diff --git a/.env.example b/.env.example
index 5f196be..1d8d160 100644
--- a/.env.example
+++ b/.env.example
@@ -5,6 +5,14 @@ WEB_PORT=4200
 PUBLIC_WEB_URL=http://localhost:4200
 API_BASE_URL=/api
 
+APP_PRODUCT_NAME=LDAP Portal
+APP_COMPANY_NAME=LDAP Portal
+APP_PRIMARY_COLOR=#0f6b6e
+APP_SUPPORT_EMAIL=support@example.com
+APP_LOGO_URL=
+APP_IMPRINT_URL=
+APP_PRIVACY_URL=
+
 DATABASE_URL=mysql://ldap_portal:change-me@mysql.example.com:3306/ldap_portal
 DATABASE_SSL=false
 JWT_SECRET=change-me-long-random-jwt-secret
diff --git a/README.md b/README.md
index 9a6ded4..d23f5ae 100644
--- a/README.md
+++ b/README.md
@@ -130,6 +130,9 @@ Die wichtigsten Variablen aus `.env.example`:
 | `API_PORT` | Interner Port der NestJS API, im Container standardmaessig `3000`. |
 | `PUBLIC_WEB_URL` | Externe Web-URL fuer CORS, Mail-Links und Registrierung aus dem SSO-Login. |
 | `API_BASE_URL` | API-Basis aus Sicht des Browsers, im Single Container `/api`. |
+| `APP_PRODUCT_NAME`, `APP_COMPANY_NAME` | Zentrale Branding-Namen fuer OIDC-Seiten und Mail-Templates. |
+| `APP_PRIMARY_COLOR` | Zentrale Primaerfarbe als sechsstelliger Hex-Wert. |
+| `APP_SUPPORT_EMAIL`, `APP_LOGO_URL`, `APP_IMPRINT_URL`, `APP_PRIVACY_URL` | Zentrale Branding-Werte; Bild- und Link-URLs muessen HTTPS verwenden. |
 | `DATABASE_URL` | MySQL-Verbindungs-URL. Alternativ `DB_HOST`, `DB_PORT`, `DB_USERNAME`, `DB_PASSWORD`, `DB_DATABASE`. |
 | `DATABASE_SSL` | `true`, wenn MySQL TLS verlangt. |
 | `JWT_SECRET` | Signatur-Secret fuer Portal-JWTs. |
@@ -156,6 +159,8 @@ Die wichtigsten Variablen aus `.env.example`:
 
 Hinweis: `REGISTRATION_MANAGER_GROUP`, `GROUP_MANAGER_GROUP` und `AUDIT_VIEWER_GROUP` stehen aktuell in `.env.example`, werden im Code aber nicht ausgewertet. Die Admin-Gruppennamen sind derzeit fest verdrahtet, siehe "Admin-Rollen".
 
+Die `APP_*`-Werte haben Vorrang. Solange sie nicht gesetzt sind, verwendet die Anwendung fuer die Rueckwaertskompatibilitaet die entsprechenden `MAIL_*`-Werte. Die OIDC-Seiten liegen unter `apps/api/src/oidc/templates` und werden beim API-Build nach `dist/oidc/templates` kopiert. Sie werden ohne clientseitiges JavaScript direkt durch NestJS gerendert.
+
 ## Datenbank
 
 Die App nutzt TypeORM mit MySQL. In `NODE_ENV=production` ist `synchronize` deaktiviert. Fuer produktive Deployments muss das Schema vorab vorhanden sein oder es muessen Migrationen ergaenzt und ausgefuehrt werden.
diff --git a/apps/api/nest-cli.json b/apps/api/nest-cli.json
index 0db9dc9..3a9e52f 100644
--- a/apps/api/nest-cli.json
+++ b/apps/api/nest-cli.json
@@ -8,6 +8,11 @@
         "include": "mail/templates/**/*",
         "outDir": "dist",
         "watchAssets": true
+      },
+      {
+        "include": "oidc/templates/**/*",
+        "outDir": "dist",
+        "watchAssets": true
       }
     ]
   }
diff --git a/apps/api/scripts/copy-mail-assets.js b/apps/api/scripts/copy-mail-assets.js
index 8a0e17c..e9ed87b 100644
--- a/apps/api/scripts/copy-mail-assets.js
+++ b/apps/api/scripts/copy-mail-assets.js
@@ -1,9 +1,6 @@
 const { copyFileSync, existsSync, mkdirSync, readdirSync, statSync } = require('node:fs');
 const { join } = require('node:path');
 
-const source = join(__dirname, '..', 'src', 'mail', 'templates');
-const target = join(__dirname, '..', 'dist', 'mail', 'templates');
-
 function copyDirectory(from, to) {
   if (!existsSync(from)) {
     return;
@@ -21,4 +18,9 @@ function copyDirectory(from, to) {
   }
 }
 
