diff --git a/SECURITY_AUDIT.md b/SECURITY_AUDIT.md
new file mode 100644
index 0000000..fe1838c
--- /dev/null
+++ b/SECURITY_AUDIT.md
@@ -0,0 +1,98 @@
+# Security-Audit — 17.09.2026
+
+Geprüfter Commit: `cb30eca`. Ergebnis: **ein Befund hoher Priorität (P1), fünf Befunde mittlerer Priorität (P2)** sowie Hinweise zu Abhängigkeiten. Keine Behebung vorgenommen.
+
+## Umfang und Nachweisgrenzen
+
+Quellcodeprüfung von Payload-Zugriffsregeln, Kunden-/Admin-Authentifizierung, Buchungen, Meetings, Analytics, Kalender-Feed, E-Mail-Versand und Deployment-Konfiguration. Die installierten Next.js-Guides zu Datensicherheit und Route Handlers sowie Payloads tatsächliche Local-API-Implementierung wurden herangezogen.
+
+`npm test`: 5/5 Tests bestanden. Zusätzlich wurden die unveränderten Route Handler für Stornierung, Meeting-Beitritt, Token-Austausch und Buchungsanfragen isoliert ausgeführt, mit simulierter Datenbank und simuliertem LiveKit. Keine Produktivzugriffe, echten E-Mails oder Datenänderungen. Diese Prüfungen belegen die Handler-Logik, nicht das Verhalten eines realen Reverse-Proxys oder Video-Servers. Produktionskonfiguration, Git-Historie und laufende Infrastruktur waren nicht Gegenstand eines Penetrationstests.
+
+## 1. P1 — Interne Buchungsnotizen gelangen in den Kundenbrowser
+
+**Stellen:** `lib/booking/queries.ts:12`, `app/(frontend)/konto/termine/page.tsx:27`, `app/(frontend)/konto/page.tsx:46`, `collections/BookingRequests.ts:364`.
+
+`getCustomerBookings()` liest vollständige Buchungsdokumente mit `depth: 2` über die Payload Local API. Ohne explizites `overrideAccess: false` umgeht diese sowohl Collection- als auch Feldzugriffsregeln. Das wurde in `node_modules/payload/dist/collections/operations/local/find.js` und `node_modules/payload/dist/fields/hooks/afterRead/promise.js` verifiziert.
+
+Die Kontoseiten übergeben das gesamte Ergebnis als `booking` an die Client Component `BookingCard`. Dadurch wird auch `internalNote` an den Browser serialisiert, obwohl es durch `isAdminFieldLevel` geschützt und als „Nur für Anna sichtbar“ bezeichnet ist. Dass die Komponente die Notiz nicht sichtbar rendert, schützt sie nicht.
+
+**Auswirkung:** Ein angemeldeter Kunde kann interne Notizen zu seinen Buchungen in der Seiten-/RSC-Antwort lesen. Kein Zugriff auf fremde Buchungen wurde hier festgestellt.
+
+**Nachweis:** Statisch vollständiger Datenfluss von privilegierter Abfrage bis zur Client-Grenze; kein Live-Abruf realer Kundendaten.
+
+**Behebung:** Kundenansichten nur explizit ausgewählte Felder als separates DTO übergeben. Wenn möglich zusätzlich mit `overrideAccess: false` und authentifiziertem Benutzer lesen. Privilegiert benötigte Meeting-Daten gesondert und minimal auflösen. Auch verschachtelte Beziehungen nicht vollständig serialisieren.
+
+**Regressionstest:** Eine Buchung mit einer eindeutigen internen Testnotiz anlegen; die Notiz darf weder in HTML noch in einer RSC-Antwort des Kundenkontos vorkommen.
+
+## 2. P2 — Stornierung widerruft den privaten Meeting-Zugang nicht
+
+**Stellen:** `app/(payload)/api/booking/[id]/cancel/route.ts:29`, `app/(payload)/api/meetings/[slug]/join/route.ts:49`, `collections/BookingRequests.ts:229`.
+
+Die Stornierung setzt nur den Buchungsstatus. Der verknüpfte Online-Event und sein Passwort bleiben gültig. Der Join-Endpunkt prüft Online-Status, Passwort und Zeitfenster, aber nicht den Status der zugehörigen privaten Buchung. Der E-Mail-Hook bei Stornierung sperrt den Event ebenfalls nicht.
+
+**Auswirkung:** Wer das zuvor erhaltene Passwort kennt, kann innerhalb des ursprünglichen Zeitfensters auch nach der Stornierung neue Meeting-Zugangsdaten erhalten.
+
+**Nachweis:** Isolierter Aufruf des Cancel-Handlers änderte die Buchung auf `cancelled`; anschließender anonymer Join mit dem alten Passwort lieferte HTTP 200 und Zugangsdaten.
+
+**Behebung:** Für private Events bei jedem Join und Connect eine weiterhin bestätigte, passend verknüpfte Buchung verlangen. Bei Stornierung bestehende Sitzungen widerrufen; gegebenenfalls aktive Teilnehmer über LiveKit entfernen.
+
+## 3. P2 — Token-Austausch umgeht das Meeting-Ende
+
+**Stelle:** `app/(payload)/api/meetings/[slug]/connect/route.ts:27`.
+
+`/connect` prüft das App-Token und die Kick-Liste, anschließend nur noch `isOnline`. Anders als `/join` prüft der Handler weder das aktuelle Meeting-Zeitfenster noch einen Widerruf durch Passwortwechsel. App-Tokens sind standardmäßig sechs Stunden gültig; neu ausgestellte LiveKit-Tokens gelten jeweils zwei Stunden.
+
+**Auswirkung:** Ein zuvor zugelassener Teilnehmer erhält nach Ende des erlaubten Beitrittsfensters weiterhin neue Video-Zugangsdaten, solange sein App-Token gültig ist. Ein Passwortwechsel allein invalidiert bereits ausgestellte App-Tokens ebenfalls nicht.
+
+**Nachweis:** Mit gültigem App-Token und einem simulierten, bereits am Vortag beendeten Event lieferte der unveränderte Connect-Handler HTTP 200 mit einem neuen Video-Token.
+
+**Behebung:** Dieselbe serverseitige Zugangsprüfung für Join und Connect verwenden. Token-Laufzeiten am erlaubten Meeting-Ende begrenzen und einen Sitzungs-/Berechtigungsstand für Widerrufe prüfen. Die beabsichtigte Admin-Testzimmer-Ausnahme separat behandeln.
+
+## 4. P2 — Krankheits- und Urlaubsgründe sind öffentlich abrufbar
+
+**Stelle:** `collections/AvailabilityOverrides.ts:17`.
+
+Die Collection erlaubt anonymes Lesen aller Dokumente. Das Feld `reason` enthält unter anderem `krankheit` und `urlaub` und besitzt keinen eigenen Leseschutz. Die generische Payload-API unter `/api/availability-overrides` macht damit Datum und Abwesenheitsgrund öffentlich; gleiches gilt grundsätzlich für GraphQL.
+
+**Auswirkung:** Persönliche Abwesenheitsgründe lassen sich ohne Anmeldung abfragen, soweit entsprechende Einträge gespeichert sind. Zur Buchung reicht die Information, welche Slots verfügbar sind.
+
+**Nachweis:** Statisch anhand von Collection-Zugriff, Felddefinition und generischem REST-Router.
+
+**Behebung:** Collection-Lesen auf Admins beschränken oder mindestens den Grund schützen. Der bestehende serverseitige Slot-Endpunkt kann weiterhin ausschließlich verfügbare Zeiten herausgeben.
+
+## 5. P2 — Registrierung und E-Mail-Wechsel umgehen die Versandlimits
+
+**Stellen:** `collections/Customers.ts:84`, `collections/Customers.ts:46`.
+
+Die öffentliche Kundenerstellung löst unmittelbar eine Bestätigungs-E-Mail aus. Änderungen der eigenen E-Mail-Adresse lösen denselben Versand erneut aus. Für diese Operationen gibt es keine entsprechenden Limits in der Collection. Die Limits des separaten `/api/auth/resend-verification`-Handlers greifen hier nicht; `maxLoginAttempts` schützt nur Login-Versuche.
+
+**Auswirkung:** Ohne bestätigte Adresse lassen sich neue Konten für verschiedene Empfänger erzeugen beziehungsweise eigene E-Mail-Adressen wiederholt ändern und damit Bestätigungsmails auslösen. Das ermöglicht Versandmissbrauch, Datenbankwachstum und Belastung des SMTP-Kontos. Ein externes Proxy-Limit könnte die Häufigkeit mindern, ist im geprüften Repository aber nicht als Schutz für diese Vorgänge implementiert.
+
+**Nachweis:** Statisch anhand der öffentlichen Collection-Operationen und Versand-Hooks. Kein Versandtest durchgeführt.
+
+**Behebung:** Erstellung und E-Mail-Änderung vor dem Versand zentral pro IP, Konto und Zieladresse begrenzen. Regeln auf Collection-/Hook-Ebene oder einem exklusiven, geschützten Einstiegspunkt durchsetzen, sodass REST und GraphQL sie nicht umgehen können.
+
+## 6. P2 — Ein bestätigtes Konto kann beliebig viele identische Buchungsanfragen erzeugen
+
+**Stellen:** `app/(payload)/api/booking/request/route.ts:75`, `collections/BookingRequests.ts:163`.
+
+Der Handler prüft Anmeldung, E-Mail-Bestätigung und Slot-Verfügbarkeit, aber weder eine Rate-Limit-Quote noch eine schon bestehende identische offene Anfrage. Offene Anfragen belegen den Slot nicht. Jeder erfolgreiche Create löst Bestätigungs- und Admin-Benachrichtigungen aus.
+
+**Auswirkung:** Ein einziges verifiziertes Konto kann den Admin-Eingang, die Buchungsliste und den Mailversand mit Duplikaten fluten.
+
+**Nachweis:** 25 unmittelbar aufeinanderfolgende identische Anfragen wurden vom unveränderten Handler mit HTTP 200 angenommen und an die simulierte Create-Operation weitergegeben. Keine echten E-Mails verschickt.
+
+**Behebung:** Pro Kunde begrenzen und identische offene Anfragen atomar deduplizieren. Wiederholte identische Requests sollten keinen weiteren Datensatz und keinen erneuten Mailversand erzeugen.
+
+## Abhängigkeiten und weitere Prüfergebnisse
+
+`npm audit --json` meldete im Lockfile **7 betroffene Pakete: 6 moderate, 1 low, 0 high, 0 critical**. Die Zahl enthält transitive Abhängigkeitsketten und bedeutet nicht sieben unabhängig ausnutzbare Anwendungslücken.
+
+- **esbuild 0.18.20** ist über `@payloadcms/db-postgres → drizzle-kit → @esbuild-kit/esm-loader → @esbuild-kit/core-utils` installiert. Das [Advisory GHSA-67mh-4wv8-2f99](https://github.com/advisories/GHSA-67mh-4wv8-2f99) betrifft esbuilds Entwicklungs-Webserver. Im geprüften App-Startpfad wurde dieser Server nicht gefunden; daraus wird keine bestätigte Produktionslücke abgeleitet. npm meldet für diese Kette keinen verfügbaren automatischen Fix.
+- **DOMPurify/Monaco:** Das Lockfile-Audit meldete mehrere DOMPurify-Advisories, darunter [GHSA-55q2-fjhq-7xh7](https://github.com/advisories/GHSA-55q2-fjhq-7xh7), mit verfügbarem Fix. Dieses Advisory setzt spezielle `IN_PLACE`-/Hook-Nutzung voraus. `npm ls dompurify monaco-editor --all` zeigte beide Pakete im aktuellen Installationsbaum nicht an. Produktionsinstallation aus dem Lockfile und tatsächliche Nutzung müssen vor einer Aussage zur Ausnutzbarkeit abgeglichen werden; ein XSS-Exploit wurde nicht nachgewiesen.
+- Ein begrenzter Musterscan der aktuell versionierten Dateien fand keine privaten Schlüsselblöcke oder GitHub-/AWS-Tokenmuster. Das ist kein vollständiger Secret- oder Historien-Scan.
+- Positiv: Adminrechte verlangen Auth-Collection und Rolle; Buchungsaktionen prüfen den Eigentümer; Verifizierungs-/Kalender-Tokens werden gehasht gespeichert; öffentliche Event-Felder geben das Meeting-Passwort nicht über die reguläre Payload-API frei; Cron-Aufrufe prüfen ein Secret.
+
+## Reihenfolge der Behebung
+
+Zuerst die Weitergabe interner Notizen stoppen. Danach private Meeting-Zugänge und Token-Austausch an den aktuellen Berechtigungsstatus binden, Abwesenheitsgründe schützen und die beiden Versand-/Buchungsmissbrauchspfade begrenzen. Abhängigkeitsupdates separat prüfen und mit dem tatsächlich ausgelieferten Installationsbaum abgleichen.
diff --git a/app/(frontend)/konto/page.tsx b/app/(frontend)/konto/page.tsx
index f541ed4..3cbd558 100644
--- a/app/(frontend)/konto/page.tsx
+++ b/app/(frontend)/konto/page.tsx
@@ -15,8 +15,8 @@ export default async function KontoOverviewPage() {
   const bookings = await getCustomerBookings(customer.id);
   const meetingSettings = await getMeetingSettingsGlobal();
   const pending = bookings.filter((b) => b.status === "pending");
-  const confirmed = bookings.filter((b) => b.status === "confirmed" && new Date(b.date) >= new Date());
-  const past = bookings.filter((b) => new Date(b.date) < new Date() || b.status === "rejected" || b.status === "cancelled");
+  const confirmed = bookings.filter((b) => b.status === "confirmed" && new Date(b.endTime) >= new Date());
+  const past = bookings.filter((b) => new Date(b.endTime) < new Date() || b.status === "rejected" || b.status === "cancelled");
 
