diff --git a/apps/contacts/apps/web/package.json b/apps/contacts/apps/web/package.json
index db0b9a64d..a40f8cb62 100644
--- a/apps/contacts/apps/web/package.json
+++ b/apps/contacts/apps/web/package.json
@@ -9,7 +9,9 @@
 		"check": "svelte-kit sync && svelte-check --tsconfig ./tsconfig.json",
 		"check:watch": "svelte-kit sync && svelte-check --tsconfig ./tsconfig.json --watch",
 		"lint": "eslint .",
-		"format": "prettier --write ."
+		"format": "prettier --write .",
+		"test": "vitest run",
+		"test:watch": "vitest"
 	},
 	"devDependencies": {
 		"@manacore/shared-pwa": "workspace:*",
diff --git a/apps/contacts/apps/web/src/lib/api/contacts.test.ts b/apps/contacts/apps/web/src/lib/api/contacts.test.ts
new file mode 100644
index 000000000..9678124eb
--- /dev/null
+++ b/apps/contacts/apps/web/src/lib/api/contacts.test.ts
@@ -0,0 +1,287 @@
+import { describe, it, expect, vi, beforeEach } from 'vitest';
+
+// Mock the client module
+vi.mock('./client', () => ({
+	fetchWithAuth: vi.fn(),
+	fetchWithAuthFormData: vi.fn(),
+}));
+
+// Mock $app/environment
+vi.mock('$app/environment', () => ({
+	browser: true,
+}));
+
+// Mock auth store
+vi.mock('$lib/stores/auth.svelte', () => ({
+	authStore: {
+		getAccessToken: vi.fn().mockResolvedValue('mock-token'),
+		getValidToken: vi.fn().mockResolvedValue('mock-token'),
+	},
+}));
+
+// Mock shared-tags
+vi.mock('@manacore/shared-tags', () => ({
+	createTagsClient: vi.fn(() => ({
+		getAll: vi.fn().mockResolvedValue([]),
+		create: vi.fn(),
+		update: vi.fn(),
+		delete: vi.fn(),
+		createDefaults: vi.fn().mockResolvedValue([]),
+	})),
+}));
+
+import { contactsApi, notesApi, activitiesApi } from './contacts';
+import { fetchWithAuth } from './client';
+
+const mockFetch = vi.mocked(fetchWithAuth);
+
+beforeEach(() => {
+	vi.clearAllMocks();
+});
+
+describe('contactsApi', () => {
+	describe('list', () => {
+		it('should fetch contacts without filters', async () => {
+			mockFetch.mockResolvedValue({ contacts: [], total: 0 });
+
+			const result = await contactsApi.list();
+
+			expect(mockFetch).toHaveBeenCalledWith('/contacts');
+			expect(result).toEqual({ contacts: [], total: 0 });
+		});
+
+		it('should build query string with search filter', async () => {
+			mockFetch.mockResolvedValue({ contacts: [], total: 0 });
+
+			await contactsApi.list({ search: 'Max' });
+
+			expect(mockFetch).toHaveBeenCalledWith('/contacts?search=Max');
+		});
+
+		it('should build query string with multiple filters', async () => {
+			mockFetch.mockResolvedValue({ contacts: [], total: 0 });
+
+			await contactsApi.list({
+				search: 'Max',
+				isFavorite: true,
+				limit: 50,
+				offset: 10,
+			});
+
+			const callArg = mockFetch.mock.calls[0][0];
+			expect(callArg).toContain('search=Max');
+			expect(callArg).toContain('isFavorite=true');
+			expect(callArg).toContain('limit=50');
+			expect(callArg).toContain('offset=10');
+		});
+
+		it('should include tagId filter', async () => {
+			mockFetch.mockResolvedValue({ contacts: [], total: 0 });
+
+			await contactsApi.list({ tagId: 'tag-123' });
+
+			expect(mockFetch).toHaveBeenCalledWith('/contacts?tagId=tag-123');
+		});
+
+		it('should include isArchived filter', async () => {
+			mockFetch.mockResolvedValue({ contacts: [], total: 0 });
+
+			await contactsApi.list({ isArchived: true });
+
+			expect(mockFetch).toHaveBeenCalledWith('/contacts?isArchived=true');
+		});
+	});
+
+	describe('get', () => {
+		it('should fetch a single contact', async () => {
+			const contact = { id: 'c1', firstName: 'Max' };