-copyDirectory(source, target);
+for (const feature of ['mail', 'oidc']) {
+  copyDirectory(
+    join(__dirname, '..', 'src', feature, 'templates'),
+    join(__dirname, '..', 'dist', feature, 'templates'),
+  );
+}
diff --git a/apps/api/src/common/application-branding.ts b/apps/api/src/common/application-branding.ts
new file mode 100644
index 0000000..a5301c6
--- /dev/null
+++ b/apps/api/src/common/application-branding.ts
@@ -0,0 +1,44 @@
+import { ConfigService } from '@nestjs/config';
+
+export interface ApplicationBranding {
+  productName: string;
+  companyName: string;
+  primaryColor: string;
+  supportEmail: string;
+  logoUrl?: string;
+  imprintUrl?: string;
+  privacyUrl?: string;
+}
+
+export function applicationBranding(config: ConfigService): ApplicationBranding {
+  return {
+    productName: configValue(config, 'APP_PRODUCT_NAME', 'MAIL_PRODUCT_NAME') ?? 'LDAP Portal',
+    companyName: configValue(config, 'APP_COMPANY_NAME', 'MAIL_COMPANY_NAME') ?? 'LDAP Portal',
+    primaryColor: validColor(configValue(config, 'APP_PRIMARY_COLOR', 'MAIL_PRIMARY_COLOR')),
+    supportEmail: configValue(config, 'APP_SUPPORT_EMAIL', 'MAIL_SUPPORT_EMAIL') ?? 'support@example.com',
+    logoUrl: validHttpsUrl(configValue(config, 'APP_LOGO_URL', 'MAIL_LOGO_URL')),
+    imprintUrl: validHttpsUrl(configValue(config, 'APP_IMPRINT_URL', 'MAIL_IMPRINT_URL')),
+    privacyUrl: validHttpsUrl(configValue(config, 'APP_PRIVACY_URL', 'MAIL_PRIVACY_URL')),
+  };
+}
+
+function configValue(config: ConfigService, primaryKey: string, fallbackKey: string): string | undefined {
+  return config.get<string>(primaryKey)?.trim() || config.get<string>(fallbackKey)?.trim() || undefined;
+}
+
+function validColor(value?: string): string {
+  return value && /^#[0-9a-f]{6}$/i.test(value) ? value : '#0f6b6e';
+}
+
+function validHttpsUrl(value?: string): string | undefined {
+  if (!value) {
+    return undefined;
+  }
+
+  try {
+    const url = new URL(value);
+    return url.protocol === 'https:' ? url.toString() : undefined;
+  } catch {
+    return undefined;
+  }
+}
diff --git a/apps/api/src/mail/mail-branding.ts b/apps/api/src/mail/mail-branding.ts
index 80b65ea..a2e5349 100644
--- a/apps/api/src/mail/mail-branding.ts
+++ b/apps/api/src/mail/mail-branding.ts
@@ -1,23 +1,11 @@
 import { ConfigService } from '@nestjs/config';
+import {
+  ApplicationBranding,
+  applicationBranding,
+} from '../common/application-branding';
 
-export interface MailBranding {
-  productName: string;
-  companyName: string;
-  primaryColor: string;
-  supportEmail: string;
-  logoUrl?: string;
-  imprintUrl?: string;
-  privacyUrl?: string;
-}
+export type MailBranding = ApplicationBranding;
 
