Bump to 1.17.0

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Add offline ticket scanning
2026-10-19 14:06:34 +02:00 · 2026-10-19 14:06:22 +02:00 · 2026-10-19 13:43:20 +02:00
33 changed files with 1462 additions and 81 deletions
@@ -7,6 +7,28 @@ and this project follows [Semantic Versioning](https://semver.org/).

 ## [Unreleased]

+## [1.17.0] - 2026-10-19
+
+### Added
+
+- Offline ticket scanning. While online, staff pick an event and section on the scanner and tap "Enable offline mode". The section (or the whole event) is locked to their device and its tickets are downloaded to the device.
+  - With no connection, scans are checked against that list and queued on the device.
+  - The panel shows when the list was downloaded and how many scans are waiting.
+  - Queued scans sync automatically when the device is back online (or with "Sync now"), and check-in messages go out then.
+  - "Release section" ends offline mode and deletes the list from the device.
+- Only one device can hold a section at a time (a whole-event lock clashes with every section). While a section is locked, other devices see who holds it and can't scan it, online or offline, so a ticket can never be redeemed twice by two offline devices.
+- Syncing is idempotent and never redeems more than is left on a ticket. Anything that needs a person to look goes into a sync report: tickets not found, cancelled registrations, used-up tickets, scans outside the locked section, and check-ins without consent.
+- Supervisor → Offline scanning page: active locks with force release (for a lost or flat phone; its scans still sync if it reconnects, and are flagged), and sync reports to review. Locks, releases, force-releases and syncs are recorded in the audit log.
+- The scanner is installable as an app (web app manifest), and a service worker caches the scanner page and its scripts so it opens with no connection.
+- The app now stays signed in with the last confirmed profile when it's reloaded without a connection, instead of sending the user to the login page.
+- New `/api/scan-locks` endpoints.
+  - Requires the `add_offline_scanning` database migration.
+
+### Changed
+
+- `POST /api/tickets/scan/:qrCode` now accepts `sectionId` and checks it on the server; this was previously only checked in the browser.
+  - It now refuses (423) scans in a section that another device has locked for offline scanning.
+
 ## [1.16.0] - 2026-10-19

 ### Added
@@ -200,6 +200,13 @@ Items & Pricing → Sections → Form → Visibility → Attachments**.
 - **Check-in confirmation** — holders get an email/WhatsApp saying how many were
  checked in and how many remain.
 - **Scan stats** — recent scans and per-event scan counts.
+- **Offline scanning** — while online, a staff member locks an event section (or the
+  whole event) to their device and downloads its tickets. They can then keep scanning
+  with no connection; scans are queued on the device and sync automatically when it's
+  back online (never redeeming more than is left). Only one device can hold a section,
+  and while it's locked nobody else can scan it, online or offline. Problems found
+  while syncing go into a report for a supervisor. Supervisors can force-release a
+  lost device. The scanner can be added to the home screen (PWA) and opens offline.
 - **Printing** — A4 sheets (8 tickets per page) and A6 single tickets.
 - **Resend** — send tickets to a different email/phone at the door.

@@ -299,6 +306,8 @@ logout controls. Disconnected sessions are recovered automatically.
  Reconcile (Yoco transactions), and Payment Link.
 - **Coupon codes** (`/dashboard/supervisor/coupons`) — create, edit and turn off
  discount codes, and see who used each one.
+- **Offline scanning** (`/dashboard/supervisor/offline-scans`) — devices holding
+  offline locks (with force release) and sync reports to review.
 - **Waitlist** (`/dashboard/supervisor/waitlist`) — the queue per event: offer a
  place now, move people up or down, or remove them.
 - **Parental consent** (`/dashboard/supervisor/consent`) — consent status per
@@ -469,5 +478,5 @@ falling back to a general guide.
 | `/set-banner` | Supervisor | Site banner |
 | `/dashboard/user` (+ `/payments`, `/donate`, `/forms`, `/profile`, `/reset-password`) | User | My Events |
 | `/dashboard/staff` (+ `/ticket-scanning`, `/event-tickets`) | Staff | Staff tools |
-| `/dashboard/supervisor` (+ `/events`, `/event-options`, `/at-the-door`, `/manual`, `/manual-registration`, `/payments`, `/coupons`, `/waitlist`, `/consent`, `/email-attendees`, `/whatsapp-attendees`, `/forms`, `/reports`) | Supervisor | Supervisor tools |
+| `/dashboard/supervisor` (+ `/events`, `/event-options`, `/at-the-door`, `/manual`, `/manual-registration`, `/payments`, `/coupons`, `/waitlist`, `/consent`, `/offline-scans`, `/email-attendees`, `/whatsapp-attendees`, `/forms`, `/reports`) | Supervisor | Supervisor tools |
 | `/dashboard/admin` (+ `/users`, `/registrations`, `/forms`, `/cashup`, `/cashup/[id]`, `/audit-log`, `/settings`) | Admin | Admin tools |
@@ -21,6 +21,7 @@ Tokens are issued by `POST /api/users/login`.
 - [Coupons](#coupons)
 - [Parental consent](#parental-consent)
 - [Waitlist](#waitlist)
+- [Offline scanning](#offline-scanning)
 - [Payments](#payments)
 - [Tickets](#tickets)
 - [Broadcasts (Email)](#broadcasts-email)
@@ -278,6 +279,29 @@ For unauthenticated (guest) registration on events with `requiresAuth: false`:

 ---

+## Offline scanning
+
+| Method | Path | Auth | Description |
+|--------|------|------|-------------|
+| GET | `/api/scan-locks?eventId=` | staff+ | Active offline locks for an event |
+| POST | `/api/scan-locks` | staff+ | Lock `{ eventId, sectionId?, deviceId, deviceName? }` to this device (409 if the scope is held elsewhere) |
+| GET | `/api/scan-locks/:id/snapshot?deviceId=` | staff+ | Tickets valid in the lock's scope (lock holder only) |
+| POST | `/api/scan-locks/:id/sync` | staff+ | `{ deviceId, scans: [{ clientScanId, qrCode, qty, scannedAt }] }` — idempotent; returns accepted, duplicates, conflicts |
+| DELETE | `/api/scan-locks/:id` | staff+ | Release (`{ deviceId }`, lock holder only) |
+| POST | `/api/scan-locks/:id/force-release` | supervisor+ | Release a lost device's lock |
+| GET | `/api/scan-locks/reports?eventId=&unreviewed=` | supervisor+ | Sync reports |
+| POST | `/api/scan-locks/reports/:id/review` | supervisor+ | Mark a report reviewed |
+
+How locks work:
+- One device per scope. A whole-event lock (`sectionId` null) clashes with every section lock on that event.
+- `POST /api/tickets/scan/:qrCode` now accepts `sectionId` and `deviceId`. It enforces the section on the server, and returns `423 { code: "SCAN_LOCKED" }` when another device holds a lock covering the ticket.
+
+How syncing works:
+- Synced scans never redeem more than is left on a ticket.
+- Conflicts are recorded in the sync report: `not_found`, `cancelled`, `wrong_scope`, `already_used`, `partly_used` and `consent`.
+- Check-in messages are sent after the sync.
+- Locks, releases, force-releases and syncs are written to the admin audit log.
+
 ## Waitlist

 Events with `waitlistEnabled` (plus `waitlistOfferHours`, default 24, and `waitlistPartialOffers`, default true) take a queue for sold-out lines.
@@ -1,12 +1,12 @@
 {
  "name": "event-management-backend",
-  "version": "1.16.0",
+  "version": "1.17.0",
  "lockfileVersion": 3,
  "requires": true,
  "packages": {
    "": {
      "name": "event-management-backend",
-      "version": "1.16.0",
+      "version": "1.17.0",
      "hasInstallScript": true,
      "dependencies": {
        "@prisma/client": "^5.4.2",
@@ -1,6 +1,6 @@
 {
  "name": "event-management-backend",
-  "version": "1.16.0",
+  "version": "1.17.0",
  "description": "Event Management System Backend",
  "main": "src/index.js",
  "scripts": {
@@ -0,0 +1,93 @@
+-- AlterEnum
+-- This migration adds more than one value to an enum.
+-- With PostgreSQL versions 11 and earlier, this is not possible
+-- in a single migration. This can be worked around by creating
+-- multiple migrations, each migration adding only one value to
+-- the enum.
+
+
+ALTER TYPE "AdminAuditAction" ADD VALUE 'scan_lock_acquired';
+ALTER TYPE "AdminAuditAction" ADD VALUE 'scan_lock_released';
+ALTER TYPE "AdminAuditAction" ADD VALUE 'scan_lock_force_released';
+ALTER TYPE "AdminAuditAction" ADD VALUE 'offline_sync';
+
+-- AlterTable
+ALTER TABLE "TicketUsage" ADD COLUMN     "clientScanId" TEXT,
+ADD COLUMN     "offline" BOOLEAN NOT NULL DEFAULT false,
+ADD COLUMN     "scanLockId" TEXT,
+ADD COLUMN     "syncedAt" TIMESTAMP(3);
+
+-- CreateTable
+CREATE TABLE "ScanLock" (
+    "id" TEXT NOT NULL,
+    "eventId" TEXT NOT NULL,
+    "sectionId" TEXT,
+    "deviceId" TEXT NOT NULL,
+    "deviceName" TEXT,
+    "userId" TEXT NOT NULL,
+    "lockedAt" TIMESTAMP(3) NOT NULL DEFAULT CURRENT_TIMESTAMP,
+    "snapshotAt" TIMESTAMP(3),
+    "lastSyncAt" TIMESTAMP(3),
+    "releasedAt" TIMESTAMP(3),
+    "forceReleasedById" TEXT,
+
+    CONSTRAINT "ScanLock_pkey" PRIMARY KEY ("id")
+);
+
+-- CreateTable
+CREATE TABLE "OfflineSyncReport" (
+    "id" TEXT NOT NULL,
+    "scanLockId" TEXT NOT NULL,
+    "accepted" INTEGER NOT NULL DEFAULT 0,
+    "duplicates" INTEGER NOT NULL DEFAULT 0,
+    "conflicts" JSONB NOT NULL DEFAULT '[]',
+    "afterForceRelease" BOOLEAN NOT NULL DEFAULT false,
+    "createdAt" TIMESTAMP(3) NOT NULL DEFAULT CURRENT_TIMESTAMP,
+    "reviewedAt" TIMESTAMP(3),
+    "reviewedById" TEXT,
+
+    CONSTRAINT "OfflineSyncReport_pkey" PRIMARY KEY ("id")
+);
+
+-- CreateIndex
+CREATE INDEX "ScanLock_eventId_releasedAt_idx" ON "ScanLock"("eventId", "releasedAt");
+
+-- CreateIndex
+CREATE INDEX "ScanLock_userId_idx" ON "ScanLock"("userId");
+
+-- CreateIndex
+CREATE INDEX "ScanLock_sectionId_idx" ON "ScanLock"("sectionId");
+
+-- CreateIndex
+CREATE INDEX "ScanLock_forceReleasedById_idx" ON "ScanLock"("forceReleasedById");
+
+-- CreateIndex
+CREATE INDEX "OfflineSyncReport_scanLockId_idx" ON "OfflineSyncReport"("scanLockId");
+
+-- CreateIndex
+CREATE INDEX "OfflineSyncReport_reviewedById_idx" ON "OfflineSyncReport"("reviewedById");
+
+-- CreateIndex
+CREATE UNIQUE INDEX "TicketUsage_clientScanId_key" ON "TicketUsage"("clientScanId");
+
+-- AddForeignKey
+ALTER TABLE "TicketUsage" ADD CONSTRAINT "TicketUsage_scanLockId_fkey" FOREIGN KEY ("scanLockId") REFERENCES "ScanLock"("id") ON DELETE SET NULL ON UPDATE CASCADE;
+
+-- AddForeignKey
+ALTER TABLE "ScanLock" ADD CONSTRAINT "ScanLock_eventId_fkey" FOREIGN KEY ("eventId") REFERENCES "Event"("id") ON DELETE CASCADE ON UPDATE CASCADE;
+
+-- AddForeignKey
+ALTER TABLE "ScanLock" ADD CONSTRAINT "ScanLock_sectionId_fkey" FOREIGN KEY ("sectionId") REFERENCES "Section"("id") ON DELETE CASCADE ON UPDATE CASCADE;
+
+-- AddForeignKey
+ALTER TABLE "ScanLock" ADD CONSTRAINT "ScanLock_userId_fkey" FOREIGN KEY ("userId") REFERENCES "User"("id") ON DELETE CASCADE ON UPDATE CASCADE;
+
+-- AddForeignKey
+ALTER TABLE "ScanLock" ADD CONSTRAINT "ScanLock_forceReleasedById_fkey" FOREIGN KEY ("forceReleasedById") REFERENCES "User"("id") ON DELETE SET NULL ON UPDATE CASCADE;
+
+-- AddForeignKey
+ALTER TABLE "OfflineSyncReport" ADD CONSTRAINT "OfflineSyncReport_scanLockId_fkey" FOREIGN KEY ("scanLockId") REFERENCES "ScanLock"("id") ON DELETE CASCADE ON UPDATE CASCADE;
+
+-- AddForeignKey
+ALTER TABLE "OfflineSyncReport" ADD CONSTRAINT "OfflineSyncReport_reviewedById_fkey" FOREIGN KEY ("reviewedById") REFERENCES "User"("id") ON DELETE SET NULL ON UPDATE CASCADE;
+
@@ -103,8 +103,11 @@ model User {
  couponsApplied    CouponRedemption[] @relation("CouponRedemptionAppliedBy")

