TrekWsTripEventName } from '@trek/shared';
 import { RealtimeService } from '../realtime/realtime.service';
 import { PermissionsService } from '../permissions/permissions.service';
 import type { Trip, User } from '../../types';
@@ -14,7 +14,19 @@ import { StorageService } from '../storage/storage.service';
 import { NotFoundError, ValidationError } from '../common/domain-errors';
 
 export const MS_PER_DAY = 86400000;
-export const MAX_TRIP_DAYS = 365;
+
+/**
+ * The date range is refused, not cut short: generateDays used to clip the day
+ * rows at the limit while the trip kept its full end date, so everything past
+ * the cut-off had dates but no day to go on (#2403). An inverted range is
+ * refused here as well, because a start date moved past the stored end date
+ * arrives on its own and would otherwise empty the trip.
+ */
+function assertTripSpan(startDate: string, endDate: string) {
+  const span = tripSpanDays(startDate, endDate);
+  if (span < 1) throw new ValidationError('End date must be after start date');
+  if (span > MAX_TRIP_DAYS) throw new ValidationError(`A trip can span at most ${MAX_TRIP_DAYS} days`);
+}
 
 /**
  * Strips `feed_token` from a trip row on its way out.
@@ -171,7 +183,7 @@ export class TripsService {
 
   // ── Day generation ────────────────────────────────────────────────────────
 
-  generateDays(tripId: number | bigint | string, startDate: string | null, endDate: string | null, maxDays?: number, dayCount?: number) {
+  generateDays(tripId: number | bigint | string, startDate: string | null, endDate: string | null, dayCount?: number) {
     const existing = this.db.prepare('SELECT id, day_number, date FROM days WHERE trip_id = ?').all(tripId) as { id: number; day_number: number; date: string | null }[];
     const setDayNumber = this.db.prepare('UPDATE days SET day_number = ? WHERE id = ?');
 
@@ -215,10 +227,8 @@ export class TripsService {
     }
 
     const [sy, sm, sd] = startDate.split('-').map(Number);
-    const [ey, em, ed] = endDate.split('-').map(Number);
     const startMs = Date.UTC(sy, sm - 1, sd);
-    const endMs = Date.UTC(ey, em - 1, ed);
-    const numDays = Math.min(Math.floor((endMs - startMs) / MS_PER_DAY) + 1, maxDays ?? MAX_TRIP_DAYS);
+    const numDays = tripSpanDays(startDate, endDate);
 
     const targetDates: string[] = [];
     for (let i = 0; i < numDays; i++) {
@@ -309,7 +319,8 @@ export class TripsService {
     `).all({ userId, archived });
   }
 
-  create(userId: number, data: CreateTripData, maxDays?: number) {
+  create(userId: number, data: CreateTripData) {
+    if (data.start_date && data.end_date) assertTripSpan(data.start_date, data.end_date);
     const rd = data.reminder_days !== undefined
       ? (Number(data.reminder_days) >= 0 && Number(data.reminder_days) <= 30 ? Number(data.reminder_days) : 3)
       : 3;
@@ -320,7 +331,7 @@ export class TripsService {
     `).run(userId, data.title, data.description || null, data.start_date || null, data.end_date || null, data.currency || 'EUR', rd);
 
     const tripId = result.lastInsertRowid;
-    this.generateDays(tripId, data.start_date || null, data.end_date || null, maxDays, data.day_count);
+    this.generateDays(tripId, data.start_date || null, data.end_date || null, data.day_count);
 
     const trip = this.db.prepare(`${TRIP_SELECT} WHERE t.id = :tripId`).get({ userId, tripId });
     return { trip, tripId: Number(tripId), reminderDays: rd };
@@ -384,15 +395,11 @@ export class TripsService {
     const trip = this.db.prepare('SELECT * FROM trips WHERE id = ?').get(tripId) as Trip & { reminder_days?: number } | undefined;
     if (!trip) throw new NotFoundError('Trip not found');
 
-    const { title, description, start_date, end_date, currency, is_archived, cover_image, reminder_days } = data;
-
-    if (start_date && end_date && new Date(end_date) < new Date(start_date))
-      throw new ValidationError('End date must be after start date');
+    const { title, description, currency, is_archived, cover_image, reminder_days } = data;
+    const { newStart, newEnd, dayCount, regenerate } = this.resolveRange(trip, data);
 
     const newTitle = title || trip.title;
     const newDesc = description !== undefined ? description : trip.description;
-    const newStart = start_date !== undefined ? start_date : trip.start_date;
-    const newEnd = end_date !== undefined ? end_date : trip.end_date;
     const newCurrency = currency || trip.currency;
     const newArchived = is_archived !== undefined ? (is_archived ? 1 : 0) : trip.is_archived;
     const newCover = cover_image !== undefined ? cover_image : trip.cover_image;
@@ -410,8 +417,7 @@ export class TripsService {
     if (trip.start_date && trip.end_date && newStart && newStart !== trip.start_date)
       this.vacay.shiftOwnerEntriesForTripWindow(trip.user_id, trip.start_date, trip.end_date, newStart);
 
-    const dayCount = data.day_count ? Math.min(Math.max(Number(data.day_count) || 7, 1), MAX_TRIP_DAYS) : undefined;
-    if (newStart !== trip.start_date || newEnd !== trip.end_date || dayCount) {
+    if (regenerate) {
       this.db.transaction(() => {
         // Accommodations have no absolute date columns, so their pre-change dates must be
         // snapshotted before generateDays re-dates the day rows in place.
@@ -419,7 +425,7 @@ export class TripsService {
           (this.db.prepare('SELECT id, date FROM days WHERE trip_id = ?').all(tripId) as { id: number; date: string | null }[])
             .map(d => [d.id, d.date]),
         );
-        this.generateDays(tripId, newStart || null, newEnd || null, undefined, dayCount);
+        this.generateDays(tripId, newStart || null, newEnd || null, dayCount);
         if (data.date_shift_mode === 'shift_all') {
           // Explicit "shift everything": bookings stay glued to their (re-dated) day rows,
           // so re-stamp reservation_time to follow — same rules as reorderDays/insertDay.
@@ -456,7 +462,31 @@ export class TripsService {
     return { updatedTrip, changes, isAdminEdit, ownerEmail, newTitle, newReminder, oldReminder };
   }
 