 export function mailBranding(config: ConfigService): MailBranding {
-  return {
-    productName: config.get<string>('MAIL_PRODUCT_NAME') ?? 'LDAP Portal',
-    companyName: config.get<string>('MAIL_COMPANY_NAME') ?? 'LDAP Portal',
-    primaryColor: config.get<string>('MAIL_PRIMARY_COLOR') ?? '#0f6b6e',
-    supportEmail: config.get<string>('MAIL_SUPPORT_EMAIL') ?? 'support@example.com',
-    logoUrl: config.get<string>('MAIL_LOGO_URL') || undefined,
-    imprintUrl: config.get<string>('MAIL_IMPRINT_URL') || undefined,
-    privacyUrl: config.get<string>('MAIL_PRIVACY_URL') || undefined,
-  };
+  return applicationBranding(config);
 }
diff --git a/apps/api/src/oidc/oidc-interaction-template.service.spec.ts b/apps/api/src/oidc/oidc-interaction-template.service.spec.ts
new file mode 100644
index 0000000..695bbd3
--- /dev/null
+++ b/apps/api/src/oidc/oidc-interaction-template.service.spec.ts
@@ -0,0 +1,66 @@
+import { OidcInteractionTemplateService } from './oidc-interaction-template.service';
+
+describe('OidcInteractionTemplateService', () => {
+  const values: Record<string, string> = {
+    APP_PRODUCT_NAME: 'ForgeCore Auth',
+    APP_COMPANY_NAME: 'ForgeCore',
+    APP_PRIMARY_COLOR: '#126466',
+    APP_SUPPORT_EMAIL: 'support@example.com',
+    APP_LOGO_URL: 'https://cdn.example.com/logo.png',
+  };
+  const config = { get: jest.fn((key: string) => values[key]) };
+  const service = new OidcInteractionTemplateService(config as any);
+
+  it('renders the login page with branding and encoded form actions', async () => {
+    const html = await service.renderLogin({
+      uid: 'uid/with spaces',
+      username: 'maria',
+      registrationUrl: 'https://portal.example.com/register',
+    });
+
+    expect(html).toContain('<title>Anmelden - ForgeCore Auth</title>');
+    expect(html).toContain('https://cdn.example.com/logo.png');
+    expect(html).toContain('/interaction/uid%2Fwith%20spaces/login');
+    expect(html).toContain('value="maria"');
+  });
+
+  it('escapes usernames and error messages', async () => {
+    const html = await service.renderLogin({
+      uid: 'uid',
+      username: '<script>alert(1)</script>',
+      errorMessage: '<b>Fehler</b>',
+      registrationUrl: 'https://portal.example.com/register',
+    });
+
+    expect(html).toContain('&lt;script&gt;alert(1)&lt;/script&gt;');
+    expect(html).toContain('&lt;b&gt;Fehler&lt;/b&gt;');
+    expect(html).not.toContain('<script>');
+  });
+
+  it('renders escaped consent details and scope descriptions', async () => {
+    const html = await service.renderConsent({
+      uid: 'consent-id',
+      clientName: '<Admin Portal>',
+      redirectUri: 'https://client.example.com/callback?x=1&y=2',
+      scopes: ['openid', '<custom>'],
+    });
+
+    expect(html).toContain('&lt;Admin Portal&gt;');
+    expect(html).toContain('https://client.example.com/callback?x&#x3D;1&amp;y&#x3D;2');
+    expect(html).toContain('Anmeldung per OpenID Connect bestaetigen.');
+    expect(html).toContain('&lt;custom&gt;');
+    expect(html).toContain('/interaction/consent-id/confirm');
+  });
+
+  it('falls back to mail branding when application branding is absent', async () => {
+    const fallbackConfig = {
+      get: jest.fn((key: string) => ({ MAIL_PRODUCT_NAME: 'Legacy Portal' })[key]),
+    };
+    const fallbackService = new OidcInteractionTemplateService(fallbackConfig as any);
+
+    const html = await fallbackService.renderError({ title: 'Fehler', message: 'Nicht verfuegbar.' });
+
+    expect(html).toContain('<title>Fehler - Legacy Portal</title>');
+    expect(html).toContain('Nicht verfuegbar.');
+  });
+});
diff --git a/apps/api/src/oidc/oidc-interaction-template.service.ts b/apps/api/src/oidc/oidc-interaction-template.service.ts
new file mode 100644
index 0000000..5c7a431
--- /dev/null
+++ b/apps/api/src/oidc/oidc-interaction-template.service.ts
@@ -0,0 +1,86 @@
+import { Injectable } from '@nestjs/common';
+import { ConfigService } from '@nestjs/config';
+import { readFile } from 'node:fs/promises';
+import { join } from 'node:path';
+import Handlebars from 'handlebars';
+import { applicationBranding } from '../common/application-branding';
+
+const oidcTemplateDir = join(__dirname, 'templates');
+
+export interface OidcLoginPageInput {
+  uid: string;
+  username?: string;
+  errorMessage?: string;
+  registrationUrl: string;
+}
+
+export interface OidcConsentPageInput {
+  uid: string;
+  clientName: string;
+  redirectUri?: string;
+  scopes: string[];
+}
+
+export interface OidcErrorPageInput {
+  title: string;
+  message: string;
+}
+
+@Injectable()