  attendeeProfiles Attendee[]
-  heldTickets      Ticket[]        @relation("TicketHolder")
+  heldTickets      Ticket[]            @relation("TicketHolder")
  waitlistEntries  WaitlistEntry[]
+  scanLocks        ScanLock[]          @relation("ScanLockOwner")
+  scanLocksForced  ScanLock[]          @relation("ScanLockForcedBy")
+  syncReportsDone  OfflineSyncReport[] @relation("SyncReportReviewer")

  twoFactorChallenges TwoFactorChallenge[]
  trustedDevices      TrustedDevice[]
@@ -175,6 +178,7 @@ model Event {
  coupons          CouponEvent[]
  consentRequests  ConsentRequest[]
  waitlistEntries  WaitlistEntry[]
+  scanLocks        ScanLock[]

  @@index([createdById])
  @@index([closedById])
@@ -370,13 +374,20 @@ model Ticket {
 }

 model TicketUsage {
-  id               String   @id @default(uuid())
+  id               String    @id @default(uuid())
  ticketId         String
  scannedById      String
-  scannedAt        DateTime @default(now())
-  quantityRedeemed Int      @default(1)
-  ticket           Ticket   @relation(fields: [ticketId], references: [id], onDelete: Restrict)
-  scannedBy        User     @relation(fields: [scannedById], references: [id], onDelete: Restrict)
+  scannedAt        DateTime  @default(now())
+  quantityRedeemed Int       @default(1)
+  // Offline scanning: the device's id for the scan (makes syncing idempotent), and
+  // the offline lock it was made under.
+  clientScanId     String?   @unique
+  offline          Boolean   @default(false)
+  scanLockId       String?
+  syncedAt         DateTime?
+  ticket           Ticket    @relation(fields: [ticketId], references: [id], onDelete: Restrict)
+  scannedBy        User      @relation(fields: [scannedById], references: [id], onDelete: Restrict)
+  scanLock         ScanLock? @relation(fields: [scanLockId], references: [id], onDelete: SetNull)

  @@index([ticketId])
  @@index([scannedAt])
@@ -461,6 +472,10 @@ enum AdminAuditAction {
  consent_override
  consent_rerequested
  medical_list_viewed
+  scan_lock_acquired
+  scan_lock_released
+  scan_lock_force_released
+  offline_sync
 }

 // Append-only audit trail for admin/supervisor-initiated actions with money or
@@ -601,6 +616,7 @@ model Section {

  event          Event           @relation(fields: [eventId], references: [id], onDelete: Cascade)
  allowedOptions SectionOption[]
+  scanLocks      ScanLock[]

  @@index([eventId])
 }
@@ -1085,3 +1101,51 @@ model WaitlistEntry {
  @@index([userId])
  @@index([registrationId])
 }
+
+// ─── Offline scanning ─────────────────────────────────────────────────────────
+
+// Locks a section (or the whole event, sectionId null) to one device for offline
+// scanning, so two devices can never redeem the same ticket while offline.
+// One active (releasedAt null) lock per scope — enforced in utils/scanLocks.js.
+model ScanLock {
+  id                String              @id @default(uuid())
+  eventId           String
+  sectionId         String?
+  deviceId          String
+  deviceName        String?
+  userId            String
+  lockedAt          DateTime            @default(now())
+  snapshotAt        DateTime?
+  lastSyncAt        DateTime?
+  releasedAt        DateTime?
+  forceReleasedById String?
+  event             Event               @relation(fields: [eventId], references: [id], onDelete: Cascade)
+  section           Section?            @relation(fields: [sectionId], references: [id], onDelete: Cascade)
+  user              User                @relation("ScanLockOwner", fields: [userId], references: [id], onDelete: Cascade)
+  forceReleasedBy   User?               @relation("ScanLockForcedBy", fields: [forceReleasedById], references: [id], onDelete: SetNull)
+  usages            TicketUsage[]
+  syncReports       OfflineSyncReport[]
+
+  @@index([eventId, releasedAt])
+  @@index([userId])
+  @@index([sectionId])
+  @@index([forceReleasedById])
+}
+
+// One sync of queued offline scans; `conflicts` lists scans that needed a person to look.
+model OfflineSyncReport {
+  id                String    @id @default(uuid())
+  scanLockId        String
+  accepted          Int       @default(0)
+  duplicates        Int       @default(0)
+  conflicts         Json      @default("[]")
+  afterForceRelease Boolean   @default(false)
+  createdAt         DateTime  @default(now())
+  reviewedAt        DateTime?
+  reviewedById      String?
+  scanLock          ScanLock  @relation(fields: [scanLockId], references: [id], onDelete: Cascade)
+  reviewedBy        User?     @relation("SyncReportReviewer", fields: [reviewedById], references: [id], onDelete: SetNull)
+
+  @@index([scanLockId])
+  @@index([reviewedById])
+}
@@ -0,0 +1,151 @@
+const prisma = require('../config/db');
+const { safeErrorMessage } = require('../utils/errorUtils');
+const { logAdminAction } = require('../utils/adminAudit');
+const { getClientIp } = require('../utils/requestUtils');
+const { LOCK_INCLUDE, activeLocks, acquireLock, snapshotFor, syncScans } = require('../utils/scanLocks');
+
+const SUPERVISORS = ['admin', 'supervisor'];
+const fail = (res, error) => res.status(error.statusCode || (res.statusCode === 200 ? 400 : res.statusCode)).json({ message: safeErrorMessage(error) });
+const audit = (req, action, lock, metadata = {}) => logAdminAction({
+  actorId: req.user.id, actorRole: req.user.role, action, targetType: 'ScanLock', targetId: lock.id,
+  metadata: { eventId: lock.eventId, sectionId: lock.sectionId, deviceName: lock.deviceName, ...metadata },
+  ip: getClientIp(req),
+});
+
+const lockView = (l) => ({
+  id: l.id, eventId: l.eventId, sectionId: l.sectionId, sectionName: l.section?.name || null,
+  deviceId: l.deviceId, deviceName: l.deviceName, user: l.user, lockedAt: l.lockedAt,
+  snapshotAt: l.snapshotAt, lastSyncAt: l.lastSyncAt, releasedAt: l.releasedAt,
+});
+
+/** The lock, if the caller is the person holding it on this device. */
+async function ownLock(req, res) {
+  const lock = await prisma.scanLock.findUnique({ where: { id: req.params.id }, include: LOCK_INCLUDE });
+  if (!lock) { res.status(404); throw new Error('Offline lock not found'); }
+  const deviceId = req.body?.deviceId || req.query?.deviceId;
+  if (lock.userId !== req.user.id || lock.deviceId !== deviceId) { res.status(403); throw new Error('This offline lock belongs to another device.'); }
+  return lock;
+}
+
+// @desc    Active offline locks for an event
+// @route   GET /api/scan-locks?eventId=
+// @access  Private/Staff
+const listLocks = async (req, res) => {
+  try {
+    if (!req.query.eventId) { res.status(400); throw new Error('eventId is required'); }
+    res.json((await activeLocks(String(req.query.eventId))).map(lockView));
+  } catch (error) {
+    fail(res, error);
+  }
+};
+
+// @desc    Lock a section (or the whole event) to this device for offline scanning
+// @route   POST /api/scan-locks   { eventId, sectionId?, deviceId, deviceName? }
+// @access  Private/Staff
+const createLock = async (req, res) => {
+  try {
+    const { eventId, sectionId, deviceId, deviceName } = req.body || {};
+    if (!eventId) { res.status(400); throw new Error('eventId is required'); }
+    const lock = await acquireLock({ eventId, sectionId: sectionId || null, deviceId, deviceName, userId: req.user.id });
+    audit(req, 'scan_lock_acquired', lock);
+    res.status(201).json(lockView(lock));
+  } catch (error) {
+    fail(res, error);
+  }
+};
+
+// @desc    Download the tickets valid for this lock, for offline scanning
+// @route   GET /api/scan-locks/:id/snapshot?deviceId=
+// @access  Private/Staff (lock holder)
+const getSnapshot = async (req, res) => {
+  try {
+    const lock = await ownLock(req, res);
+    if (lock.releasedAt) { res.status(410); throw new Error('This offline lock has been released.'); }
+    res.json({ lock: lockView(lock), ...(await snapshotFor(lock)) });
+  } catch (error) {
+    fail(res, error);
+  }
+};
+
+// @desc    Upload scans made offline
+// @route   POST /api/scan-locks/:id/sync   { deviceId, scans: [{ clientScanId, qrCode, qty, scannedAt }] }
+// @access  Private/Staff (lock holder — also after a release, so nothing made offline is lost)
+const syncLock = async (req, res) => {
+  try {
+    const lock = await ownLock(req, res);
+    const result = await syncScans(lock, req.body?.scans);
+    if (result.accepted || result.conflicts.length) {
+      audit(req, 'offline_sync', lock, { accepted: result.accepted, conflicts: result.conflicts.length, duplicates: result.duplicates, afterForceRelease: !!lock.forceReleasedById });
+    }
+    res.json({ accepted: result.accepted, duplicates: result.duplicates, conflicts: result.conflicts, reportId: result.report.id, released: !!lock.releasedAt });
+  } catch (error) {
+    fail(res, error);
+  }
+};
+
+// @desc    End offline mode (the device should sync first)
+// @route   DELETE /api/scan-locks/:id   { deviceId }
+// @access  Private/Staff (lock holder)
+const releaseLock = async (req, res) => {
+  try {
+    const lock = await ownLock(req, res);
+    if (!lock.releasedAt) {
+      await prisma.scanLock.update({ where: { id: lock.id }, data: { releasedAt: new Date() } });
+      audit(req, 'scan_lock_released', lock);
+    }
+    res.json({ message: 'Offline mode ended.' });
+  } catch (error) {
+    fail(res, error);
+  }
+};
+
+// @desc    Release someone else's lock (e.g. a lost or flat phone)
+// @route   POST /api/scan-locks/:id/force-release
+// @access  Private/Supervisor
+const forceRelease = async (req, res) => {
+  try {
+    const lock = await prisma.scanLock.findUnique({ where: { id: req.params.id }, include: LOCK_INCLUDE });
+    if (!lock) { res.status(404); throw new Error('Offline lock not found'); }
+    if (lock.releasedAt) return res.json({ message: 'Already released.' });
+    await prisma.scanLock.update({ where: { id: lock.id }, data: { releasedAt: new Date(), forceReleasedById: req.user.id } });
+    audit(req, 'scan_lock_force_released', lock, { heldBy: lock.user?.name });
+    res.json({ message: `Released. If ${lock.user?.name || 'that device'} reconnects, its offline scans will still sync and be flagged for review.` });
+  } catch (error) {
+    fail(res, error);
+  }
+};
+
+// @desc    Offline sync reports for an event (with anything that needs review)
+// @route   GET /api/scan-locks/reports?eventId=&unreviewed=true
+// @access  Private/Supervisor
+const listReports = async (req, res) => {
+  try {
+    const where = {
+      scanLock: { eventId: String(req.query.eventId || '') },
+      ...(req.query.unreviewed === 'true' ? { reviewedAt: null } : {}),
+    };
+    const reports = await prisma.offlineSyncReport.findMany({
+      where,
+      include: { scanLock: { include: LOCK_INCLUDE }, reviewedBy: { select: { name: true } } },
+      orderBy: { createdAt: 'desc' },
+      take: 200,
+    });
+    res.json(reports.map(r => ({ ...r, scanLock: lockView(r.scanLock) })));
+  } catch (error) {
+    fail(res, error);
+  }
+};
+
+// @desc    Mark a sync report as reviewed
+// @route   POST /api/scan-locks/reports/:id/review
+// @access  Private/Supervisor
+const reviewReport = async (req, res) => {
+  try {
+    const report = await prisma.offlineSyncReport.update({ where: { id: req.params.id }, data: { reviewedAt: new Date(), reviewedById: req.user.id } });
+    res.json(report);
+  } catch (error) {
+    fail(res, error);
+  }
+};
+
+module.exports = { SUPERVISORS, listLocks, createLock, getSnapshot, syncLock, releaseLock, forceRelease, listReports, reviewReport };
@@ -372,6 +372,27 @@ const scanTicket = async (req, res) => {
      return res.status(400).json({ message: 'Ticket belongs to a different event', ticket });
    }

