diff --git a/apps/api/src/tenders/tender-saved-search.service.spec.ts b/apps/api/src/tenders/tender-saved-search.service.spec.ts
new file mode 100644
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+++ b/apps/api/src/tenders/tender-saved-search.service.spec.ts
@@ -0,0 +1,187 @@
+import { ConflictException, NotFoundException } from '@nestjs/common';
+import { describe, expect, it } from 'vitest';
+import { TenderSavedSearchService } from './tender-saved-search.service';
+
+/**
+ * TenderSavedSearchService.spec — RED-first (TDD) proof for FILTER-06
+ * (D-08/D-11) and the V4/IDOR access-control invariant (T-11-14):
+ *
+ * - create() scopes to (userId, tenantId); a second profile with the same
+ *   name for the SAME user is rejected (@@unique([userId,name])) — the
+ *   same name IS allowed across different users (scoped per-user, not
+ *   globally unique).
+ * - list() is scoped strictly by userId — a foreign userId sees nothing
+ *   (IDOR).
+ * - update()/remove() verify userId ownership before mutating, throwing
+ *   NotFoundException for both a missing row AND a foreign-owned row
+ *   (FavoritesService pattern — never distinguishes the two, to avoid
+ *   leaking existence of another user's profile).
+ *
+ * Uses the same hand-rolled prisma-shaped fake convention as
+ * tender-triage.service.spec.ts / tenders.controller.spec.ts (in-memory
+ * Map, no live DB connection). The fake simulates Prisma's P2002 unique-
+ * constraint violation the same way a live Postgres unique index would.
+ */
+
+function makeFakePrisma() {
+  const rows = new Map<string, any>();
+  let counter = 0;
+
+  function findByUserAndName(userId: string, name: string, excludeId?: string) {
+    return Array.from(rows.values()).find(
+      (r) => r.userId === userId && r.name === name && r.id !== excludeId,
+    );
+  }
+
+  function throwUniqueViolation(): never {
+    const err: any = new Error('Unique constraint failed on the fields: (`userId`,`name`)');
+    err.code = 'P2002';
+    throw err;
+  }
+
+  return {
+    tenderSavedSearch: {
+      create: async ({ data }: any) => {
+        if (findByUserAndName(data.userId, data.name)) throwUniqueViolation();
+        counter += 1;
+        const record = {
+          id: `ss-${counter}`,
+          ...data,
+          createdAt: new Date(),
+          updatedAt: new Date(),
+        };
+        rows.set(record.id, record);
+        return record;
+      },
+      findMany: async ({ where }: any) =>
+        Array.from(rows.values()).filter((r) => r.userId === where.userId),
+      findUnique: async ({ where }: any) => rows.get(where.id) ?? null,
+      update: async ({ where, data }: any) => {
+        const existing = rows.get(where.id);
+        const nextName = data.name ?? existing.name;
+        if (findByUserAndName(existing.userId, nextName, existing.id)) {
+          throwUniqueViolation();
+        }
+        const record = { ...existing, ...data, updatedAt: new Date() };
+        rows.set(where.id, record);
+        return record;
+      },
+      delete: async ({ where }: any) => {
+        rows.delete(where.id);
+      },
+    },
+  };
+}
+
+describe('TenderSavedSearchService', () => {
+  it('create() creates a row scoped to userId + tenantId', async () => {
+    const prisma = makeFakePrisma();
+    const service = new TenderSavedSearchService(prisma as any);
+
+    const result = await service.create('u1', 'tenant1', {
+      name: 'Bau NRW',
+      filters: { q: 'Bau', bundesland: 'Nordrhein-Westfalen' },
+    });
+
+    expect(result.userId).toBe('u1');
+    expect(result.tenantId).toBe('tenant1');
+    expect(result.name).toBe('Bau NRW');
+    expect(result.filters).toEqual({ q: 'Bau', bundesland: 'Nordrhein-Westfalen' });
+  });
+
+  it('create() rejects a second profile with the same name for the same user (@@unique([userId,name]))', async () => {
