diff --git a/ApiCore-Backend/src/app.config.spec.ts b/ApiCore-Backend/src/app.config.spec.ts
new file mode 100644
index 0000000..2a81592
--- /dev/null
+++ b/ApiCore-Backend/src/app.config.spec.ts
@@ -0,0 +1,67 @@
+import { Logger } from '@nestjs/common';
+import type { NestExpressApplication } from '@nestjs/platform-express';
+import {
+  configureApp,
+  describeTrustProxy,
+  trustProxySetting,
+} from './app.config';
+
+describe('trustProxySetting', () => {
+  const original = process.env.TRUST_PROXY;
+  afterEach(() => {
+    if (original === undefined) delete process.env.TRUST_PROXY;
+    else process.env.TRUST_PROXY = original;
+  });
+
+  it('defaults to one hop when unset or blank', () => {
+    delete process.env.TRUST_PROXY;
+    expect(trustProxySetting()).toBe(1);
+    process.env.TRUST_PROXY = '  ';
+    expect(trustProxySetting()).toBe(1);
+  });
+
+  it('parses a number as hop count and anything else as a list', () => {
+    process.env.TRUST_PROXY = '2';
+    expect(trustProxySetting()).toBe(2);
+    process.env.TRUST_PROXY = 'loopback, 10.42.0.0/16';
+    expect(trustProxySetting()).toBe('loopback, 10.42.0.0/16');
+  });
+});
+
+describe('describeTrustProxy', () => {
+  it('reports the hop count mode and the default fallback', () => {
+    expect(describeTrustProxy(1, false)).toBe(
+      'TRUST_PROXY not set, using default of 1 trusted hop',
+    );
+    expect(describeTrustProxy(2, true)).toBe('TRUST_PROXY: 2 trusted hop(s)');
+  });
+
+  it('reports the list mode with entry count but not the entries', () => {
+    const text = describeTrustProxy(
+      'loopback, 10.42.0.0/16, 2400:cb00::/32',
+      true,
+    );
+    expect(text).toBe('TRUST_PROXY: list of 3 trusted proxy range(s)');
+  });
+});
+
+describe('configureApp trust proxy logging', () => {
+  it('logs the active mode once at startup', () => {
+    const log = jest.spyOn(Logger.prototype, 'log').mockImplementation();
+    const app = {
+      set: jest.fn(),
+      useBodyParser: jest.fn(),
+      use: jest.fn(),
+      useGlobalFilters: jest.fn(),
+      enableCors: jest.fn(),
+      setGlobalPrefix: jest.fn(),
+      enableVersioning: jest.fn(),
+      useGlobalPipes: jest.fn(),
+    };
+    configureApp(app as unknown as NestExpressApplication);
+    expect(
+      log.mock.calls.filter(([m]) => String(m).startsWith('TRUST_PROXY')),
+    ).toHaveLength(1);
+    log.mockRestore();
+  });
+});
diff --git a/ApiCore-Backend/src/app.config.ts b/ApiCore-Backend/src/app.config.ts
index 6a9b67c..f04f2b8 100644
--- a/ApiCore-Backend/src/app.config.ts
+++ b/ApiCore-Backend/src/app.config.ts
@@ -1,4 +1,9 @@
-import { RequestMethod, ValidationPipe, VersioningType } from '@nestjs/common';
+import {
+  Logger,
+  RequestMethod,
+  ValidationPipe,
+  VersioningType,
+} from '@nestjs/common';
 import { NestExpressApplication } from '@nestjs/platform-express';
 import helmet from 'helmet';
 import cookieParser from 'cookie-parser';
@@ -7,11 +12,15 @@ import { requestLoggerMiddleware } from './common/middleware/request-logger.midd
 import { noStoreMiddleware } from './common/middleware/no-store.middleware';
 
 /**
- * How many reverse-proxy hops to trust for X-Forwarded-For. It decides the
- * client IP behind every rate limit and API-key IP allowlist: too few and
- * all users share the proxy's IP, too many and a client can forge its own.
- * A hop count ("1", the single K8s ingress) or Express' list syntax
- * ("loopback, 10.0.0.0/8").
+ * Which proxies to trust for X-Forwarded-For. It decides the client IP behind
+ * every rate limit and API-key IP allowlist: trust too little and all users
+ * share the proxy's IP, trust too much and a client can forge its own.
+ *
+ * Production runs client -> Cloudflare -> Traefik -> backend, so the hop
+ * count is not stable; TRUST_PROXY is an Express list there ("loopback,
+ * 10.42.0.0/16, <Cloudflare IPv4+IPv6 ranges>", see
+ * deploy/k8s/backend/configmap.example.yaml). A plain number ("1") is a hop
+ * count and stays the default when the variable is unset.