   return (
     <div className="space-y-10">
diff --git a/app/(payload)/api/admin/meetings/start/route.ts b/app/(payload)/api/admin/meetings/start/route.ts
index 77cf9f3..e2d3aa4 100644
--- a/app/(payload)/api/admin/meetings/start/route.ts
+++ b/app/(payload)/api/admin/meetings/start/route.ts
@@ -2,6 +2,7 @@ import { NextResponse } from "next/server";
 import { getPayload } from "payload";
 import config from "@payload-config";
 import { createMeetingToken } from "@/lib/meeting/token";
+import { authorizeMeeting } from "@/lib/meeting/access";
 
 export const dynamic = "force-dynamic";
 
@@ -12,6 +13,7 @@ export async function POST(request: Request) {
   let body: Body;
   try {
     body = await request.json();
+    if (!body || typeof body !== "object" || Array.isArray(body)) throw new Error("Invalid body");
   } catch {
     return NextResponse.json({ error: "Ungültige Anfrage." }, { status: 400 });
   }
@@ -36,10 +38,14 @@ export async function POST(request: Request) {
       return NextResponse.json({ error: "Dieser Termin ist kein Online-Termin." }, { status: 404 });
     }
 
+    const access = await authorizeMeeting(payload, event, "host");
+    if (!access) return NextResponse.json({ error: "Dieser Termin ist nicht offen oder wurde storniert." }, { status: 403 });
     const { token } = createMeetingToken({
       eventSlug,
       name: typeof user.name === "string" && user.name.trim() ? user.name.trim() : "Host",
       role: "host",
+      accessVersion: access.accessVersion,
+      ttlMs: Math.min(6 * 3600000, access.expiresAt - Date.now()),
     });
 
     // Keep the token in the URL fragment: browsers do not send fragments to
diff --git a/app/(payload)/api/admin/meetings/test/route.ts b/app/(payload)/api/admin/meetings/test/route.ts
index f2b2b49..762dc4e 100644
--- a/app/(payload)/api/admin/meetings/test/route.ts
+++ b/app/(payload)/api/admin/meetings/test/route.ts
@@ -20,6 +20,7 @@ export async function POST(request: Request) {
       eventSlug,
       name: typeof user.name === "string" && user.name.trim() ? user.name.trim() : "Host",
       role: "host",
+      testRoom: true,
       ttlMs: 60 * 60 * 1000,
     });
     const baseUrl = process.env.NEXT_PUBLIC_SERVER_URL || new URL(request.url).origin;
diff --git a/app/(payload)/api/analytics/track/route.ts b/app/(payload)/api/analytics/track/route.ts
index 6b26d2e..bed5e99 100644
--- a/app/(payload)/api/analytics/track/route.ts
+++ b/app/(payload)/api/analytics/track/route.ts
@@ -53,6 +53,7 @@ export async function POST(request: Request) {
   try {
     const raw = await request.text();
     body = JSON.parse(raw);
+    if (!body || typeof body !== "object" || Array.isArray(body)) throw new Error("Invalid body");
   } catch {
     return new NextResponse(null, { status: 204 });
   }
diff --git a/app/(payload)/api/auth/resend-verification/route.ts b/app/(payload)/api/auth/resend-verification/route.ts
index ecdce8c..af5b64c 100644
--- a/app/(payload)/api/auth/resend-verification/route.ts
+++ b/app/(payload)/api/auth/resend-verification/route.ts
@@ -2,6 +2,7 @@ import { NextResponse } from "next/server";
 import { getPayload } from "payload";
 import config from "@payload-config";
 import { checkRateLimit, getClientIp } from "@/lib/auth/rateLimit";
+import { allowVerificationEmail } from "@/lib/auth/verificationRateLimit";
 import { EMAIL_VERIFICATION_TTL_MS, generateVerificationToken, hashVerificationToken, verificationExpiryISO } from "@/lib/auth/verification";
 import { verificationEmail } from "@/lib/email/authTemplates";
 import { sendEmail } from "@/lib/email/sendBookingEmails";
@@ -57,11 +58,12 @@ export async function POST(request: Request) {
       let body: { email?: unknown } = {};
       try {
         body = await request.json();
+    if (!body || typeof body !== "object" || Array.isArray(body)) throw new Error("Invalid body");
       } catch {
         // no body — handled below as a missing email
       }
-      const email = typeof body.email === "string" ? body.email.trim().toLowerCase() : "";
-      if (!email) {
+      const email = typeof body?.email === "string" ? body.email.trim().toLowerCase() : "";
+      if (!email || email.length > 254) {
         return NextResponse.json({ error: "E-Mail-Adresse erforderlich." }, { status: 400 });
       }
       if (!checkRateLimit(`resend-verification:email:${email}`, { max: 3, windowMs: 60 * 60 * 1000 })) {
@@ -77,8 +79,8 @@ export async function POST(request: Request) {
     }
 
     if (customer && !customer.emailVerified) {
-      if (!checkRateLimit(`resend-verification:customer:${customer.id}`, { max: 3, windowMs: 60 * 60 * 1000 })) {
-        return NextResponse.json({ error: "Zu viele Anfragen. Bitte versuche es später erneut." }, { status: 429 });
+      if (!allowVerificationEmail(request, customer.email, customer.id)) {
+        return NextResponse.json(GENERIC_RESPONSE);
       }
       await issueAndSend(payload, customer);
     }
diff --git a/app/(payload)/api/booking/[id]/accept-alternative/route.ts b/app/(payload)/api/booking/[id]/accept-alternative/route.ts
index 445e691..d59b124 100644
--- a/app/(payload)/api/booking/[id]/accept-alternative/route.ts
+++ b/app/(payload)/api/booking/[id]/accept-alternative/route.ts
@@ -1,6 +1,8 @@
 import { NextResponse } from "next/server";
 import { getPayload } from "payload";
 import config from "@payload-config";
+import { combineDateAndTime } from "@/lib/meeting/status";
+import { withBookingTransaction } from "@/lib/booking/transaction";
 
 export const dynamic = "force-dynamic";
 
@@ -19,31 +21,40 @@ export async function POST(request: Request, { params }: Args) {
       return NextResponse.json({ error: "Bitte bestätige zuerst deine E-Mail-Adresse.", code: "EMAIL_NOT_VERIFIED" }, { status: 403 });
     }
 
-    const booking = await payload.findByID({ collection: "booking-requests", id, depth: 0 }).catch(() => null);
-    if (!booking || Number(booking.user) !== Number(user.id)) {
-      return NextResponse.json({ error: "Buchung nicht gefunden." }, { status: 404 });
-    }
-    const alternative = booking.proposedAlternative;
-    if (booking.status !== "pending" || !alternative?.date || !alternative.startTime || !alternative.endTime) {
-      return NextResponse.json({ error: "Für diese Buchung liegt kein alternativer Termin vor." }, { status: 409 });
-    }
+    return await withBookingTransaction(payload, `booking:${id}`, async (req) => {
+      const { docs } = await payload.find({ collection: "booking-requests", where: { id: { equals: id } }, depth: 0, limit: 1, req });
+      const booking = docs[0];
+      if (!booking || Number(booking.user) !== Number(user.id)) {
+        return NextResponse.json({ error: "Buchung nicht gefunden." }, { status: 404 });
+      }
+      const alternative = booking.proposedAlternative;
+      if (booking.status !== "pending" || !alternative?.date || !alternative.startTime || !alternative.endTime) {
+        return NextResponse.json({ error: "Für diese Buchung liegt kein alternativer Termin vor." }, { status: 409 });
+      }
 
-    // The beforeChange hook on booking-requests re-checks for conflicts
-    // (with an advisory lock) before allowing this to become "confirmed" —
-    // the alternative slot may have been taken by someone else since it was
-    // proposed.
-    await payload.update({
-      collection: "booking-requests",
-      id,
-      data: {
-        status: "confirmed",
-        date: alternative.date,
-        startTime: alternative.startTime,
-        endTime: alternative.endTime,
-      },
+      const alternativeStart = combineDateAndTime(alternative.date, alternative.startTime);
+      if (!Number.isFinite(alternativeStart.getTime()) || alternativeStart <= new Date()) {
+        return NextResponse.json({ error: "Dieser Terminvorschlag liegt bereits in der Vergangenheit." }, { status: 409 });
+      }
+
+      // The beforeChange hook on booking-requests re-checks for conflicts
+      // (with an advisory lock) before allowing this to become "confirmed" —
+      // the alternative slot may have been taken by someone else since it was
+      // proposed.
+      await payload.update({
+        collection: "booking-requests",
+        id,
+        req,
+        data: {
+          status: "confirmed",
+          date: alternative.date,
+          startTime: alternative.startTime,
+          endTime: alternative.endTime,
+        },
+      });
+
+      return NextResponse.json({ ok: true });
     });
-
-    return NextResponse.json({ ok: true });
   } catch (error) {
     if (error instanceof Error && "status" in error && (error as { status: number }).status === 409) {
       return NextResponse.json({ error: error.message }, { status: 409 });
diff --git a/app/(payload)/api/booking/[id]/cancel/route.ts b/app/(payload)/api/booking/[id]/cancel/route.ts
index 8cd7f67..091935a 100644
--- a/app/(payload)/api/booking/[id]/cancel/route.ts
+++ b/app/(payload)/api/booking/[id]/cancel/route.ts
@@ -1,6 +1,7 @@
 import { NextResponse } from "next/server";
 import { getPayload } from "payload";
 import config from "@payload-config";
+import { withBookingTransaction } from "@/lib/booking/transaction";
 
 export const dynamic = "force-dynamic";
 
@@ -18,16 +19,19 @@ export async function POST(request: Request, { params }: Args) {
     // Cancelling is deliberately allowed regardless of verification status —
     // only creating/confirming a booking is a gated "protected" action.
 