+    // Section checks used to happen only in the browser; enforce them here too.
+    const sectionId = String((req.query?.sectionId || req.body?.sectionId) || '').trim() || null;
+    if (sectionId) {
+      const section = await prisma.section.findUnique({ where: { id: sectionId }, include: { allowedOptions: true } });
+      if (!section || section.eventId !== ticket.eventId) {
+        return res.status(400).json({ message: 'Section not found for this event', ticket });
+      }
+      if (!section.allowedOptions.some(o => o.eventOptionId === r.eventOptionId)) {
+        return res.status(400).json({ message: 'This ticket is not valid for this section', ticket });
+      }
+    }
+
+    // A section (or the whole event) locked to another device for offline scanning
+    // can't be scanned online — those scans would be invisible to the offline device.
+    const { blockingLock } = require('../utils/scanLocks');
+    const lock = await blockingLock({ eventId: ticket.eventId, optionId: r.eventOptionId }, { sectionId, deviceId: req.body?.deviceId || null });
+    if (lock) {
+      const scope = lock.section ? `"${lock.section.name}"` : 'This event';
+      return res.status(423).json({ message: `${scope} is offline-locked by ${lock.user?.name || 'another device'}${lock.deviceName ? ` on ${lock.deviceName}` : ''}. Scan it on that device, or ask a supervisor to release the lock.`, code: 'SCAN_LOCKED' });
+    }
+
    // Compute how many have already been redeemed
    const totalRedeemed = (ticket.usages || []).reduce((s, u) => s + (u.quantityRedeemed || 1), 0);
    const remaining = (ticket.quantity || 1) - totalRedeemed;
@@ -178,6 +178,7 @@ app.use('/api/admin', adminRoutes);
 app.use('/api/coupons', require('./routes/couponRoutes'));
 app.use('/api/consent', require('./routes/consentRoutes'));
 app.use('/api/waitlist', require('./routes/waitlistRoutes'));
+app.use('/api/scan-locks', require('./routes/scanLockRoutes'));
 app.use('/api/backups', backupRoutes);

 // Pre-warm the settings cache so synchronous helpers have DB values from startup
@@ -634,6 +635,20 @@ app.get('/docs', async (req, res) => {
        ]},
    ]},