  */
 export function trustProxySetting(): number | string {
   const raw = process.env.TRUST_PROXY?.trim();
@@ -21,11 +30,29 @@ export function trustProxySetting(): number | string {
   return /^\d+$/.test(raw) ? Number(raw) : raw;
 }
 
+/** Startup log line for the active mode; never includes the addresses. */
+export function describeTrustProxy(
+  setting: number | string,
+  isExplicit: boolean,
+): string {
+  if (typeof setting === 'number') {
+    return isExplicit
+      ? `TRUST_PROXY: ${setting} trusted hop(s)`
+      : `TRUST_PROXY not set, using default of ${setting} trusted hop`;
+  }
+  const entries = setting.split(',').filter((e) => e.trim()).length;
+  return `TRUST_PROXY: list of ${entries} trusted proxy range(s)`;
+}
+
 export function configureApp(app: NestExpressApplication): void {
-  // Trust the single reverse-proxy hop (K8s ingress) so req.ip reflects the
+  // Trust the configured proxies (Traefik, Cloudflare) so req.ip reflects the
   // real client IP from X-Forwarded-For — required for per-client throttling
   // to work correctly rather than rate-limiting all traffic together.
-  app.set('trust proxy', trustProxySetting());
+  const trustProxy = trustProxySetting();
+  app.set('trust proxy', trustProxy);
+  new Logger('Bootstrap').log(
+    describeTrustProxy(trustProxy, !!process.env.TRUST_PROXY?.trim()),
+  );
   // No ETags: they let caches and proxies revalidate (and keep) personal
   // responses that are meant to be no-store.
   app.set('etag', false);
diff --git a/ApiCore-Backend/src/app.module.ts b/ApiCore-Backend/src/app.module.ts
index cd19ec1..4fc1cfd 100644
--- a/ApiCore-Backend/src/app.module.ts
+++ b/ApiCore-Backend/src/app.module.ts
@@ -1,7 +1,8 @@
 import { Module } from '@nestjs/common';
 import { ConfigModule } from '@nestjs/config';
 import { APP_GUARD, APP_INTERCEPTOR } from '@nestjs/core';
-import { ThrottlerGuard, ThrottlerModule } from '@nestjs/throttler';
+import { ThrottlerModule } from '@nestjs/throttler';
+import { ClientIpThrottlerGuard } from './common/throttler/client-ip-throttler.guard';
 import { ScheduleModule } from '@nestjs/schedule';
 import { PrismaModule } from './prisma/prisma.module';
 import { HealthModule } from './health/health.module';
@@ -114,7 +115,7 @@ import { IdempotencyCleanupService } from './common/idempotency/idempotency-clea
   providers: [
     // Throttle first: a request with a wrong token or API key must count
     // against the limit too, before any database lookup is spent on it.
-    { provide: APP_GUARD, useClass: ThrottlerGuard },
+    { provide: APP_GUARD, useClass: ClientIpThrottlerGuard },
     { provide: APP_GUARD, useClass: JwtAuthGuard },
     { provide: APP_GUARD, useClass: PermissionsGuard },
     { provide: APP_INTERCEPTOR, useClass: IdempotencyInterceptor },
diff --git a/ApiCore-Backend/src/common/throttler/client-ip-throttler.guard.spec.ts b/ApiCore-Backend/src/common/throttler/client-ip-throttler.guard.spec.ts
new file mode 100644
index 0000000..34ce441
--- /dev/null
+++ b/ApiCore-Backend/src/common/throttler/client-ip-throttler.guard.spec.ts
@@ -0,0 +1,26 @@
+import { ClientIpThrottlerGuard } from './client-ip-throttler.guard';
+
+describe('ClientIpThrottlerGuard.getTracker', () => {
+  // getTracker is protected and needs none of the guard's dependencies.