+export class OidcInteractionTemplateService {
+  constructor(private readonly config: ConfigService) {}
+
+  async renderLogin(input: OidcLoginPageInput): Promise<string> {
+    const encodedUid = encodeURIComponent(input.uid);
+    return this.render('login', 'Anmelden', {
+      username: input.username ?? '',
+      errorMessage: input.errorMessage,
+      loginAction: `/interaction/${encodedUid}/login`,
+      abortAction: `/interaction/${encodedUid}/abort`,
+      registrationUrl: input.registrationUrl,
+    });
+  }
+
+  async renderConsent(input: OidcConsentPageInput): Promise<string> {
+    const encodedUid = encodeURIComponent(input.uid);
+    return this.render('consent', 'Zugriff erlauben', {
+      clientName: input.clientName,
+      redirectUri: input.redirectUri,
+      scopes: input.scopes.map((name) => ({ name, description: this.scopeDescription(name) })),
+      confirmAction: `/interaction/${encodedUid}/confirm`,
+      abortAction: `/interaction/${encodedUid}/abort`,
+    });
+  }
+
+  async renderError(input: OidcErrorPageInput): Promise<string> {
+    return this.render('error', input.title, { message: input.message });
+  }
+
+  private async render(templateName: string, title: string, context: Record<string, unknown>): Promise<string> {
+    const [layoutSource, templateSource] = await Promise.all([
+      readFile(join(oidcTemplateDir, 'layouts', 'base.hbs'), 'utf8'),
+      readFile(join(oidcTemplateDir, `${templateName}.hbs`), 'utf8'),
+    ]);
+    const branding = applicationBranding(this.config);
+    const body = Handlebars.compile(templateSource)(context);
+
+    return Handlebars.compile(layoutSource)({
+      ...context,
+      branding,
+      title,
+      body,
+    });
+  }
+
+  private scopeDescription(scope: string): string {
+    const descriptions: Record<string, string> = {
+      openid: 'Anmeldung per OpenID Connect bestaetigen.',
+      profile: 'Profilinformationen wie Name und Anzeigename lesen.',
+      email: 'E-Mail-Adresse lesen.',
+      groups: 'Gruppenmitgliedschaften lesen.',
+      offline_access: 'Laengerfristigen Zugriff ueber Refresh Tokens erlauben.',
+    };
+
+    return descriptions[scope] ?? 'Diese Berechtigung wurde von der Anwendung angefordert.';
+  }
+}
diff --git a/apps/api/src/oidc/oidc-interaction.controller.spec.ts b/apps/api/src/oidc/oidc-interaction.controller.spec.ts
new file mode 100644
index 0000000..6218aae
--- /dev/null
+++ b/apps/api/src/oidc/oidc-interaction.controller.spec.ts
@@ -0,0 +1,154 @@
+import { Logger, UnauthorizedException } from '@nestjs/common';
+import { OidcInteractionController } from './oidc-interaction.controller';
+
+describe('OidcInteractionController', () => {
+  const request = {
+    method: 'GET',
+    originalUrl: '/interaction/uid',
+    url: '/interaction/uid',
+    headers: { host: 'auth.example.com', 'x-forwarded-proto': 'https' },
+  } as any;
+
+  function responseMock() {
+    const response: any = {
+      send: jest.fn(),
+      status: jest.fn(),
+    };
+    response.status.mockReturnValue(response);
+    return response;
+  }
+
+  function createController() {
+    const oidc = {
+      interactionDetails: jest.fn(),
+      isFirstPartyClient: jest.fn().mockResolvedValue(false),
+      finishConsent: jest.fn().mockResolvedValue(undefined),
+      finishLogin: jest.fn().mockResolvedValue(undefined),
+      abortInteraction: jest.fn().mockResolvedValue(undefined),
+    };
+    const templates = {
+      renderLogin: jest.fn().mockResolvedValue('<html>login</html>'),
+      renderConsent: jest.fn().mockResolvedValue('<html>consent</html>'),
+      renderError: jest.fn().mockResolvedValue('<html>error</html>'),
+    };
+    const config = { get: jest.fn().mockReturnValue('https://portal.example.com/') };
+    const errorLogger = { log: jest.fn().mockResolvedValue(undefined) };
+    const requestContext = { get: jest.fn().mockReturnValue({ correlationId: 'correlation-id' }) };
+    const controller = new OidcInteractionController(
+      oidc as any,
+      config as any,
+      templates as any,
+      errorLogger as any,
+      requestContext as any,
+    );
+
+    return { controller, oidc, templates, errorLogger };
+  }
+
+  it('renders the login interaction without changing its route', async () => {
+    const { controller, oidc, templates } = createController();
+    const response = responseMock();
+    oidc.interactionDetails.mockResolvedValue({ uid: 'uid', prompt: { name: 'login' }, params: {} });
+
+    await controller.view('uid', request, response);
+
+    expect(templates.renderLogin).toHaveBeenCalledWith({
+      uid: 'uid',