-    const booking = await payload.findByID({ collection: "booking-requests", id, depth: 0 }).catch(() => null);
-    if (!booking || Number(booking.user) !== Number(user.id)) {
-      return NextResponse.json({ error: "Buchung nicht gefunden." }, { status: 404 });
-    }
-    if (booking.status === "cancelled") {
-      return NextResponse.json({ ok: true });
-    }
+    return await withBookingTransaction(payload, `booking:${id}`, async (req) => {
+      const { docs } = await payload.find({ collection: "booking-requests", where: { id: { equals: id } }, depth: 0, limit: 1, req });
+      const booking = docs[0];
+      if (!booking || Number(booking.user) !== Number(user.id)) {
+        return NextResponse.json({ error: "Buchung nicht gefunden." }, { status: 404 });
+      }
+      if (booking.status === "cancelled") {
+        return NextResponse.json({ ok: true });
+      }
 
-    await payload.update({ collection: "booking-requests", id, data: { status: "cancelled" } });
-    return NextResponse.json({ ok: true });
+      await payload.update({ collection: "booking-requests", id, req, data: { status: "cancelled" } });
+      return NextResponse.json({ ok: true });
+    });
   } catch (error) {
     console.error("booking cancel failed", error);
     return NextResponse.json({ error: "Der Termin konnte nicht storniert werden." }, { status: 500 });
diff --git a/app/(payload)/api/booking/request/route.ts b/app/(payload)/api/booking/request/route.ts
index 9817eca..d078983 100644
--- a/app/(payload)/api/booking/request/route.ts
+++ b/app/(payload)/api/booking/request/route.ts
@@ -2,6 +2,8 @@ import { NextResponse } from "next/server";
 import { getPayload } from "payload";
 import config from "@payload-config";
 import { getAvailableSlots } from "@/lib/booking/slots";
+import { withBookingTransaction } from "@/lib/booking/transaction";
+import { checkRateLimit, getClientIp } from "@/lib/auth/rateLimit";
 import { berlinDayBounds } from "@/lib/calendar/timezone";
 
 export const dynamic = "force-dynamic";
@@ -17,13 +19,15 @@ export async function POST(request: Request) {
   let body: Body;
   try {
     body = await request.json();
+    if (!body || typeof body !== "object" || Array.isArray(body)) throw new Error("Invalid body");
   } catch {
     return NextResponse.json({ error: "Ungültige Anfrage." }, { status: 400 });
   }
 
   const offerSlug = typeof body.offerSlug === "string" ? body.offerSlug : "";
   const startISO = typeof body.start === "string" ? body.start : "";
-  const appointmentType = body.appointmentType === "online" ? "online" : "onsite";
+  const appointmentType = body.appointmentType;
+  if (appointmentType !== "online" && appointmentType !== "onsite") return NextResponse.json({ error: "Ungültige Terminart." }, { status: 400 });
   const message = typeof body.message === "string" ? body.message.trim().slice(0, 2000) : "";
 
   if (!offerSlug || !startISO) {
@@ -40,6 +44,11 @@ export async function POST(request: Request) {
       return NextResponse.json({ error: "Bitte bestätige zuerst deine E-Mail-Adresse.", code: "EMAIL_NOT_VERIFIED" }, { status: 403 });
     }
 
+    if (!checkRateLimit(`booking:ip:${getClientIp(request)}`, { max: 30, windowMs: 3600000 }) ||
+        !checkRateLimit(`booking:customer:${user.id}`, { max: 10, windowMs: 3600000 })) {
+      return NextResponse.json({ error: "Zu viele Terminanfragen. Bitte versuche es später erneut." }, { status: 429 });
+    }
+
     const { docs } = await payload.find({
       collection: "offers",
       where: { slug: { equals: offerSlug } },
@@ -61,32 +70,44 @@ export async function POST(request: Request) {
     // stale slot list) — the hard, race-safe check still runs again when
     // Anna confirms (see collections/BookingRequests.ts).
     const dayBounds = berlinDayBounds(start);
-    const slotsByDay = await getAvailableSlots(payload, {
-      durationMinutes: offer.durationMinutes,
-      from: dayBounds.start,
-      to: dayBounds.end,
-    });
-    const key = dayBounds.key;
-    const isStillFree = (slotsByDay.get(key) ?? []).some((s) => s.start.getTime() === start.getTime());
-    if (!isStillFree) {
-      return NextResponse.json({ error: "Dieser Termin ist leider nicht mehr verfügbar." }, { status: 409 });
-    }
+    return await withBookingTransaction(payload, dayBounds.key, async (req) => {
+      const { docs: existing } = await payload.find({ collection: "booking-requests", req, depth: 0, limit: 1,
+        where: { and: [
+          { user: { equals: user.id } }, { offer: { equals: offer.id } },
+          { startTime: { equals: start.toISOString() } }, { appointmentType: { equals: appointmentType } },
+          { status: { in: ["pending", "confirmed"] } },
+        ] },
+      });
+      if (existing[0]) return NextResponse.json({ ok: true });
+      const slotsByDay = await getAvailableSlots(payload, {
+        durationMinutes: offer.durationMinutes!,
+        req,
+        from: dayBounds.start,
+        to: dayBounds.end,
+      });
+      const key = dayBounds.key;
+      const isStillFree = (slotsByDay.get(key) ?? []).some((s) => s.start.getTime() === start.getTime());
+      if (!isStillFree) {
+        return NextResponse.json({ error: "Dieser Termin ist leider nicht mehr verfügbar." }, { status: 409 });
+      }
 
-    await payload.create({
-      collection: "booking-requests",
-      data: {
-        user: user.id,
-        offer: offer.id,
-        date: start.toISOString(),
-        startTime: start.toISOString(),
-        endTime: end.toISOString(),
-        appointmentType,
-        status: "pending",
-        userMessage: message || undefined,
-      },
-    });
+      await payload.create({
+        collection: "booking-requests",
+        req,
+        data: {
+          user: user.id,
+          offer: offer.id,
+          date: start.toISOString(),
+          startTime: start.toISOString(),
+          endTime: end.toISOString(),
+          appointmentType,
+          status: "pending",
+          userMessage: message || undefined,
+        },
+      });
 
-    return NextResponse.json({ ok: true });
+      return NextResponse.json({ ok: true });
+    });
   } catch (error) {
     console.error("booking request failed", error);
     return NextResponse.json({ error: "Die Anfrage konnte nicht gesendet werden. Bitte versuche es später erneut." }, { status: 500 });
diff --git a/app/(payload)/api/booking/slots/route.ts b/app/(payload)/api/booking/slots/route.ts
index 95396f8..c0d0338 100644
--- a/app/(payload)/api/booking/slots/route.ts
+++ b/app/(payload)/api/booking/slots/route.ts
@@ -2,6 +2,7 @@ import { NextResponse } from "next/server";
 import { getPayload } from "payload";
 import config from "@payload-config";
 import { getAvailableSlots } from "@/lib/booking/slots";
+import { berlinDayBounds, parseBerlinDate } from "@/lib/calendar/timezone";
 
 export const dynamic = "force-dynamic";
 
@@ -29,16 +30,15 @@ export async function GET(request: Request) {
       return NextResponse.json({ error: "Dieses Angebot ist nicht buchbar." }, { status: 404 });
     }
 
-    const from = fromParam ? new Date(`${fromParam}T00:00:00`) : new Date();
-    if (Number.isNaN(from.getTime())) {
+    const from = fromParam ? parseBerlinDate(fromParam) : berlinDayBounds(new Date()).start;
+    if (!from) {
       return NextResponse.json({ error: "Ungültiges Startdatum." }, { status: 400 });
     }
-    from.setHours(0, 0, 0, 0);
-    const to = toParam ? new Date(`${toParam}T00:00:00`) : new Date(from.getTime() + 21 * 24 * 60 * 60 * 1000);
-    if (Number.isNaN(to.getTime())) {
+    const toDate = toParam ? parseBerlinDate(toParam) : new Date(from.getTime() + 21 * 24 * 60 * 60 * 1000);
+    if (!toDate) {
       return NextResponse.json({ error: "Ungültiges Enddatum." }, { status: 400 });
     }
-    to.setHours(23, 59, 59, 999);
+    const to = berlinDayBounds(toDate).end;
 
     if (to < from) {
       return NextResponse.json({ error: "Das Enddatum muss nach dem Startdatum liegen." }, { status: 400 });
diff --git a/app/(payload)/api/meetings/[slug]/connect/route.ts b/app/(payload)/api/meetings/[slug]/connect/route.ts
index 6ea4758..933852b 100644
--- a/app/(payload)/api/meetings/[slug]/connect/route.ts
+++ b/app/(payload)/api/meetings/[slug]/connect/route.ts
@@ -4,6 +4,7 @@ import config from "@payload-config";
 import { createLiveKitToken, getLiveKitClientUrl } from "@/lib/meeting/livekit";
 import { isMeetingParticipantKicked } from "@/lib/meeting/kicks";
 import { verifyMeetingToken } from "@/lib/meeting/token";
+import { authorizeMeeting } from "@/lib/meeting/access";
 
 export const dynamic = "force-dynamic";
 
@@ -23,11 +24,17 @@ export async function POST(request: Request, { params }: Args) {
   }
 
   try {
-    const isAdminTestRoom = meetingToken.role === "host" && slug.startsWith("test-");
+    let expiresAt = meetingToken.exp;
+    const isAdminTestRoom = meetingToken.role === "host" && meetingToken.testRoom === true && slug.startsWith("test-");
     if (!isAdminTestRoom) {
       const payload = await getPayload({ config });
       const { docs } = await payload.find({ collection: "events", where: { slug: { equals: slug } }, limit: 1 });
       if (!docs[0]?.isOnline) return NextResponse.json({ error: "Dieser Online-Termin wurde nicht gefunden." }, { status: 404 });
+      const access = await authorizeMeeting(payload, docs[0], meetingToken.role);
+      if (!access || access.accessVersion !== meetingToken.accessVersion) {
+        return NextResponse.json({ error: "Dieser Meeting-Zugang ist nicht mehr gültig. Bitte tritt erneut bei." }, { status: 403 });
+      }
+      expiresAt = Math.min(expiresAt, access.expiresAt);
     }
 
     const participantToken = await createLiveKitToken({
@@ -36,6 +43,8 @@ export async function POST(request: Request, { params }: Args) {
       name: meetingToken.name,
       role: meetingToken.role,
       clientId: meetingToken.clientId,
+      accessVersion: meetingToken.accessVersion,
+      expiresAt,
     });
     return NextResponse.json({ serverUrl: getLiveKitClientUrl(), participantToken });
   } catch (error) {
diff --git a/app/(payload)/api/meetings/[slug]/join/route.ts b/app/(payload)/api/meetings/[slug]/join/route.ts
index 64a4860..3596767 100644
--- a/app/(payload)/api/meetings/[slug]/join/route.ts
+++ b/app/(payload)/api/meetings/[slug]/join/route.ts
@@ -3,7 +3,8 @@ import { NextResponse } from "next/server";
 import { getPayload } from "payload";
 import config from "@payload-config";
 import { createMeetingToken } from "@/lib/meeting/token";
-import { canJoinMeeting, combineDateAndTime, getMeetingStatus } from "@/lib/meeting/status";
+import { authorizeMeeting } from "@/lib/meeting/access";
+import { checkRateLimit, getClientIp } from "@/lib/auth/rateLimit";
 import { createLiveKitToken, getLiveKitClientUrl } from "@/lib/meeting/livekit";
 import { isMeetingParticipantKicked } from "@/lib/meeting/kicks";
 
@@ -20,10 +21,14 @@ type Args = { params: Promise<{ slug: string }> };
 
 export async function POST(request: Request, { params }: Args) {
   const { slug } = await params;
+  if (!checkRateLimit(`meeting-join:${getClientIp(request)}`, { max: 30, windowMs: 60000 })) {
+    return NextResponse.json({ error: "Zu viele Beitrittsversuche." }, { status: 429 });
+  }
 
   let body: { name?: unknown; password?: unknown; clientId?: unknown };
   try {
     body = await request.json();
+    if (!body || typeof body !== "object" || Array.isArray(body)) throw new Error("Invalid body");
   } catch {
     return NextResponse.json({ error: "Ungültige Anfrage." }, { status: 400 });
   }
@@ -65,31 +70,17 @@ export async function POST(request: Request, { params }: Args) {
       }
     }
 