+    { title: 'Offline scanning', base: '/api/scan-locks', endpoints: [
+      { method:'GET', path:'/api/scan-locks', auth:'staff+', desc:'Active offline locks for an event (?eventId=)' },
+      { method:'POST', path:'/api/scan-locks', auth:'staff+', desc:'Lock a section (or the whole event) to this device for offline scanning',
+        request:{ body:{ eventId:'ev-uuid-...', sectionId:'sec-uuid-...', deviceId:'device-uuid', deviceName:'Chrome on Android' }},
+        responses:[{ status:201, desc:'Locked', body:{ id:'lock-uuid-...', sectionName:'Main hall' }}, { status:409, desc:'Held elsewhere', body:{ message:'"Main hall" is offline-locked by Ann on Chrome on Android.' }}]},
+      { method:'GET', path:'/api/scan-locks/:id/snapshot', auth:'staff+', desc:'Tickets valid in the lock scope, for the device to keep offline (lock holder, ?deviceId=)' },
+      { method:'POST', path:'/api/scan-locks/:id/sync', auth:'staff+', desc:'Upload offline scans (idempotent by clientScanId; capped at what is left on each ticket)',
+        request:{ body:{ deviceId:'device-uuid', scans:[{ clientScanId:'scan-uuid', qrCode:'qr-uuid', qty:1, scannedAt:'2025-07-10T08:15:00.000Z' }] }},
+        responses:[{ status:200, desc:'Synced', body:{ accepted:1, duplicates:0, conflicts:[] }}]},
+      { method:'DELETE', path:'/api/scan-locks/:id', auth:'staff+', desc:'End offline mode (lock holder)' },
+      { method:'POST', path:'/api/scan-locks/:id/force-release', auth:'supervisor+', desc:'Release a lost device\'s lock' },
+      { method:'GET', path:'/api/scan-locks/reports', auth:'supervisor+', desc:'Offline sync reports for an event' },
+      { method:'POST', path:'/api/scan-locks/reports/:id/review', auth:'supervisor+', desc:'Mark a sync report reviewed' },
+    ]},
    { title: 'Waitlist', base: '/api/waitlist', endpoints: [
      { method:'POST', path:'/api/waitlist', auth:'public', desc:'Join the waitlist for a sold-out line (login needed when the event requires it)',
        request:{ body:{ eventId:'ev-uuid-...', eventOptionId:'opt-uuid-...', quantity:2 }},
@@ -0,0 +1,15 @@
+const express = require('express');
+const router = express.Router();
+const { listLocks, createLock, getSnapshot, syncLock, releaseLock, forceRelease, listReports, reviewReport } = require('../controllers/scanLockController');
+const { protect, staff, supervisor } = require('../middleware/authMiddleware');
+
+router.get('/', protect, staff, listLocks);
+router.post('/', protect, staff, createLock);
+router.get('/reports', protect, supervisor, listReports);
+router.post('/reports/:id/review', protect, supervisor, reviewReport);
+router.get('/:id/snapshot', protect, staff, getSnapshot);
+router.post('/:id/sync', protect, staff, syncLock);
+router.post('/:id/force-release', protect, supervisor, forceRelease);
+router.delete('/:id', protect, staff, releaseLock);
+
+module.exports = router;
@@ -0,0 +1,213 @@
+/**
+ * Offline scanning — locks, snapshots and syncing.
+ *
+ * Rules:
+ * - Offline mode is per section (or the whole event), and only one device may hold a
+ *   scope at a time: while offline, devices can't see each other's scans, so two
+ *   devices on the same scope could redeem one ticket twice. A whole-event lock clashes
+ *   with every section of that event, and a section lock with the whole event.
+ * - While a scope is locked, other devices can't scan it online either.
+ * - The lock holder downloads a snapshot of valid tickets; scans made offline are
+ *   queued on the device and synced later. Syncing is idempotent (each scan carries a
+ *   clientScanId) and never redeems more than is left on a ticket.
+ * - Anything that needs a person to look — unknown ticket, cancelled registration, used
+ *   up, outside the locked scope, consent not given — goes into an OfflineSyncReport.
+ * - A supervisor can force-release a lock (lost phone). If that device syncs later its
+ *   scans are still recorded, and the report is flagged.
+ */
+
+const prisma = require('../config/db');
+
+function lockError(message, statusCode = 400) {
+  const err = new Error(message);
+  err.statusCode = statusCode;
+  return err;
+}
+
+// ─── Pure helpers ─────────────────────────────────────────────────────────────
+
+/** Whether a new lock on `sectionId` (null = whole event) clashes with `existing`. */
+function locksClash(existing, sectionId) {
+  if (!existing.sectionId || !sectionId) return true;
+  return existing.sectionId === sectionId;
+}
+
+/**
+ * Whether `lock` covers a scan of a ticket with option `optionId`. When the scanner has
+ * picked a section, only a lock on that section (or the whole event) covers it; with no
+ * section picked, any lock on a section that admits the ticket does.
+ * @param {object} lock - { sectionId, section?: { allowedOptions: [{ eventOptionId }] } }
+ */
+function lockCovers(lock, { sectionId = null, optionId }) {
+  if (!lock.sectionId) return true;
+  if (sectionId) return sectionId === lock.sectionId;
+  return (lock.section?.allowedOptions || []).some(o => o.eventOptionId === optionId);
+}
+
+/**
+ * What to do with one synced scan, given the ticket as the server sees it now. Pure.
+ * @param {object|null} ticket - { remaining, cancelled, inScope, consentOk }
+ * @param {number} qty - quantity the device redeemed
+ * @returns {{ redeem: number, conflict: string|null }}
+ */
+function judgeSyncedScan(ticket, qty) {
+  if (!ticket) return { redeem: 0, conflict: 'not_found' };
+  if (ticket.cancelled) return { redeem: 0, conflict: 'cancelled' };
+  if (!ticket.inScope) return { redeem: 0, conflict: 'wrong_scope' };
+  if (ticket.remaining <= 0) return { redeem: 0, conflict: 'already_used' };
+  const redeem = Math.min(Math.max(1, qty || 1), ticket.remaining);
+  if (!ticket.consentOk) return { redeem, conflict: 'consent' };
+  return { redeem, conflict: redeem < (qty || 1) ? 'partly_used' : null };
+}
+
+const CONFLICT_TEXT = {
+  not_found: 'Ticket not found (possibly transferred or reissued)',
+  cancelled: 'Registration was cancelled',
+  wrong_scope: 'Ticket is not valid for this section',
+  already_used: 'Ticket had already been fully used',
+  partly_used: 'Fewer places were left than were checked in offline',
+  consent: 'Checked in without parental consent',
+};
+
+// ─── Database helpers ─────────────────────────────────────────────────────────
+
+const LOCK_INCLUDE = {
+  section: { include: { allowedOptions: true } },
+  user: { select: { id: true, name: true } },
+};
+
+async function activeLocks(eventId, db = prisma) {
+  return db.scanLock.findMany({ where: { eventId, releasedAt: null }, include: LOCK_INCLUDE, orderBy: { lockedAt: 'asc' } });
+}
+
+/** Locks a scope to this device. Re-locking by the same device and person returns the existing lock. */
+async function acquireLock({ eventId, sectionId = null, deviceId, deviceName, userId }) {
+  if (!deviceId || typeof deviceId !== 'string' || deviceId.length > 100) throw lockError('A device id is required');
+  return prisma.$transaction(async (tx) => {
+    await tx.$executeRaw`SELECT pg_advisory_xact_lock(hashtext(${'scanlock:' + eventId}))`;
+    const event = await tx.event.findUnique({ where: { id: eventId } });
+    if (!event) throw lockError('Event not found', 404);
+    if (sectionId) {
+      const section = await tx.section.findUnique({ where: { id: sectionId } });
+      if (!section || section.eventId !== eventId) throw lockError('Section not found for this event', 404);
+    }
+    const existing = await activeLocks(eventId, tx);
+    const same = existing.find(l => (l.sectionId || null) === (sectionId || null) && l.deviceId === deviceId && l.userId === userId);
+    if (same) return same;
+    const clash = existing.find(l => locksClash(l, sectionId));
+    if (clash) {
+      const scope = clash.section ? `"${clash.section.name}"` : 'the whole event';
+      throw lockError(`${scope} is offline-locked by ${clash.user.name}${clash.deviceName ? ` on ${clash.deviceName}` : ''}.`, 409);
+    }
+    return tx.scanLock.create({ data: { eventId, sectionId: sectionId || null, deviceId, deviceName: deviceName ? String(deviceName).slice(0, 100) : null, userId }, include: LOCK_INCLUDE });
+  });
+}
+
+/**
+ * The lock (other than the scanner's own device) that stops this online scan, or null.
+ * @param {object} ticket - { eventId, optionId }
+ */
+async function blockingLock(ticket, { sectionId = null, deviceId = null } = {}) {
+  const locks = await activeLocks(ticket.eventId);
+  return locks.find(l => l.deviceId !== deviceId && lockCovers(l, { sectionId, optionId: ticket.optionId })) || null;
+}
+
+/** Tickets valid in a lock's scope, for the device to keep offline. */
+async function snapshotFor(lock) {
+  const optionIds = lock.section ? lock.section.allowedOptions.map(o => o.eventOptionId) : null;
+  const tickets = await prisma.ticket.findMany({
+    where: {
+      eventId: lock.eventId,
+      registrationOption: { registration: { status: { not: 'cancelled' } }, ...(optionIds ? { eventOptionId: { in: optionIds } } : {}) },
+    },
+    include: {
+      usages: { select: { quantityRedeemed: true } },
+      attendee: { select: { name: true } },
+      user: { select: { name: true } },
+      registrationOption: { include: { eventOption: { select: { id: true, name: true, isMainTicket: true } }, variant: { select: { name: true } } } },
+    },
+  });
+  const { consentStatusForTickets } = require('./consent');
+  const consent = await consentStatusForTickets(tickets.map(t => t.id));
+  const snapshotAt = new Date();
+  await prisma.scanLock.update({ where: { id: lock.id }, data: { snapshotAt } });
+  return {
+    snapshotAt,
+    tickets: tickets.map(t => {
+      const redeemed = t.usages.reduce((s, u) => s + (u.quantityRedeemed || 1), 0);
+      return {
+        id: t.id,
+        qrCode: t.qrCode,
+        holder: t.attendee?.name || t.user?.name || '',
+        bookedBy: t.attendee ? t.user?.name || '' : '',
+        option: t.registrationOption.eventOption.name,
+        variant: t.registrationOption.variant?.name || null,
+        quantity: t.quantity || 1,
+        remaining: Math.max(0, (t.quantity || 1) - redeemed),
+        consentStatus: consent.get(t.id) || 'not_required',
+      };
+    }),
+  };
+}
+
+/**
+ * Records queued offline scans. Each scan: { clientScanId, qrCode, qty, scannedAt }.
+ * @returns {Promise<{ accepted, duplicates, conflicts, report }>}
+ */
+async function syncScans(lock, scans) {
+  const results = { accepted: 0, duplicates: 0, conflicts: [] };
+  const optionIds = lock.section ? new Set(lock.section.allowedOptions.map(o => o.eventOptionId)) : null;
+  const { consentStatusForTickets } = require('./consent');
+  const checkIns = [];
+
+  for (const scan of (scans || []).slice(0, 2000)) {
+    const clientScanId = String(scan?.clientScanId || '').slice(0, 100);
+    if (!clientScanId) continue;
+    if (await prisma.ticketUsage.findUnique({ where: { clientScanId } })) { results.duplicates += 1; continue; }
+
+    const qty = Math.max(1, parseInt(scan.qty, 10) || 1);
+    const scannedAt = scan.scannedAt && !isNaN(new Date(scan.scannedAt)) ? new Date(scan.scannedAt) : new Date();
+    const ticket = await prisma.ticket.findUnique({
+      where: { qrCode: String(scan.qrCode || '') },
+      include: { usages: true, registrationOption: { include: { registration: { select: { status: true } }, eventOption: { select: { isMainTicket: true } } } } },
+    });
+    let state = null;
+    if (ticket && ticket.eventId === lock.eventId) {
+      const redeemed = ticket.usages.reduce((s, u) => s + (u.quantityRedeemed || 1), 0);
+      const consent = (await consentStatusForTickets([ticket.id])).get(ticket.id);
+      state = {
+        remaining: (ticket.quantity || 1) - redeemed,
+        cancelled: ticket.registrationOption.registration.status === 'cancelled',
+        inScope: !optionIds || optionIds.has(ticket.registrationOption.eventOptionId),
+        consentOk: ['not_required', 'given'].includes(consent),
+      };
+    }
+    const verdict = judgeSyncedScan(state, qty);
+    if (verdict.redeem > 0) {
+      await prisma.ticketUsage.create({
+        data: { ticketId: ticket.id, scannedById: lock.userId, scannedAt, quantityRedeemed: verdict.redeem, clientScanId, offline: true, scanLockId: lock.id, syncedAt: new Date() },
+      });
+      await prisma.ticket.update({ where: { id: ticket.id }, data: { isUsed: state.remaining - verdict.redeem <= 0, updatedAt: new Date() } });
+      results.accepted += 1;
+      if (ticket.registrationOption.eventOption.isMainTicket) {
+        checkIns.push({ ticketId: ticket.id, qty: verdict.redeem, total: (ticket.quantity || 1) - state.remaining + verdict.redeem, left: state.remaining - verdict.redeem });
+      }
+    }
+    if (verdict.conflict) {
+      results.conflicts.push({ clientScanId, qrCode: scan.qrCode, ticketId: ticket?.id || null, qty, redeemed: verdict.redeem, scannedAt, reason: verdict.conflict, message: CONFLICT_TEXT[verdict.conflict] });
+    }
+  }
+
+  await prisma.scanLock.update({ where: { id: lock.id }, data: { lastSyncAt: new Date() } });
+  const report = await prisma.offlineSyncReport.create({
+    data: { scanLockId: lock.id, accepted: results.accepted, duplicates: results.duplicates, conflicts: results.conflicts, afterForceRelease: !!lock.forceReleasedById },
+  });
+
+  // Check-in confirmations go out after sync, not at the moment of the offline scan.
+  const { sendCheckInEmails } = require('./notifications');
+  for (const c of checkIns) sendCheckInEmails(c.ticketId, c.qty, c.total, c.left).catch(() => {});
+
+  return { ...results, report };
+}
+
+module.exports = { lockError, locksClash, lockCovers, judgeSyncedScan, CONFLICT_TEXT, LOCK_INCLUDE, activeLocks, acquireLock, blockingLock, snapshotFor, syncScans };
@@ -0,0 +1,54 @@
+const { locksClash, lockCovers, judgeSyncedScan } = require('../src/utils/scanLocks');
+
+describe('locksClash', () => {
+  test('a whole-event lock clashes with everything', () => {
+    expect(locksClash({ sectionId: null }, 'hall')).toBe(true);
+    expect(locksClash({ sectionId: 'hall' }, null)).toBe(true);
+  });
+
+  test('section locks only clash with the same section', () => {
+    expect(locksClash({ sectionId: 'hall' }, 'hall')).toBe(true);
+    expect(locksClash({ sectionId: 'hall' }, 'dinner')).toBe(false);
+  });
+});
+
+describe('lockCovers', () => {
+  const dinnerLock = { sectionId: 'dinner', section: { allowedOptions: [{ eventOptionId: 'meal' }] } };
+
+  test('a whole-event lock covers every scan', () => {
+    expect(lockCovers({ sectionId: null }, { sectionId: 'x', optionId: 'y' })).toBe(true);
+  });
+
+  test('with a section picked, only that section is covered', () => {
+    expect(lockCovers(dinnerLock, { sectionId: 'dinner', optionId: 'meal' })).toBe(true);
+    expect(lockCovers(dinnerLock, { sectionId: 'hall', optionId: 'meal' })).toBe(false);
+  });
+
+  test('with no section picked, tickets the locked section admits are covered', () => {
+    expect(lockCovers(dinnerLock, { optionId: 'meal' })).toBe(true);
+    expect(lockCovers(dinnerLock, { optionId: 'entry' })).toBe(false);
+  });
+});
+
+describe('judgeSyncedScan', () => {
+  const ok = { remaining: 2, cancelled: false, inScope: true, consentOk: true };
+
+  test('records a normal scan', () => {
+    expect(judgeSyncedScan(ok, 1)).toEqual({ redeem: 1, conflict: null });
+  });
+
+  test('never redeems more than is left', () => {
+    expect(judgeSyncedScan(ok, 3)).toEqual({ redeem: 2, conflict: 'partly_used' });
+    expect(judgeSyncedScan({ ...ok, remaining: 0 }, 1)).toEqual({ redeem: 0, conflict: 'already_used' });
+  });
+
+  test('flags unknown, cancelled and out-of-scope tickets without recording them', () => {
+    expect(judgeSyncedScan(null, 1)).toEqual({ redeem: 0, conflict: 'not_found' });
+    expect(judgeSyncedScan({ ...ok, cancelled: true }, 1)).toEqual({ redeem: 0, conflict: 'cancelled' });
+    expect(judgeSyncedScan({ ...ok, inScope: false }, 1)).toEqual({ redeem: 0, conflict: 'wrong_scope' });
+  });
+
+  test('records but flags a check-in without consent', () => {
+    expect(judgeSyncedScan({ ...ok, consentOk: false }, 1)).toEqual({ redeem: 1, conflict: 'consent' });
+  });
+});
@@ -1,12 +1,12 @@
 {
  "name": "hope-events-frontend",
-  "version": "1.16.0",
+  "version": "1.17.0",
  "lockfileVersion": 3,
  "requires": true,
  "packages": {
    "": {
      "name": "hope-events-frontend",
-      "version": "1.16.0",
+      "version": "1.17.0",
      "dependencies": {
        "@hookform/resolvers": "^5.2.1",
        "@radix-ui/react-accordion": "^1.2.11",
@@ -31,6 +31,7 @@
        "class-variance-authority": "^0.7.1",
        "clsx": "^2.1.1",
        "date-fns": "^4.1.0",
+        "idb": "^8.0.4",
        "lucide-react": "^0.536.0",
        "next": "^15.5.24",
        "qrcode": "^1.5.4",
@@ -869,9 +870,6 @@
      "cpu": [
        "arm"
      ],
-      "libc": [
-        "glibc"
-      ],
      "license": "LGPL-3.0-or-later",
      "optional": true,
      "os": [
@@ -888,9 +886,6 @@
      "cpu": [
        "arm64"
      ],
-      "libc": [
-        "glibc"
-      ],
      "license": "LGPL-3.0-or-later",
      "optional": true,
      "os": [
@@ -907,9 +902,6 @@
      "cpu": [
        "ppc64"
      ],
-      "libc": [
-        "glibc"
-      ],
      "license": "LGPL-3.0-or-later",
      "optional": true,
      "os": [
@@ -926,9 +918,6 @@
      "cpu": [
        "riscv64"
      ],
-      "libc": [
-        "glibc"
-      ],
      "license": "LGPL-3.0-or-later",
      "optional": true,
      "os": [
@@ -945,9 +934,6 @@
      "cpu": [
        "s390x"
      ],
-      "libc": [
-        "glibc"
-      ],
      "license": "LGPL-3.0-or-later",
      "optional": true,
      "os": [
@@ -964,9 +950,6 @@
      "cpu": [
        "x64"
      ],
-      "libc": [
-        "glibc"
-      ],
      "license": "LGPL-3.0-or-later",
      "optional": true,
      "os": [
@@ -983,9 +966,6 @@
      "cpu": [
        "arm64"
      ],
-      "libc": [
-        "musl"
-      ],
      "license": "LGPL-3.0-or-later",
      "optional": true,
      "os": [
@@ -1002,9 +982,6 @@
      "cpu": [
        "x64"
      ],
-      "libc": [
-        "musl"
-      ],
      "license": "LGPL-3.0-or-later",
      "optional": true,
      "os": [
@@ -1021,9 +998,6 @@
      "cpu": [
        "arm"
      ],
-      "libc": [
-        "glibc"
-      ],
      "license": "Apache-2.0",
      "optional": true,
      "os": [
@@ -1046,9 +1020,6 @@
      "cpu": [
        "arm64"
      ],
-      "libc": [
-        "glibc"
-      ],
      "license": "Apache-2.0",
      "optional": true,
      "os": [
@@ -1071,9 +1042,6 @@
      "cpu": [
        "ppc64"
      ],
-      "libc": [
-        "glibc"
-      ],
      "license": "Apache-2.0",
      "optional": true,
      "os": [
@@ -1096,9 +1064,6 @@
      "cpu": [
        "riscv64"
      ],
-      "libc": [
-        "glibc"
-      ],
      "license": "Apache-2.0",
      "optional": true,
      "os": [
@@ -1121,9 +1086,6 @@
      "cpu": [
        "s390x"
      ],
-      "libc": [
-        "glibc"
-      ],
      "license": "Apache-2.0",
      "optional": true,
      "os": [
@@ -1146,9 +1108,6 @@
      "cpu": [
        "x64"
      ],
-      "libc": [
-        "glibc"
-      ],
      "license": "Apache-2.0",
      "optional": true,
      "os": [
@@ -1171,9 +1130,6 @@
      "cpu": [
        "arm64"
      ],
-      "libc": [
-        "musl"
-      ],
      "license": "Apache-2.0",
      "optional": true,
      "os": [
@@ -1196,9 +1152,6 @@
      "cpu": [
        "x64"
      ],
-      "libc": [
-        "musl"
-      ],
      "license": "Apache-2.0",
      "optional": true,
      "os": [
@@ -1455,9 +1408,6 @@
      "cpu": [
        "arm64"
      ],
-      "libc": [
-        "glibc"
-      ],
      "license": "MIT",
      "optional": true,
      "os": [
@@ -1474,9 +1424,6 @@
      "cpu": [
        "arm64"
      ],
-      "libc": [
-        "musl"
-      ],
      "license": "MIT",
      "optional": true,
      "os": [
@@ -1493,9 +1440,6 @@
      "cpu": [
        "x64"
      ],
-      "libc": [
-        "glibc"
-      ],
      "license": "MIT",
      "optional": true,
      "os": [
@@ -1512,9 +1456,6 @@
      "cpu": [
        "x64"
      ],
-      "libc": [
-        "musl"
-      ],
      "license": "MIT",
      "optional": true,
      "os": [
@@ -6865,6 +6806,12 @@
        "node": ">= 6"
      }
    },
+    "node_modules/idb": {
+      "version": "8.0.4",
+      "resolved": "https://registry.npmjs.org/idb/-/idb-8.0.4.tgz",
+      "integrity": "sha512-jd0ITCrN+Zah4J7R/Z2jnR3W7A4BXDAjmo62MwWuSjxCiueUAf7X5rbodEdidWzeknwXHmLpdZkoiiCppNi30Q==",
+      "license": "ISC"
+    },
    "node_modules/ignore": {
      "version": "5.3.2",
      "resolved": "https://registry.npmjs.org/ignore/-/ignore-5.3.2.tgz",
@@ -1,6 +1,6 @@
 {
  "name": "hope-events-frontend",
-  "version": "1.16.0",
+  "version": "1.17.0",
  "private": true,
  "scripts": {
    "dev": "next dev --turbopack",
@@ -32,6 +32,7 @@
    "class-variance-authority": "^0.7.1",
    "clsx": "^2.1.1",
    "date-fns": "^4.1.0",
+    "idb": "^8.0.4",
    "lucide-react": "^0.536.0",
    "next": "^15.5.24",
    "qrcode": "^1.5.4",
@@ -0,0 +1,67 @@
+/*
+ * Service worker for offline ticket scanning.
+ *
+ * Only the scanner page and the static files it needs are cached:
+ * - /_next/static/* (hashed, never change): cache-first.
+ * - The scanner page itself: network-first, falling back to the cached copy offline.
+ * - The page can ask (postMessage { type: 'cache-urls', urls }) for the files it has
+ *   loaded to be cached up front, so it works offline straight after "Enable offline mode".
+ * API calls are never cached — offline scans go through IndexedDB instead.
+ */
+const CACHE = 'hope-scanner-v1';
+const SCANNER_PATH = '/dashboard/staff/ticket-scanning';
+
+self.addEventListener('install', () => self.skipWaiting());
+self.addEventListener('activate', (event) => {
+  event.waitUntil((async () => {
+    const keys = await caches.keys();
+    await Promise.all(keys.filter(k => k.startsWith('hope-scanner-') && k !== CACHE).map(k => caches.delete(k)));
+    await self.clients.claim();
+  })());
+});
+
+self.addEventListener('message', (event) => {
+  const data = event.data || {};
+  if (data.type !== 'cache-urls' || !Array.isArray(data.urls)) return;
+  event.waitUntil((async () => {
+    const cache = await caches.open(CACHE);
+    const sameOrigin = data.urls.filter(u => {
+      try { return new URL(u, self.location.origin).origin === self.location.origin; } catch { return false; }
+    });
+    await Promise.all(sameOrigin.map(u => cache.add(u).catch(() => {})));
+  })());
+});
+
+self.addEventListener('fetch', (event) => {
+  const req = event.request;
+  if (req.method !== 'GET') return;
+  const url = new URL(req.url);
+  if (url.origin !== self.location.origin) return;
+
+  if (url.pathname.startsWith('/_next/static/')) {
+    event.respondWith((async () => {
+      const cache = await caches.open(CACHE);
+      const hit = await cache.match(req);
+      if (hit) return hit;
+      const res = await fetch(req);
+      if (res.ok) cache.put(req, res.clone());
+      return res;
+    })());
+    return;
+  }
+
+  if (url.pathname === SCANNER_PATH) {
+    event.respondWith((async () => {
+      const cache = await caches.open(CACHE);
+      try {
+        const res = await fetch(req);
+        if (res.ok) cache.put(SCANNER_PATH, res.clone());
+        return res;
+      } catch {
+        const hit = (await cache.match(req, { ignoreSearch: true })) || (await cache.match(SCANNER_PATH));
+        if (hit) return hit;
+        throw new Error('offline and not cached');
+      }
+    })());
+  }
+});
@@ -25,6 +25,10 @@ const ACTIONS = [
  "consent_override",
  "consent_rerequested",
  "medical_list_viewed",
+  "scan_lock_acquired",
+  "scan_lock_released",
+  "scan_lock_force_released",
+  "offline_sync",
 ] as const;