+			mockFetch.mockResolvedValue({ contact });
+
+			const result = await contactsApi.get('c1');
+
+			expect(mockFetch).toHaveBeenCalledWith('/contacts/c1');
+			expect(result).toEqual(contact);
+		});
+	});
+
+	describe('create', () => {
+		it('should POST new contact', async () => {
+			const contact = { id: 'c1', firstName: 'Max' };
+			mockFetch.mockResolvedValue({ contact });
+
+			const result = await contactsApi.create({ firstName: 'Max' });
+
+			expect(mockFetch).toHaveBeenCalledWith('/contacts', {
+				method: 'POST',
+				body: JSON.stringify({ firstName: 'Max' }),
+			});
+			expect(result).toEqual(contact);
+		});
+	});
+
+	describe('update', () => {
+		it('should PATCH existing contact', async () => {
+			const contact = { id: 'c1', firstName: 'Maximilian' };
+			mockFetch.mockResolvedValue({ contact });
+
+			const result = await contactsApi.update('c1', { firstName: 'Maximilian' });
+
+			expect(mockFetch).toHaveBeenCalledWith('/contacts/c1', {
+				method: 'PATCH',
+				body: JSON.stringify({ firstName: 'Maximilian' }),
+			});
+			expect(result).toEqual(contact);
+		});
+	});
+
+	describe('delete', () => {
+		it('should DELETE contact', async () => {
+			mockFetch.mockResolvedValue(undefined);
+
+			await contactsApi.delete('c1');
+
+			expect(mockFetch).toHaveBeenCalledWith('/contacts/c1', {
+				method: 'DELETE',
+			});
+		});
+	});
+
+	describe('toggleFavorite', () => {
+		it('should POST to favorite endpoint', async () => {
+			const contact = { id: 'c1', isFavorite: true };
+			mockFetch.mockResolvedValue({ contact });
+
+			const result = await contactsApi.toggleFavorite('c1');
+
+			expect(mockFetch).toHaveBeenCalledWith('/contacts/c1/favorite', {
+				method: 'POST',
+			});
+			expect(result).toEqual(contact);
+		});
+	});
+
+	describe('toggleArchive', () => {
+		it('should POST to archive endpoint', async () => {
+			const contact = { id: 'c1', isArchived: true };
+			mockFetch.mockResolvedValue({ contact });
+
+			const result = await contactsApi.toggleArchive('c1');
+
+			expect(mockFetch).toHaveBeenCalledWith('/contacts/c1/archive', {
+				method: 'POST',
+			});
+			expect(result).toEqual(contact);
+		});
+	});
+});
+
+describe('notesApi', () => {
+	describe('list', () => {
+		it('should fetch notes for a contact', async () => {
+			mockFetch.mockResolvedValue({ notes: [] });
+
+			const result = await notesApi.list('c1');
+
+			expect(mockFetch).toHaveBeenCalledWith('/contacts/c1/notes');
+			expect(result).toEqual({ notes: [] });
+		});
+	});
+
+	describe('create', () => {
+		it('should POST a new note', async () => {
+			const note = { id: 'n1', content: 'Test note' };
+			mockFetch.mockResolvedValue({ note });
+
+			const result = await notesApi.create('c1', { content: 'Test note' });
+
+			expect(mockFetch).toHaveBeenCalledWith('/contacts/c1/notes', {
+				method: 'POST',
+				body: JSON.stringify({ content: 'Test note' }),
+			});
+			expect(result).toEqual({ note });
+		});
+	});
+
+	describe('update', () => {
+		it('should PATCH a note', async () => {
+			const note = { id: 'n1', content: 'Updated' };
+			mockFetch.mockResolvedValue({ note });
+
+			const result = await notesApi.update('n1', { content: 'Updated' });
+
+			expect(mockFetch).toHaveBeenCalledWith('/notes/n1', {
+				method: 'PATCH',
+				body: JSON.stringify({ content: 'Updated' }),
+			});
+			expect(result).toEqual({ note });
+		});
+	});
+
+	describe('delete', () => {
+		it('should DELETE a note', async () => {
+			mockFetch.mockResolvedValue(undefined);
+
+			await notesApi.delete('n1');