+      registrationUrl: 'https://portal.example.com/register',
+    });
+    expect(response.send).toHaveBeenCalledWith('<html>login</html>');
+  });
+
+  it('automatically finishes consent for first-party clients', async () => {
+    const { controller, oidc, templates } = createController();
+    const response = responseMock();
+    oidc.interactionDetails.mockResolvedValue({
+      uid: 'uid',
+      prompt: { name: 'consent' },
+      params: { client_id: 'first-party' },
+    });
+    oidc.isFirstPartyClient.mockResolvedValue(true);
+
+    await controller.view('uid', request, response);
+
+    expect(oidc.finishConsent).toHaveBeenCalledWith(request, response, 'uid', { autoGranted: true });
+    expect(templates.renderConsent).not.toHaveBeenCalled();
+  });
+
+  it('renders consent details for third-party clients', async () => {
+    const { controller, oidc, templates } = createController();
+    const response = responseMock();
+    oidc.interactionDetails.mockResolvedValue({
+      uid: 'uid',
+      prompt: { name: 'consent' },
+      params: {
+        client_id: 'client-id',
+        name: 'Listify',
+        redirect_uri: 'https://listify.example.com/callback',
+        scope: 'openid profile email',
+      },
+    });
+
+    await controller.view('uid', request, response);
+
+    expect(templates.renderConsent).toHaveBeenCalledWith({
+      uid: 'uid',
+      clientName: 'Listify',
+      redirectUri: 'https://listify.example.com/callback',
+      scopes: ['openid', 'profile', 'email'],
+    });
+  });
+
+  it('keeps a successful login delegated to the provider', async () => {
+    const { controller, oidc } = createController();
+    const response = responseMock();
+
+    await controller.login('uid', { username: 'maria', password: 'secret' }, request, response);
+
+    expect(oidc.finishLogin).toHaveBeenCalledWith(request, response, 'uid', 'maria', 'secret');
+    expect(response.send).not.toHaveBeenCalled();
+  });
+
+  it('returns the rendered login page for invalid credentials', async () => {
+    const { controller, oidc, templates } = createController();
+    const response = responseMock();
+    oidc.finishLogin.mockRejectedValue(new UnauthorizedException('Ungueltige Zugangsdaten.'));
+
+    await controller.login('uid', { username: 'maria', password: 'wrong' }, request, response);
+
+    expect(response.status).toHaveBeenCalledWith(401);
+    expect(templates.renderLogin).toHaveBeenCalledWith(expect.objectContaining({
+      uid: 'uid',
+      username: 'maria',
+      errorMessage: 'Ungueltige Zugangsdaten.',
+    }));
+  });
+
+  it('logs an expired interaction and returns a controlled page', async () => {
+    const { controller, oidc, templates, errorLogger } = createController();
+    const response = responseMock();
+    oidc.interactionDetails.mockRejectedValue(new Error('SessionNotFound'));
+    jest.spyOn(console, 'error').mockImplementation();
+    jest.spyOn(Logger.prototype, 'warn').mockImplementation();
+
+    await controller.view('uid', request, response);
+
+    expect(errorLogger.log).toHaveBeenCalledWith(expect.objectContaining({
+      code: 'OIDC_INTERACTION_SESSION_NOT_FOUND',
+      handled: true,
+    }));
+    expect(templates.renderError).toHaveBeenCalledWith(expect.objectContaining({ title: 'Anmeldung abgelaufen' }));
+    expect(response.status).toHaveBeenCalledWith(400);
+    jest.restoreAllMocks();
+  });
+
+  it('rethrows unexpected login errors for global error handling', async () => {
+    const { controller, oidc } = createController();
+    const response = responseMock();
+    oidc.finishLogin.mockRejectedValue(new Error('provider unavailable'));
+
+    await expect(
+      controller.login('uid', { username: 'maria', password: 'secret' }, request, response),
+    ).rejects.toThrow('provider unavailable');
+  });
+});
diff --git a/apps/api/src/oidc/oidc-interaction.controller.ts b/apps/api/src/oidc/oidc-interaction.controller.ts
index 8bdc746..07a1fc2 100644
--- a/apps/api/src/oidc/oidc-interaction.controller.ts
+++ b/apps/api/src/oidc/oidc-interaction.controller.ts
@@ -5,6 +5,7 @@ import type { Interaction } from 'oidc-provider';
 import { ApplicationErrorCategory, ApplicationErrorCode } from '../application-error-log/application-error-codes';
 import { ApplicationErrorLoggerService } from '../application-error-log/application-error-logger.service';
 import { RequestContextService } from '../common/request-context.service';
+import { OidcInteractionTemplateService } from './oidc-interaction-template.service';
 import { OidcProviderService } from './oidc-provider.service';
 