+  /**
+   * The dates the update leaves the trip with, checked before anything is
+   * written. The day grid is rebuilt whenever a date moves or a day_count
+   * arrives, and a dated rebuild runs over the whole range, so the range is
+   * held to the limit exactly then. A trip stored with a longer range can
+   * still be renamed.
+   */
+  private resolveRange(trip: Trip, data: UpdateTripData) {
+    const { start_date, end_date } = data;
+    if (start_date && end_date && new Date(end_date) < new Date(start_date))
+      throw new ValidationError('End date must be after start date');
+    const newStart = start_date !== undefined ? start_date : trip.start_date;
+    const newEnd = end_date !== undefined ? end_date : trip.end_date;
+    const dayCount = data.day_count ? Math.min(Math.max(Number(data.day_count) || 7, 1), MAX_TRIP_DAYS) : undefined;
+    const regenerate = newStart !== trip.start_date || newEnd !== trip.end_date || dayCount !== undefined;
+    if (regenerate && newStart && newEnd) assertTripSpan(newStart, newEnd);
+    return { newStart, newEnd, dayCount, regenerate };
+  }
+
   async update(tripId: string | number, userId: number, body: UpdateTripData, role: string) {
+    // A refused range must not leave the budget rebased onto a currency the trip
+    // never took, so the dates are checked before the first write.
+    const trip = this.getRaw(tripId);
+    if (!trip) throw new NotFoundError('Trip not found');
+    this.resolveRange(trip, body);
     // Re-anchor the budget while the outgoing currency is still on the trip row,
     // otherwise the frozen FX rates and the currency-less expenses that inherit the
     // trip's base are left pointing at a currency that no longer exists (#1543).
diff --git a/server/tests/e2e/trips.e2e.test.ts b/server/tests/e2e/trips.e2e.test.ts
index f70c761dd..21ba5a733 100644
--- a/server/tests/e2e/trips.e2e.test.ts
+++ b/server/tests/e2e/trips.e2e.test.ts
@@ -12,6 +12,7 @@ import { DatabaseModule } from '../../src/nest/database/database.module';
 import { RealtimeModule } from '../../src/nest/realtime/realtime.module';
 import { Test } from '@nestjs/testing';
 import { seedUser, sessionCookie } from './harness';
+import { MAX_TRIP_DAYS } from '@trek/shared';
 
 const { db } = vi.hoisted(() => {
   // eslint-disable-next-line @typescript-eslint/no-require-imports
@@ -197,6 +198,33 @@ describe('Trips e2e (real auth guard + temp SQLite)', () => {
     expect(forbidden.status).toBe(403);
   });
 
+  it('201 create keeps every day of a trip longer than a year (#2403)', async () => {
+    // 2025-01-26 .. 2026-01-28 is 368 days; the day list used to stop at 365.
+    const res = await request(server).post('/api/trips').set('Cookie', sessionCookie(1))
+      .send({ title: 'Gap year', start_date: '2025-01-26', end_date: '2026-01-28' });
+    expect(res.status).toBe(201);
+    expect(res.body.trip).toMatchObject({ start_date: '2025-01-26', end_date: '2026-01-28', day_count: 368 });
+    const last = db.prepare('SELECT day_number, date FROM days WHERE trip_id = ? ORDER BY day_number DESC LIMIT 1')
+      .get(res.body.trip.id) as { day_number: number; date: string };
+    expect(last).toEqual({ day_number: 368, date: '2026-01-28' });
+  });
+
+  it('400 on a date range past MAX_TRIP_DAYS, for create and update alike', async () => {
+    const tooLong = await request(server).post('/api/trips').set('Cookie', sessionCookie(1))
+      .send({ title: 'Decade', start_date: '2026-01-01', end_date: '2036-01-01' });
+    expect(tooLong.status).toBe(400);
+    expect(tooLong.body).toEqual({ error: `A trip can span at most ${MAX_TRIP_DAYS} days` });
+    expect(db.prepare('SELECT COUNT(*) AS n FROM trips').get()).toEqual({ n: 0 });
+
+    const week = await request(server).post('/api/trips').set('Cookie', sessionCookie(1))
+      .send({ title: 'Week', start_date: '2026-07-01', end_date: '2026-07-07' });
+    const stretched = await request(server).put(`/api/trips/${week.body.trip.id}`).set('Cookie', sessionCookie(1))
+      .send({ end_date: '2036-07-01' });
+    expect(stretched.status).toBe(400);
+    expect(stretched.body).toEqual({ error: `A trip can span at most ${MAX_TRIP_DAYS} days` });
+    expect(db.prepare('SELECT end_date FROM trips WHERE id = ?').get(week.body.trip.id)).toEqual({ end_date: '2026-07-07' });
+  });
+
   it('404 on a missing trip', async () => {
     const res = await request(server).get('/api/trips/77').set('Cookie', sessionCookie(1));
     expect(res.status).toBe(404);
diff --git a/server/tests/unit/mcp/tools-trips.test.ts b/server/tests/unit/mcp/tools-trips.test.ts
index a87550953..af761f32c 100644
--- a/server/tests/unit/mcp/tools-trips.test.ts
+++ b/server/tests/unit/mcp/tools-trips.test.ts
@@ -43,6 +43,7 @@ import { runMigrations } from '../../../src/db/migrations';
 import { resetTestDb } from '../../helpers/test-db';
 import { createUser, createTrip, createDay, createPlace, addTripMember, createBudgetItem, createPackingItem, createReservation, createDayNote, createCollabNote, createDayAssignment, createDayAccommodation } from '../../helpers/factories';
 import { createMcpHarness, parseToolResult, parseResourceResult, type McpHarness } from '../../helpers/mcp-harness';
+import { MAX_TRIP_DAYS } from '@trek/shared';
 
 beforeAll(() => {
   createTables(testDb);
@@ -99,16 +100,29 @@ describe('Tool: create_trip', () => {
     });
   });
 
-  it('caps days at 90 for very long trips', async () => {
+  it('generates every day of a trip longer than a year (#2403)', async () => {
     const { user } = createUser(testDb);
     await withHarness(user.id, async (h) => {
       const result = await h.client.callTool({
         name: 'create_trip',
-        arguments: { title: 'Long Trip', start_date: '2026-01-01', end_date: '2027-12-31' },
+        arguments: { title: 'Long Trip', start_date: '2025-01-26', end_date: '2026-01-28' },
       });
       const data = parseToolResult(result) as any;
       const days = testDb.prepare('SELECT COUNT(*) as c FROM days WHERE trip_id = ?').get(data.trip.id) as { c: number };
-      expect(days.c).toBe(90);
+      expect(days.c).toBe(368);
+    });
+  });
+
+  it('refuses a date range longer than MAX_TRIP_DAYS instead of cutting the days short', async () => {
+    const { user } = createUser(testDb);
+    await withHarness(user.id, async (h) => {
+      const result = await h.client.callTool({
+        name: 'create_trip',
+        arguments: { title: 'Decade', start_date: '2026-01-01', end_date: '2036-01-01' },
+      });
+      expect(result.isError).toBe(true);
+      expect(JSON.stringify(result.content)).toContain(`at most ${MAX_TRIP_DAYS} days`);
+      expect(testDb.prepare('SELECT COUNT(*) as c FROM trips').get()).toEqual({ c: 0 });
     });
   });
 
@@ -153,11 +167,11 @@ describe('Tool: create_trip', () => {
     });
   });
 
-  it('refuses a day_count outside 1..365', async () => {
+  it('refuses a day_count outside 1..MAX_TRIP_DAYS', async () => {
     const { user } = createUser(testDb);
     await withHarness(user.id, async (h) => {
       expect((await h.client.callTool({ name: 'create_trip', arguments: { title: 'Zero', day_count: 0 } })).isError).toBe(true);
-      expect((await h.client.callTool({ name: 'create_trip', arguments: { title: 'Huge', day_count: 400 } })).isError).toBe(true);
+      expect((await h.client.callTool({ name: 'create_trip', arguments: { title: 'Huge', day_count: MAX_TRIP_DAYS + 1 } })).isError).toBe(true);
       expect(testDb.prepare('SELECT COUNT(*) as c FROM trips').get()).toEqual({ c: 0 });
     });
   });
@@ -378,16 +392,28 @@ describe('Tool: update_trip', () => {
     });
   });
 