+  const guard = Object.create(
+    ClientIpThrottlerGuard.prototype,
+  ) as ClientIpThrottlerGuard & {
+    getTracker(req: Record<string, any>): Promise<string>;
+  };
+
+  it('tracks IPv6 clients by their /64 prefix', async () => {
+    await expect(guard.getTracker({ ip: '2001:db8:1:2::9' })).resolves.toBe(
+      '2001:db8:1:2::/64',
+    );
+  });
+
+  it('tracks IPv4 clients by address', async () => {
+    await expect(guard.getTracker({ ip: '203.0.113.7' })).resolves.toBe(
+      '203.0.113.7',
+    );
+  });
+
+  it('falls back to a stable key when req.ip is missing', async () => {
+    await expect(guard.getTracker({})).resolves.toBe('unknown');
+  });
+});
diff --git a/ApiCore-Backend/src/common/throttler/client-ip-throttler.guard.ts b/ApiCore-Backend/src/common/throttler/client-ip-throttler.guard.ts
new file mode 100644
index 0000000..a0c20f6
--- /dev/null
+++ b/ApiCore-Backend/src/common/throttler/client-ip-throttler.guard.ts
@@ -0,0 +1,14 @@
+import { Injectable } from '@nestjs/common';
+import { ThrottlerGuard } from '@nestjs/throttler';
+import { rateLimitSubject } from './rate-limit-subject';
+
+/** ThrottlerGuard that counts per client network (IPv6 /64), not per address. */
+@Injectable()
+export class ClientIpThrottlerGuard extends ThrottlerGuard {
+  protected getTracker(req: Record<string, any>): Promise<string> {
+    const ip: unknown = req.ip;
+    return Promise.resolve(
+      typeof ip === 'string' && ip ? rateLimitSubject(ip) : 'unknown',
+    );
+  }
+}
diff --git a/ApiCore-Backend/src/common/throttler/rate-limit-subject.spec.ts b/ApiCore-Backend/src/common/throttler/rate-limit-subject.spec.ts
new file mode 100644
index 0000000..e63f830
--- /dev/null
+++ b/ApiCore-Backend/src/common/throttler/rate-limit-subject.spec.ts
@@ -0,0 +1,56 @@
+import { rateLimitSubject } from './rate-limit-subject';
+
+describe('rateLimitSubject', () => {
+  it('returns IPv4 unchanged', () => {
+    expect(rateLimitSubject('203.0.113.7')).toBe('203.0.113.7');
+  });
+
+  it('unwraps IPv4-mapped IPv6 addresses', () => {
+    expect(rateLimitSubject('::ffff:203.0.113.7')).toBe('203.0.113.7');
+    expect(rateLimitSubject('::FFFF:203.0.113.7')).toBe('203.0.113.7');
+  });
+
+  it('reduces a compressed IPv6 address to its /64 prefix', () => {
+    expect(rateLimitSubject('2001:db8:1:2::5')).toBe('2001:db8:1:2::/64');
+  });
+
+  it('reduces a full-form IPv6 address to its /64 prefix', () => {
+    expect(rateLimitSubject('2001:0db8:0001:0002:aaaa:bbbb:cccc:dddd')).toBe(
+      '2001:db8:1:2::/64',
+    );
+  });
+
+  it('normalises uppercase', () => {
+    expect(rateLimitSubject('2001:DB8:1:2::ABCD')).toBe('2001:db8:1:2::/64');
+  });
+
+  it('handles :: at the start and for the unspecified address', () => {
+    expect(rateLimitSubject('::1')).toBe('0:0:0:0::/64');
+    expect(rateLimitSubject('::')).toBe('0:0:0:0::/64');
+  });
+
+  it('handles :: that swallows part of the prefix', () => {
+    expect(rateLimitSubject('2001:db8::1')).toBe('2001:db8:0:0::/64');
+  });
+
+  it('maps different interface identifiers in one /64 to the same key', () => {
+    expect(rateLimitSubject('2001:db8:1:2:1::1')).toBe(
+      rateLimitSubject('2001:db8:1:2:ffff:eeee:dddd:cccc'),
+    );
+  });
+
+  it('maps different /64 networks to different keys', () => {
+    expect(rateLimitSubject('2001:db8:1:2::1')).not.toBe(
+      rateLimitSubject('2001:db8:1:3::1'),
+    );
+  });
+
+  it('ignores an IPv6 zone id', () => {
+    expect(rateLimitSubject('fe80::1%eth0')).toBe('fe80:0:0:0::/64');
+  });
+
+  it('returns unparseable input unchanged', () => {
+    expect(rateLimitSubject('not-an-ip')).toBe('not-an-ip');
+    expect(rateLimitSubject('')).toBe('');
+  });
+});
diff --git a/ApiCore-Backend/src/common/throttler/rate-limit-subject.ts b/ApiCore-Backend/src/common/throttler/rate-limit-subject.ts
new file mode 100644
index 0000000..3e5e569
--- /dev/null
+++ b/ApiCore-Backend/src/common/throttler/rate-limit-subject.ts
@@ -0,0 +1,47 @@
+import { isIPv4, isIPv6 } from 'node:net';
+
+const MAPPED_V4_PREFIX = /^::ffff:(\d{1,3}(?:\.\d{1,3}){3})$/i;
+const PREFIX_GROUPS = 4; // /64 = first four 16-bit groups
+
+/** Expands an IPv6 address (no zone id) into its eight 16-bit groups. */
+function expandIPv6(address: string): number[] {
+  let text = address;
+  // Embedded IPv4 tail (e.g. 64:ff9b::1.2.3.4) becomes two hex groups.