 const ACTION_LABELS: Record<string, string> = {
@@ -44,6 +48,10 @@ const ACTION_LABELS: Record<string, string> = {
  consent_override: "Consent overridden at check-in",
  consent_rerequested: "Consent re-requested",
  medical_list_viewed: "Medical list viewed",
+  scan_lock_acquired: "Offline scanning started",
+  scan_lock_released: "Offline scanning ended",
+  scan_lock_force_released: "Offline lock force-released",
+  offline_sync: "Offline scans synced",
 };

 interface AuditLogEntry {
@@ -8,7 +8,7 @@ import { useStableState } from "@/hooks/useStableState";
 import { useVisiblePolling } from "@/hooks/useVisiblePolling";
 import {
  Calendar, Banknote, Gift, Users, Ticket, QrCode, ClipboardList,
-  UserPlus, FileText, MessageCircle, BarChart2, Mail, Wallet, DoorOpen, History, TicketPercent, ShieldCheck, ListChecks,
+  UserPlus, FileText, MessageCircle, BarChart2, Mail, Wallet, DoorOpen, History, TicketPercent, ShieldCheck, ListChecks, WifiOff,
 } from "lucide-react";
 import { StatCard, StatCardRow } from "@/components/shared/StatCard";
 import { QuickActionTile, QuickActionGrid } from "@/components/shared/QuickActionTile";
@@ -27,6 +27,7 @@ const QUICK_ACTIONS = [
  { href: "/dashboard/supervisor/manual", label: "Manual registration", description: "Register a guest and issue tickets", icon: UserPlus },
  { href: "/dashboard/supervisor/at-the-door", label: "At the door", description: "Walk-ins, payments, ticket printing", icon: DoorOpen },
  { href: "/dashboard/supervisor/payments", label: "Payments & donations", description: "Manual payments and assignment", icon: Wallet },
+  { href: "/dashboard/supervisor/offline-scans", label: "Offline scanning", description: "Devices scanning offline and their synced scans", icon: WifiOff },
  { href: "/dashboard/supervisor/waitlist", label: "Waitlist", description: "People waiting for sold-out tickets", icon: ListChecks },
  { href: "/dashboard/supervisor/consent", label: "Parental consent", description: "Youth events: consent status and medical list", icon: ShieldCheck },
  { href: "/dashboard/supervisor/coupons", label: "Coupon codes", description: "Discounts for staff, leaders and promotions", icon: TicketPercent },
@@ -7,6 +7,9 @@ import { apiFetch } from "@/lib/api";
 import { useDismissingState } from "@/hooks/useDismissingState";
 import { useRouter } from "next/navigation";
 import { QrCode } from "lucide-react";
+import { useOfflineScanning } from "@/components/scanner/useOfflineScanning";
+import { OfflineScanPanel } from "@/components/scanner/OfflineScanPanel";
+import type { SnapshotTicket } from "@/lib/offlineScan";

 export default function TicketScanningPage() {
  const router = useRouter();
@@ -17,6 +20,7 @@ export default function TicketScanningPage() {
  const [alreadyUsedModal, setAlreadyUsedModal] = useState<{ message: string; ticket?: any } | null>(null);
  const [errorModal, setErrorModal] = useState<string | null>(null);
  const { token, user } = useAuth();
+  const offline = useOfflineScanning(token);
  const [recentScans, setRecentScans] = useState<any[]>([]);
  const [stats, setStats] = useState<any | null>(null);
  const [loadingStats, setLoadingStats] = useState<boolean>(false);
@@ -34,6 +38,7 @@ export default function TicketScanningPage() {
    qrCode: string;
    ticket: any;
    remaining: number;
+    offlineTicket?: SnapshotTicket; // scanned against the downloaded list (offline mode)
  } | null>(null);
  const [confirmQty, setConfirmQty] = useState(1);
  // Youth events: the preview says whether parental consent allows check-in.
@@ -96,6 +101,16 @@ export default function TicketScanningPage() {
    })();
  }, [selectedEventId, token]);

+  // In offline mode the event and section are fixed to the locked scope.
+  useEffect(() => {
+    if (!offline.lock) return;
+    setSelectedEventId(offline.lock.eventId);
+  }, [offline.lock]);
+  useEffect(() => {
+    if (!offline.lock) return;
+    setSelectedSectionId(offline.lock.sectionId || "all");
+  }, [offline.lock, sections]);
+
  // Bug fix: stop the scanner when the event or section filter changes so stale scan
  // context is never used. The user must press "Scan Ticket" again to resume.
  const isFirstFilterRender = useRef(true);
@@ -114,6 +129,32 @@ export default function TicketScanningPage() {
        return;
      }

+      // Offline mode: check the ticket against the list downloaded to this device.
+      if (offline.lock) {
+        const t = await offline.findTicket(text);
+        if (!t) { setErrorModal("Not found in the offline ticket list. Check at the door desk."); return; }
+        if (t.remaining <= 0) { setAlreadyUsedModal({ message: "Ticket has already been fully used", ticket: { id: t.id } }); return; }
+        if (!["not_required", "given"].includes(t.consentStatus)) {
+          setErrorModal(t.consentStatus === "declined" ? "Parental consent was declined — this ticket can't be checked in." : "Parental consent is missing or pending — this ticket can't be checked in offline. Check at the door desk.");
+          return;
+        }
+        setConfirmQty(t.remaining);
+        setConfirmQtyRaw(String(t.remaining));
+        setConfirmModal({
+          qrCode: text,
+          remaining: t.remaining,
+          offlineTicket: t,
+          ticket: {
+            id: t.id, quantity: t.quantity, consentStatus: t.consentStatus,
+            event: { title: offline.lock.eventTitle },
+            registrationOption: { eventOption: { name: t.option }, variant: t.variant ? { name: t.variant } : null },
+            attendee: t.bookedBy ? { name: t.holder } : null,
+            user: { name: t.bookedBy || t.holder },
+          },
+        });
+        return;
+      }
+
      // Always preview first to validate the ticket before showing confirm step
      // Uses the lightweight scan-preview endpoint (only fetches fields needed for the confirm modal)
      let preview: any;
@@ -172,7 +213,7 @@ export default function TicketScanningPage() {
    if (!confirmModal || !token) return;

    // Capture everything before clearing modal state
-    const { qrCode, ticket, remaining } = confirmModal;
+    const { qrCode, ticket, remaining, offlineTicket } = confirmModal;
    const qty = confirmQty;
    const baseName = ticket?.registrationOption?.eventOption?.name || "Ticket";
    const variantName = ticket?.registrationOption?.variant?.name;
@@ -194,6 +235,17 @@ export default function TicketScanningPage() {
      total: ticket?.quantity || 1,
    });

+    // Offline mode: saved on this device, synced when there's a connection.
+    if (offlineTicket) {
+      try {
+        await offline.scanLocally(offlineTicket, qty);
+      } catch (e: any) {
+        setSuccessModal(null);
+        setErrorModal(e?.message || "Couldn't save the scan on this device");
+      }
+      return;
+    }
+
    // Background write — reverse the optimistic update on failure
    try {
      const url = `/api/tickets/scan/${encodeURIComponent(qrCode)}${
@@ -202,7 +254,12 @@ export default function TicketScanningPage() {
      await apiFetch<any>(url, {
        method: "POST",
        authToken: token,
-        body: { qty, ...(overrideConsent ? { overrideConsent: true } : {}) },
+        body: {
+          qty,
+          deviceId: offline.deviceId(),
+          ...(selectedSectionId && selectedSectionId !== "all" ? { sectionId: selectedSectionId } : {}),
+          ...(overrideConsent ? { overrideConsent: true } : {}),
+        },
      });
      refreshStatsAndRecent();
    } catch (e: any) {
@@ -270,8 +327,10 @@ export default function TicketScanningPage() {
              className="border rounded px-3 py-2 w-full sm:w-56 max-w-full"
              value={selectedEventId}
              onChange={(e) => setSelectedEventId(e.target.value)}
+              disabled={!!offline.lock}
            >
              <option value="all">All events</option>
+              {offline.lock && !events.some(ev => ev.id === offline.lock!.eventId) && <option value={offline.lock.eventId}>{offline.lock.eventTitle}</option>}
              {events.map((ev) => (
                <option key={ev.id} value={ev.id}>{ev.title}</option>
              ))}
@@ -289,6 +348,7 @@ export default function TicketScanningPage() {
                className="border rounded px-3 py-2 w-full sm:w-56 max-w-full"
                value={selectedSectionId}
                onChange={(e) => setSelectedSectionId(e.target.value)}
+                disabled={!!offline.lock}
              >
                <option value="all">All sections</option>
                {sections.map(section => (
@@ -299,6 +359,16 @@ export default function TicketScanningPage() {
            </div>
          )}