-  it('refuses a day_count outside 1..365', async () => {
+  it('refuses a day_count outside 1..MAX_TRIP_DAYS', async () => {
     const { user } = createUser(testDb);
     const trip = createTrip(testDb, user.id, { title: 'Untouched' });
     await withHarness(user.id, async (h) => {
       expect((await h.client.callTool({ name: 'update_trip', arguments: { tripId: trip.id, day_count: 0 } })).isError).toBe(true);
-      expect((await h.client.callTool({ name: 'update_trip', arguments: { tripId: trip.id, day_count: 400 } })).isError).toBe(true);
+      expect((await h.client.callTool({ name: 'update_trip', arguments: { tripId: trip.id, day_count: MAX_TRIP_DAYS + 1 } })).isError).toBe(true);
       expect(testDb.prepare('SELECT COUNT(*) as c FROM days WHERE trip_id = ?').get(trip.id)).toEqual({ c: 0 });
     });
   });
 
+  it('refuses a date range longer than MAX_TRIP_DAYS and leaves the trip untouched', async () => {
+    const { user } = createUser(testDb);
+    const trip = createTrip(testDb, user.id, { title: 'Untouched', start_date: '2026-07-01', end_date: '2026-07-07' });
+    await withHarness(user.id, async (h) => {
+      const result = await h.client.callTool({ name: 'update_trip', arguments: { tripId: trip.id, end_date: '2036-07-01' } });
+      expect(result.isError).toBe(true);
+      expect(JSON.stringify(result.content)).toContain(`at most ${MAX_TRIP_DAYS} days`);
+      const row = testDb.prepare('SELECT end_date FROM trips WHERE id = ?').get(trip.id) as { end_date: string };
+      expect(row.end_date).toBe('2026-07-07');
+    });
+  });
+
   it('changes reminder_days and can turn the reminder off', async () => {
     const { user } = createUser(testDb);
     const trip = createTrip(testDb, user.id);
diff --git a/server/tests/unit/nest/trips.controller.test.ts b/server/tests/unit/nest/trips.controller.test.ts
index 1857d43f7..b675a1bb2 100644
--- a/server/tests/unit/nest/trips.controller.test.ts
+++ b/server/tests/unit/nest/trips.controller.test.ts
@@ -23,7 +23,7 @@ import type { CalendarService } from '../../../src/nest/calendar/calendar.servic
 import type { TripReadModelService } from '../../../src/nest/trip-read-model/trip-read-model.service';
 import { NotFoundError, ValidationError } from '../../../src/nest/trips/trips.service';
 import type { User } from '../../../src/types';
-import { activeTripResponseSchema, tripCreateRequestSchema, tripTransferOwnershipRequestSchema } from '@trek/shared';
+import { MAX_TRIP_DAYS, activeTripResponseSchema, tripCreateRequestSchema, tripTransferOwnershipRequestSchema } from '@trek/shared';
 
 const user = { id: 1, role: 'user', email: 'u@example.test' } as User;
 const req = { headers: {} } as Request;
@@ -180,6 +180,24 @@ describe('TripsController (parity with the legacy /api/trips route)', () => {
       expect(create).toHaveBeenCalledWith(1, expect.objectContaining({ day_count: 7 }));
     });
 
+    it('clamps day_count to MAX_TRIP_DAYS', () => {
+      const create = vi.fn().mockReturnValue({ trip: { id: 9 }, tripId: 9, reminderDays: 0 });
+      tc(svc({ create } as Partial<TripsService>)).create(user, { title: 'T', day_count: MAX_TRIP_DAYS + 1 }, req);
+      expect(create).toHaveBeenCalledWith(1, expect.objectContaining({ day_count: MAX_TRIP_DAYS }));
+    });
+
+    it('maps a ValidationError from create to 400 (range past MAX_TRIP_DAYS)', () => {
+      const create = vi.fn().mockImplementation(() => { throw new ValidationError(`A trip can span at most ${MAX_TRIP_DAYS} days`); });
+      expect(thrown(() => tc(svc({ create } as Partial<TripsService>)).create(user, { title: 'T', start_date: '2026-01-01', end_date: '2036-01-01' }, req))).toEqual({
+        status: 400, body: { error: `A trip can span at most ${MAX_TRIP_DAYS} days` },
+      });
+    });
+
+    it('re-throws an unknown error from create', () => {
+      const create = vi.fn().mockImplementation(() => { throw new Error('boom'); });
+      expect(() => tc(svc({ create } as Partial<TripsService>)).create(user, { title: 'T' }, req)).toThrow('boom');
+    });
+
     it('logs the reminder when reminderDays is set', () => {
       const create = vi.fn().mockReturnValue({ trip: { id: 9 }, tripId: 9, reminderDays: 3 });
       expect(tc(svc({ create } as Partial<TripsService>)).create(user, { title: 'T' }, req)).toEqual({ trip: { id: 9 } });
diff --git a/server/tests/unit/nest/trips.service.test.ts b/server/tests/unit/nest/trips.service.test.ts
index 77c56fc0a..b478a4a83 100644
--- a/server/tests/unit/nest/trips.service.test.ts
+++ b/server/tests/unit/nest/trips.service.test.ts
@@ -54,6 +54,7 @@ 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, addTripMember } from '../../helpers/factories';
+import { MAX_TRIP_DAYS } from '@trek/shared';
 import { DatabaseService } from '../../../src/nest/database/database.service';
 import { DaysService } from '../../../src/nest/days/days.service';
 import { PermissionsService } from '../../../src/nest/permissions/permissions.service';
@@ -169,6 +170,10 @@ function getNotes(dayId: number) {
   return testDb.prepare('SELECT * FROM day_notes WHERE day_id = ?').all(dayId) as { id: number; day_id: number }[];
 }
 
+function addDaysIso(date: string, n: number) {
+  return new Date(Date.parse(date + 'T00:00:00Z') + n * 86400000).toISOString().slice(0, 10);
+}
+
 // ── Tests ─────────────────────────────────────────────────────────────────────
 
 describe('generateDays', () => {
@@ -260,6 +265,24 @@ describe('generateDays', () => {
     expect(getAssignments(daysAfter[4].id)).toHaveLength(0);
   });
 
+  it('TRIP-SVC-062: a range longer than a year gets every one of its days (#2403)', () => {
+    const { user } = createUser(testDb);
+    const trip = createTrip(testDb, user.id, { start_date: '2025-01-26', end_date: '2025-01-28' });
+    // The reporter's range: 368 days, and the days used to stop at 365.
+    svc.generateDays(trip.id, '2025-01-26', '2026-01-28');
+    const days = getDays(trip.id);
+    expect(days).toHaveLength(368);
+    expect(days[364].date).toBe('2026-01-25');
+    expect(days[367]).toMatchObject({ day_number: 368, date: '2026-01-28' });
+  });
+
+  it('TRIP-SVC-063: a dateless day_count is clamped to MAX_TRIP_DAYS', () => {
+    const { user } = createUser(testDb);
+    const trip = createTrip(testDb, user.id);
+    svc.generateDays(trip.id, null, null, MAX_TRIP_DAYS + 50);
+    expect(getDays(trip.id)).toHaveLength(MAX_TRIP_DAYS);
+  });
+
   it('TRIP-SVC-013: clearing dates converts all days to dateless without destroying assignments', () => {
     const { user } = createUser(testDb);
     const trip = createTrip(testDb, user.id, { start_date: '2025-09-01', end_date: '2025-09-04' });
@@ -722,6 +745,17 @@ describe('folded trip CRUD', () => {
     expect(getDays(tripId)).toHaveLength(3);
   });
 