-    const settings = await payload.findGlobal({ slug: "meeting-settings" });
-    const start = combineDateAndTime(event.date, event.startTime);
-    const end = event.endTime
-      ? combineDateAndTime(event.date, event.endTime)
-      : new Date(start.getTime() + 60 * 60_000);
-
-    const status = getMeetingStatus({
-      start,
-      end,
-      joinWindowMinutes: isHost ? settings.hostJoinWindowMinutes : settings.participantJoinWindowMinutes,
-      closeAfterMinutes: settings.meetingCloseAfterMinutes,
-    });
-
-    if (!canJoinMeeting(status)) {
-      const message =
-        status === "scheduled"
-          ? "Dieser Termin ist noch nicht offen. Bitte versuche es näher am Beginn erneut."
-          : "Dieser Termin ist bereits beendet.";
-      return NextResponse.json({ error: message }, { status: 403 });
+    const access = await authorizeMeeting(payload, event, isHost ? "host" : "participant");
+    if (!access) {
+      return NextResponse.json({ error: "Dieser Termin ist nicht offen oder wurde storniert." }, { status: 403 });
     }
 
     const { token, participantId } = createMeetingToken({
       eventSlug: slug,
       name,
       role: isHost ? "host" : "participant",
+      accessVersion: access.accessVersion,
+      ttlMs: Math.min(6 * 3600000, access.expiresAt - Date.now()),
       // Only meaningful for participants — a host authenticates via a real
       // session already, so there's no need to anchor a kick to it (and
       // hosts can't be kicked in the first place.
@@ -101,6 +92,8 @@ export async function POST(request: Request, { params }: Args) {
     }
     const participantToken = await createLiveKitToken({
       eventSlug: slug,
+      accessVersion: access.accessVersion,
+      expiresAt: access.expiresAt,
       participantId,
       name,
       role: isHost ? "host" : "participant",
diff --git a/app/(payload)/api/meetings/[slug]/kick/route.ts b/app/(payload)/api/meetings/[slug]/kick/route.ts
index 87c6d7d..f505168 100644
--- a/app/(payload)/api/meetings/[slug]/kick/route.ts
+++ b/app/(payload)/api/meetings/[slug]/kick/route.ts
@@ -19,6 +19,7 @@ export async function POST(request: Request, { params }: Args) {
   let body: { participantId?: unknown };
   try {
     body = await request.json();
+    if (!body || typeof body !== "object" || Array.isArray(body)) throw new Error("Invalid body");
   } catch {
     return NextResponse.json({ error: "Ungültige Anfrage." }, { status: 400 });
   }
@@ -29,7 +30,7 @@ export async function POST(request: Request, { params }: Args) {
 
   try {
     const roomService = getLiveKitRoomService();
-    const room = getLiveKitRoomName(slug);
+    const room = getLiveKitRoomName(slug, host.accessVersion);
     const participant = (await roomService.listParticipants(room)).find((item) => item.identity === participantId);
     if (!participant) return NextResponse.json({ error: "Teilnehmer nicht gefunden." }, { status: 404 });
 
diff --git a/app/(payload)/api/meetings/[slug]/register/route.ts b/app/(payload)/api/meetings/[slug]/register/route.ts
index e1b0302..86f5e31 100644
--- a/app/(payload)/api/meetings/[slug]/register/route.ts
+++ b/app/(payload)/api/meetings/[slug]/register/route.ts
@@ -38,6 +38,7 @@ export async function POST(request: Request, { params }: Args) {
   let body: { name?: unknown; email?: unknown };
   try {
     body = await request.json();
+    if (!body || typeof body !== "object" || Array.isArray(body)) throw new Error("Invalid body");
   } catch {
     return NextResponse.json({ error: "Ungültige Anfrage." }, { status: 400 });
   }
diff --git a/collections/AvailabilityOverrides.ts b/collections/AvailabilityOverrides.ts
index 0ea5bb4..95a50a9 100644
--- a/collections/AvailabilityOverrides.ts
+++ b/collections/AvailabilityOverrides.ts
@@ -14,7 +14,7 @@ export const AvailabilityOverrides: CollectionConfig = {
     description: "Einzelne Abweichungen von den wiederkehrenden Verfügbarkeiten — Urlaub, Feiertage, Krankheit oder Sonderöffnungszeiten.",
   },
   access: {
-    read: () => true,
+    read: isAdmin,
     create: isAdmin,
     update: isAdmin,
     delete: isAdmin,
diff --git a/collections/BookingRequests.ts b/collections/BookingRequests.ts
index 5bc844e..b70689b 100644
--- a/collections/BookingRequests.ts
+++ b/collections/BookingRequests.ts
@@ -1,6 +1,8 @@
+import { randomUUID } from "node:crypto";
 import { APIError } from "payload";
 import type { CollectionAfterChangeHook, CollectionBeforeChangeHook, CollectionConfig, Where } from "payload";
 import { isAdmin, isAdminFieldLevel } from "@/access";
+import { combineDateAndTime } from "@/lib/meeting/status";
 import { acquireBookingDayLock } from "@/lib/booking/lock";
 import {
   alternativeProposedEmail,
@@ -12,7 +14,7 @@ import {
 } from "@/lib/email/bookingTemplates";
 import { sendEmail } from "@/lib/email/sendBookingEmails";
 import type { Customer, Event, Offer } from "@/payload-types";
-import { berlinDateKey, berlinDayBounds, formatBerlinDate, formatBerlinTime } from "@/lib/calendar/timezone";
+import { berlinDateKey, formatBerlinDate, formatBerlinTime } from "@/lib/calendar/timezone";
 
 export const APPOINTMENT_TYPES = [
   { label: "Vor Ort", value: "onsite" },
@@ -49,88 +51,73 @@ async function notifyAdmins(
   await Promise.all(admins.filter((admin) => admin.email).map((admin) => sendEmail(admin.email, template)));
 }
 
-// Runs whenever a booking is about to become "confirmed": locks the day
-// (see lib/booking/lock.ts), re-checks for overlapping confirmed bookings
-// inside that same lock/transaction, and — for online appointments — creates
-// the linked video-call Event (reusing the existing meeting/password system)
-// before the booking itself is written.
-const handleConfirmation: CollectionBeforeChangeHook = async ({ data, originalDoc, req }) => {
-  // Covers both paths: an existing request being confirmed, AND Anna
-  // manually creating a booking that's already "confirmed" from the start
-  // (e.g. a phone booking) — both must go through the same conflict check.
-  const wasAlreadyConfirmed = originalDoc?.status === "confirmed";
-  if (data.status !== "confirmed" || wasAlreadyConfirmed) {
-    return data;
-  }
-
+// Normalize Payload time-only inputs before conflict checks and synchronize
+// the private meeting whenever a booking is moved, cancelled or reactivated.
+export const handleConfirmation: CollectionBeforeChangeHook = async ({ data, originalDoc, req }) => {
+  const status = data.status ?? originalDoc?.status ?? "pending";
   const date = data.date ?? originalDoc?.date;
   const startTime = data.startTime ?? originalDoc?.startTime;
   const endTime = data.endTime ?? originalDoc?.endTime;
   const appointmentType = data.appointmentType ?? originalDoc?.appointmentType;
-  if (!date || !startTime || !endTime) return data; // Field-level validation will reject this anyway.
+  if (!date || !startTime || !endTime) return data;
+  const start = combineDateAndTime(date, startTime);
+  const end = combineDateAndTime(date, endTime);
+  if (!Number.isFinite(start.getTime()) || !Number.isFinite(end.getTime()) || end <= start) {
+    throw new APIError("Das Ende muss nach dem Beginn am selben Tag liegen.", 400, undefined, true);
+  }
+  data.date = start.toISOString();
+  data.startTime = start.toISOString();
+  data.endTime = end.toISOString();
 
-  await acquireBookingDayLock(req, dateKey(date));
-
-  const dayBounds = berlinDayBounds(new Date(date));
-  const dayStart = dayBounds.start.toISOString();
-  const dayEnd = dayBounds.end.toISOString();
-  const conflictClauses: Where[] = [
-    { status: { equals: "confirmed" } },
-    { date: { greater_than_equal: dayStart } },
-    { date: { less_than_equal: dayEnd } },
-  ];
-  if (originalDoc?.id) conflictClauses.push({ id: { not_equals: originalDoc.id } });
-
-  const { docs: sameDayConfirmed } = await req.payload.find({
-    collection: "booking-requests",
-    where: { and: conflictClauses },
-    req,
-    limit: 200,
-  });
-
-  const newStart = new Date(startTime).getTime();
-  const newEnd = new Date(endTime).getTime();
-  const conflict = sameDayConfirmed.some((doc) => {
-    const s = new Date(doc.startTime).getTime();
-    const e = new Date(doc.endTime).getTime();
-    return newStart < e && s < newEnd;
-  });
-
-  if (conflict) {
-    throw new APIError(
-      "Dieser Zeitraum ist bereits mit einem anderen bestätigten Termin belegt. Bitte wähle eine andere Zeit oder lehne den überschneidenden Termin zuerst ab.",
-      409,
-      undefined,
-      true,
-    );
+  const alternative = data.proposedAlternative;
+  if (alternative && (alternative.date || alternative.startTime || alternative.endTime)) {
+    if (!alternative.date || !alternative.startTime || !alternative.endTime) {
+      throw new APIError("Bitte den alternativen Termin vollständig angeben.", 400, undefined, true);
+    }
+    const altStart = combineDateAndTime(alternative.date, alternative.startTime);
+    const altEnd = combineDateAndTime(alternative.date, alternative.endTime);
+    if (!Number.isFinite(altStart.getTime()) || !Number.isFinite(altEnd.getTime()) || altEnd <= altStart) {
+      throw new APIError("Der alternative Zeitraum ist ungültig.", 400, undefined, true);
+    }
+    data.proposedAlternative = { date: altStart.toISOString(), startTime: altStart.toISOString(), endTime: altEnd.toISOString() };
   }
 
-  if (appointmentType === "online" && !data.linkedEvent && !originalDoc?.linkedEvent) {
-    const offer = (await req.payload.findByID({ collection: "offers", id: data.offer ?? originalDoc?.offer, req })) as Offer;
-    const event = (await req.payload.create({
-      collection: "events",
-      req,
-      data: {
-        title: offer.title,
-        date,
-        startTime,
-        endTime,
-        category: "sonstiges",
-        isOnline: true, // Events' own beforeChange hook auto-generates the password.
-        isPrivateBooking: true,
-        // Only set on the update-to-confirmed path — on create-as-confirmed
-        // this booking doesn't have an id yet (assigned after insert), so
-        // the back-reference is simply left blank in that one case.
-        ...(originalDoc?.id ? { bookingRequest: originalDoc.id } : {}),
-      },
-      // Created as a draft so it never appears in public /termine listings
-      // (see lib/payload/content.ts) — it's still reachable via its direct
-      // join link, which is exactly what a private 1:1 booking needs.
-      draft: true,
-    })) as Event;
+  if (status === "confirmed") {
+    await acquireBookingDayLock(req, dateKey(data.date));
+    const conflictClauses: Where[] = [
+      { status: { equals: "confirmed" } },
+      { startTime: { less_than: data.endTime } },
+      { endTime: { greater_than: data.startTime } },
+    ];
+    if (originalDoc?.id) conflictClauses.push({ id: { not_equals: originalDoc.id } });
+    const { totalDocs } = await req.payload.count({ collection: "booking-requests", where: { and: conflictClauses }, req });
+    if (totalDocs) throw new APIError("Dieser Zeitraum ist bereits mit einem bestätigten Termin belegt.", 409, undefined, true);
+  }
+
+  const linked = data.linkedEvent ?? originalDoc?.linkedEvent;
+  const linkedId = typeof linked === "object" ? linked?.id : linked;
+  if (linkedId) {
+    const existing = await req.payload.findByID({ collection: "events", id: linkedId, depth: 0, req });
+    if (existing.isPrivateBooking) {
+      const isOnline = status === "confirmed" && appointmentType === "online";
+      if (existing.date !== data.date || existing.startTime !== data.startTime || existing.endTime !== data.endTime || existing.isOnline !== isOnline) {
+        await req.payload.update({ collection: "events", id: existing.id, req, data: {
+          date: data.date, startTime: data.startTime, endTime: data.endTime, isOnline,
+        } });
+      }
+    }
+  } else if (status === "confirmed" && appointmentType === "online") {
+    const relatedOffer = data.offer ?? originalDoc?.offer;
+    const offer = await req.payload.findByID({ collection: "offers", id: typeof relatedOffer === "object" ? relatedOffer.id : relatedOffer, req });
+    const event = await req.payload.create({ collection: "events", req, draft: true, data: {
+      title: offer.title,
+      slug: `buchung-${randomUUID()}`,
+      date: data.date, startTime: data.startTime, endTime: data.endTime,
+      category: "sonstiges", isOnline: true, isPrivateBooking: true,
+      ...(originalDoc?.id ? { bookingRequest: originalDoc.id } : {}),
+    } });
     data.linkedEvent = event.id;
   }
-
   return data;
 };
 