 @Controller('interaction')
@@ -14,6 +15,7 @@ export class OidcInteractionController {
   constructor(
     private readonly oidc: OidcProviderService,
     private readonly config: ConfigService,
+    private readonly templates: OidcInteractionTemplateService,
     private readonly applicationErrorLogger: ApplicationErrorLoggerService,
     private readonly requestContext: RequestContextService,
   ) {}
@@ -25,21 +27,24 @@ export class OidcInteractionController {
       details = await this.oidc.interactionDetails(request, response);
     } catch (error) {
       await this.logInteractionSessionError(error, uid, request);
-      response.status(400).send(
-        this.page(
-          'Anmeldung abgelaufen',
-          '<p>Die Anmeldung konnte nicht fortgesetzt werden. Bitte starte den Login in der Anwendung erneut.</p>',
-        ),
-      );
+      const page = await this.templates.renderError({
+        title: 'Anmeldung abgelaufen',
+        message: 'Die Anmeldung konnte nicht fortgesetzt werden. Bitte starte den Login in der Anwendung erneut.',
+      });
+      response.status(400).send(page);
       return;
     }
     if (details.uid !== uid) {
-      response.status(400).send(this.page('Ungueltige Anfrage', '<p>Die OIDC-Interaktion ist ungueltig.</p>'));
+      const page = await this.templates.renderError({
+        title: 'Ungueltige Anfrage',
+        message: 'Die OIDC-Interaktion ist ungueltig.',
+      });
+      response.status(400).send(page);
       return;
     }
 