+  it('TRIP-SVC-064: create refuses a range past MAX_TRIP_DAYS and writes nothing', () => {
+    const { user } = createUser(testDb);
+    const before = (testDb.prepare('SELECT COUNT(*) AS n FROM trips').get() as { n: number }).n;
+    expect(() => svc.create(user.id, { title: 'Decade', start_date: '2026-01-01', end_date: '2036-01-01' }))
+      .toThrow(`A trip can span at most ${MAX_TRIP_DAYS} days`);
+    expect((testDb.prepare('SELECT COUNT(*) AS n FROM trips').get() as { n: number }).n).toBe(before);
+    // The longest allowed range goes through in full.
+    const { tripId } = svc.create(user.id, { title: 'Longest', start_date: '2026-01-01', end_date: addDaysIso('2026-01-01', MAX_TRIP_DAYS - 1) });
+    expect(getDays(tripId)).toHaveLength(MAX_TRIP_DAYS);
+  });
+
   it('TRIP-SVC-045: remove deletes the trip, cleans skeleton journey entries and detaches filled ones', () => {
     const { user } = createUser(testDb);
     const trip = createTrip(testDb, user.id);
@@ -930,13 +964,15 @@ describe('folded trip CRUD', () => {
 
 describe('TripsService wrapper helpers', () => {
   it('re-anchors the budget before the trip row leaves its old currency (#1543)', async () => {
+    const { user } = createUser(testDb);
+    const trip = createTrip(testDb, user.id);
     const order: string[] = [];
     const rebaseSpy = vi.spyOn(budgetSvc, 'rebaseTripCurrency').mockImplementation(async () => { order.push('rebase'); });
     const updateSpy = vi.spyOn(svc, 'updateTrip').mockImplementation(() => { order.push('update'); return {} as never; });
     try {
-      await svc.update('9', 1, { currency: 'RUB' } as never, 'user');
+      await svc.update(trip.id, user.id, { currency: 'RUB' } as never, 'user');
       // The rebase reads the outgoing currency off the trip row, so it has to run first.
-      expect(rebaseSpy).toHaveBeenCalledWith('9', 'RUB');
+      expect(rebaseSpy).toHaveBeenCalledWith(trip.id, 'RUB');
       expect(order).toEqual(['rebase', 'update']);
     } finally {
       rebaseSpy.mockRestore();
@@ -944,6 +980,22 @@ describe('TripsService wrapper helpers', () => {
     }
   });
 
+  it('TRIP-SVC-068: update refuses a bad range before the budget is rebased (#2403)', async () => {
+    const { user } = createUser(testDb);
+    const trip = createTrip(testDb, user.id, { start_date: '2026-07-01', end_date: '2026-07-07' });
+    const rebaseSpy = vi.spyOn(budgetSvc, 'rebaseTripCurrency').mockResolvedValue();
+    try {
+      await expect(svc.update(trip.id, user.id, { currency: 'USD', end_date: '2036-07-01' }, 'user'))
+        .rejects.toThrow(`A trip can span at most ${MAX_TRIP_DAYS} days`);
+      await expect(svc.update(trip.id, user.id, { currency: 'USD', start_date: '2026-07-10' }, 'user'))
+        .rejects.toThrow('End date must be after start date');
+      expect(rebaseSpy).not.toHaveBeenCalled();
+      await expect(svc.update(99999, user.id, { currency: 'USD' }, 'user')).rejects.toThrow('Trip not found');
+    } finally {
+      rebaseSpy.mockRestore();
+    }
+  });
+
   it('canAccessTrip delegates to the db helper; can() delegates to checkPermission; broadcast forwards', () => {
     const { user } = createUser(testDb);
     const trip = createTrip(testDb, user.id);
@@ -1006,6 +1058,40 @@ describe('folded quirk branches', () => {
     expect(() => svc.updateTrip(trip.id, owner.id, { start_date: '2025-06-10', end_date: '2025-06-01' }, 'user')).toThrow('End date must be after start date');
   });
 
+  it('TRIP-SVC-065: updateTrip refuses a range past MAX_TRIP_DAYS before touching the row', () => {
+    const { user } = createUser(testDb);
+    const trip = createTrip(testDb, user.id, { title: 'Week', start_date: '2026-07-01', end_date: '2026-07-07' });
+    expect(() => svc.updateTrip(trip.id, user.id, { title: 'Decade', end_date: '2036-07-01' }, 'user'))
+      .toThrow(`A trip can span at most ${MAX_TRIP_DAYS} days`);
+    expect(testDb.prepare('SELECT title, end_date FROM trips WHERE id = ?').get(trip.id)).toEqual({ title: 'Week', end_date: '2026-07-07' });
+    expect(getDays(trip.id)).toHaveLength(7);
+    // Moving only the start keeps the stored end and is measured against it.
+    expect(() => svc.updateTrip(trip.id, user.id, { start_date: '2020-01-01' }, 'user'))
+      .toThrow(`A trip can span at most ${MAX_TRIP_DAYS} days`);
+  });
+
+  it('TRIP-SVC-066: a trip whose stored range already exceeds the limit can still be renamed', () => {
+    const { user } = createUser(testDb);
+    const trip = createTrip(testDb, user.id, { title: 'Legacy' });
+    testDb.prepare("UPDATE trips SET start_date = '2020-01-01', end_date = '2030-01-01' WHERE id = ?").run(trip.id);
+    const result = svc.updateTrip(trip.id, user.id, { title: 'Renamed' }, 'user');
+    expect(result.newTitle).toBe('Renamed');
+    expect(result.changes).toEqual({ title: 'Renamed' });
+    // A day_count would rebuild the grid over the whole stored range, so it is held to the limit too.
+    expect(() => svc.updateTrip(trip.id, user.id, { day_count: 5 }, 'user'))
+      .toThrow(`A trip can span at most ${MAX_TRIP_DAYS} days`);
+    expect(getDays(trip.id)).toHaveLength(0);
+  });
+
+  it('TRIP-SVC-067: a start date moved past the stored end is refused instead of emptying the trip', () => {
+    const { user } = createUser(testDb);
+    const trip = createTrip(testDb, user.id, { title: 'Week', start_date: '2026-07-01', end_date: '2026-07-07' });
+    expect(() => svc.updateTrip(trip.id, user.id, { start_date: '2026-07-10' }, 'user'))
+      .toThrow('End date must be after start date');
+    expect(testDb.prepare('SELECT start_date FROM trips WHERE id = ?').get(trip.id)).toEqual({ start_date: '2026-07-01' });
+    expect(getDays(trip.id)).toHaveLength(7);
+  });
+
   it('TRIP-SVC-049: addMember inserts the membership and reports the trip title; removeMember deletes it', () => {
     const { user: owner } = createUser(testDb);
     const { user: invitee } = createUser(testDb);
diff --git a/server/tests/unit/trips/trips.rpc.test.ts b/server/tests/unit/trips/trips.rpc.test.ts
index f5fc0c655..b27e01ccf 100644
--- a/server/tests/unit/trips/trips.rpc.test.ts
+++ b/server/tests/unit/trips/trips.rpc.test.ts
@@ -15,6 +15,7 @@ import { PluginGuards } from '../../../src/nest/plugins/host/plugin-guards.servi
 import { TripsRpc } from '../../../src/nest/trips/trips.rpc';
 import { TripsModule } from '../../../src/nest/trips/trips.module';
 import { NotFoundError, ValidationError } from '../../../src/nest/trips/trips.service';
+import { MAX_TRIP_DAYS } from '@trek/shared';
 import type { TripsService } from '../../../src/nest/trips/trips.service';
 import type { ReservationsService } from '../../../src/nest/reservations/reservations.service';
 import type { DaysService } from '../../../src/nest/days/days.service';
@@ -33,14 +34,17 @@ const req = (method: string, params: Record<string, unknown> = {}): RpcRequest =
 const ALL_TRIP_GRANTS = ['db:read:trips', 'db:write:trips', 'db:create:trips', 'db:write:members'];
 