@@ -183,7 +170,8 @@ const notifyByEmail: CollectionAfterChangeHook = async ({ doc, previousDoc, oper
 
     const statusChanged = operation === "create" || previousDoc?.status !== doc.status;
 
-    if (statusChanged && doc.status === "confirmed") {
+    const scheduleChanged = previousDoc && ["date", "startTime", "endTime", "appointmentType"].some((field) => doc[field] !== previousDoc[field]);
+    if ((statusChanged || scheduleChanged) && doc.status === "confirmed") {
       let online: { joinUrl: string; password: string } | undefined;
       let onsite: { address: string; mapsUrl: string } | undefined;
 
@@ -239,7 +227,7 @@ const notifyByEmail: CollectionAfterChangeHook = async ({ doc, previousDoc, oper
       );
     }
 
-    const proposedNew = doc.proposedAlternative?.date && doc.proposedAlternative.date !== previousDoc?.proposedAlternative?.date;
+    const proposedNew = doc.proposedAlternative?.date && JSON.stringify(doc.proposedAlternative) !== JSON.stringify(previousDoc?.proposedAlternative);
     if (proposedNew && doc.status === "pending") {
       await sendEmail(
         user.email,
@@ -282,7 +270,7 @@ export const BookingRequests: CollectionConfig = {
     // setting their own status to "confirmed" directly.
     create: isAdmin,
     read: ({ req }) => {
-      if (req.user?.collection === "users") return true;
+      if (req.user?.collection === "users") return req.user.role === "admin";
       if (req.user?.collection === "customers") return { user: { equals: req.user.id } };
       return false;
     },
@@ -290,8 +278,19 @@ export const BookingRequests: CollectionConfig = {
     delete: isAdmin,
   },
   hooks: {
+    beforeOperation: [async ({ args, operation, req }) => {
+      if (operation === "create" || operation === "update" || operation === "delete") {
+        await acquireBookingDayLock(req, "booking-calendar");
+      }
+      return args;
+    }],
     beforeChange: [handleConfirmation],
     afterChange: [notifyByEmail],
+    afterDelete: [async ({ doc, req }) => {
+      const id = typeof doc.linkedEvent === "object" ? doc.linkedEvent?.id : doc.linkedEvent;
+      if (id) await req.payload.update({ collection: "events", id, req, data: { isOnline: false } });
+      return doc;
+    }],
   },
   fields: [
     {
diff --git a/collections/Customers.ts b/collections/Customers.ts
index 6d58420..c876443 100644
--- a/collections/Customers.ts
+++ b/collections/Customers.ts
@@ -1,4 +1,6 @@
 import type { CollectionAfterChangeHook, CollectionBeforeChangeHook, CollectionConfig } from "payload";
+import { APIError } from "payload";
+import { allowVerificationEmail } from "@/lib/auth/verificationRateLimit";
 import { isAdmin, isAdminFieldLevel } from "@/access";
 import { EMAIL_VERIFICATION_TTL_MS, generateVerificationToken, hashVerificationToken, verificationExpiryISO } from "@/lib/auth/verification";
 import { verificationEmail } from "@/lib/email/authTemplates";
@@ -35,6 +37,10 @@ const issueVerificationToken: CollectionBeforeChangeHook = ({ data, originalDoc,
     data.email !== originalDoc.email;
   if (operation !== "create" && !emailChanged) return data;
 
+  if (!allowVerificationEmail(req, String(data.email ?? originalDoc?.email ?? ""), originalDoc?.id)) {
+    throw new APIError("Zu viele Bestätigungs-E-Mails. Bitte versuche es später erneut.", 429, undefined, true);
+  }
+
   const token = generateVerificationToken();
   data.emailVerified = false;
   data.emailVerificationTokenHash = hashVerificationToken(token);
@@ -46,6 +52,7 @@ const issueVerificationToken: CollectionBeforeChangeHook = ({ data, originalDoc,
 const sendVerificationEmail: CollectionAfterChangeHook = async ({ doc, req }) => {
   const token = req.context.pendingVerificationToken;
   if (typeof token !== "string") return doc;
+  delete req.context.pendingVerificationToken;
   try {
     const serverUrl = process.env.NEXT_PUBLIC_SERVER_URL || "http://localhost:3000";
     await sendEmail(
diff --git a/collections/Events.ts b/collections/Events.ts
index bdc114f..6b36a2c 100644
--- a/collections/Events.ts
+++ b/collections/Events.ts
@@ -3,6 +3,7 @@ import { isAdmin, isAdminFieldLevel, publishedOrAdmin } from "@/access";
 import { slugField } from "@/fields/slug";
 import { seoFields } from "@/fields/seo";
 import { generateMeetingPassword } from "@/lib/meeting/password";
+import { revokeChangedMeeting } from "@/lib/meeting/revoke";
 
 export const EVENT_CATEGORIES = [
   { label: "Prozessbegleitung", value: "prozessbegleitung" },
@@ -18,9 +19,9 @@ export const EVENT_CATEGORIES = [
 // Auto-generates the meeting password for new online events, and
 // regenerates it whenever the admin ticks "Neues Passwort generieren".
 // Never derived from the event id/slug — always a fresh random value.
-const setMeetingPassword: CollectionBeforeChangeHook = ({ data }) => {
-  if (!data?.isOnline) return data;
-  if (!data.meetingPassword || data.regeneratePassword) {
+const setMeetingPassword: CollectionBeforeChangeHook = ({ data, originalDoc }) => {
+  if (!(data.isOnline ?? originalDoc?.isOnline)) return data;
+  if (!(data.meetingPassword ?? originalDoc?.meetingPassword) || data.regeneratePassword || originalDoc?.isOnline === false) {
     data.meetingPassword = generateMeetingPassword();
   }
   data.regeneratePassword = false;
@@ -52,6 +53,7 @@ export const Events: CollectionConfig = {
   },
   hooks: {
     beforeChange: [setMeetingPassword],
+    afterChange: [revokeChangedMeeting],
   },
   fields: [
     {
diff --git a/components/auth/LoginForm.tsx b/components/auth/LoginForm.tsx
index a39a658..712e34c 100644
--- a/components/auth/LoginForm.tsx
+++ b/components/auth/LoginForm.tsx
@@ -4,6 +4,7 @@ import { useState, type FormEvent } from "react";
 import { useRouter, useSearchParams } from "next/navigation";
 import { ResendVerificationButton } from "./ResendVerificationButton";
 import { TextField, FormError } from "@/components/FormField";
+import { safeLoginRedirect } from "@/lib/auth/redirect";
 
 export function LoginForm() {
   const router = useRouter();
@@ -32,7 +33,7 @@ export function LoginForm() {
         setLoading(false);
         return;
       }
-      router.push(searchParams.get("next") || "/konto");
+      router.push(safeLoginRedirect(searchParams.get("next")));
       router.refresh();
     } catch {
       setError("Verbindung fehlgeschlagen. Bitte versuche es erneut.");
diff --git a/components/booking/BookingCard.tsx b/components/booking/BookingCard.tsx
index 66b74e6..85ace66 100644
--- a/components/booking/BookingCard.tsx
+++ b/components/booking/BookingCard.tsx
@@ -3,18 +3,18 @@
 import { useState } from "react";
 import { useRouter } from "next/navigation";
 import { BookingStatusBadge, resolveDisplayStatus } from "./BookingStatusBadge";
-import type { BookingRequest, Event, Offer } from "@/payload-types";
+import type { CustomerBooking } from "@/lib/booking/customerView";
 import { formatBerlinDate, formatBerlinTime } from "@/lib/calendar/timezone";
 import type { MeetingStatus } from "@/lib/meeting/status";
 
-export function BookingCard({ booking, meetingStatus }: { booking: BookingRequest; meetingStatus?: MeetingStatus | null }) {
+export function BookingCard({ booking, meetingStatus }: { booking: CustomerBooking; meetingStatus?: MeetingStatus | null }) {
   const router = useRouter();
   const [busy, setBusy] = useState(false);
   const [error, setError] = useState<string | null>(null);
 
-  const offer = typeof booking.offer === "object" ? (booking.offer as Offer) : null;
-  const event = typeof booking.linkedEvent === "object" ? (booking.linkedEvent as Event) : null;
-  const displayStatus = resolveDisplayStatus(booking.status, booking.date);
+  const offer = booking.offer;
+  const event = booking.linkedEvent;
+  const displayStatus = resolveDisplayStatus(booking.status, booking.endTime);
   const hasAlternative = booking.status === "pending" && Boolean(booking.proposedAlternative?.date);
 
   async function callAction(path: string) {
diff --git a/components/booking/BookingWidget.tsx b/components/booking/BookingWidget.tsx
index 605bd5f..21c6372 100644
--- a/components/booking/BookingWidget.tsx
+++ b/components/booking/BookingWidget.tsx
@@ -27,6 +27,7 @@ export function BookingWidget({
 }) {
   const [slotsByDay, setSlotsByDay] = useState<SlotsResponse["slots"]>({});
   const [loading, setLoading] = useState(true);
+  const [loadError, setLoadError] = useState(false);
   const [selectedDay, setSelectedDay] = useState<Date | null>(null);
   const [selectedSlot, setSelectedSlot] = useState<string | null>(null);
   const [appointmentType, setAppointmentType] = useState<"onsite" | "online">("onsite");
@@ -35,12 +36,15 @@ export function BookingWidget({
   const [result, setResult] = useState<{ ok: boolean; error?: string } | null>(null);
 
   useEffect(() => {
+    const controller = new AbortController();
     const from = new Date();
     const to = new Date(from.getTime() + 28 * 24 * 60 * 60 * 1000);
-    fetch(`/api/booking/slots?offer=${encodeURIComponent(offerSlug)}&from=${dateKey(from)}&to=${dateKey(to)}`)
-      .then((res) => res.json())
+    fetch(`/api/booking/slots?offer=${encodeURIComponent(offerSlug)}&from=${dateKey(from)}&to=${dateKey(to)}`, { signal: controller.signal })
+      .then((res) => { if (!res.ok) throw new Error("Slots unavailable"); return res.json(); })
       .then((data: SlotsResponse) => setSlotsByDay(data.slots ?? {}))
-      .finally(() => setLoading(false));
+      .catch(() => { if (!controller.signal.aborted) setLoadError(true); })
+      .finally(() => { if (!controller.signal.aborted) setLoading(false); });
+    return () => controller.abort();
   }, [offerSlug]);
 
   if (result?.ok) {
@@ -126,11 +130,12 @@ export function BookingWidget({
   if (loading) {
     return <p className="text-sm text-anouma-plum/70">Verfügbare Termine werden geladen …</p>;
   }
+  if (loadError) return <FormError>Verfügbare Termine konnten nicht geladen werden. Bitte lade die Seite erneut.</FormError>;
 
   return (
     <div className="space-y-6">
       <div className="grid gap-6 lg:grid-cols-[minmax(0,340px)_1fr]">
-        <MonthCalendar markers={markers} onSelectDay={setSelectedDay} selectedDay={selectedDay} />
+        <MonthCalendar markers={markers} onSelectDay={(day) => { setSelectedDay(day); setSelectedSlot(null); }} selectedDay={selectedDay} />
         <div>
           {!selectedDay && <p className="text-sm text-anouma-plum/70">Wähle einen markierten Tag, um freie Zeiten zu sehen.</p>}
           {selectedDay && daySlots.length === 0 && (
diff --git a/components/booking/PersonalCalendar.tsx b/components/booking/PersonalCalendar.tsx
index 1897ed7..7cd4e02 100644
--- a/components/booking/PersonalCalendar.tsx
+++ b/components/booking/PersonalCalendar.tsx
@@ -4,16 +4,17 @@ import { useState } from "react";
 import { MonthCalendar, type CalendarMarker } from "./MonthCalendar";
 import { BookingCard } from "./BookingCard";
 import { resolveDisplayStatus } from "./BookingStatusBadge";
-import type { BookingRequest, MeetingSetting } from "@/payload-types";
+import type { MeetingSetting } from "@/payload-types";
+import type { CustomerBooking } from "@/lib/booking/customerView";
 import { berlinDateKey } from "@/lib/calendar/timezone";
 import { getBookingMeetingStatus } from "@/lib/booking/meetingAccess";
 