+
+			expect(mockFetch).toHaveBeenCalledWith('/notes/n1', {
+				method: 'DELETE',
+			});
+		});
+	});
+
+	describe('togglePin', () => {
+		it('should POST to pin endpoint', async () => {
+			const note = { id: 'n1', isPinned: true };
+			mockFetch.mockResolvedValue({ note });
+
+			const result = await notesApi.togglePin('n1');
+
+			expect(mockFetch).toHaveBeenCalledWith('/notes/n1/pin', {
+				method: 'POST',
+			});
+			expect(result).toEqual({ note });
+		});
+	});
+});
+
+describe('activitiesApi', () => {
+	describe('list', () => {
+		it('should fetch activities for a contact', async () => {
+			mockFetch.mockResolvedValue({ activities: [] });
+
+			const result = await activitiesApi.list('c1');
+
+			expect(mockFetch).toHaveBeenCalledWith('/contacts/c1/activities');
+			expect(result).toEqual({ activities: [] });
+		});
+
+		it('should include limit parameter', async () => {
+			mockFetch.mockResolvedValue({ activities: [] });
+
+			await activitiesApi.list('c1', 10);
+
+			expect(mockFetch).toHaveBeenCalledWith('/contacts/c1/activities?limit=10');
+		});
+	});
+
+	describe('create', () => {
+		it('should POST a new activity', async () => {
+			const activity = { id: 'a1', activityType: 'called' };
+			mockFetch.mockResolvedValue({ activity });
+
+			const result = await activitiesApi.create('c1', {
+				activityType: 'called',
+				description: 'Called about project',
+			});
+
+			expect(mockFetch).toHaveBeenCalledWith('/contacts/c1/activities', {
+				method: 'POST',
+				body: JSON.stringify({
+					activityType: 'called',
+					description: 'Called about project',
+				}),
+			});
+			expect(result).toEqual({ activity });
+		});
+	});
+});
diff --git a/apps/contacts/apps/web/src/lib/stores/filter.test.ts b/apps/contacts/apps/web/src/lib/stores/filter.test.ts
new file mode 100644
index 000000000..bdf770135
--- /dev/null
+++ b/apps/contacts/apps/web/src/lib/stores/filter.test.ts
@@ -0,0 +1,155 @@
+import { describe, it, expect, vi, beforeEach } from 'vitest';
+
+// Mock $app/environment
+vi.mock('$app/environment', () => ({
+	browser: true,
+}));
+
+// Mock localStorage
+const mockStorage: Record<string, string> = {};
+const localStorageMock = {
+	getItem: vi.fn((key: string) => mockStorage[key] || null),
+	setItem: vi.fn((key: string, value: string) => {
+		mockStorage[key] = value;
+	}),
+	removeItem: vi.fn((key: string) => {
+		delete mockStorage[key];
+	}),
+	clear: vi.fn(() => {
+		Object.keys(mockStorage).forEach((key) => delete mockStorage[key]);
+	}),
+};
+Object.defineProperty(globalThis, 'localStorage', { value: localStorageMock });
+
+import { contactsFilterStore } from './filter.svelte';
+
+beforeEach(() => {
+	vi.clearAllMocks();
+	localStorageMock.clear();
+	// Reset to defaults
+	contactsFilterStore.resetFilters();
+});
+
+describe('contactsFilterStore', () => {
+	describe('default state', () => {
+		it('should have default sort field', () => {
+			expect(contactsFilterStore.sortField).toBe('lastName');
+		});
+
+		it('should have default contact filter', () => {
+			expect(contactsFilterStore.contactFilter).toBe('all');
+		});
+
+		it('should have default birthday filter', () => {
+			expect(contactsFilterStore.birthdayFilter).toBe('all');
+		});
+
+		it('should have no selected tag', () => {
+			expect(contactsFilterStore.selectedTagId).toBeNull();
+		});
+
+		it('should have no selected company', () => {
+			expect(contactsFilterStore.selectedCompany).toBeNull();
+		});
+
+		it('should have toolbar collapsed by default', () => {
+			expect(contactsFilterStore.isToolbarCollapsed).toBe(true);