+    const prisma = makeFakePrisma();
+    const service = new TenderSavedSearchService(prisma as any);
+
+    await service.create('u1', 'tenant1', { name: 'Bau NRW', filters: {} });
+
+    await expect(
+      service.create('u1', 'tenant1', { name: 'Bau NRW', filters: {} }),
+    ).rejects.toBeInstanceOf(ConflictException);
+  });
+
+  it('create() allows the same name for two different users (unique is scoped per-user, not global)', async () => {
+    const prisma = makeFakePrisma();
+    const service = new TenderSavedSearchService(prisma as any);
+
+    await service.create('u1', 'tenant1', { name: 'Bau NRW', filters: {} });
+    const result = await service.create('u2', 'tenant1', { name: 'Bau NRW', filters: {} });
+
+    expect(result.userId).toBe('u2');
+  });
+
+  it('list() scopes strictly by userId — a foreign user sees nothing (V4 / IDOR)', async () => {
+    const prisma = makeFakePrisma();
+    const service = new TenderSavedSearchService(prisma as any);
+
+    await service.create('u1', 'tenant1', { name: 'Bau NRW', filters: {} });
+
+    expect(await service.list('u2')).toEqual([]);
+    expect(await service.list('u1')).toHaveLength(1);
+  });
+
+  it('update() applies a rename + filters change when owned by the caller', async () => {
+    const prisma = makeFakePrisma();
+    const service = new TenderSavedSearchService(prisma as any);
+
+    const created = await service.create('u1', 'tenant1', { name: 'Alt', filters: { q: 'x' } });
+    const updated = await service.update(created.id, 'u1', {
+      name: 'Neu',
+      filters: { q: 'y' },
+    });
+
+    expect(updated.name).toBe('Neu');
+    expect(updated.filters).toEqual({ q: 'y' });
+  });
+
+  it('update() throws NotFoundException when the row is owned by a different user (ownership check, IDOR)', async () => {
+    const prisma = makeFakePrisma();
+    const service = new TenderSavedSearchService(prisma as any);
+
+    const created = await service.create('u1', 'tenant1', { name: 'Alt', filters: {} });
+
+    await expect(
+      service.update(created.id, 'u2', { name: 'Uebernahme' }),
+    ).rejects.toBeInstanceOf(NotFoundException);
+  });
+
+  it('update() throws NotFoundException for a nonexistent id', async () => {
+    const prisma = makeFakePrisma();
+    const service = new TenderSavedSearchService(prisma as any);
+
+    await expect(
+      service.update('missing', 'u1', { name: 'x' }),
+    ).rejects.toBeInstanceOf(NotFoundException);
+  });
+
+  it('update() rejects a rename that collides with another of this user\'s existing profiles', async () => {
+    const prisma = makeFakePrisma();
+    const service = new TenderSavedSearchService(prisma as any);
+
+    await service.create('u1', 'tenant1', { name: 'Erstes Profil', filters: {} });
+    const second = await service.create('u1', 'tenant1', { name: 'Zweites Profil', filters: {} });
+
+    await expect(
+      service.update(second.id, 'u1', { name: 'Erstes Profil' }),
+    ).rejects.toBeInstanceOf(ConflictException);
+  });
+
+  it('remove() throws NotFoundException when the row is owned by a different user (ownership check, IDOR)', async () => {
+    const prisma = makeFakePrisma();
+    const service = new TenderSavedSearchService(prisma as any);
+
+    const created = await service.create('u1', 'tenant1', { name: 'Alt', filters: {} });
+
+    await expect(service.remove(created.id, 'u2')).rejects.toBeInstanceOf(NotFoundException);
+  });
+
+  it('remove() deletes the row when owned by the caller', async () => {
+    const prisma = makeFakePrisma();
+    const service = new TenderSavedSearchService(prisma as any);
+
+    const created = await service.create('u1', 'tenant1', { name: 'Alt', filters: {} });
+    await service.remove(created.id, 'u1');
+
+    expect(await service.list('u1')).toEqual([]);
+  });
+});