+          <OfflineScanPanel
+            offline={offline}
+            token={token}
+            eventId={selectedEventId}
+            eventTitle={events.find(ev => ev.id === selectedEventId)?.title || offline.lock?.eventTitle || ""}
+            sectionId={selectedSectionId !== "all" ? selectedSectionId : null}
+            sectionName={sections.find(s => s.id === selectedSectionId)?.name || null}
+            onError={setError}
+            onInfo={setScanInfo}
+          />
          <QRScanner
            ref={scannerRef}
            onResult={handleResult}
@@ -0,0 +1,163 @@
+"use client";
+
+import React, { useCallback, useEffect, useMemo, useState } from "react";
+import { useAuth } from "@/hooks/useAuth";
+import { useRouter } from "next/navigation";
+import { apiFetch } from "@/lib/api";
+import { formatDate } from "@/lib/date";
+import { useDismissingState } from "@/hooks/useDismissingState";
+import { WifiOff, Unlock, CheckCircle2 } from "lucide-react";
+
+type Lock = { id: string; sectionName: string | null; deviceName: string | null; user: { name: string }; lockedAt: string; snapshotAt: string | null; lastSyncAt: string | null };
+type Report = {
+  id: string; accepted: number; duplicates: number; afterForceRelease: boolean; createdAt: string; reviewedAt: string | null;
+  reviewedBy: { name: string } | null;
+  conflicts: { clientScanId: string; qrCode: string; qty: number; redeemed: number; scannedAt: string; reason: string; message: string }[];
+  scanLock: Lock;
+};
+
+const when = (iso: string | null) => (iso ? new Date(iso).toLocaleString() : "—");
+
+export default function OfflineScansPage() {
+  const { user, loading, token } = useAuth();
+  const router = useRouter();
+  const canView = useMemo(() => user?.role === "admin" || user?.role === "supervisor", [user]);
+
+  useEffect(() => {
+    if (loading) return;
+    if (!user) router.replace("/login");
+  }, [user, loading, router]);
+
+  const [events, setEvents] = useState<any[]>([]);
+  const [eventId, setEventId] = useState("");
+  const [locks, setLocks] = useState<Lock[]>([]);
+  const [reports, setReports] = useState<Report[]>([]);
+  const [onlyOpen, setOnlyOpen] = useState(true);
+  const [error, setError] = useDismissingState<string | null>(null);
+  const [info, setInfo] = useDismissingState<string | null>(null);
+
+  useEffect(() => {
+    if (!token || !canView) return;
+    apiFetch<any[]>("/api/events/all?includePast=true", { authToken: token })
+      .then(evs => {
+        const recent = (evs || []).filter(e => new Date(e.endDate).getTime() > Date.now() - 14 * 864e5);
+        setEvents(recent);
+        if (recent.length && !eventId) setEventId(recent[0].id);
+      })
+      .catch(e => setError(e?.message || "Failed to load events"));
+    // eslint-disable-next-line react-hooks/exhaustive-deps
+  }, [token, canView]);
+
+  const load = useCallback(async () => {
+    if (!token || !eventId) return;
+    try {
+      const [l, r] = await Promise.all([
+        apiFetch<Lock[]>(`/api/scan-locks?eventId=${encodeURIComponent(eventId)}`, { authToken: token }),
+        apiFetch<Report[]>(`/api/scan-locks/reports?eventId=${encodeURIComponent(eventId)}${onlyOpen ? "&unreviewed=true" : ""}`, { authToken: token }),
+      ]);
+      setLocks(l);
+      setReports(r.filter(x => !onlyOpen || x.conflicts.length > 0 || x.afterForceRelease));
+    } catch (e: any) {
+      setError(e?.message || "Failed to load offline scanning");
+    }
+  }, [token, eventId, onlyOpen, setError]);
+  useEffect(() => { load(); }, [load]);
+
+  const forceRelease = async (l: Lock) => {
+    try {
+      const res = await apiFetch<{ message: string }>(`/api/scan-locks/${l.id}/force-release`, { method: "POST", authToken: token! });
+      setInfo(res.message);
+      load();
+    } catch (e: any) { setError(e?.message || "Failed"); }
+  };
+  const review = async (r: Report) => {
+    try {
+      await apiFetch(`/api/scan-locks/reports/${r.id}/review`, { method: "POST", authToken: token! });
+      load();
+    } catch (e: any) { setError(e?.message || "Failed"); }
+  };
+
+  return (
+    <div className="max-w-5xl mx-auto w-full p-6">
+      <div className="flex items-center gap-3 mb-4">
+        <div className="w-10 h-10 rounded-xl bg-brand-50 flex items-center justify-center shrink-0">
+          <WifiOff className="w-5 h-5 text-brand-600" />
+        </div>
+        <div>
+          <button className="text-xs text-brand-600 hover:underline" onClick={() => router.push("/dashboard")}>← Back to dashboard</button>
+          <h1 className="text-2xl font-semibold text-gray-900 mt-0.5">Offline scanning</h1>
+          <p className="text-sm text-gray-500">Devices scanning without a connection, and their synced scans</p>
+        </div>
+      </div>
+
+      {!canView && <div className="p-3 border rounded bg-yellow-50 text-yellow-800 text-sm mb-4">You need supervisor access to manage offline scanning.</div>}
+      {error && <div className="mb-3 p-3 border rounded bg-red-50 text-red-800 text-sm">{error}</div>}
+      {info && <div className="mb-3 p-3 border rounded bg-green-50 text-green-800 text-sm">{info}</div>}
+
+      {canView && (
+        <div className="space-y-4">
+          <div className="flex flex-wrap items-end gap-3">
+            <div>
+              <label className="block text-xs text-gray-600 mb-1">Event</label>
+              <select className="border rounded-lg px-3 py-2 text-sm min-w-[16rem]" value={eventId} onChange={e => setEventId(e.target.value)}>
+                {events.map(ev => <option key={ev.id} value={ev.id}>{ev.title} ({formatDate(new Date(ev.startDate))})</option>)}
+              </select>
+            </div>
+            <label className="flex items-center gap-2 text-sm text-gray-700 pb-2">
+              <input type="checkbox" checked={onlyOpen} onChange={e => setOnlyOpen(e.target.checked)} /> Only reports that need review
+            </label>
+          </div>
+
+          <section className="border rounded-xl p-4 bg-white shadow-sm">
+            <h2 className="font-semibold mb-2">Locked sections</h2>
+            {locks.length === 0 ? <p className="text-sm text-gray-500">No device is scanning offline for this event.</p> : (
+              <ul className="divide-y">
+                {locks.map(l => (
+                  <li key={l.id} className="py-2 flex items-center justify-between gap-3 text-sm">
+                    <div>
+                      <div className="font-medium">{l.sectionName || "Whole event"} — {l.user.name}{l.deviceName ? ` on ${l.deviceName}` : ""}</div>
+                      <div className="text-xs text-gray-500">Locked {when(l.lockedAt)} · list downloaded {when(l.snapshotAt)} · last sync {when(l.lastSyncAt)}</div>
+                    </div>
+                    <button onClick={() => forceRelease(l)} className="inline-flex items-center gap-1 px-2.5 py-1 text-xs rounded border hover:bg-gray-50 shrink-0" title="For a lost or flat device. If it reconnects later, its scans still sync and are flagged here.">
+                      <Unlock className="w-3.5 h-3.5" /> Force release
+                    </button>
+                  </li>
+                ))}
+              </ul>
+            )}
+          </section>
+
+          <section className="border rounded-xl p-4 bg-white shadow-sm">
+            <h2 className="font-semibold mb-2">Sync reports</h2>
+            {reports.length === 0 ? <p className="text-sm text-gray-500">{onlyOpen ? "Nothing needs review." : "No offline scans have been synced for this event."}</p> : (
+              <div className="space-y-3">
+                {reports.map(r => (
+                  <div key={r.id} className={`border rounded-lg p-3 ${r.reviewedAt ? "opacity-60" : ""}`}>
+                    <div className="flex items-center justify-between gap-3 text-sm">
+                      <div>
+                        <span className="font-medium">{when(r.createdAt)}</span> — {r.scanLock.user?.name}{r.scanLock.deviceName ? ` on ${r.scanLock.deviceName}` : ""}{r.scanLock.sectionName ? `, ${r.scanLock.sectionName}` : ""}
+                        <div className="text-xs text-gray-500">{r.accepted} scan(s) recorded{r.duplicates ? ` · ${r.duplicates} already synced` : ""}{r.afterForceRelease ? " · synced after the lock was force-released" : ""}</div>
+                      </div>
+                      {r.reviewedAt
+                        ? <span className="text-xs text-gray-500 inline-flex items-center gap-1"><CheckCircle2 className="w-3.5 h-3.5" /> Reviewed by {r.reviewedBy?.name}</span>
+                        : <button onClick={() => review(r)} className="px-2.5 py-1 text-xs rounded bg-brand-600 text-white hover:bg-brand-700 shrink-0">Mark reviewed</button>}
+                    </div>
+                    {r.conflicts.length > 0 && (
+                      <ul className="mt-2 text-xs space-y-1">
+                        {r.conflicts.map(c => (
+                          <li key={c.clientScanId} className="text-red-800">
+                            {new Date(c.scannedAt).toLocaleTimeString()} · ticket {String(c.qrCode).slice(0, 8)}… · {c.message}{c.redeemed ? ` (recorded ${c.redeemed} of ${c.qty})` : " (not recorded)"}
+                          </li>
+                        ))}
+                      </ul>
+                    )}
+                  </div>
+                ))}
+              </div>
+            )}
+          </section>
+        </div>
+      )}
+    </div>
+  );
+}
@@ -8,7 +8,7 @@ import { useStableState } from "@/hooks/useStableState";
 import { useVisiblePolling } from "@/hooks/useVisiblePolling";
 import {
  Calendar, Banknote, Gift, Users, Ticket, QrCode, DoorOpen, Wallet,
-  UserPlus, FileText, MessageCircle, BarChart2, Mail, TicketPercent, ShieldCheck, ListChecks,
+  UserPlus, FileText, MessageCircle, BarChart2, Mail, TicketPercent, ShieldCheck, ListChecks, WifiOff,
 } from "lucide-react";
 import { StatCard, StatCardRow } from "@/components/shared/StatCard";
 import { QuickActionTile, QuickActionGrid } from "@/components/shared/QuickActionTile";
@@ -24,6 +24,7 @@ const QUICK_ACTIONS = [
  { href: "/dashboard/supervisor/manual", label: "Manual registration", description: "Register a guest and issue tickets", icon: UserPlus },
  { href: "/dashboard/supervisor/events", label: "Manage events", description: "Create, edit, and update ticket types", icon: Calendar },
  { href: "/dashboard/supervisor/payments", label: "Payments & donations", description: "Manual payments and assignment", icon: Wallet },
+  { href: "/dashboard/supervisor/offline-scans", label: "Offline scanning", description: "Devices scanning offline and their synced scans", icon: WifiOff },
  { href: "/dashboard/supervisor/waitlist", label: "Waitlist", description: "People waiting for sold-out tickets", icon: ListChecks },
  { href: "/dashboard/supervisor/consent", label: "Parental consent", description: "Youth events: consent status and medical list", icon: ShieldCheck },
  { href: "/dashboard/supervisor/coupons", label: "Coupon codes", description: "Discounts for staff, leaders and promotions", icon: TicketPercent },
@@ -0,0 +1,17 @@
+import type { MetadataRoute } from "next";
+
+// Lets staff "Add to home screen" and open the ticket scanner like an app (it also
+// works offline once offline mode has been enabled — see public/sw.js).
+export default function manifest(): MetadataRoute.Manifest {
+  return {
+    name: "Ticket scanner",
+    short_name: "Scanner",
+    description: "Scan event tickets, online or offline",
+    start_url: "/dashboard/staff/ticket-scanning",
+    scope: "/",
+    display: "standalone",
+    background_color: "#ffffff",
+    theme_color: "#4F46E5",
+    icons: [{ src: "/favicon.ico", sizes: "any", type: "image/x-icon" }],
+  };
+}
@@ -0,0 +1,106 @@
+"use client";
+
+import React, { useEffect, useState } from "react";
+import { Wifi, WifiOff, CloudUpload, Lock } from "lucide-react";
+import { apiFetch } from "@/lib/api";
+import type { OtherLock } from "./useOfflineScanning";
+
+type Offline = ReturnType<typeof import("./useOfflineScanning").useOfflineScanning>;
+
+/**
+ * Offline-mode controls above the scanner: shows who holds which section, lets this
+ * device lock the selected section and download its tickets, and shows the sync queue.
+ */
+export function OfflineScanPanel({ offline, token, eventId, eventTitle, sectionId, sectionName, onError, onInfo }: {
+  offline: Offline;
+  token: string | null;
+  eventId: string;
+  eventTitle: string;
+  sectionId: string | null;
+  sectionName: string | null;
+  onError: (m: string) => void;
+  onInfo: (m: string) => void;
+}) {
+  const [locks, setLocks] = useState<OtherLock[]>([]);
+  const [busy, setBusy] = useState(false);
+  const { lock, pending, online, syncing } = offline;
+
+  useEffect(() => {
+    if (!token || !eventId || eventId === "all" || !online) { setLocks([]); return; }
+    apiFetch<OtherLock[]>(`/api/scan-locks?eventId=${encodeURIComponent(eventId)}`, { authToken: token })
+      .then(setLocks).catch(() => setLocks([]));
+  }, [token, eventId, online, lock]);
+
+  const others = locks.filter(l => l.deviceId !== offline.deviceId());
+
+  const enable = async () => {
+    setBusy(true);
+    try {
+      const n = await offline.enable(eventId, eventTitle, sectionId, sectionName);
+      onInfo(`Offline mode on — ${n} ticket(s) downloaded. You can keep scanning without a connection.`);
+    } catch (e: any) {
+      onError(e?.message || "Couldn't turn on offline mode");
+    } finally {
+      setBusy(false);
+    }
+  };
+  const release = async () => {
+    setBusy(true);
+    try {
+      await offline.release();
+      onInfo("Offline mode ended and the section is unlocked.");
+    } catch (e: any) {
+      onError(e?.message || "Couldn't end offline mode");
+    } finally {
+      setBusy(false);
+    }
+  };
+  const syncNow = async () => {
+    try {
+      const r = await offline.sync();
+      if (r) onInfo(`Synced ${r.accepted} scan(s)${r.conflicts ? ` — ${r.conflicts} need a supervisor to review` : ""}.`);
+    } catch (e: any) {
+      onError(e?.message || "Sync failed — scans are kept on this device and will retry.");
+    }
+  };
+
+  return (
+    <div className={`rounded-xl border p-3 mb-4 text-sm ${lock ? "bg-amber-50 border-amber-200" : "bg-white"}`}>
+      <div className="flex flex-wrap items-center gap-2">
+        {online ? <Wifi className="w-4 h-4 text-green-600" /> : <WifiOff className="w-4 h-4 text-red-600" />}
+        <span className={online ? "text-green-700" : "text-red-700"}>{online ? "Online" : "Offline"}</span>
+        {lock ? (
+          <>
+            <span className="text-gray-400">·</span>
+            <span className="font-medium text-amber-900">Offline mode: {lock.eventTitle}{lock.sectionName ? ` — ${lock.sectionName}` : " — whole event"}</span>
+            <span className="text-xs text-gray-600">Ticket list downloaded at {new Date(lock.snapshotAt).toLocaleTimeString()}</span>
+            <span className="text-xs text-gray-600">· {pending} scan(s) waiting to sync</span>
+            <div className="ml-auto flex gap-2">
+              <button onClick={syncNow} disabled={!online || syncing || pending === 0} className="inline-flex items-center gap-1 px-2.5 py-1 rounded border bg-white text-xs disabled:opacity-50"><CloudUpload className="w-3.5 h-3.5" /> {syncing ? "Syncing…" : "Sync now"}</button>
+              <button onClick={release} disabled={!online || busy} className="px-2.5 py-1 rounded bg-amber-600 text-white text-xs disabled:opacity-50">Release section</button>
+            </div>
+          </>
+        ) : eventId && eventId !== "all" ? (
+          <div className="ml-auto">
+            <button onClick={enable} disabled={!online || busy || others.some(l => !l.sectionId || !sectionId || l.sectionId === sectionId)} className="px-2.5 py-1 rounded border border-brand-300 text-brand-700 text-xs hover:bg-brand-50 disabled:opacity-50" title="Lock this section to this device and download its tickets, so you can keep scanning if the connection drops">
+              {busy ? "Preparing…" : `Enable offline mode${sectionName ? ` for ${sectionName}` : " (whole event)"}`}
+            </button>
+          </div>
+        ) : (
+          <span className="text-xs text-gray-500 ml-1">Pick an event to use offline mode.</span>
+        )}
+      </div>
+      {others.length > 0 && (
+        <ul className="mt-2 space-y-0.5">
+          {others.map(l => (
+            <li key={l.id} className="flex items-center gap-1.5 text-xs text-gray-700">
+              <Lock className="w-3.5 h-3.5 text-amber-600" />
+              {l.sectionName ? `"${l.sectionName}"` : "The whole event"} is offline-locked by {l.user.name}{l.deviceName ? ` on ${l.deviceName}` : ""} — scan it on that device.
+            </li>
+          ))}
+        </ul>
+      )}
+      {lock && !online && <p className="mt-2 text-xs text-amber-900">Scans are saved on this device and will sync when the connection is back. Tickets bought after the download time won&apos;t be on the list.</p>}
+    </div>
+  );
+}
@@ -0,0 +1,115 @@
+"use client";
+
+import { useCallback, useEffect, useRef, useState } from "react";
+import { apiFetch } from "@/lib/api";
+import {
+  OfflineLock, SnapshotTicket, clearOffline, deviceId, deviceName, findTicket, getOfflineLock,
+  queuedScans, recordScan, removeQueued, startOffline,
+} from "@/lib/offlineScan";
+
+export type OtherLock = { id: string; sectionId: string | null; sectionName: string | null; deviceId: string; deviceName: string | null; user: { name: string } };
+
+/**
+ * Offline mode for the ticket scanner: lock a section to this device, download its
+ * tickets, scan against them with no connection, and sync the queued scans whenever
+ * the device is back online.
+ */
+export function useOfflineScanning(token: string | null) {
+  const [lock, setLock] = useState<OfflineLock | null>(null);
+  const [pending, setPending] = useState(0);
+  const [online, setOnline] = useState(true);
+  const [syncing, setSyncing] = useState(false);
+  const [lastSync, setLastSync] = useState<{ accepted: number; conflicts: number; at: string } | null>(null);
+  const syncingRef = useRef(false);
+
+  const refreshPending = useCallback(async () => {
+    try { setPending((await queuedScans()).length); } catch { setPending(0); }
+  }, []);
+
+  useEffect(() => {
+    setLock(getOfflineLock());
+    refreshPending();
+    setOnline(typeof navigator === "undefined" ? true : navigator.onLine);
+    const up = () => setOnline(true);
+    const down = () => setOnline(false);
+    window.addEventListener("online", up);
+    window.addEventListener("offline", down);
+    // Cache the scanner page and everything it has loaded, so it opens offline.
+    if ("serviceWorker" in navigator) {
+      navigator.serviceWorker.register("/sw.js").then(async () => {
+        const reg = await navigator.serviceWorker.ready;
+        const urls = [window.location.pathname, ...performance.getEntriesByType("resource").map(e => e.name)];
+        reg.active?.postMessage({ type: "cache-urls", urls });
+      }).catch(() => {});
+    }
+    return () => { window.removeEventListener("online", up); window.removeEventListener("offline", down); };
+  }, [refreshPending]);
+
+  /** Uploads queued scans. Returns the server's verdict, or null when nothing was sent. */
+  const sync = useCallback(async () => {
+    if (!token || syncingRef.current) return null;
+    const queue = await queuedScans();
+    if (queue.length === 0) return null;
+    syncingRef.current = true;
+    setSyncing(true);
+    try {
+      const byLock = new Map<string, typeof queue>();
+      queue.forEach(q => byLock.set(q.lockId, [...(byLock.get(q.lockId) || []), q]));
+      let accepted = 0, conflicts = 0;
+      for (const [lockId, scans] of byLock) {
+        const res = await apiFetch<{ accepted: number; duplicates: number; conflicts: any[] }>(`/api/scan-locks/${lockId}/sync`, {
+          method: "POST", authToken: token, body: { deviceId: deviceId(), scans },
+        });
+        accepted += res.accepted;
+        conflicts += res.conflicts.length;
+        // Synced (or already on the server) — either way they're done on this device.
+        await removeQueued(scans.map(s => s.clientScanId));
+      }
+      const result = { accepted, conflicts, at: new Date().toISOString() };
+      setLastSync(result);
+      return result;
+    } finally {
+      syncingRef.current = false;
+      setSyncing(false);
+      refreshPending();
+    }
+  }, [token, refreshPending]);
+
+  // Sync as soon as the connection is back, and every 30 seconds while online.
+  useEffect(() => {
+    if (!online || !token) return;
+    sync().catch(() => {});
+    const t = setInterval(() => { if (navigator.onLine) sync().catch(() => {}); }, 30000);
+    return () => clearInterval(t);
+  }, [online, token, sync]);
+
+  const enable = useCallback(async (eventId: string, eventTitle: string, sectionId: string | null, sectionName: string | null) => {
+    if (!token) throw new Error("Log in first.");
+    const created = await apiFetch<{ id: string }>("/api/scan-locks", {
+      method: "POST", authToken: token, body: { eventId, sectionId, deviceId: deviceId(), deviceName: deviceName() },
+    });
+    const snap = await apiFetch<{ snapshotAt: string; tickets: SnapshotTicket[] }>(`/api/scan-locks/${created.id}/snapshot?deviceId=${encodeURIComponent(deviceId())}`, { authToken: token });
+    const next: OfflineLock = { lockId: created.id, eventId, eventTitle, sectionId, sectionName, snapshotAt: snap.snapshotAt };
+    await startOffline(next, snap.tickets);
+    setLock(next);
+    return snap.tickets.length;
+  }, [token]);
+
+  const release = useCallback(async () => {
+    if (!lock || !token) return;
+    await sync();
+    if ((await queuedScans()).length > 0) throw new Error("Some scans haven't synced yet. Try again when you're online.");
+    await apiFetch(`/api/scan-locks/${lock.lockId}`, { method: "DELETE", authToken: token, body: { deviceId: deviceId() } });
+    await clearOffline();
+    setLock(null);
+  }, [lock, token, sync]);
+
+  const scanLocally = useCallback(async (ticket: SnapshotTicket, qty: number) => {
+    if (!lock) throw new Error("Offline mode is not on.");
+    await recordScan(lock.lockId, ticket, qty);
+    await refreshPending();
+    if (navigator.onLine) sync().catch(() => {});
+  }, [lock, refreshPending, sync]);
+
+  return { lock, pending, online, syncing, lastSync, enable, release, sync, scanLocally, findTicket, deviceId };
+}
@@ -24,6 +24,7 @@ import { supervisorFormsHelpContent } from "./supervisor-forms";
 import { supervisorCouponsHelpContent } from "./supervisor-coupons";
 import { supervisorConsentHelpContent } from "./supervisor-consent";
 import { supervisorWaitlistHelpContent } from "./supervisor-waitlist";
+import { supervisorOfflineScansHelpContent } from "./supervisor-offline-scans";
 import { supervisorEmailAttendeesHelpContent } from "./supervisor-email-attendees";
 import { supervisorWhatsappAttendeesHelpContent } from "./supervisor-whatsapp-attendees";
 import { staffEventTicketsHelpContent } from "./staff-event-tickets";
@@ -150,6 +151,11 @@ const REGISTRY: HelpRegistryEntry[] = [
    matches: pathname => pathname === "/dashboard/supervisor/payments",
    content: supervisorPaymentsHelpContent,
  },
+  {
+    slug: "supervisor-offline-scans",
+    matches: pathname => pathname === "/dashboard/supervisor/offline-scans",
+    content: supervisorOfflineScansHelpContent,
+  },
  {
    slug: "supervisor-waitlist",
    matches: pathname => pathname === "/dashboard/supervisor/waitlist",
@@ -1,5 +1,5 @@
 import React from "react";
-import { QrCode, Filter, CheckCircle2, ShieldAlert } from "lucide-react";
+import { QrCode, Filter, CheckCircle2, ShieldAlert, WifiOff } from "lucide-react";
 import { GuideItem } from "@/components/shared/GuideItem";
 import type { HelpContent } from "./types";