+		});
+
+		it('should have alphabet nav expanded by default', () => {
+			expect(contactsFilterStore.isAlphabetNavCollapsed).toBe(false);
+		});
+
+		it('should have empty search query', () => {
+			expect(contactsFilterStore.searchQuery).toBe('');
+		});
+	});
+
+	describe('setters', () => {
+		it('should set sort field', () => {
+			contactsFilterStore.setSortField('firstName');
+			expect(contactsFilterStore.sortField).toBe('firstName');
+		});
+
+		it('should set contact filter', () => {
+			contactsFilterStore.setContactFilter('favorites');
+			expect(contactsFilterStore.contactFilter).toBe('favorites');
+		});
+
+		it('should set birthday filter', () => {
+			contactsFilterStore.setBirthdayFilter('thisWeek');
+			expect(contactsFilterStore.birthdayFilter).toBe('thisWeek');
+		});
+
+		it('should set selected tag ID', () => {
+			contactsFilterStore.setSelectedTagId('tag-1');
+			expect(contactsFilterStore.selectedTagId).toBe('tag-1');
+		});
+
+		it('should set selected company', () => {
+			contactsFilterStore.setSelectedCompany('ACME');
+			expect(contactsFilterStore.selectedCompany).toBe('ACME');
+		});
+
+		it('should set search query without persisting', () => {
+			contactsFilterStore.setSearchQuery('Max');
+			expect(contactsFilterStore.searchQuery).toBe('Max');
+		});
+	});
+
+	describe('toggles', () => {
+		it('should toggle toolbar collapsed state', () => {
+			expect(contactsFilterStore.isToolbarCollapsed).toBe(true);
+			contactsFilterStore.toggleToolbar();
+			expect(contactsFilterStore.isToolbarCollapsed).toBe(false);
+			contactsFilterStore.toggleToolbar();
+			expect(contactsFilterStore.isToolbarCollapsed).toBe(true);
+		});
+
+		it('should toggle alphabet nav collapsed state', () => {
+			expect(contactsFilterStore.isAlphabetNavCollapsed).toBe(false);
+			contactsFilterStore.toggleAlphabetNav();
+			expect(contactsFilterStore.isAlphabetNavCollapsed).toBe(true);
+			contactsFilterStore.toggleAlphabetNav();
+			expect(contactsFilterStore.isAlphabetNavCollapsed).toBe(false);
+		});
+	});
+
+	describe('resetFilters', () => {
+		it('should reset filters to defaults but keep toolbar/nav state', () => {
+			contactsFilterStore.setContactFilter('favorites');
+			contactsFilterStore.setBirthdayFilter('thisMonth');
+			contactsFilterStore.setSelectedTagId('tag-1');
+			contactsFilterStore.setSelectedCompany('ACME');
+			contactsFilterStore.setSearchQuery('Max');
+			contactsFilterStore.setToolbarCollapsed(false);
+
+			contactsFilterStore.resetFilters();
+
+			expect(contactsFilterStore.contactFilter).toBe('all');
+			expect(contactsFilterStore.birthdayFilter).toBe('all');
+			expect(contactsFilterStore.selectedTagId).toBeNull();
+			expect(contactsFilterStore.selectedCompany).toBeNull();
+			expect(contactsFilterStore.searchQuery).toBe('');
+			// Toolbar state is preserved in resetFilters
+		});
+	});
+
+	describe('persistence', () => {
+		it('should save state to localStorage on setter call', () => {
+			contactsFilterStore.setSortField('firstName');
+
+			expect(localStorageMock.setItem).toHaveBeenCalledWith(
+				'contacts-filter-state',
+				expect.any(String)
+			);
+		});
+
+		it('should NOT persist search query', () => {
+			vi.clearAllMocks();
+			contactsFilterStore.setSearchQuery('test');
+
+			expect(localStorageMock.setItem).not.toHaveBeenCalled();
+		});
+	});
+});
diff --git a/apps/contacts/apps/web/src/lib/utils/contact-parser.test.ts b/apps/contacts/apps/web/src/lib/utils/contact-parser.test.ts
new file mode 100644
index 000000000..2d5282999