-export function PersonalCalendar({ bookings, meetingSettings }: { bookings: BookingRequest[]; meetingSettings: MeetingSetting }) {
+export function PersonalCalendar({ bookings, meetingSettings }: { bookings: CustomerBooking[]; meetingSettings: MeetingSetting }) {
   const [selectedDay, setSelectedDay] = useState<Date | null>(null);
 
   const markers: CalendarMarker[] = bookings.map((b) => ({
     date: new Date(b.date),
-    status: resolveDisplayStatus(b.status, b.date) as CalendarMarker["status"],
+    status: resolveDisplayStatus(b.status, b.endTime) as CalendarMarker["status"],
   }));
 
   const selectedBookings = selectedDay
diff --git a/components/meeting/CallRoom.tsx b/components/meeting/CallRoom.tsx
index 9f1ff1d..61a7da3 100644
--- a/components/meeting/CallRoom.tsx
+++ b/components/meeting/CallRoom.tsx
@@ -171,9 +171,9 @@ export function CallRoom({ slug }: { slug: string }) {
     localTracksRef.current = previewTracks;
 
     try {
-      let serverUrl = session.serverUrl;
-      let participantToken = session.participantToken;
-      if (!serverUrl || !participantToken) {
+      let serverUrl: string;
+      let participantToken: string;
+      {
         const response = await fetch(`/api/meetings/${encodeURIComponent(slug)}/connect`, {
           method: "POST",
           headers: { Authorization: `Bearer ${session.token}` },
diff --git a/lib/auth/rateLimit.ts b/lib/auth/rateLimit.ts
index d2a8077..b396705 100644
--- a/lib/auth/rateLimit.ts
+++ b/lib/auth/rateLimit.ts
@@ -13,16 +13,17 @@ const MAX_TRACKED_KEYS = 5000;
 
 function sweepExpired(now: number) {
   for (const [key, bucket] of buckets) {
-    if (bucket.resetAt < now) buckets.delete(key);
+    if (bucket.resetAt <= now) buckets.delete(key);
   }
 }
 
 export function checkRateLimit(key: string, opts: { max: number; windowMs: number }): boolean {
   const now = Date.now();
-  if (buckets.size > MAX_TRACKED_KEYS) sweepExpired(now);
+  if (buckets.size >= MAX_TRACKED_KEYS) sweepExpired(now);
 
   const bucket = buckets.get(key);
-  if (!bucket || bucket.resetAt < now) {
+  if (!bucket || bucket.resetAt <= now) {
+    if (!bucket && buckets.size >= MAX_TRACKED_KEYS) return false;
     buckets.set(key, { count: 1, resetAt: now + opts.windowMs });
     return true;
   }
@@ -31,7 +32,7 @@ export function checkRateLimit(key: string, opts: { max: number; windowMs: numbe
   return true;
 }
 
-export function getClientIp(request: Request): string {
+export function getClientIp(request: { headers: Headers }): string {
   // Deployment is always behind exactly one trusted reverse proxy (see
   // DEPLOYMENT.md — Nginx Proxy Manager; the app port isn't published
   // directly to the host). nginx's default `$proxy_add_x_forwarded_for`
diff --git a/lib/auth/redirect.ts b/lib/auth/redirect.ts
new file mode 100644
index 0000000..c5c8362
--- /dev/null
+++ b/lib/auth/redirect.ts
@@ -0,0 +1,5 @@
+/** Only origin-relative application paths may be used after login. */
+export function safeLoginRedirect(value: string | null): string {
+  if (!value || !value.startsWith("/") || value.startsWith("//") || /[\\\u0000-\u0020]/.test(value)) return "/konto";
+  return value;
+}
diff --git a/lib/auth/verificationRateLimit.ts b/lib/auth/verificationRateLimit.ts
new file mode 100644
index 0000000..8cc9da4
--- /dev/null
+++ b/lib/auth/verificationRateLimit.ts
@@ -0,0 +1,9 @@
+import { checkRateLimit, getClientIp } from "./rateLimit";
+
+/** Shared budgets for registration, email changes and resend (REST and GraphQL). */
+export function allowVerificationEmail(request: { headers: Headers }, email: string, customerId?: string | number): boolean {
+  const windowMs = 60 * 60 * 1000;
+  return checkRateLimit(`verification:ip:${getClientIp(request)}`, { max: 10, windowMs }) &&
+    (customerId === undefined || checkRateLimit(`verification:customer:${customerId}`, { max: 3, windowMs })) &&
+    checkRateLimit(`verification:email:${email.trim().toLowerCase()}`, { max: 3, windowMs });
+}
diff --git a/lib/booking/customerView.ts b/lib/booking/customerView.ts
new file mode 100644
index 0000000..60ff90a
--- /dev/null
+++ b/lib/booking/customerView.ts
@@ -0,0 +1,25 @@
+import type { BookingRequest } from "@/payload-types";
+
+/** Explicit allow-list at the server/client boundary, including relationships. */
+export function customerBookingView(booking: BookingRequest) {
+  const offer = typeof booking.offer === "object" ? booking.offer : null;
+  const event = typeof booking.linkedEvent === "object" ? booking.linkedEvent : null;
+  const alternative = booking.proposedAlternative;
+  return {
+    id: booking.id,
+    date: booking.date,
+    startTime: booking.startTime,
+    endTime: booking.endTime,
+    status: booking.status,
+    appointmentType: booking.appointmentType,
+    offer: offer ? { title: offer.title } : null,
+    linkedEvent: event ? { slug: event.slug, isOnline: event.isOnline } : null,
+    proposedAlternative: alternative ? {
+      date: alternative.date,
+      startTime: alternative.startTime,
+      endTime: alternative.endTime,
+    } : null,
+  };
+}
+
+export type CustomerBooking = ReturnType<typeof customerBookingView>;
diff --git a/lib/booking/lock.ts b/lib/booking/lock.ts
index 0e3fab9..6e76f29 100644
--- a/lib/booking/lock.ts
+++ b/lib/booking/lock.ts
@@ -13,13 +13,14 @@ import type { PayloadRequest } from "payload";
  */
 export async function acquireBookingDayLock(req: PayloadRequest, dateKey: string): Promise<void> {
   const txID = req.transactionID ? String(await req.transactionID) : undefined;
-  if (!txID) return; // No active transaction — nothing to lock against.
+  if (!txID) throw new Error("A booking lock requires an active transaction");
 
   const adapter = req.payload.db as unknown as {
     sessions?: Record<string, { db: { execute: (query: unknown) => Promise<unknown> } }>;
     drizzle: { execute: (query: unknown) => Promise<unknown> };
   };
-  const tx = adapter.sessions?.[txID]?.db ?? adapter.drizzle;
+  const tx = adapter.sessions?.[txID]?.db;
+  if (!tx) throw new Error("Booking transaction not found");
 
   await tx.execute(sql`SELECT pg_advisory_xact_lock(hashtext(${dateKey}))`);
 }
diff --git a/lib/booking/meetingAccess.ts b/lib/booking/meetingAccess.ts
index 2f65afe..6b2ab0a 100644
--- a/lib/booking/meetingAccess.ts
+++ b/lib/booking/meetingAccess.ts
@@ -1,8 +1,9 @@
-import type { BookingRequest, Event, MeetingSetting } from "@/payload-types";
+import type { MeetingSetting } from "@/payload-types";
+import type { CustomerBooking } from "./customerView";
 import { canJoinMeeting, combineDateAndTime, getMeetingStatus, type MeetingStatus } from "@/lib/meeting/status";
 
-export function getBookingMeetingStatus(booking: BookingRequest, settings: MeetingSetting): MeetingStatus | null {
-  const event = typeof booking.linkedEvent === "object" ? (booking.linkedEvent as Event) : null;
+export function getBookingMeetingStatus(booking: CustomerBooking, settings: MeetingSetting): MeetingStatus | null {
+  const event = booking.linkedEvent;
   if (booking.status !== "confirmed" || booking.appointmentType !== "online" || !event?.isOnline) return null;
 
   const start = combineDateAndTime(booking.date, booking.startTime);
@@ -17,7 +18,7 @@ export function getBookingMeetingStatus(booking: BookingRequest, settings: Meeti
   });
 }
 
-export function canJoinBookingMeeting(booking: BookingRequest, settings: MeetingSetting): boolean {
+export function canJoinBookingMeeting(booking: CustomerBooking, settings: MeetingSetting): boolean {
   const status = getBookingMeetingStatus(booking, settings);
   return status !== null && canJoinMeeting(status);
 }
diff --git a/lib/booking/queries.ts b/lib/booking/queries.ts
index e8aaa34..36e99bd 100644
--- a/lib/booking/queries.ts
+++ b/lib/booking/queries.ts
@@ -1,13 +1,13 @@
 import { cache } from "react";
 import { getCMS } from "@/lib/payload/getPayload";
-import type { BookingRequest } from "@/payload-types";
+import { customerBookingView, type CustomerBooking } from "./customerView";
 
 /**
  * These are called only after the caller has already verified who the
  * current customer is (see lib/auth/customer.ts) — the `where: { user }`
  * filter below is what actually scopes results to that one customer.
  */
-export const getCustomerBookings = cache(async (customerId: number): Promise<BookingRequest[]> => {
+export const getCustomerBookings = cache(async (customerId: number): Promise<CustomerBooking[]> => {
   const payload = await getCMS();
   const result = await payload.find({
     collection: "booking-requests",
@@ -16,10 +16,10 @@ export const getCustomerBookings = cache(async (customerId: number): Promise<Boo
     depth: 2,
     limit: 200,
   });
-  return result.docs;
+  return result.docs.map(customerBookingView);
 });
 
-export async function getCustomerBookingById(customerId: number, id: number): Promise<BookingRequest | null> {
+export async function getCustomerBookingById(customerId: number, id: number): Promise<CustomerBooking | null> {
   const payload = await getCMS();
   const result = await payload.find({
     collection: "booking-requests",
@@ -27,5 +27,5 @@ export async function getCustomerBookingById(customerId: number, id: number): Pr
     depth: 2,
     limit: 1,
   });
-  return result.docs[0] ?? null;
+  return result.docs[0] ? customerBookingView(result.docs[0]) : null;
 }
diff --git a/lib/booking/slots.ts b/lib/booking/slots.ts
index 883a304..f95b5f9 100644
--- a/lib/booking/slots.ts
+++ b/lib/booking/slots.ts
@@ -1,4 +1,4 @@
-import type { Payload } from "payload";
+import type { Payload, PayloadRequest } from "payload";
 import { WEEKDAYS } from "@/collections/Availability";
 import { berlinParts, berlinWallTimeToUTC, type CalendarDate } from "@/lib/calendar/timezone";
 
@@ -63,17 +63,20 @@ function overlaps(aStart: Date, aEnd: Date, bStart: Date, bEnd: Date): boolean {
  */
 export async function getAvailableSlots(
   payload: Payload,
-  args: { durationMinutes: number; from: Date; to: Date },
+  args: { durationMinutes: number; from: Date; to: Date; req?: PayloadRequest },
 ): Promise<Map<string, TimeSlot[]>> {
-  const { durationMinutes, from, to } = args;
+  const { durationMinutes, from, to, req } = args;
   const result = new Map<string, TimeSlot[]>();
+  if (!Number.isInteger(durationMinutes) || durationMinutes <= 0 || durationMinutes > 1440 ||
+      !Number.isFinite(from.getTime()) || !Number.isFinite(to.getTime()) || to < from ||
+      to.getTime() - from.getTime() > 63 * 86400000) return result;
 
   const [{ docs: weekly }, { docs: overrides }, { docs: busyBookings }] = await Promise.all([
-    payload.find({ collection: "availability", where: { active: { equals: true } }, limit: 100 }),
+    payload.find({ collection: "availability", where: { active: { equals: true } }, pagination: false, req }),
     payload.find({
       collection: "availability-overrides",
       where: { and: [{ date: { greater_than_equal: from.toISOString() } }, { date: { less_than_equal: to.toISOString() } }] },
-      limit: 200,
+      pagination: false, req,
     }),
     payload.find({
       collection: "booking-requests",
@@ -84,7 +87,7 @@ export async function getAvailableSlots(
           { date: { less_than_equal: to.toISOString() } },
         ],
       },
-      limit: 500,
+      pagination: false, req,
     }),
   ]);
 