@@ -19,6 +19,9 @@ export const staffTicketScanningHelpContent: HelpContent = {
            <GuideItem icon={CheckCircle2} title="Outcomes" tone="green">
              You&apos;ll see Success (with redeemed/remaining counts), Already Used, or an Error if something&apos;s wrong with the ticket.
            </GuideItem>
+            <GuideItem icon={WifiOff} title="Offline mode" tone="amber">
+              Worried about the venue Wi-Fi? While you&apos;re online, pick the event and section and tap &quot;Enable offline mode&quot;. The section is locked to your device and its tickets are downloaded, so you can keep scanning with no connection. Scans sync automatically when you&apos;re back online. Tickets bought after the download won&apos;t be on your list — send those people to the door desk. Tap &quot;Release section&quot; when you&apos;re done. Tip: add this page to your home screen so it opens offline.
+            </GuideItem>
            <GuideItem icon={ShieldAlert} title="Parental consent" tone="rose">
              On youth events, the confirm screen warns when a parent hasn&apos;t given consent yet (or declined). That person can&apos;t be checked in; a supervisor can override, and the override is recorded in the audit log.
            </GuideItem>
@@ -0,0 +1,32 @@
+import React from "react";
+import { WifiOff, Unlock, CheckCircle2, Lock } from "lucide-react";
+import { GuideItem } from "@/components/shared/GuideItem";
+import type { HelpContent } from "./types";
+
+/** Help content for /dashboard/supervisor/offline-scans. */
+export const supervisorOfflineScansHelpContent: HelpContent = {
+  title: "Offline scanning",
+  subtitle: "Devices scanning without a connection, and what they synced.",
+  tabs: [
+    {
+      key: "page",
+      label: "This page",
+      icon: WifiOff,
+      content: (
+        <div className="space-y-4">
+          <div className="space-y-4">
+            <GuideItem icon={Lock} title="Locked sections" tone="brand">
+              Each section (or the whole event) in offline mode is locked to one device, so two devices can never check in the same ticket while offline. You can see who holds each lock, when their ticket list was downloaded, and when they last synced.
+            </GuideItem>
+            <GuideItem icon={Unlock} title="Force release" tone="amber">
+              For a lost or flat device. The section is unlocked straight away. If the device reconnects later, its offline scans still sync and are flagged here.
+            </GuideItem>
+            <GuideItem icon={CheckCircle2} title="Sync reports" tone="rose">
+              Scans that need a person to look: tickets not found (e.g. transferred), cancelled registrations, tickets already used up, scans outside the locked section, or check-ins without parental consent. Mark each report reviewed once it&apos;s been dealt with.
+            </GuideItem>
+          </div>
+        </div>
+      ),
+    },
+  ],
+};
@@ -18,6 +18,25 @@ export type AuthContextValue = {