 /** Trip 1 belongs to user 42. `allow` decides each individual permission check. */
-export function build(opts: { allow?: (action: string) => boolean; updateThrows?: Error } = {}) {
+export function build(opts: { allow?: (action: string) => boolean; updateThrows?: Error; createThrows?: Error } = {}) {
   const trips = {
     list: vi.fn(() => [{ id: 1, title: 'Japan' }]),
     updateTrip: vi.fn(() => {
       if (opts.updateThrows) throw opts.updateThrows;
       return { updatedTrip: { id: 1, title: 'Japan' } };
     }),
-    create: vi.fn((userId: number) => ({ trip: { id: 99, user_id: userId } })),
+    create: vi.fn((userId: number) => {
+      if (opts.createThrows) throw opts.createThrows;
+      return { trip: { id: 99, user_id: userId } };
+    }),
     removeMember: vi.fn(),
   } as unknown as TripsService & Record<string, ReturnType<typeof vi.fn>>;
   const reservations = { list: vi.fn(() => [{ id: 5 }]) } as unknown as ReservationsService & Record<string, ReturnType<typeof vi.fn>>;
@@ -169,6 +173,12 @@ describe('TripsRpc writes', () => {
     expect(res.error.message).toBe('no permission to create trips');
     expect(f.trips.create).not.toHaveBeenCalled();
   });
+
+  it('TRIPS-RPC-017 a range the service refuses comes back as BAD_PARAMS (#2403)', async () => {
+    const f = build({ createThrows: new ValidationError(`A trip can span at most ${MAX_TRIP_DAYS} days`) });
+    const res = (await f.host().dispatch(req('trips.create', { input: { title: 'Decade', start_date: '2026-01-01', end_date: '2036-01-01' } }), 42)) as RpcError;
+    expect(res.error).toMatchObject({ code: 'BAD_PARAMS', message: `A trip can span at most ${MAX_TRIP_DAYS} days` });
+  });
 });
 
