diff --git a/apps/web/src/app/(portal)/modules/tender-radar/components/TenderDetail.test.tsx b/apps/web/src/app/(portal)/modules/tender-radar/components/TenderDetail.test.tsx
new file mode 100644
index 0000000..5e792bb
--- /dev/null
+++ b/apps/web/src/app/(portal)/modules/tender-radar/components/TenderDetail.test.tsx
@@ -0,0 +1,125 @@
+import { cleanup, render, screen, waitFor } from '@testing-library/react';
+import { afterEach, describe, expect, it, vi } from 'vitest';
+
+/**
+ * TenderDetail.test — RED-first (TDD) proof for Plan 11-04 (UI-02, D-07).
+ * Mirrors the SourceConfigForm.test.tsx pattern: mock the api client
+ * module (getTender), render with a tenderId prop, assert via waitFor.
+ *
+ * Covers the three must-have truths from the plan:
+ * (a) a source link is rendered and points at the tender's sourceUrl
+ *     with a safe target/rel combination (T-11-09).
+ * (b) estimatedValue=null and deadlineAt=null render graceful German
+ *     placeholders instead of blank/error output (D-05 applies equally
+ *     to the detail view, not just the list).
+ * (c) the mandatory no-local-mirroring notice is always present — no
+ *     Vergabeunterlagen are fetched or mirrored locally (rawPayload is
+ *     100% NULL in the live DB; research finding, no document URLs
+ *     exist to mirror in the first place).
+ */
+
+const mockGetTender = vi.fn();
+
+vi.mock('@/lib/tender-radar-api', () => ({
+  getTender: (...args: unknown[]) => mockGetTender(...args),
+}));
+
+afterEach(() => {
+  cleanup();
+  mockGetTender.mockReset();
+  vi.restoreAllMocks();
+});
+
+describe('TenderDetail', () => {
+  it('renders a source link pointing at the tender sourceUrl with safe target/rel', async () => {
+    mockGetTender.mockResolvedValue({
+      id: 't1',
+      sourcePortal: 'doe-opendata',
+      title: 'Sanierung Rathaus',
+      buyerName: 'Stadt Musterhausen',
+      cpvCodes: ['45000000'],
+      region: 'Oberbayern',
+      plz: '80331',
+      bundesland: 'Bayern',
+      deadlineAt: '2026-09-01T00:00:00.000Z',
+      estimatedValue: '150000.00',
+      procedureType: 'Offenes Verfahren',
+      status: 'active',
+      sourceUrl: 'https://example-portal.de/ausschreibung/t1',
+      publishedAt: '2026-07-01T00:00:00.000Z',
+    });
+
+    const { TenderDetail } = await import('./TenderDetail');
+    render(<TenderDetail tenderId="t1" onClose={() => {}} />);
+
+    await waitFor(() => {
+      expect(screen.getByText('Sanierung Rathaus')).toBeInTheDocument();
+    });
+
+    const link = screen.getByRole('link', { name: /Quellportal/i });
+    expect(link).toHaveAttribute(
+      'href',
+      'https://example-portal.de/ausschreibung/t1',
+    );
+    expect(link).toHaveAttribute('target', '_blank');
+    expect(link).toHaveAttribute('rel', 'noopener noreferrer');
+    expect(mockGetTender).toHaveBeenCalledWith('t1');
+  });
+
+  it('shows graceful placeholders when estimatedValue and deadlineAt are null', async () => {
+    mockGetTender.mockResolvedValue({
+      id: 't2',
+      sourcePortal: 'doe-opendata',
+      title: 'Straßenbau Projekt X',
+      buyerName: null,
+      cpvCodes: [],
+      region: null,
+      plz: null,
+      bundesland: null,
+      deadlineAt: null,
+      estimatedValue: null,
+      procedureType: null,
+      status: 'active',
+      sourceUrl: null,
+      publishedAt: '2026-07-01T00:00:00.000Z',
+    });
+
+    const { TenderDetail } = await import('./TenderDetail');
+    render(<TenderDetail tenderId="t2" onClose={() => {}} />);
+
+    await waitFor(() => {
+      expect(screen.getByText('Straßenbau Projekt X')).toBeInTheDocument();
+    });
+    expect(screen.getByText('keine Wertangabe')).toBeInTheDocument();
+    expect(screen.getByText('keine Frist angegeben')).toBeInTheDocument();
+  });
+
+  it('always shows the no-local-mirroring notice for Vergabeunterlagen', async () => {
+    mockGetTender.mockResolvedValue({
+      id: 't3',
+      sourcePortal: 'doe-opendata',
+      title: 'Beschaffung IT-Ausstattung',
+      buyerName: 'Landkreis Beispiel',
+      cpvCodes: ['30200000'],
+      region: null,
+      plz: null,
+      bundesland: null,
+      deadlineAt: '2026-08-15T00:00:00.000Z',
+      estimatedValue: '25000.00',
+      procedureType: 'Verhandlungsverfahren',
+      status: 'active',
+      sourceUrl: 'https://example-portal.de/ausschreibung/t3',
+      publishedAt: '2026-07-01T00:00:00.000Z',
+    });
+
+    const { TenderDetail } = await import('./TenderDetail');
+    render(<TenderDetail tenderId="t3" onClose={() => {}} />);
+
+    await waitFor(() => {
+      expect(screen.getByText('Beschaffung IT-Ausstattung')).toBeInTheDocument();
+    });
+    expect(
+      screen.getByText(/Vergabeunterlagen werden nicht lokal gespiegelt/i),
+    ).toBeInTheDocument();
+  });
+});