+  const tail = /(\d{1,3}(?:\.\d{1,3}){3})$/.exec(text);
+  if (tail) {
+    const [a, b, c, d] = tail[1].split('.').map(Number);
+    const hi = ((a << 8) | b).toString(16);
+    const lo = ((c << 8) | d).toString(16);
+    text = `${text.slice(0, tail.index)}${hi}:${lo}`;
+  }
+  const [head, rest] = text.split('::');
+  const headGroups = head ? head.split(':') : [];
+  const restGroups = rest === undefined ? [] : rest ? rest.split(':') : [];
+  const missing = 8 - headGroups.length - restGroups.length;
+  const groups =
+    rest === undefined
+      ? headGroups
+      : [...headGroups, ...Array<string>(missing).fill('0'), ...restGroups];
+  return groups.map((g) => parseInt(g, 16));
+}
+
+/**
+ * Rate-limit key for a client IP. IPv4 stays as is, IPv4-mapped IPv6 becomes
+ * plain IPv4, and IPv6 collapses to its /64 prefix: a single subscriber
+ * controls a whole /64, so keying on the full address would let it rotate
+ * addresses to dodge every limit. Unparseable input is returned unchanged.
+ */
+export function rateLimitSubject(ip: string): string {
+  const mapped = MAPPED_V4_PREFIX.exec(ip);
+  if (mapped && isIPv4(mapped[1])) {
+    return mapped[1];
+  }
+  const address = ip.split('%')[0];
+  if (!isIPv6(address)) {
+    return ip;
+  }
+  const prefix = expandIPv6(address)
+    .slice(0, PREFIX_GROUPS)
+    .map((g) => g.toString(16));
+  return `${prefix.join(':')}::/64`;
+}
diff --git a/deploy/k8s/backend/ingress.yaml b/deploy/k8s/backend/ingress.yaml
index ca1e39d..72f331f 100644
--- a/deploy/k8s/backend/ingress.yaml
+++ b/deploy/k8s/backend/ingress.yaml
@@ -6,8 +6,13 @@ metadata:
     # Requires cert-manager with a ClusterIssuer named "letsencrypt-prod"
     # (or swap for whatever issuer/cert mechanism the cluster already uses).
     cert-manager.io/cluster-issuer: letsencrypt-prod
+    # Nur Traffic ueber Cloudflare zulassen. Die Middleware liegt im Repo
+    # rke2-cluster (security/cloudflare-only-middlewares.yaml). Sie schuetzt vor
+    # Direktzugriff am Origin vorbei, nicht vor fremden Cloudflare-Zonen.
+    traefik.ingress.kubernetes.io/router.middlewares: apicore-cloudflare-only@kubernetescrd
 spec:
-  ingressClassName: nginx
+  # Der Cluster (RKE2) nutzt Traefik; nur damit wirkt die Middleware-Annotation oben.
+  ingressClassName: traefik
   tls:
     - hosts:
         - api.apicore.example.com
diff --git a/deploy/k8s/frontend/ingress.yaml b/deploy/k8s/frontend/ingress.yaml
index 08a91b9..aef77a3 100644
--- a/deploy/k8s/frontend/ingress.yaml
+++ b/deploy/k8s/frontend/ingress.yaml
@@ -6,8 +6,13 @@ metadata:
     # Requires cert-manager with a ClusterIssuer named "letsencrypt-prod"
     # (or swap for whatever issuer/cert mechanism the cluster already uses).
     cert-manager.io/cluster-issuer: letsencrypt-prod
+    # Nur Traffic ueber Cloudflare zulassen. Die Middleware liegt im Repo
+    # rke2-cluster (security/cloudflare-only-middlewares.yaml). Sie schuetzt vor
+    # Direktzugriff am Origin vorbei, nicht vor fremden Cloudflare-Zonen.
+    traefik.ingress.kubernetes.io/router.middlewares: apicore-cloudflare-only@kubernetescrd
 spec:
-  ingressClassName: nginx
+  # Der Cluster (RKE2) nutzt Traefik; nur damit wirkt die Middleware-Annotation oben.
+  ingressClassName: traefik
   tls:
     - hosts:
         - apicore.example.com