 describe('TripsRpc membership', () => {
diff --git a/shared/src/i18n/ar/dashboard.ts b/shared/src/i18n/ar/dashboard.ts
index 1d6176895..62f4dec4a 100644
--- a/shared/src/i18n/ar/dashboard.ts
+++ b/shared/src/i18n/ar/dashboard.ts
@@ -87,6 +87,7 @@ const dashboard: TranslationStrings = {
   'dashboard.useUnsplashPhoto': 'استخدم صورة من Unsplash بواسطة {photographer}',
   'dashboard.titleRequired': 'العنوان مطلوب',
   'dashboard.endDateError': 'يجب أن يكون تاريخ النهاية بعد البداية',
+  'dashboard.tripTooLong': 'لا يمكن أن تتجاوز مدة الرحلة {days} يومًا',
   'dashboard.dateShiftTitle': 'تاريخ بداية جديد',
   'dashboard.dateShiftIntro': 'لقد غيّرت موعد بداية هذه الرحلة. كيف تريد أن تتبع خططك التواريخ الجديدة؟',
   'dashboard.dateShiftKeepBookings': 'إبقاء الحجوزات في تواريخها',
diff --git a/shared/src/i18n/br/dashboard.ts b/shared/src/i18n/br/dashboard.ts
index 38d5fa711..dea693c89 100644
--- a/shared/src/i18n/br/dashboard.ts
+++ b/shared/src/i18n/br/dashboard.ts
@@ -87,6 +87,7 @@ const dashboard: TranslationStrings = {
   'dashboard.useUnsplashPhoto': 'Usar foto do Unsplash por {photographer}',
   'dashboard.titleRequired': 'O título é obrigatório',
   'dashboard.endDateError': 'A data final deve ser depois da inicial',
+  'dashboard.tripTooLong': 'Uma viagem pode ter no máximo {days} dias',
   'dashboard.dateShiftTitle': 'Nova data de início',
   'dashboard.dateShiftIntro': 'Você alterou o início desta viagem. Como seus planos devem acompanhar as novas datas?',
   'dashboard.dateShiftKeepBookings': 'Manter reservas em suas datas',
diff --git a/shared/src/i18n/ca/dashboard.ts b/shared/src/i18n/ca/dashboard.ts
index 2ecfbfd9a..e0ce84374 100644
--- a/shared/src/i18n/ca/dashboard.ts
+++ b/shared/src/i18n/ca/dashboard.ts
@@ -75,6 +75,7 @@ const dashboard: TranslationStrings = {
   'dashboard.coverRemoveError': 'Error en eliminar la imatge',
   'dashboard.titleRequired': 'El títol és obligatori',
   'dashboard.endDateError': "La data de fi ha de ser posterior a la d'inici",
+  'dashboard.tripTooLong': 'Un viatge pot durar com a màxim {days} dies',
   'dashboard.greeting.morning': 'Bon dia,',
   'dashboard.greeting.afternoon': 'Bona tarda,',
   'dashboard.greeting.evening': 'Bona nit,',
diff --git a/shared/src/i18n/cs/dashboard.ts b/shared/src/i18n/cs/dashboard.ts
index 03f5e4349..2a7f51de1 100644
--- a/shared/src/i18n/cs/dashboard.ts
+++ b/shared/src/i18n/cs/dashboard.ts
@@ -87,6 +87,7 @@ const dashboard: TranslationStrings = {
   'dashboard.useUnsplashPhoto': 'Použít fotku z Unsplash od {photographer}',
   'dashboard.titleRequired': 'Název je povinný',
   'dashboard.endDateError': 'Datum konce musí být po datu začátku',
+  'dashboard.tripTooLong': 'Cesta může trvat nejvýše {days} dní',
   'dashboard.dateShiftTitle': 'Nové datum začátku',
   'dashboard.dateShiftIntro': 'Změnili jste začátek této cesty. Jak se mají vaše plány přizpůsobit novým termínům?',
   'dashboard.dateShiftKeepBookings': 'Ponechat rezervace v původních termínech',
diff --git a/shared/src/i18n/de/dashboard.ts b/shared/src/i18n/de/dashboard.ts
index ebe6e0535..8d94408f2 100644
--- a/shared/src/i18n/de/dashboard.ts
+++ b/shared/src/i18n/de/dashboard.ts
@@ -88,6 +88,7 @@ const dashboard: TranslationStrings = {
   'dashboard.useUnsplashPhoto': 'Unsplash-Foto von {photographer} verwenden',
   'dashboard.titleRequired': 'Titel ist erforderlich',
   'dashboard.endDateError': 'Enddatum muss nach dem Startdatum liegen',
+  'dashboard.tripTooLong': 'Eine Reise kann höchstens {days} Tage umfassen',
   'dashboard.dateShiftTitle': 'Neues Startdatum',
   'dashboard.dateShiftIntro':
     'Du hast den Beginn dieser Reise geändert. Wie sollen deine Pläne den neuen Daten folgen?',
diff --git a/shared/src/i18n/en/dashboard.ts b/shared/src/i18n/en/dashboard.ts
index 36e4c7fc8..bce9a8446 100644
--- a/shared/src/i18n/en/dashboard.ts
+++ b/shared/src/i18n/en/dashboard.ts
@@ -101,6 +101,7 @@ const dashboard: TranslationStrings = {
   'dashboard.useUnsplashPhoto': 'Use Unsplash photo by {photographer}',
   'dashboard.titleRequired': 'Title is required',
   'dashboard.endDateError': 'End date must be after start date',
+  'dashboard.tripTooLong': 'A trip can span at most {days} days',
   'dashboard.dateShiftTitle': 'New start date',
   'dashboard.dateShiftIntro': 'You changed when this trip starts. How should your plans follow the new dates?',
   'dashboard.dateShiftKeepBookings': 'Keep bookings on their dates',
diff --git a/shared/src/i18n/es/dashboard.ts b/shared/src/i18n/es/dashboard.ts
index 81df36070..90520a60e 100644
--- a/shared/src/i18n/es/dashboard.ts
+++ b/shared/src/i18n/es/dashboard.ts
@@ -87,6 +87,7 @@ const dashboard: TranslationStrings = {
   'dashboard.useUnsplashPhoto': 'Usar foto de Unsplash de {photographer}',
   'dashboard.titleRequired': 'El título es obligatorio',
   'dashboard.endDateError': 'La fecha de fin debe ser posterior a la de inicio',
+  'dashboard.tripTooLong': 'Un viaje puede durar como máximo {days} días',
   'dashboard.dateShiftTitle': 'Nueva fecha de inicio',
   'dashboard.dateShiftIntro':
     'Has cambiado cuándo empieza este viaje. ¿Cómo deben seguir tus planes las nuevas fechas?',
diff --git a/shared/src/i18n/fr/dashboard.ts b/shared/src/i18n/fr/dashboard.ts
index 5d03f4f25..6caf781c0 100644
--- a/shared/src/i18n/fr/dashboard.ts
+++ b/shared/src/i18n/fr/dashboard.ts
@@ -89,6 +89,7 @@ const dashboard: TranslationStrings = {
   'dashboard.useUnsplashPhoto': 'Utiliser la photo Unsplash de {photographer}',
   'dashboard.titleRequired': 'Le titre est obligatoire',
   'dashboard.endDateError': 'La date de fin doit être postérieure à la date de début',
+  'dashboard.tripTooLong': 'Un voyage ne peut pas dépasser {days} jours',
   'dashboard.dateShiftTitle': 'Nouvelle date de début',
   'dashboard.dateShiftIntro':
     'Vous avez modifié la date de début de ce voyage. Comment vos plans doivent-ils suivre les nouvelles dates ?',
diff --git a/shared/src/i18n/gr/dashboard.ts b/shared/src/i18n/gr/dashboard.ts
index f2cd0d479..8fddf5375 100644
--- a/shared/src/i18n/gr/dashboard.ts
+++ b/shared/src/i18n/gr/dashboard.ts
@@ -99,6 +99,7 @@ const dashboard: TranslationStrings = {
   'dashboard.useUnsplashPhoto': 'Χρήση φωτογραφίας Unsplash από {photographer}',
   'dashboard.titleRequired': 'Ο τίτλος είναι υποχρεωτικός',
   'dashboard.endDateError': 'Η ημερομηνία λήξης πρέπει να είναι μετά την ημερομηνία έναρξης',
+  'dashboard.tripTooLong': 'Ένα ταξίδι μπορεί να διαρκεί το πολύ {days} ημέρες',
   'dashboard.dateShiftTitle': 'Νέα ημερομηνία έναρξης',
   'dashboard.dateShiftIntro':
     'Αλλάξατε την ημερομηνία έναρξης αυτού του ταξιδιού. Πώς θέλετε να ακολουθήσουν τα σχέδιά σας τις νέες ημερομηνίες;',
diff --git a/shared/src/i18n/hu/dashboard.ts b/shared/src/i18n/hu/dashboard.ts
index a73e0ba7c..88a9e37f3 100644
--- a/shared/src/i18n/hu/dashboard.ts
+++ b/shared/src/i18n/hu/dashboard.ts
@@ -89,6 +89,7 @@ const dashboard: TranslationStrings = {
   'dashboard.useUnsplashPhoto': '{photographer} Unsplash-fotójának használata',
   'dashboard.titleRequired': 'A cím megadása kötelező',
   'dashboard.endDateError': 'A záró dátumnak a kezdő dátum után kell lennie',
+  'dashboard.tripTooLong': 'Egy utazás legfeljebb {days} napos lehet',
   'dashboard.dateShiftTitle': 'Új kezdő dátum',
   'dashboard.dateShiftIntro': 'Megváltoztattad az út kezdetét. Hogyan kövessék a terveid az új dátumokat?',
   'dashboard.dateShiftKeepBookings': 'A foglalások maradjanak a saját dátumaikon',
diff --git a/shared/src/i18n/id/dashboard.ts b/shared/src/i18n/id/dashboard.ts
index 763dd42e3..0bcc208ef 100644
--- a/shared/src/i18n/id/dashboard.ts
+++ b/shared/src/i18n/id/dashboard.ts
@@ -87,6 +87,7 @@ const dashboard: TranslationStrings = {
   'dashboard.useUnsplashPhoto': 'Gunakan foto Unsplash oleh {photographer}',
   'dashboard.titleRequired': 'Judul wajib diisi',
   'dashboard.endDateError': 'Tanggal selesai harus setelah tanggal mulai',
+  'dashboard.tripTooLong': 'Perjalanan paling lama {days} hari',
   'dashboard.dateShiftTitle': 'Tanggal mulai baru',
   'dashboard.dateShiftIntro':
     'Kamu mengubah tanggal mulai perjalanan ini. Bagaimana rencanamu harus mengikuti tanggal baru?',
diff --git a/shared/src/i18n/it/dashboard.ts b/shared/src/i18n/it/dashboard.ts
index a50fabfc4..58f25a44f 100644
--- a/shared/src/i18n/it/dashboard.ts
+++ b/shared/src/i18n/it/dashboard.ts
@@ -89,6 +89,7 @@ const dashboard: TranslationStrings = {
   'dashboard.useUnsplashPhoto': 'Usa foto Unsplash di {photographer}',
   'dashboard.titleRequired': 'Il titolo è obbligatorio',
   'dashboard.endDateError': 'La data di fine deve essere successiva alla data di inizio',
+  'dashboard.tripTooLong': 'Un viaggio può durare al massimo {days} giorni',
   'dashboard.dateShiftTitle': 'Nuova data di inizio',
   'dashboard.dateShiftIntro':
     'Hai modificato la data di inizio di questo viaggio. Come devono adattarsi i tuoi piani alle nuove date?',
diff --git a/shared/src/i18n/ja/dashboard.ts b/shared/src/i18n/ja/dashboard.ts
index 1a16807b7..35760b586 100644
--- a/shared/src/i18n/ja/dashboard.ts
+++ b/shared/src/i18n/ja/dashboard.ts
@@ -102,6 +102,7 @@ const dashboard: TranslationStrings = {
   'dashboard.useUnsplashPhoto': '{photographer}さんのUnsplash写真を使用',
   'dashboard.titleRequired': 'タイトルは必須です',
   'dashboard.endDateError': '終了日は開始日より後にしてください',
+  'dashboard.tripTooLong': '旅行の期間は最大{days}日までです',
   'dashboard.dateShiftTitle': '新しい開始日',
   'dashboard.dateShiftIntro': '旅行の開始日が変更されました。予定を新しい日程にどのように合わせますか？',
   'dashboard.dateShiftKeepBookings': '予約を元の日付のままにする',
diff --git a/shared/src/i18n/ko/dashboard.ts b/shared/src/i18n/ko/dashboard.ts
index 56be14dab..314c67a8c 100644
--- a/shared/src/i18n/ko/dashboard.ts
+++ b/shared/src/i18n/ko/dashboard.ts
@@ -102,6 +102,7 @@ const dashboard: TranslationStrings = {
   'dashboard.useUnsplashPhoto': '{photographer}님의 Unsplash 사진 사용',
   'dashboard.titleRequired': '제목을 입력하세요',
   'dashboard.endDateError': '종료일은 시작일 이후여야 합니다',
+  'dashboard.tripTooLong': '여행 기간은 최대 {days}일까지입니다',
   'dashboard.dateShiftTitle': '새 시작일',
   'dashboard.dateShiftIntro': '여행 시작일이 변경되었습니다. 계획을 새 날짜에 어떻게 맞출까요?',
   'dashboard.dateShiftKeepBookings': '예약은 원래 날짜에 유지',
diff --git a/shared/src/i18n/nl/dashboard.ts b/shared/src/i18n/nl/dashboard.ts
index 21d1c6374..650a98323 100644
--- a/shared/src/i18n/nl/dashboard.ts
+++ b/shared/src/i18n/nl/dashboard.ts
@@ -87,6 +87,7 @@ const dashboard: TranslationStrings = {
   'dashboard.useUnsplashPhoto': 'Unsplash-foto van {photographer} gebruiken',
   'dashboard.titleRequired': 'Titel is verplicht',
   'dashboard.endDateError': 'Einddatum moet na de startdatum liggen',
+  'dashboard.tripTooLong': 'Een reis kan maximaal {days} dagen duren',
   'dashboard.dateShiftTitle': 'Nieuwe startdatum',
   'dashboard.dateShiftIntro':
     'Je hebt gewijzigd wanneer deze reis begint. Hoe moeten je plannen de nieuwe datums volgen?',
diff --git a/shared/src/i18n/pl/dashboard.ts b/shared/src/i18n/pl/dashboard.ts
index c8ba9972c..89298608b 100644
--- a/shared/src/i18n/pl/dashboard.ts
+++ b/shared/src/i18n/pl/dashboard.ts
@@ -83,6 +83,7 @@ const dashboard: TranslationStrings = {
   'dashboard.useUnsplashPhoto': 'Użyj zdjęcia z Unsplash autorstwa {photographer}',
   'dashboard.titleRequired': 'Nazwa podróży jest wymagana',
   'dashboard.endDateError': 'Data zakończenia musi być po dacie rozpoczęcia',
+  'dashboard.tripTooLong': 'Podróż może trwać maksymalnie {days} dni',
   'dashboard.dateShiftTitle': 'Nowa data rozpoczęcia',
   'dashboard.dateShiftIntro':
     'Data rozpoczęcia podróży została zmieniona. Jak plany mają dostosować się do nowych dat?',
diff --git a/shared/src/i18n/ru/dashboard.ts b/shared/src/i18n/ru/dashboard.ts
index 7a7b5040d..c01dd8fbe 100644
--- a/shared/src/i18n/ru/dashboard.ts
+++ b/shared/src/i18n/ru/dashboard.ts
@@ -87,6 +87,7 @@ const dashboard: TranslationStrings = {
   'dashboard.useUnsplashPhoto': 'Использовать фото Unsplash от {photographer}',
   'dashboard.titleRequired': 'Название обязательно',
   'dashboard.endDateError': 'Дата окончания должна быть позже даты начала',
+  'dashboard.tripTooLong': 'Поездка может длиться не более {days} дней',
   'dashboard.dateShiftTitle': 'Новая дата начала',
   'dashboard.dateShiftIntro': 'Вы изменили дату начала поездки. Как перенести ваши планы на новые даты?',
   'dashboard.dateShiftKeepBookings': 'Оставить бронирования на своих датах',
diff --git a/shared/src/i18n/sv/dashboard.ts b/shared/src/i18n/sv/dashboard.ts
index 1bc4b8a83..ef19adf19 100644
--- a/shared/src/i18n/sv/dashboard.ts
+++ b/shared/src/i18n/sv/dashboard.ts
@@ -101,6 +101,7 @@ const dashboard: TranslationStrings = {
   'dashboard.useUnsplashPhoto': 'Använd Unsplash-foto av {photographer}',
   'dashboard.titleRequired': 'Titel är obligatoriskt',
   'dashboard.endDateError': 'Slutdatumet måste ligga efter startdatumet',
+  'dashboard.tripTooLong': 'En resa kan vara högst {days} dagar',
   'dashboard.dateShiftTitle': 'Nytt startdatum',
   'dashboard.dateShiftIntro': 'Du har ändrat när resan börjar. Hur ska dina planer följa de nya datumen?',
   'dashboard.dateShiftKeepBookings': 'Behåll bokningar på sina datum',
diff --git a/shared/src/i18n/tr/dashboard.ts b/shared/src/i18n/tr/dashboard.ts
index 37f6391b1..a191dee85 100644
--- a/shared/src/i18n/tr/dashboard.ts
+++ b/shared/src/i18n/tr/dashboard.ts
@@ -101,6 +101,7 @@ const dashboard: TranslationStrings = {
   'dashboard.useUnsplashPhoto': '{photographer} tarafından çekilen Unsplash fotoğrafını kullan',
   'dashboard.titleRequired': 'Başlık gerekli',
   'dashboard.endDateError': 'Bitiş tarihi başlangıçtan sonra olmalı',
+  'dashboard.tripTooLong': 'Bir seyahat en fazla {days} gün sürebilir',
   'dashboard.dateShiftTitle': 'Yeni başlangıç tarihi',
   'dashboard.dateShiftIntro':
     'Bu seyahatin başlangıç tarihini değiştirdiniz. Planlarınız yeni tarihlere nasıl uyum sağlasın?',
diff --git a/shared/src/i18n/uk/dashboard.ts b/shared/src/i18n/uk/dashboard.ts
index 80c60ff8b..566fbae78 100644
--- a/shared/src/i18n/uk/dashboard.ts
+++ b/shared/src/i18n/uk/dashboard.ts
@@ -103,6 +103,7 @@ const dashboard: TranslationStrings = {
   'dashboard.useUnsplashPhoto': 'Використати фото Unsplash від {photographer}',
   'dashboard.titleRequired': "Назва обов'язкова",
   'dashboard.endDateError': 'Дата закінчення повинна бути пізніше дати початку',
+  'dashboard.tripTooLong': 'Подорож може тривати не більше {days} днів',
   'dashboard.dateShiftTitle': 'Нова дата початку',
   'dashboard.dateShiftIntro': 'Ви змінили дату початку поїздки. Як ваші плани мають перейти на нові дати?',
   'dashboard.dateShiftKeepBookings': 'Залишити бронювання на своїх датах',
diff --git a/shared/src/i18n/vi/dashboard.ts b/shared/src/i18n/vi/dashboard.ts
index 73792eadc..1c09460f3 100644
--- a/shared/src/i18n/vi/dashboard.ts
+++ b/shared/src/i18n/vi/dashboard.ts
@@ -95,6 +95,7 @@ const dashboard: TranslationStrings = {
   'dashboard.coverRemoveError': 'Không thể xóa',
   'dashboard.titleRequired': 'Tiêu đề là bắt buộc',
   'dashboard.endDateError': 'Ngày kết thúc phải sau ngày bắt đầu',
+  'dashboard.tripTooLong': 'Một chuyến đi có thể kéo dài tối đa {days} ngày',
   'dashboard.dateShiftTitle': 'Ngày bắt đầu mới',
   'dashboard.dateShiftIntro':
     'Bạn đã thay đổi thời điểm bắt đầu chuyến đi. Các kế hoạch của bạn nên theo ngày mới như thế nào?',
diff --git a/shared/src/i18n/zh-TW/dashboard.ts b/shared/src/i18n/zh-TW/dashboard.ts
index ae09d0fc0..3a5a1e41e 100644
--- a/shared/src/i18n/zh-TW/dashboard.ts
+++ b/shared/src/i18n/zh-TW/dashboard.ts
@@ -87,6 +87,7 @@ const dashboard: TranslationStrings = {
   'dashboard.useUnsplashPhoto': '使用 {photographer} 的 Unsplash 照片',
   'dashboard.titleRequired': '標題為必填項',
   'dashboard.endDateError': '結束日期必須晚於開始日期',
+  'dashboard.tripTooLong': '行程最長為 {days} 天',
   'dashboard.dateShiftTitle': '新的開始日期',
   'dashboard.dateShiftIntro': '你變更了旅行的開始時間。你的計劃要如何配合新日期？',
   'dashboard.dateShiftKeepBookings': '預訂保留在原日期',
diff --git a/shared/src/i18n/zh/dashboard.ts b/shared/src/i18n/zh/dashboard.ts
index 49306ca04..6083d29a9 100644
--- a/shared/src/i18n/zh/dashboard.ts
+++ b/shared/src/i18n/zh/dashboard.ts
@@ -87,6 +87,7 @@ const dashboard: TranslationStrings = {
   'dashboard.useUnsplashPhoto': '使用 {photographer} 的 Unsplash 照片',
   'dashboard.titleRequired': '标题为必填项',
   'dashboard.endDateError': '结束日期必须晚于开始日期',
+  'dashboard.tripTooLong': '行程最长为 {days} 天',
   'dashboard.dateShiftTitle': '新的开始日期',
   'dashboard.dateShiftIntro': '您更改了旅行的开始时间。您的计划应如何适应新的日期？',
   'dashboard.dateShiftKeepBookings': '保留预订的原定日期',
diff --git a/shared/src/trip/trip.schema.spec.ts b/shared/src/trip/trip.schema.spec.ts
index 07e5706a6..ba84982d3 100644
--- a/shared/src/trip/trip.schema.spec.ts
+++ b/shared/src/trip/trip.schema.spec.ts
@@ -1,4 +1,6 @@
 import {
+  MAX_TRIP_DAYS,
+  tripSpanDays,
   tripCreateRequestSchema,
   tripUpdateRequestSchema,
   tripAddMemberRequestSchema,
@@ -21,6 +23,26 @@ describe('tripCreateRequestSchema', () => {
   });
 });
 