 const AuthContext = createContext<AuthContextValue | undefined>(undefined);

+// The last profile the server confirmed, so a page reloaded with no connection (e.g. the
+// ticket scanner in offline mode) still knows who's signed in. The server checks the
+// token on every API call regardless, so this never grants anything by itself.
+const USER_CACHE_KEY = "hope_events_user_cache";
+function cacheUser(u: AuthUser | null) {
+  try {
+    if (u) localStorage.setItem(USER_CACHE_KEY, JSON.stringify(u));
+    else localStorage.removeItem(USER_CACHE_KEY);
+  } catch { /* storage unavailable */ }
+}
+function cachedUser(): AuthUser | null {
+  try {
+    const raw = localStorage.getItem(USER_CACHE_KEY);
+    return raw ? JSON.parse(raw) : null;
+  } catch {
+    return null;
+  }
+}
+
 export function AuthProvider({ children }: { children: React.ReactNode }) {
  const [token, setToken] = useState<string | null>(null);
  const [user, setUser] = useState<AuthUser | null>(null);
@@ -34,6 +53,7 @@ export function AuthProvider({ children }: { children: React.ReactNode }) {
          const me = await apiFetch<AuthUser>("/api/users/profile", { authToken: t });
          setToken(t);
          setUser(me);
+          cacheUser(me);
        }
      } catch (e) {
        // Only wipe the stored token when the server explicitly rejects it (401).
@@ -41,8 +61,17 @@ export function AuthProvider({ children }: { children: React.ReactNode }) {
        // token stays in localStorage so the next page load can retry.
        if (e instanceof ApiError && e.status === 401) {
          clearToken();
+          cacheUser(null);
          setToken(null);
          setUser(null);
+        } else {
+          // No connection: carry on as the last confirmed user.
+          const t = getToken();
+          const cached = cachedUser();
+          if (t && cached) {
+            setToken(t);
+            setUser(cached);
+          }
        }
      } finally {
        setLoading(false);
@@ -57,6 +86,7 @@ export function AuthProvider({ children }: { children: React.ReactNode }) {
    saveToken(token);
    setToken(token);
    setUser(loggedInUser);
+    cacheUser(loggedInUser);
    return loggedInUser;
  }, []);

@@ -99,6 +129,7 @@ export function AuthProvider({ children }: { children: React.ReactNode }) {

  const logout = useCallback(() => {
    clearToken();
+    cacheUser(null);
    setToken(null);
    setUser(null);
  }, []);
@@ -121,6 +121,7 @@ export async function apiFetch<T = any>(path: string, options: ApiOptions = {}):
    // end it and send them to log in, where they enrol.
    if (res.status === 401 && data?.code === "TWO_FACTOR_REQUIRED" && typeof window !== "undefined") {
      localStorage.removeItem("hope_events_token");
+      localStorage.removeItem("hope_events_user_cache");
      if (!window.location.pathname.startsWith("/login")) {
        const back = window.location.pathname + window.location.search;
        window.location.href = `/login?reason=2fa&redirect=${encodeURIComponent(back)}`;
@@ -0,0 +1,130 @@
+"use client";
+
+/**
+ * Offline scanning on this device: the ticket snapshot for a locked section and the
+ * queue of scans waiting to sync, both kept in IndexedDB (via `idb`). The active lock
+ * itself is in localStorage so the scanner page knows it's in offline mode after a
+ * reload with no connection.
+ */
+import { openDB, type IDBPDatabase } from "idb";
+
+export type SnapshotTicket = {
+  id: string;
+  qrCode: string;
+  holder: string;
+  bookedBy: string;
+  option: string;
+  variant: string | null;
+  quantity: number;
+  remaining: number;
+  consentStatus: string;
+};
+
+export type QueuedScan = { clientScanId: string; lockId: string; qrCode: string; qty: number; scannedAt: string };
+
+export type OfflineLock = {
+  lockId: string;
+  eventId: string;
+  eventTitle: string;
+  sectionId: string | null;
+  sectionName: string | null;
+  snapshotAt: string;
+};
+
+const DB_NAME = "hope-events-offline-scan";
+const LOCK_KEY = "hope_events_offline_lock";
+const DEVICE_KEY = "hope_events_scan_device";
+
+let dbPromise: Promise<IDBPDatabase> | null = null;
+function db() {
+  if (!dbPromise) {
+    dbPromise = openDB(DB_NAME, 1, {
+      upgrade(d) {
+        d.createObjectStore("tickets", { keyPath: "qrCode" });
+        d.createObjectStore("queue", { keyPath: "clientScanId" });
+      },
+    });
+  }
+  return dbPromise;
+}
+
+/** A stable id for this browser, used to tie an offline lock to one device. */
+export function deviceId(): string {
+  try {
+    let id = localStorage.getItem(DEVICE_KEY);
+    if (!id) {
+      id = crypto.randomUUID();
+      localStorage.setItem(DEVICE_KEY, id);
+    }
+    return id;
+  } catch {
+    return "unknown-device";
+  }
+}
+
+/** A short, human name for this device ("Chrome on Android"). */
+export function deviceName(): string {
+  const ua = typeof navigator !== "undefined" ? navigator.userAgent : "";
+  const browser = /Edg\//.test(ua) ? "Edge" : /Chrome\//.test(ua) ? "Chrome" : /Firefox\//.test(ua) ? "Firefox" : /Safari\//.test(ua) ? "Safari" : "Browser";
+  const os = /Android/.test(ua) ? "Android" : /iPhone|iPad/.test(ua) ? "iOS" : /Windows/.test(ua) ? "Windows" : /Mac OS/.test(ua) ? "Mac" : "device";
+  return `${browser} on ${os}`;
+}
+
+export function getOfflineLock(): OfflineLock | null {
+  try {
+    const raw = localStorage.getItem(LOCK_KEY);
+    return raw ? JSON.parse(raw) : null;
+  } catch {
+    return null;
+  }
+}
+
+function setOfflineLock(lock: OfflineLock | null) {
+  try {
+    if (lock) localStorage.setItem(LOCK_KEY, JSON.stringify(lock));
+    else localStorage.removeItem(LOCK_KEY);
+  } catch { /* storage unavailable */ }
+}
+
+/** Keeps the downloaded ticket list and marks this device as in offline mode. */
+export async function startOffline(lock: OfflineLock, tickets: SnapshotTicket[]) {
+  const d = await db();
+  const tx = d.transaction("tickets", "readwrite");
+  await tx.store.clear();
+  for (const t of tickets) await tx.store.put(t);
+  await tx.done;
+  setOfflineLock(lock);
+}
+
+export async function findTicket(qrCode: string): Promise<SnapshotTicket | undefined> {
+  return (await db()).get("tickets", qrCode);
+}
+
+/** Records a scan locally: lowers the ticket's remaining count and queues it for sync. */
+export async function recordScan(lockId: string, ticket: SnapshotTicket, qty: number): Promise<QueuedScan> {
+  const d = await db();
+  const scan: QueuedScan = { clientScanId: crypto.randomUUID(), lockId, qrCode: ticket.qrCode, qty, scannedAt: new Date().toISOString() };
+  const tx = d.transaction(["tickets", "queue"], "readwrite");
+  await tx.objectStore("tickets").put({ ...ticket, remaining: Math.max(0, ticket.remaining - qty) });
+  await tx.objectStore("queue").put(scan);
+  await tx.done;
+  return scan;
+}
+
+export async function queuedScans(): Promise<QueuedScan[]> {
+  return (await db()).getAll("queue");
+}
+
+export async function removeQueued(ids: string[]) {
+  const d = await db();
+  const tx = d.transaction("queue", "readwrite");
+  for (const id of ids) await tx.store.delete(id);
+  await tx.done;
+}
+
+/** Ends offline mode on this device: the ticket list is deleted (the queue must be empty). */
+export async function clearOffline() {
+  const d = await db();
+  await d.clear("tickets");
+  setOfflineLock(null);
+}
@@ -30,6 +30,7 @@ It runs in any web browser — on a phone, tablet, or computer — with nothing
 ### For staff on the day

 - **QR code scanner** — check people in by scanning their ticket with any phone camera. A single ticket can cover a whole family and be checked in a few people at a time.
+- **Works without Wi-Fi** — lock a check-in point to a phone and keep scanning with no signal; scans sync automatically when the connection is back.
 - **Scan points** — set up separate check-in points (e.g. main hall, dinner) that only accept the right tickets.
 - **At-the-door desk** — search by name, phone, or ticket number; register walk-ins; take cash, card, or EFT payments; check people in; and print or resend tickets on the spot.
 - **Self-service kiosk** — set up a tablet where visitors register themselves. Returning visitors are recognised by their email or phone number.
@@ -1,12 +1,12 @@
 {
  "name": "hope-events",
-  "version": "1.16.0",
+  "version": "1.17.0",
  "lockfileVersion": 3,
  "requires": true,
  "packages": {
    "": {
      "name": "hope-events",
-      "version": "1.16.0",
+      "version": "1.17.0",
      "license": "ISC",
      "devDependencies": {
        "concurrently": "^9.2.1"
@@ -1,6 +1,6 @@
 {
  "name": "hope-events",
-  "version": "1.16.0",
+  "version": "1.17.0",
  "main": "index.js",
  "scripts": {
    "dev:backend": "cd backend && npm run dev",