@@ -131,11 +134,11 @@ export async function getAvailableSlots(
         const slotEnd = atMinutesOfDay(day, start + durationMinutes);
         if (slotStart < now) continue;
         if (dayBusy.some((b) => overlaps(slotStart, slotEnd, b.start, b.end))) continue;
-        slots.push({ start: slotStart, end: slotEnd });
+        if (!slots.some((slot) => slot.start.getTime() === slotStart.getTime())) slots.push({ start: slotStart, end: slotEnd });
       }
     }
 
-    if (slots.length > 0) result.set(key, slots);
+    if (slots.length > 0) result.set(key, slots.sort((a, b) => a.start.getTime() - b.start.getTime()));
   }
 
   return result;
diff --git a/lib/booking/transaction.ts b/lib/booking/transaction.ts
new file mode 100644
index 0000000..e175504
--- /dev/null
+++ b/lib/booking/transaction.ts
@@ -0,0 +1,17 @@
+import { commitTransaction, createLocalReq, initTransaction, killTransaction, type Payload, type PayloadRequest } from "payload";
+import { acquireBookingDayLock } from "./lock";
+
+export async function withBookingTransaction<T>(payload: Payload, key: string, action: (req: PayloadRequest) => Promise<T>): Promise<T> {
+  const req = await createLocalReq({}, payload);
+  try {
+    if (!await initTransaction(req)) throw new Error("Booking transaction unavailable");
+    await acquireBookingDayLock(req, "booking-calendar");
+    await acquireBookingDayLock(req, key);
+    const result = await action(req);
+    await commitTransaction(req);
+    return result;
+  } catch (error) {
+    await killTransaction(req);
+    throw error;
+  }
+}
diff --git a/lib/calendar/timezone.ts b/lib/calendar/timezone.ts
index 4f793f8..abe22e9 100644
--- a/lib/calendar/timezone.ts
+++ b/lib/calendar/timezone.ts
@@ -2,6 +2,15 @@ const BERLIN_TZ = "Europe/Berlin";
 
 export type CalendarDate = { year: number; month: number; day: number };
 
+/** Strict calendar input, interpreted in Berlin regardless of server TZ. */
+export function parseBerlinDate(value: string): Date | null {
+  if (!/^\d{4}-\d{2}-\d{2}$/.test(value)) return null;
+  const [year, month, day] = value.split("-").map(Number);
+  if (year < 1000 || month < 1 || month > 12 || day < 1 || day > 31) return null;
+  const date = berlinWallTimeToUTC({ year, month, day }, 0, 0);
+  return berlinDateKey(date) === value ? date : null;
+}
+
 export function berlinDateKey(date: Date): string {
   const { year, month, day } = berlinParts(date);
   return `${year}-${String(month).padStart(2, "0")}-${String(day).padStart(2, "0")}`;
diff --git a/lib/email/transport.ts b/lib/email/transport.ts
index eac57ab..5825a26 100644
--- a/lib/email/transport.ts
+++ b/lib/email/transport.ts
@@ -15,6 +15,9 @@ export function getMailTransport(): nodemailer.Transporter {
     host: SMTP_HOST,
     port: Number(SMTP_PORT),
     secure: Number(SMTP_PORT) === 465,
+    connectionTimeout: 10000,
+    greetingTimeout: 10000,
+    socketTimeout: 20000,
     auth: { user: SMTP_USER, pass: SMTP_PASSWORD },
   });
   return cached;
diff --git a/lib/meeting/access.ts b/lib/meeting/access.ts
new file mode 100644
index 0000000..5d57c50
--- /dev/null
+++ b/lib/meeting/access.ts
@@ -0,0 +1,42 @@
+import { createHmac } from "node:crypto";
+import type { Payload } from "payload";
+import type { Event, MeetingSetting } from "@/payload-types";
+import { canJoinMeeting, combineDateAndTime, getMeetingStatus } from "./status";
+import type { MeetingRole } from "./token";
+
+export function meetingAccessVersion(event: Event): string {
+  const secret = process.env.MEETING_SESSION_SECRET;
+  if (!secret) throw new Error("MEETING_SESSION_SECRET is not set");
+  return createHmac("sha256", secret).update(JSON.stringify([
+    event.id, event.slug, event.meetingPassword, event.date, event.startTime,
+    event.endTime, event.isOnline, event._status, event.isPrivateBooking,
+  ])).digest("hex");
+}
+
+export function meetingWindow(event: Event, settings: MeetingSetting, role: MeetingRole, now = new Date()) {
+  const start = combineDateAndTime(event.date, event.startTime);
+  const end = event.endTime ? combineDateAndTime(event.date, event.endTime) : new Date(start.getTime() + 3600000);
+  const closeAt = end.getTime() + settings.meetingCloseAfterMinutes * 60000;
+  const status = getMeetingStatus({ start, end,
+    joinWindowMinutes: role === "host" ? settings.hostJoinWindowMinutes : settings.participantJoinWindowMinutes,
+    closeAfterMinutes: settings.meetingCloseAfterMinutes, now });
+  return { allowed: Number.isFinite(closeAt) && end > start && canJoinMeeting(status), closeAt, status };
+}
+
+/** Shared by every issuer: existing credentials are not a substitute for current access. */
+export async function authorizeMeeting(payload: Payload, event: Event, role: MeetingRole) {
+  if (!event.isOnline || (!event.isPrivateBooking && event._status !== "published" && role !== "host")) return null;
+  if (event.isPrivateBooking) {
+    const { docs } = await payload.find({ collection: "booking-requests", depth: 0, limit: 1,
+      where: { and: [
+        { linkedEvent: { equals: event.id } }, { status: { equals: "confirmed" } },
+        { appointmentType: { equals: "online" } },
+      ] },
+    });
+    if (!docs[0]) return null;
+  }
+  const settings = await payload.findGlobal({ slug: "meeting-settings" });
+  const window = meetingWindow(event, settings, role);
+  if (!window.allowed) return null;
+  return { accessVersion: meetingAccessVersion(event), expiresAt: window.closeAt };
+}
diff --git a/lib/meeting/livekit.ts b/lib/meeting/livekit.ts
index 2349ad3..b02bf48 100644
--- a/lib/meeting/livekit.ts
+++ b/lib/meeting/livekit.ts
@@ -17,9 +17,9 @@ function getLiveKitApiUrl(): string {
 }
 
 /** Stable opaque room name; the public event slug is never sent to LiveKit logs. */
-export function getLiveKitRoomName(eventSlug: string): string {
+export function getLiveKitRoomName(eventSlug: string, accessVersion?: string): string {
   const secret = requiredEnv("LIVEKIT_API_SECRET");
-  return `anouma-${createHmac("sha256", secret).update(eventSlug).digest("hex").slice(0, 32)}`;
+  return `anouma-${createHmac("sha256", secret).update(JSON.stringify([eventSlug, accessVersion])).digest("hex").slice(0, 32)}`;
 }
 
 export async function createLiveKitToken(args: {
@@ -28,12 +28,18 @@ export async function createLiveKitToken(args: {
   name: string;
   role: MeetingRole;
   clientId?: string;
+  accessVersion?: string;
+  expiresAt: number;
 }): Promise<string> {
-  const room = getLiveKitRoomName(args.eventSlug);
+  const room = getLiveKitRoomName(args.eventSlug, args.accessVersion);
+  const remainingSeconds = Math.floor((args.expiresAt - Date.now()) / 1000);
+  if (remainingSeconds <= 0) throw new Error("Meeting access has expired");
   const token = new AccessToken(requiredEnv("LIVEKIT_API_KEY"), requiredEnv("LIVEKIT_API_SECRET"), {
     identity: args.participantId,
     name: args.name,
-    ttl: "2h",
+    // Self-hosted LiveKit cannot revoke already issued JWTs. Keep the
+    // connection credential short-lived; the app re-authorizes reconnects.
+    ttl: Math.min(60, remainingSeconds),
     metadata: JSON.stringify({ role: args.role, clientId: args.clientId }),
   });
   token.addGrant({
diff --git a/lib/meeting/revoke.ts b/lib/meeting/revoke.ts
new file mode 100644
index 0000000..80b9775
--- /dev/null
+++ b/lib/meeting/revoke.ts
@@ -0,0 +1,19 @@
+import type { CollectionAfterChangeHook } from "payload";
+import type { Event } from "@/payload-types";
+import { meetingAccessVersion } from "./access";
+import { getLiveKitRoomName, getLiveKitRoomService } from "./livekit";
+
+/** Disconnect the previous room when its password, schedule or access changes. */
+export const revokeChangedMeeting: CollectionAfterChangeHook<Event> = async ({ doc, previousDoc, req }) => {
+  if (!previousDoc?.isOnline || !previousDoc.slug || !process.env.LIVEKIT_URL || !process.env.MEETING_SESSION_SECRET) return doc;
+  const previousVersion = meetingAccessVersion(previousDoc);
+  if (previousVersion === meetingAccessVersion(doc)) return doc;
+  try {
+    const service = getLiveKitRoomService();
+    const name = getLiveKitRoomName(previousDoc.slug, previousVersion);
+    if ((await service.listRooms([name])).length) await service.deleteRoom(name);
+  } catch (err) {
+    req.payload.logger.error({ err, msg: "Could not disconnect revoked meeting room" });
+  }
+  return doc;
+};
diff --git a/lib/meeting/status.ts b/lib/meeting/status.ts
index 0df4611..7cc5cbe 100644
--- a/lib/meeting/status.ts
+++ b/lib/meeting/status.ts
@@ -36,6 +36,8 @@ export function getMeetingStatus({
   const closeAt = end.getTime() + closeAfterMinutes * 60_000;
   const t = now.getTime();
 
+  if (![openAt, closeAt, t].every(Number.isFinite) || end <= start) return "ended";
+
   if (t >= closeAt) return "ended";
   if (t >= start.getTime()) return "live";
   if (t >= openAt) return "open";
diff --git a/lib/meeting/token.ts b/lib/meeting/token.ts
index 570195b..4a6efbb 100644
--- a/lib/meeting/token.ts
+++ b/lib/meeting/token.ts
@@ -17,6 +17,8 @@ export type MeetingTokenPayload = {
   clientId?: string;
   name: string;
   role: MeetingRole;
+  accessVersion?: string;
+  testRoom?: boolean;
   exp: number; // unix ms
 };
 