+describe('MAX_TRIP_DAYS', () => {
+  it('lets a trip run past a year and keeps day numbers to three digits (#2403)', () => {
+    expect(MAX_TRIP_DAYS).toBeGreaterThan(366);
+    expect(MAX_TRIP_DAYS).toBeLessThan(1000);
+  });
+});
+
+describe('tripSpanDays', () => {
+  it('counts both ends, across a leap day and a year boundary', () => {
+    expect(tripSpanDays('2026-07-01', '2026-07-01')).toBe(1);
+    expect(tripSpanDays('2026-07-01', '2026-07-07')).toBe(7);
+    expect(tripSpanDays('2024-02-28', '2024-03-01')).toBe(3);
+    expect(tripSpanDays('2025-01-26', '2026-01-28')).toBe(368);
+  });
+
+  it('goes below one when the end precedes the start', () => {
+    expect(tripSpanDays('2026-07-07', '2026-07-01')).toBe(-5);
+  });
+});
+
 describe('tripUpdateRequestSchema', () => {
   it('is fully partial and accepts is_archived + cover_image', () => {
     expect(tripUpdateRequestSchema.safeParse({}).success).toBe(true);
diff --git a/shared/src/trip/trip.schema.ts b/shared/src/trip/trip.schema.ts
index c47a0fb80..69906c63b 100644
--- a/shared/src/trip/trip.schema.ts
+++ b/shared/src/trip/trip.schema.ts
@@ -13,6 +13,25 @@ import { z } from 'zod';
  * permission checks + audit logging. Trip rows are wide, so responses stay open.
  */
 