     if (details.prompt.name === 'login') {
-      response.send(this.page('Anmelden', this.loginForm(uid)));
+      response.send(await this.templates.renderLogin({ uid, registrationUrl: this.registrationUrl }));
       return;
     }
 
@@ -50,11 +55,21 @@ export class OidcInteractionController {
         return;
       }
 
-      response.send(this.page('Zugriff erlauben', this.consentView(uid, details)));
+      const clientName = String(details.params.name ?? (clientId || 'Unbekannte Anwendung'));
+      const redirectUri = String(details.params.redirect_uri ?? '');
+      const scopes = String(details.params.scope ?? 'openid')
+        .split(/\s+/)
+        .map((item) => item.trim())
+        .filter(Boolean);
+      response.send(await this.templates.renderConsent({ uid, clientName, redirectUri, scopes }));
       return;
     }
 
-    response.status(400).send(this.page('OIDC', '<p>Diese Interaktion wird noch nicht unterstuetzt.</p>'));
+    const page = await this.templates.renderError({
+      title: 'OIDC',
+      message: 'Diese Interaktion wird noch nicht unterstuetzt.',
+    });
+    response.status(400).send(page);
   }
 
   @Post(':uid/login')
@@ -69,9 +84,13 @@ export class OidcInteractionController {
       await this.oidc.finishLogin(request, response, uid, username, body.password ?? '');
     } catch (error) {
       if (this.isInvalidCredentialsError(error)) {
-        response
-          .status(401)
-          .send(this.page('Anmelden', this.loginForm(uid, username, 'Ungueltige Zugangsdaten.')));
+        const page = await this.templates.renderLogin({
+          uid,
+          username,
+          errorMessage: 'Ungueltige Zugangsdaten.',
+          registrationUrl: this.registrationUrl,
+        });
+        response.status(401).send(page);
         return;
       }
 
@@ -89,122 +108,6 @@ export class OidcInteractionController {
     await this.oidc.abortInteraction(request, response);
   }
 
-  private loginForm(uid: string, username = '', errorMessage = ''): string {
-    const encodedUid = encodeURIComponent(uid);
-    const error = errorMessage
-      ? `<p class="message error" role="alert">${this.escape(errorMessage)}</p>`
-      : '';
-
-    return `
-            ${error}
-            <form method="post" action="/interaction/${encodedUid}/login">
-              <label>Benutzername <input name="username" autocomplete="username" value="${this.escape(username)}" required></label>
-              <label>Passwort <input name="password" type="password" autocomplete="current-password" required autofocus></label>
-              <button type="submit">Anmelden</button>
-            </form>
-            <form method="post" action="/interaction/${encodedUid}/abort">
-              <button class="secondary" type="submit">Abbrechen</button>
-            </form>
-            <p class="form-link"><a href="${this.escape(this.registrationUrl)}">Neues Konto registrieren</a></p>
-          `;
-  }
-
-  private consentView(uid: string, details: Interaction): string {
-    const encodedUid = encodeURIComponent(uid);
-    const clientId = String(details.params.client_id ?? '');
-    const clientName = String(details.params.name ?? (clientId || 'Unbekannte Anwendung'));
-    const redirectUri = String(details.params.redirect_uri ?? '');
-    const scope = String(details.params.scope ?? 'openid');
-
-    return `
-            <p class="intro">Die Anwendung <strong>${this.escape(clientName)}</strong> moechte auf dein Konto zugreifen.</p>
-            ${redirectUri ? `<dl class="consent-details"><div><dt>Weiterleitung</dt><dd>${this.escape(redirectUri)}</dd></div></dl>` : ''}
-            <div class="scope-list" aria-label="Angeforderte Berechtigungen">
-              ${this.scopeItems(scope)}
-            </div>
-            <form method="post" action="/interaction/${encodedUid}/confirm">
-              <button type="submit">Zugriff erlauben</button>
-            </form>
-            <form method="post" action="/interaction/${encodedUid}/abort">
-              <button class="secondary" type="submit">Ablehnen</button>
-            </form>
-          `;
-  }
-
-  private scopeItems(scope: string): string {
-    const scopes = scope
-      .split(/\s+/)
-      .map((item) => item.trim())
-      .filter(Boolean);
-
-    return scopes
-      .map(
-        (item) => `
-              <section class="scope-item">
-                <strong>${this.escape(item)}</strong>
-                <span>${this.escape(this.scopeDescription(item))}</span>
-              </section>
-            `,
-      )
-      .join('');
-  }
-
-  private scopeDescription(scope: string): string {
-    const descriptions: Record<string, string> = {
-      openid: 'Anmeldung per OpenID Connect bestaetigen.',
-      profile: 'Profilinformationen wie Name und Anzeigename lesen.',
-      email: 'E-Mail-Adresse lesen.',
-      groups: 'Gruppenmitgliedschaften lesen.',
-      offline_access: 'Laengerfristigen Zugriff ueber Refresh Tokens erlauben.',
-    };
-
-    return descriptions[scope] ?? 'Diese Berechtigung wurde von der Anwendung angefordert.';
-  }
-
-  private page(title: string, body: string): string {
-    return `<!doctype html>
-      <html lang="de">
-        <head>
-          <meta charset="utf-8">
-          <meta name="viewport" content="width=device-width, initial-scale=1">
-          <title>${this.escape(title)} - LDAP Portal</title>
-          <style>
-            body { background: #f5f7f9; color: #18202a; font-family: Inter, system-ui, sans-serif; margin: 0; min-height: 100vh; display: grid; place-items: center; padding: 20px; }
-            main { background: white; border: 1px solid #d8e0e7; border-radius: 8px; box-shadow: 0 16px 40px rgb(24 32 42 / 8%); max-width: 460px; padding: 28px; width: 100%; }
-            h1 { font-size: 1.45rem; margin: 0 0 22px; }
-            form { display: grid; gap: 16px; margin-top: 16px; }
-            label { display: grid; gap: 7px; font-weight: 700; }
-            input { border: 1px solid #bcc8d3; border-radius: 6px; font: inherit; min-height: 44px; padding: 10px 12px; }
-            button { background: #0f6b6e; border: 1px solid #0f6b6e; border-radius: 6px; color: white; cursor: pointer; font: inherit; font-weight: 700; min-height: 44px; padding: 10px 14px; }
-            button.secondary { background: white; color: #0f6b6e; }
-            a { color: #0f6b6e; font-weight: 700; text-decoration: none; }
-            a:hover { text-decoration: underline; }
-            .form-link { margin: 16px 0 0; text-align: center; }
-            .intro { color: #3a4551; line-height: 1.45; margin: 0 0 16px; }
-            .message { background: #edf7f4; border: 1px solid #b8ddd3; border-radius: 6px; color: #24564f; margin: 0 0 16px; padding: 12px; }
-            .message.error { background: #fff1f0; border-color: #efb5ae; color: #8d2b20; }
-            .consent-details { display: grid; gap: 10px; margin: 0 0 16px; }
-            .consent-details div { display: grid; gap: 5px; }
-            dt { color: #637083; font-size: 0.82rem; font-weight: 700; }
-            dd { margin: 0; overflow-wrap: anywhere; }
-            .scope-list { display: grid; gap: 8px; margin: 16px 0; }
-            .scope-item { border: 1px solid #d8e0e7; border-radius: 6px; display: grid; gap: 4px; padding: 10px 12px; }
-            .scope-item span { color: #637083; font-size: 0.9rem; line-height: 1.35; }
-          </style>
-        </head>
-        <body><main><h1>${this.escape(title)}</h1>${body}</main></body>
-      </html>`;
-  }
-
-  private escape(value: string): string {
-    return value
-      .replaceAll('&', '&amp;')
-      .replaceAll('<', '&lt;')
-      .replaceAll('>', '&gt;')
-      .replaceAll('"', '&quot;')
-      .replaceAll("'", '&#039;');
-  }
-
   private get registrationUrl(): string {
     const publicWebUrl = this.config.get<string>('PUBLIC_WEB_URL') ?? 'http://localhost:4200';
     return `${publicWebUrl.replace(/\/+$/, '')}/register`;
diff --git a/apps/api/src/oidc/oidc.module.ts b/apps/api/src/oidc/oidc.module.ts
index 5a7cb3b..d8a1c79 100644
--- a/apps/api/src/oidc/oidc.module.ts
+++ b/apps/api/src/oidc/oidc.module.ts
@@ -11,6 +11,7 @@ import { OidcAdminClientsController } from './oidc-admin-clients.controller';
 import { OidcAdminGuard } from './oidc-admin.guard';
 import { OidcClientService } from './oidc-client.service';
 import { OidcInteractionController } from './oidc-interaction.controller';
+import { OidcInteractionTemplateService } from './oidc-interaction-template.service';
 import { OidcProviderService } from './oidc-provider.service';
 