--- /dev/null
+++ b/apps/contacts/apps/web/src/lib/utils/contact-parser.test.ts
@@ -0,0 +1,175 @@
+import { describe, it, expect } from 'vitest';
+import { parseContactInput, resolveContactIds, formatParsedContactPreview } from './contact-parser';
+
+describe('parseContactInput', () => {
+	it('should parse a simple name', () => {
+		const result = parseContactInput('Max Mustermann');
+		expect(result.displayName).toBe('Max Mustermann');
+		expect(result.firstName).toBe('Max');
+		expect(result.lastName).toBe('Mustermann');
+	});
+
+	it('should parse a single name as firstName', () => {
+		const result = parseContactInput('Max');
+		expect(result.displayName).toBe('Max');
+		expect(result.firstName).toBe('Max');
+		expect(result.lastName).toBeUndefined();
+	});
+
+	it('should treat @ in email as company reference (known limitation)', () => {
+		// extractAtReference runs before email extraction,
+		// so "user@domain" is treated as @reference, not email.
+		// This is a known parser limitation - emails with @ conflict with @company.
+		const result = parseContactInput('Max Mustermann max@example.com');
+		// The @ gets consumed by extractAtReference
+		expect(result.company).toBeDefined();
+		expect(result.email).toBeUndefined();
+	});
+
+	it('should parse email when preceded by bei company', () => {
+		// When using bei/von for company, there's no @ to conflict
+		const result = parseContactInput('Max Mustermann bei ACME');
+		expect(result.company).toBe('ACME');
+		expect(result.displayName).toBe('Max Mustermann');
+	});
+
+	it('should parse name with @company (single word)', () => {
+		const result = parseContactInput('Max Mustermann @ACME');
+		expect(result.displayName).toBe('Max Mustermann');
+		expect(result.company).toBe('ACME');
+	});
+
+	it('should parse name with @company (multi-word leaves remainder in name)', () => {
+		// extractAtReference only captures the first word after @
+		const result = parseContactInput('Max Mustermann @ACME Corp');
+		expect(result.company).toBe('ACME');
+		expect(result.displayName).toContain('Max Mustermann');
+	});
+
+	it('should parse name with bei company', () => {
+		const result = parseContactInput('Anna Schmidt bei Google');
+		expect(result.displayName).toBe('Anna Schmidt');
+		expect(result.company).toBe('Google');
+	});
+
+	it('should parse name with von company', () => {
+		const result = parseContactInput('Peter Müller von Siemens');
+		expect(result.displayName).toBe('Peter Müller');
+		expect(result.company).toBe('Siemens');
+	});
+
+	it('should parse name with phone (international)', () => {
+		const result = parseContactInput('Max +49 123 456789');
+		expect(result.displayName).toBe('Max');
+		expect(result.phone).toBe('+49 123 456789');
+	});
+
+	it('should parse name with phone (German format)', () => {
+		const result = parseContactInput('Max 0123 456789');
+		expect(result.displayName).toBe('Max');
+		expect(result.phone).toBe('0123 456789');
+	});
+
+	it('should parse tags', () => {
+		const result = parseContactInput('Max #kunde #wichtig');
+		expect(result.displayName).toBe('Max');
+		expect(result.tagNames).toEqual(['kunde', 'wichtig']);
+	});
+
+	it('should parse complex input with all fields', () => {
+		const result = parseContactInput(
+			'Max Mustermann @ACME max@example.com +49 123 456789 #kunde #wichtig'
+		);
+		expect(result.displayName).toContain('Max Mustermann');
+		expect(result.company).toBe('ACME');
+		expect(result.email).toBe('max@example.com');
+		expect(result.phone).toBe('+49 123 456789');