+/**
+ * The most days a trip can have, whether from its date range or from the
+ * `day_count` of a dateless trip. A range longer than this is refused rather
+ * than cut short: a trip whose end date lies past its last day is exactly the
+ * kind of half-state #2403 reported, and a mistyped year is easier to spot as
+ * an error than as a few hundred empty days. Three digits keep every day badge
+ * in the planner intact.
+ */
+export const MAX_TRIP_DAYS = 999;
+
+/** Calendar days in an inclusive YYYY-MM-DD range, counted the same way on both sides of the wire. */
+export function tripSpanDays(startDate: string, endDate: string): number {
+  const utcDay = (date: string) => {
+    const [y = NaN, m = NaN, d = NaN] = date.split('-').map(Number);
+    return Date.UTC(y, m - 1, d);
+  };
+  return Math.floor((utcDay(endDate) - utcDay(startDate)) / 86400000) + 1;
+}
+
 /**
  * Trip entity as returned by the trip list / get / create / update endpoints
  * (server/src/services/tripService.ts -> TRIP_SELECT). Columns of the `trips`
diff --git a/wiki/Creating-a-Trip.md b/wiki/Creating-a-Trip.md
index 51b0315c0..a6db49439 100644
--- a/wiki/Creating-a-Trip.md
+++ b/wiki/Creating-a-Trip.md
@@ -20,9 +20,9 @@ A short free-text description. It is not shown on the trip card or on the Spotli
 
 ### Dates
 
-Set a **Start date** and **End date** using the date picker. The day count is calculated automatically when both are set.
+Set a **Start date** and **End date** using the date picker. The day count is calculated automatically when both are set. A trip can span up to **999 days**.
 
-On desktop, if you leave **both** dates empty, a separate **Day count** field appears. Enter a number between **1 and 365** to create a date-less itinerary with a fixed number of days. The mobile sheet has no such field: a date-less trip created there always starts with 7 days.
+On desktop, if you leave **both** dates empty, a separate **Day count** field appears. Enter a number between **1 and 999** to create a date-less itinerary with a fixed number of days. The mobile sheet has no such field: a date-less trip created there always starts with 7 days.
 
 Only the **start** date is linked to the other one. Picking a start date fills the end date to match it, and moving the start date of an already-dated trip shifts the end date so the previous duration is kept. Nothing links them the other way round: you can pick an end date on its own, and the picker's **✕** button clears either field afterwards. A trip can therefore be saved with both dates, with only a start date, with only an end date, or with neither. A trip left with exactly one date gets an undated day grid (7 days by default), just like a date-less one.