diff --git a/mobile/src/api/note-prompts.test.ts b/mobile/src/api/note-prompts.test.ts
new file mode 100644
index 0000000..a622532
--- /dev/null
+++ b/mobile/src/api/note-prompts.test.ts
@@ -0,0 +1,64 @@
+import { describe, expect, it, vi, beforeEach } from 'vitest';
+
+const fetchMock = vi.fn();
+
+vi.mock('./client', () => ({
+  getApiClient: () => ({
+    fetch: fetchMock,
+  }),
+}));
+
+import {
+  listPromptTemplates,
+  runPrompt,
+  suggestTags,
+  extractFromUrl,
+  copilotTransform,
+  getReadingTime,
+} from './note-prompts';
+
+describe('note-prompts API client', () => {
+  beforeEach(() => {
+    fetchMock.mockReset();
+  });
+
+  it('listPromptTemplates returns items', async () => {
+    fetchMock.mockResolvedValue({ items: [{ id: 't1', slug: 'summarize' }] });
+    const result = await listPromptTemplates();
+    expect(result).toEqual([{ id: 't1', slug: 'summarize' }]);
+    expect(fetchMock).toHaveBeenCalledWith('/note-prompts');
+  });
+
+  it('runPrompt posts input', async () => {
+    fetchMock.mockResolvedValue({ content: 'Summary', templateSlug: 'summarize' });
+    const result = await runPrompt({ templateId: 'summarize', noteId: 'n1', workspaceId: 'ws1' });
+    expect(result.content).toBe('Summary');
+    expect(fetchMock).toHaveBeenCalledWith('/note-prompts/run', expect.objectContaining({ method: 'POST' }));
+  });
+
+  it('suggestTags returns tag array', async () => {
+    fetchMock.mockResolvedValue({ tags: ['tag1', 'tag2'] });
+    const tags = await suggestTags('n1', 'ws1');
+    expect(tags).toEqual(['tag1', 'tag2']);
+  });
+
+  it('extractFromUrl sends url and workspaceId', async () => {
+    fetchMock.mockResolvedValue({ title: 'Page', content: 'text', url: 'https://example.com', summarized: true });
+    const result = await extractFromUrl('https://example.com', 'ws1');
+    expect(result.title).toBe('Page');
+    expect(fetchMock).toHaveBeenCalledWith('/note-prompts/url-extract', expect.objectContaining({ method: 'POST' }));
+  });
+
+  it('copilotTransform sends action and text', async () => {
+    fetchMock.mockResolvedValue({ text: 'Transformed' });
+    const result = await copilotTransform('n1', 'ws1', 'shorten', 'Long text');
+    expect(result).toBe('Transformed');
+  });
+
+  it('getReadingTime returns word count and minutes', async () => {
+    fetchMock.mockResolvedValue({ wordCount: 500, readingTimeMinutes: 3 });
+    const result = await getReadingTime('n1', 'ws1');
+    expect(result.wordCount).toBe(500);
+    expect(result.readingTimeMinutes).toBe(3);
+  });
+});
diff --git a/mobile/src/store/prompt-store.test.ts b/mobile/src/store/prompt-store.test.ts
new file mode 100644
index 0000000..2eff7f2
--- /dev/null
+++ b/mobile/src/store/prompt-store.test.ts
@@ -0,0 +1,113 @@
+import { describe, expect, it, vi, beforeEach } from 'vitest';
+
+const listPromptTemplatesMock = vi.fn();
+const runPromptMock = vi.fn();
+
+vi.mock('../api/note-prompts', () => ({
+  listPromptTemplates: (...args: unknown[]) => listPromptTemplatesMock(...args),
+  runPrompt: (...args: unknown[]) => runPromptMock(...args),
+}));
+
+import { usePromptStore } from './prompt-store';
+
+function resetStore() {
+  usePromptStore.setState({
+    templates: [],
+    isLoading: false,
+    isRunning: false,
+    lastResult: null,
+    error: null,
+  });
+}
+
+describe('prompt-store', () => {
+  beforeEach(() => {
+    vi.clearAllMocks();
+    resetStore();
+  });
+
+  it('initial state is empty', () => {
+    const state = usePromptStore.getState();
+    expect(state.templates).toEqual([]);
+    expect(state.isLoading).toBe(false);
+    expect(state.isRunning).toBe(false);
+    expect(state.lastResult).toBeNull();
+    expect(state.error).toBeNull();
+  });
+
+  it('fetchTemplates populates templates on success', async () => {
+    listPromptTemplatesMock.mockResolvedValue([
+      { id: 't1', slug: 'summarize', name: 'Summarize' },
+    ]);
+
+    await usePromptStore.getState().fetchTemplates();
+
+    const state = usePromptStore.getState();
+    expect(state.templates).toHaveLength(1);
+    expect(state.templates[0].slug).toBe('summarize');
+    expect(state.isLoading).toBe(false);
+  });
+
+  it('fetchTemplates sets error on failure', async () => {
+    listPromptTemplatesMock.mockRejectedValue(new Error('Network error'));
+
+    await usePromptStore.getState().fetchTemplates();
+
+    const state = usePromptStore.getState();
+    expect(state.error).toBe('Network error');
+    expect(state.isLoading).toBe(false);
+  });
+
+  it('runPrompt stores result on success', async () => {
+    runPromptMock.mockResolvedValue({
+      content: 'Summary text',
+      templateSlug: 'summarize',
+      outputType: 'new_note',
+    });
+
+    const result = await usePromptStore.getState().runPrompt({
+      templateId: 'summarize',
+      noteId: 'n1',
+      workspaceId: 'ws1',
+    });
+
+    expect(result).toBeTruthy();
+    expect(result!.content).toBe('Summary text');
+    const state = usePromptStore.getState();
+    expect(state.lastResult!.content).toBe('Summary text');
+    expect(state.isRunning).toBe(false);
+  });
+
+  it('runPrompt sets error on failure', async () => {
+    runPromptMock.mockRejectedValue(new Error('LLM timeout'));
+
+    const result = await usePromptStore.getState().runPrompt({
+      templateId: 'summarize',
+      noteId: 'n1',
+      workspaceId: 'ws1',
+    });
+
+    expect(result).toBeNull();
+    const state = usePromptStore.getState();
+    expect(state.error).toBe('LLM timeout');
+    expect(state.isRunning).toBe(false);
+  });
+
+  it('clearResult resets lastResult', async () => {
+    runPromptMock.mockResolvedValue({ content: 'Result', templateSlug: 'x', outputType: 'new_note' });
+    await usePromptStore.getState().runPrompt({ templateId: 'x', noteId: 'n1', workspaceId: 'ws1' });
+    expect(usePromptStore.getState().lastResult).not.toBeNull();
+
+    usePromptStore.getState().clearResult();
+    expect(usePromptStore.getState().lastResult).toBeNull();
+  });
+
+  it('clearError resets error', async () => {
+    runPromptMock.mockRejectedValue(new Error('fail'));
+    await usePromptStore.getState().runPrompt({ templateId: 'x', noteId: 'n1', workspaceId: 'ws1' });
+    expect(usePromptStore.getState().error).toBe('fail');
+
+    usePromptStore.getState().clearError();
+    expect(usePromptStore.getState().error).toBeNull();
+  });
+});