+		expect(result.tagNames).toEqual(['kunde', 'wichtig']);
+	});
+
+	it('should handle empty input', () => {
+		const result = parseContactInput('');
+		expect(result.displayName).toBe('');
+		expect(result.tagNames).toEqual([]);
+	});
+
+	it('should handle only tags', () => {
+		const result = parseContactInput('#privat #freunde');
+		expect(result.tagNames).toEqual(['privat', 'freunde']);
+	});
+
+	it('should handle multi-part last names', () => {
+		const result = parseContactInput('Ludwig van Beethoven');
+		expect(result.firstName).toBe('Ludwig');
+		expect(result.lastName).toBe('van Beethoven');
+	});
+});
+
+describe('resolveContactIds', () => {
+	const tags = [
+		{ id: 'tag-1', name: 'Kunde' },
+		{ id: 'tag-2', name: 'Privat' },
+		{ id: 'tag-3', name: 'Wichtig' },
+	];
+
+	it('should resolve tag names to IDs (case-insensitive)', () => {
+		const parsed = parseContactInput('Max #kunde #wichtig');
+		const resolved = resolveContactIds(parsed, tags);
+		expect(resolved.tagIds).toEqual(['tag-1', 'tag-3']);
+	});
+
+	it('should skip unknown tags', () => {
+		const parsed = parseContactInput('Max #unbekannt');
+		const resolved = resolveContactIds(parsed, tags);
+		expect(resolved.tagIds).toEqual([]);
+	});
+
+	it('should preserve other fields', () => {
+		const parsed = parseContactInput('Max bei TestCorp #kunde');
+		const resolved = resolveContactIds(parsed, tags);
+		expect(resolved.displayName).toBe('Max');
+		expect(resolved.company).toBe('TestCorp');
+		expect(resolved.tagIds).toEqual(['tag-1']);
+	});
+});
+
+describe('formatParsedContactPreview', () => {
+	it('should format company', () => {
+		const parsed = parseContactInput('Max @ACME');
+		expect(formatParsedContactPreview(parsed)).toContain('ACME');
+	});
+
+	it('should format email', () => {
+		// Construct parsed result directly to test formatting
+		const parsed = {
+			displayName: 'Max',
+			firstName: 'Max',
+			email: 'max@test.com',
+			tagNames: [],
+		};
+		expect(formatParsedContactPreview(parsed)).toContain('max@test.com');
+	});
+
+	it('should format phone', () => {
+		const parsed = parseContactInput('Max +49 123 456');
+		expect(formatParsedContactPreview(parsed)).toContain('+49 123 456');
+	});
+
+	it('should format tags', () => {
+		const parsed = parseContactInput('Max #kunde #privat');
+		const preview = formatParsedContactPreview(parsed);
+		expect(preview).toContain('kunde');
+		expect(preview).toContain('privat');
+	});
+
+	it('should return empty string for name-only input', () => {
+		const parsed = parseContactInput('Max');
+		expect(formatParsedContactPreview(parsed)).toBe('');
+	});
+
+	it('should join parts with separator', () => {
+		const parsed = parseContactInput('Max @ACME max@test.com');
+		const preview = formatParsedContactPreview(parsed);
+		expect(preview).toContain(' · ');
+	});
+});
diff --git a/apps/contacts/apps/web/vite.config.ts b/apps/contacts/apps/web/vite.config.ts
index 244cb227a..64eb78a6c 100644
--- a/apps/contacts/apps/web/vite.config.ts
+++ b/apps/contacts/apps/web/vite.config.ts
@@ -5,6 +5,7 @@ import { SvelteKitPWA } from '@vite-pwa/sveltekit';
 import { createPWAConfig } from '@manacore/shared-pwa';
 import { MANACORE_SHARED_PACKAGES } from '@manacore/shared-vite-config';
 
+/// <reference types="vitest/config" />
 export default defineConfig({
 	plugins: [
 		tailwindcss(),
@@ -28,4 +29,9 @@ export default defineConfig({
 	optimizeDeps: {
 		exclude: [...MANACORE_SHARED_PACKAGES],
 	},
+	test: {
+		environment: 'jsdom',
+		include: ['src/**/*.test.ts'],
+		globals: true,
+	},
 });