diff --git a/app/src/lib/render/markdown.node.test.ts b/app/src/lib/render/markdown.node.test.ts
new file mode 100644
index 0000000..2b45889
--- /dev/null
+++ b/app/src/lib/render/markdown.node.test.ts
@@ -0,0 +1,26 @@
+// app/src/lib/render/markdown.node.test.ts
+// @vitest-environment node
+import { describe, it, expect } from 'vitest';
+import { renderMarkdown } from './markdown';
+
+describe('renderMarkdown (Node-Kontext)', () => {
+  it('rendert einfaches Markdown im Node-Build ohne window', () => {
+    const html = renderMarkdown('# Hallo\n\nWelt mit *Kursiv* und [Link](https://example.com)');
+    expect(html).toContain('<h1');
+    expect(html).toContain('Hallo');
+    expect(html).toContain('<em>Kursiv</em>');
+    expect(html).toContain('href="https://example.com"');
+  });
+
+  it('sanitisiert XSS-Versuche', () => {
+    const html = renderMarkdown('<script>alert(1)</script>\n\nText');
+    expect(html).not.toContain('<script');
+    expect(html).toContain('Text');
+  });
+
+  it('hebt code-blocks mit highlight.js hervor', () => {
+    const html = renderMarkdown('```ts\nconst x: number = 1;\n```');
+    expect(html).toContain('class="hljs');
+    expect(html).toContain('language-ts');
+  });
+});