@@ -41,6 +43,8 @@ export function createMeetingToken(args: {
   role: MeetingRole;
   clientId?: string;
   ttlMs?: number;
+  accessVersion?: string;
+  testRoom?: boolean;
 }): { token: string; participantId: string } {
   const participantId = randomUUID();
   const clientId =
@@ -53,6 +57,8 @@ export function createMeetingToken(args: {
     clientId,
     name: args.name,
     role: args.role,
+    accessVersion: args.accessVersion,
+    testRoom: args.testRoom,
     exp: Date.now() + (args.ttlMs ?? 6 * 60 * 60 * 1000), // 6h default
   };
   const body = base64url(JSON.stringify(payload));
@@ -76,7 +82,9 @@ export function verifyMeetingToken(token: unknown): MeetingTokenPayload | null {
     const payload = JSON.parse(Buffer.from(body, "base64url").toString("utf8")) as MeetingTokenPayload;
     if (
       !Number.isFinite(payload.exp) ||
-      payload.exp < Date.now() ||
+      payload.exp <= Date.now() ||
+      (payload.accessVersion !== undefined && !/^[0-9a-f]{64}$/.test(payload.accessVersion)) ||
+      (payload.testRoom !== undefined && typeof payload.testRoom !== "boolean") ||
       typeof payload.eventSlug !== "string" ||
       payload.eventSlug.length > 200 ||
       typeof payload.participantId !== "string" ||
diff --git a/package-lock.json b/package-lock.json
index b4a180c..9c6da15 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -566,395 +566,6 @@
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-        "@esbuild/linux-mips64el": "0.18.20",
-        "@esbuild/linux-ppc64": "0.18.20",
-        "@esbuild/linux-riscv64": "0.18.20",
-        "@esbuild/linux-s390x": "0.18.20",
-        "@esbuild/linux-x64": "0.18.20",
-        "@esbuild/netbsd-x64": "0.18.20",
-        "@esbuild/openbsd-x64": "0.18.20",
-        "@esbuild/sunos-x64": "0.18.20",
-        "@esbuild/win32-arm64": "0.18.20",
-        "@esbuild/win32-ia32": "0.18.20",
-        "@esbuild/win32-x64": "0.18.20"
-      }
-    },
     "node_modules/@esbuild-kit/esm-loader": {
       "version": "2.6.5",
       "resolved": "https://registry.npmjs.org/@esbuild-kit/esm-loader/-/esm-loader-2.6.5.tgz",
@@ -5999,9 +5610,9 @@
       }
     },
     "node_modules/dompurify": {
-      "version": "3.4.8",
-      "resolved": "https://registry.npmjs.org/dompurify/-/dompurify-3.4.8.tgz",
-      "integrity": "sha512-yb1cEmaOum7wFvOCSQxyfgVlv5D47Rc30iZWoMpbDIWTnJ6grDDQyu2KFJzB2k7u0pMuJcQ1zphH//fFnw2tjQ==",
+      "version": "3.4.15",
+      "resolved": "https://registry.npmjs.org/dompurify/-/dompurify-3.4.15.tgz",
+      "integrity": "sha512-EUBjM+B+lkDE41iE82DDSCfkoPGfXx8IxFxPMjNzm/Uk4xDet77rTN9wqlxlVg71kK7XGuUMv6wUxJUwwv+Xyw==",
       "license": "(MPL-2.0 OR Apache-2.0)",
       "peer": true,
       "optionalDependencies": {
diff --git a/package.json b/package.json
index 6aa2e3c..6dbd688 100644
--- a/package.json
+++ b/package.json
@@ -46,5 +46,11 @@
     "eslint-config-next": "^16.3.5",
     "tailwindcss": "^4",
     "typescript": "^5"
+  },
+  "overrides": {
+    "dompurify": "^3.4.15",
+    "@esbuild-kit/core-utils": {
+      "esbuild": "^0.25.12"
+    }
   }
 }
diff --git a/tests/security.test.ts b/tests/security.test.ts
new file mode 100644
index 0000000..0204eff
--- /dev/null
+++ b/tests/security.test.ts
@@ -0,0 +1,144 @@
+import assert from "node:assert/strict";
+import { test } from "node:test";
+import type { Payload, PayloadRequest } from "payload";
+import type { BookingRequest, Event, MeetingSetting } from "../payload-types";
+import { customerBookingView } from "../lib/booking/customerView";
+import { authorizeMeeting, meetingAccessVersion, meetingWindow } from "../lib/meeting/access";
+import { createMeetingToken, verifyMeetingToken } from "../lib/meeting/token";
+import { createLiveKitToken, getLiveKitRoomName } from "../lib/meeting/livekit";
+import { allowVerificationEmail } from "../lib/auth/verificationRateLimit";
+import { safeLoginRedirect } from "../lib/auth/redirect";
+import { parseBerlinDate, berlinDayBounds } from "../lib/calendar/timezone";
+import { getAvailableSlots } from "../lib/booking/slots";
+import { handleConfirmation } from "../collections/BookingRequests";
+import { Events } from "../collections/Events";
+import { AvailabilityOverrides } from "../collections/AvailabilityOverrides";
+
+process.env.MEETING_SESSION_SECRET = "test-only-meeting-secret";
+process.env.LIVEKIT_API_KEY = "test-api-key";
+process.env.LIVEKIT_API_SECRET = "test-only-livekit-secret-long-enough";
+
+const settings = { hostJoinWindowMinutes: 30, participantJoinWindowMinutes: 10, meetingCloseAfterMinutes: 10 } as MeetingSetting;
+const event = { id: 1, slug: "private-call", title: "Fixture", date: "2027-07-01T10:00:00.000Z", startTime: "2027-07-01T10:00:00.000Z", endTime: "2027-07-01T11:00:00.000Z", isOnline: true, _status: "published", meetingPassword: "fixture" } as Event;
+
+test("customer props exclude private fields, even inside populated relationships", () => {
+  const booking = { id: 1, internalNote: "SECRET_NOTE", user: { emailVerificationTokenHash: "SECRET_HASH" },
+    offer: { title: "Consultation", internalNote: "SECRET_OFFER" },
+    linkedEvent: { slug: "private-call", isOnline: true, meetingPassword: "SECRET_PASSWORD", bookingRequest: { internalNote: "SECRET_NESTED" } },
+    proposedAlternative: { date: "2027-07-01", internalNote: "SECRET_ALTERNATIVE" },
+  } as unknown as BookingRequest;
+  const serialized = JSON.stringify(customerBookingView(booking));
+  assert.ok(!serialized.includes("SECRET"));
+  assert.ok(serialized.includes("Consultation"));
+  assert.ok(serialized.includes("private-call"));
+});
+
+test("closed and malformed meeting windows never grant access", () => {
+  assert.equal(meetingWindow(event, settings, "participant", new Date("2027-07-01T11:10:00Z")).allowed, false);
+  assert.equal(meetingWindow({ ...event, endTime: "invalid" }, settings, "participant").allowed, false);
+  assert.equal(meetingWindow(event, settings, "participant", new Date("2027-07-01T09:49:59Z")).allowed, false);
+  assert.equal(meetingWindow(event, settings, "participant", new Date("2027-07-01T10:00:00Z")).allowed, true);
+});
+
+test("cancelled private meetings are rejected using the current booking status", async () => {
+  let queried = false;
+  const payload = { find: async (args: { where: unknown }) => {
+    queried = true;
+    assert.ok(JSON.stringify(args.where).includes('"confirmed"'));
+    return { docs: [] };
+  } } as unknown as Payload;
+  assert.equal(await authorizeMeeting(payload, { ...event, isPrivateBooking: true }, "participant"), null);
+  assert.equal(queried, true);
+});
+
+test("password and schedule changes invalidate credentials and isolate the new room", () => {
+  const version = meetingAccessVersion(event);
+  const changed = meetingAccessVersion({ ...event, meetingPassword: "replacement" });
+  assert.notEqual(version, changed);
+  assert.notEqual(version, meetingAccessVersion({ ...event, endTime: "2027-07-01T12:00:00Z" }));
+  assert.notEqual(getLiveKitRoomName(event.slug!, version), getLiveKitRoomName(event.slug!, changed));
+  const issued = createMeetingToken({ eventSlug: event.slug!, name: "Guest", role: "participant", accessVersion: version });
+  assert.equal(verifyMeetingToken(issued.token)?.accessVersion, version);
+  const expired = createMeetingToken({ eventSlug: event.slug!, name: "Guest", role: "participant", ttlMs: 0 });
+  assert.equal(verifyMeetingToken(expired.token), null);
+});
+
+test("LiveKit connection credentials expire within the allowed window and one minute", async () => {
+  const deadline = Date.now() + 30000;
+  const jwt = await createLiveKitToken({ eventSlug: "fixture", participantId: "guest", name: "Guest", role: "participant", expiresAt: deadline });
+  const claims = JSON.parse(Buffer.from(jwt.split(".")[1], "base64url").toString());
+  assert.ok(claims.exp * 1000 <= deadline);
+  assert.ok(claims.exp - claims.nbf <= 60);
+  assert.equal(claims.video.roomAdmin, undefined);
+});
+
+test("verification budgets apply across operations, address casing and changing IPs", () => {
+  for (let i = 0; i < 3; i++) assert.equal(allowVerificationEmail({ headers: new Headers({ "x-forwarded-for": `fixture-${i}` }) }, "Target@example.com"), true);
+  assert.equal(allowVerificationEmail({ headers: new Headers({ "x-forwarded-for": "fixture-new" }) }, "target@EXAMPLE.com"), false);
+  for (let i = 0; i < 3; i++) assert.equal(allowVerificationEmail({ headers: new Headers({ "x-forwarded-for": `account-${i}` }) }, `target${i}@example.com`, 17), true);
+  assert.equal(allowVerificationEmail({ headers: new Headers({ "x-forwarded-for": "account-new" }) }, "fresh@example.com", 17), false);
+});
+
+test("login rejects external, script and backslash redirects", () => {
+  for (const value of ["javascript:alert(1)", "https://other.invalid", "//other.invalid", "/\\other.invalid", "/\n/other.invalid", null]) assert.equal(safeLoginRedirect(value), "/konto");
+  assert.equal(safeLoginRedirect("/angebote/beratung?x=1"), "/angebote/beratung?x=1");
+});
+
+test("slot date parsing uses Berlin boundaries and rejects impossible calendar dates", () => {
+  assert.equal(parseBerlinDate("2027-07-01")?.toISOString(), "2027-06-30T22:00:00.000Z");
+  assert.equal(parseBerlinDate("2027-02-30"), null);
+  assert.equal(parseBerlinDate("2027-7-1"), null);
+  assert.equal(berlinDayBounds(parseBerlinDate("2027-03-28")!).end.getTime() - parseBerlinDate("2027-03-28")!.getTime() + 1, 23 * 3600000);
+});
+
+test("invalid slot durations terminate safely without querying the database", async () => {
+  const payload = { find: () => { throw new Error("Unexpected query"); } } as unknown as Payload;
+  for (const durationMinutes of [0, -1, NaN, Infinity, 0.5]) {
+    assert.equal((await getAvailableSlots(payload, { durationMinutes, from: new Date(), to: new Date() })).size, 0);
+  }
+});
+
+test("public users cannot read absence reasons", () => {
+  const read = AvailabilityOverrides.access!.read!;
+  assert.equal(read({ req: { user: null } } as Parameters<typeof read>[0]), false);
+});
+
+function hookArgs(data: Record<string, unknown>, originalDoc: Record<string, unknown>, payload: Record<string, unknown>) {
+  return { data, originalDoc, req: { transactionID: "fixture", payload: { ...payload,
+    db: { sessions: { fixture: { db: { execute: async () => undefined } } } },
+  } } as unknown as PayloadRequest } as Parameters<typeof handleConfirmation>[0];
+}
+
+test("rescheduling a confirmed booking checks conflicts instead of silently overlapping", async () => {
+  const original = { id: 1, status: "confirmed", appointmentType: "onsite", date: event.date, startTime: event.startTime, endTime: event.endTime };
+  await assert.rejects(() => handleConfirmation(hookArgs({ startTime: "2027-07-01T10:30:00Z" }, original, {
+    count: async () => ({ totalDocs: 1 }),
+  })), { status: 409 });
+});
+
+test("cancelling a private booking disables its event", async () => {
+  let updated = false;
+  await handleConfirmation(hookArgs({ status: "cancelled" }, { id: 1, status: "confirmed", appointmentType: "online", date: event.date, startTime: event.startTime, endTime: event.endTime, linkedEvent: 2 }, {
+    findByID: async () => ({ ...event, id: 2, isPrivateBooking: true }),
+    update: async (args: { data: { isOnline: boolean } }) => { assert.equal(args.data.isOnline, false); updated = true; },
+  }));
+  assert.equal(updated, true);
+});
+
+test("repeated bookings for one offer get distinct private meeting slugs", async () => {
+  const slugs: string[] = [];
+  const payload = { count: async () => ({ totalDocs: 0 }), findByID: async () => ({ title: "Same offer" }),
+    create: async (args: { data: { slug: string } }) => { slugs.push(args.data.slug); return { id: slugs.length }; },
+  };
+  for (let i = 0; i < 2; i++) await handleConfirmation(hookArgs({ status: "confirmed", offer: 1, appointmentType: "online", date: event.date, startTime: event.startTime, endTime: event.endTime }, {}, payload));
+  assert.equal(new Set(slugs).size, 2);
+});
+
+test("ordinary event edits preserve the password; explicit regeneration changes it", async () => {
+  const hook = Events.hooks!.beforeChange![0];
+  const unchanged = await hook({ data: { isOnline: true }, originalDoc: event } as unknown as Parameters<typeof hook>[0]);
+  assert.equal(unchanged.meetingPassword, undefined);
+  const changed = await hook({ data: { regeneratePassword: true }, originalDoc: event } as unknown as Parameters<typeof hook>[0]);
+  assert.ok(changed.meetingPassword);
+  assert.notEqual(changed.meetingPassword, event.meetingPassword);
+});