 @Module({
@@ -26,6 +27,6 @@ import { OidcProviderService } from './oidc-provider.service';
     AuditModule,
   ],
   controllers: [OidcAdminClientsController, OidcInteractionController],
-  providers: [OidcAdminGuard, OidcClientService, OidcProviderService],
+  providers: [OidcAdminGuard, OidcClientService, OidcInteractionTemplateService, OidcProviderService],
 })
 export class OidcModule {}
diff --git a/apps/api/src/oidc/templates/consent.hbs b/apps/api/src/oidc/templates/consent.hbs
new file mode 100644
index 0000000..d560eb1
--- /dev/null
+++ b/apps/api/src/oidc/templates/consent.hbs
@@ -0,0 +1,23 @@
+<p class="intro">Die Anwendung <strong>{{clientName}}</strong> m&ouml;chte auf dein Konto zugreifen.</p>
+{{#if redirectUri}}
+  <dl class="consent-details">
+    <div>
+      <dt>Weiterleitung</dt>
+      <dd>{{redirectUri}}</dd>
+    </div>
+  </dl>
+{{/if}}
+<div class="scope-list" aria-label="Angeforderte Berechtigungen">
+  {{#each scopes}}
+    <section class="scope-item">
+      <strong>{{name}}</strong>
+      <span>{{description}}</span>
+    </section>
+  {{/each}}
+</div>
+<form method="post" action="{{confirmAction}}">
+  <button type="submit">Zugriff erlauben</button>
+</form>
+<form method="post" action="{{abortAction}}">
+  <button class="secondary" type="submit">Ablehnen</button>
+</form>
diff --git a/apps/api/src/oidc/templates/error.hbs b/apps/api/src/oidc/templates/error.hbs
new file mode 100644
index 0000000..101d58a
--- /dev/null
+++ b/apps/api/src/oidc/templates/error.hbs
@@ -0,0 +1 @@
+<p class="intro">{{message}}</p>
diff --git a/apps/api/src/oidc/templates/layouts/base.hbs b/apps/api/src/oidc/templates/layouts/base.hbs
new file mode 100644
index 0000000..75103e4
--- /dev/null
+++ b/apps/api/src/oidc/templates/layouts/base.hbs
@@ -0,0 +1,113 @@
+<!doctype html>
+<html lang="de">
+  <head>
+    <meta charset="utf-8">
+    <meta name="viewport" content="width=device-width, initial-scale=1">
+    <meta name="color-scheme" content="light">
+    <title>{{title}} - {{branding.productName}}</title>
+    <style>
+      * { box-sizing: border-box; }
+      body {
+        background: #f3f6f7;
+        color: #18202a;
+        font-family: Arial, Helvetica, sans-serif;
+        margin: 0;
+        min-height: 100vh;
+        padding: 24px;
+      }
+      .page {
+        align-items: center;
+        display: flex;
+        justify-content: center;
+        min-height: calc(100vh - 48px);
+      }
+      main {
+        background: #ffffff;
+        border: 1px solid #d8e0e7;
+        border-radius: 8px;
+        box-shadow: 0 16px 40px rgb(24 32 42 / 8%);
+        max-width: 460px;
+        overflow: hidden;
+        width: 100%;
+      }
+      .brand {
+        align-items: center;
+        border-bottom: 1px solid #e7ecef;
+        display: flex;
+        gap: 12px;
+        min-height: 68px;
+        padding: 16px 28px;
+      }
+      .brand img { display: block; max-height: 36px; max-width: 180px; }
+      .brand-name { color: #26313d; font-size: 1rem; font-weight: 700; }
+      .content { padding: 28px; }
+      h1 { font-size: 1.45rem; letter-spacing: 0; margin: 0 0 22px; }
+      form { display: grid; gap: 16px; margin-top: 16px; }
+      label { display: grid; gap: 7px; font-weight: 700; }
+      input {
+        border: 1px solid #aebbc7;
+        border-radius: 6px;
+        color: #18202a;
+        font: inherit;
+        min-height: 44px;
+        padding: 10px 12px;
+        width: 100%;
+      }
+      input:focus { border-color: {{branding.primaryColor}}; outline: 3px solid rgb(15 107 110 / 18%); }
+      button {
+        background: {{branding.primaryColor}};
+        border: 1px solid {{branding.primaryColor}};
+        border-radius: 6px;
+        color: #ffffff;
+        cursor: pointer;
+        font: inherit;
+        font-weight: 700;
+        min-height: 44px;
+        padding: 10px 14px;
+        width: 100%;
+      }
+      button:hover { filter: brightness(0.92); }
+      button:focus-visible, a:focus-visible { outline: 3px solid rgb(15 107 110 / 25%); outline-offset: 2px; }
+      button.secondary { background: #ffffff; color: {{branding.primaryColor}}; }
+      a { color: {{branding.primaryColor}}; font-weight: 700; overflow-wrap: anywhere; text-decoration: none; }
+      a:hover { text-decoration: underline; }
+      .form-link { margin: 18px 0 0; text-align: center; }
+      .intro { color: #3a4551; line-height: 1.5; margin: 0 0 16px; }
+      .message { border-radius: 6px; line-height: 1.45; margin: 0 0 16px; padding: 12px; }
+      .message.error { background: #fff1f0; border: 1px solid #efb5ae; color: #8d2b20; }
+      .consent-details { display: grid; gap: 10px; margin: 0 0 16px; }
+      .consent-details div { display: grid; gap: 5px; }
+      dt { color: #637083; font-size: 0.82rem; font-weight: 700; }
+      dd { margin: 0; overflow-wrap: anywhere; }
+      .scope-list { display: grid; gap: 8px; margin: 16px 0; }
+      .scope-item { border: 1px solid #d8e0e7; border-radius: 6px; display: grid; gap: 4px; padding: 10px 12px; }
+      .scope-item span { color: #637083; font-size: 0.9rem; line-height: 1.35; }
+      footer { color: #637083; font-size: 0.78rem; line-height: 1.4; padding: 0 28px 24px; text-align: center; }
+      @media (max-width: 520px) {
+        body { padding: 12px; }
+        .page { min-height: calc(100vh - 24px); }
+        .brand { padding: 14px 20px; }
+        .content { padding: 24px 20px; }
+        footer { padding: 0 20px 20px; }
+      }
+    </style>
+  </head>
+  <body>
+    <div class="page">
+      <main>
+        <header class="brand">
+          {{#if branding.logoUrl}}
+            <img src="{{branding.logoUrl}}" alt="{{branding.productName}}">
+          {{else}}
+            <span class="brand-name">{{branding.productName}}</span>
+          {{/if}}
+        </header>
+        <section class="content">
+          <h1>{{title}}</h1>
+          {{{body}}}
+        </section>
+        <footer>{{branding.companyName}}</footer>
+      </main>
+    </div>
+  </body>
+</html>
diff --git a/apps/api/src/oidc/templates/login.hbs b/apps/api/src/oidc/templates/login.hbs
new file mode 100644
index 0000000..ddd28e9
--- /dev/null
+++ b/apps/api/src/oidc/templates/login.hbs
@@ -0,0 +1,18 @@
+{{#if errorMessage}}
+  <p class="message error" role="alert">{{errorMessage}}</p>
+{{/if}}
+<form method="post" action="{{loginAction}}">
+  <label>
+    Benutzername
+    <input name="username" autocomplete="username" value="{{username}}" required>
+  </label>
+  <label>
+    Passwort
+    <input name="password" type="password" autocomplete="current-password" required autofocus>
+  </label>
+  <button type="submit">Anmelden</button>
+</form>
+<form method="post" action="{{abortAction}}">
+  <button class="secondary" type="submit">Abbrechen</button>
+</form>
+<p class="form-link"><a href="{{registrationUrl}}">Neues Konto registrieren</a></p>