diff --git a/tests/api/goodreads-shelves-id.routes.test.ts b/tests/api/goodreads-shelves-id.routes.test.ts
new file mode 100644
index 0000000..97bff25
--- /dev/null
+++ b/tests/api/goodreads-shelves-id.routes.test.ts
@@ -0,0 +1,186 @@
+/**
+ * Component: Goodreads Shelves [id] API Route Tests
+ * Documentation: documentation/backend/services/goodreads-sync.md
+ */
+
+import { beforeEach, describe, expect, it, vi } from 'vitest';
+import { createPrismaMock } from '../helpers/prisma';
+
+let authRequest: any;
+
+const requireAuthMock = vi.hoisted(() => vi.fn());
+const prismaMock = createPrismaMock();
+const jobQueueMock = vi.hoisted(() => ({
+  addSyncShelvesJob: vi.fn(() => Promise.resolve()),
+}));
+
+vi.mock('@/lib/middleware/auth', () => ({
+  requireAuth: requireAuthMock,
+}));
+
+vi.mock('@/lib/db', () => ({
+  prisma: prismaMock,
+}));
+
+vi.mock('@/lib/services/job-queue.service', () => ({
+  getJobQueueService: () => jobQueueMock,
+}));
+
+const SHELF = {
+  id: 'shelf-1',
+  userId: 'user-1',
+  name: 'Want to Read',
+  rssUrl: 'https://www.goodreads.com/review/list_rss/12345',
+  lastSyncAt: null,
+  bookCount: 5,
+  coverUrls: null,
+  createdAt: new Date().toISOString(),
+};
+
+describe('DELETE /api/user/goodreads-shelves/[id]', () => {
+  beforeEach(() => {
+    vi.clearAllMocks();
+    authRequest = { user: { id: 'user-1', role: 'user' } };
+    requireAuthMock.mockImplementation((_req: any, handler: any) => handler(authRequest));
+  });
+
+  it('returns 404 when shelf does not exist', async () => {
+    prismaMock.goodreadsShelf.findUnique.mockResolvedValueOnce(null);
+
+    const { DELETE } = await import('@/app/api/user/goodreads-shelves/[id]/route');
+    const response = await DELETE({} as any, { params: Promise.resolve({ id: 'shelf-1' }) });
+    const payload = await response.json();
+
+    expect(response.status).toBe(404);
+    expect(payload.error).toBe('Shelf not found');
+  });
+
+  it('returns 403 when shelf belongs to another user', async () => {
+    prismaMock.goodreadsShelf.findUnique.mockResolvedValueOnce({ ...SHELF, userId: 'other-user' });
+
+    const { DELETE } = await import('@/app/api/user/goodreads-shelves/[id]/route');
+    const response = await DELETE({} as any, { params: Promise.resolve({ id: 'shelf-1' }) });
+    const payload = await response.json();
+
+    expect(response.status).toBe(403);
+    expect(payload.error).toBe('Forbidden');
+  });
+
+  it('deletes the shelf and returns success', async () => {
+    prismaMock.goodreadsShelf.findUnique.mockResolvedValueOnce(SHELF);
+    prismaMock.goodreadsShelf.delete.mockResolvedValueOnce({});
+
+    const { DELETE } = await import('@/app/api/user/goodreads-shelves/[id]/route');
+    const response = await DELETE({} as any, { params: Promise.resolve({ id: 'shelf-1' }) });
+    const payload = await response.json();
+
+    expect(response.status).toBe(200);
+    expect(payload.success).toBe(true);
+    expect(prismaMock.goodreadsShelf.delete).toHaveBeenCalledWith({ where: { id: 'shelf-1' } });
+  });
+
+  it('returns 500 when deletion throws', async () => {
+    prismaMock.goodreadsShelf.findUnique.mockResolvedValueOnce(SHELF);
+    prismaMock.goodreadsShelf.delete.mockRejectedValueOnce(new Error('db error'));
+
+    const { DELETE } = await import('@/app/api/user/goodreads-shelves/[id]/route');
+    const response = await DELETE({} as any, { params: Promise.resolve({ id: 'shelf-1' }) });
+    const payload = await response.json();
+
+    expect(response.status).toBe(500);
+    expect(payload.error).toBe('Failed to delete shelf');
+  });
+});
+
+describe('PATCH /api/user/goodreads-shelves/[id]', () => {
+  const NEW_RSS = 'https://www.goodreads.com/review/list_rss/99999';
+
+  beforeEach(() => {
+    vi.clearAllMocks();
+    authRequest = {
+      user: { id: 'user-1', role: 'user' },
+      json: vi.fn().mockResolvedValue({ rssUrl: NEW_RSS }),
+    };
+    requireAuthMock.mockImplementation((_req: any, handler: any) => handler(authRequest));
+  });
+
+  it('returns 404 when shelf does not exist', async () => {
+    prismaMock.goodreadsShelf.findUnique.mockResolvedValueOnce(null);
+
+    const { PATCH } = await import('@/app/api/user/goodreads-shelves/[id]/route');
+    const response = await PATCH(
+      { json: vi.fn().mockResolvedValue({ rssUrl: NEW_RSS }) } as any,
+      { params: Promise.resolve({ id: 'shelf-1' }) }
+    );
+    const payload = await response.json();
+
+    expect(response.status).toBe(404);
+    expect(payload.error).toBe('Shelf not found');
+  });
+
+  it('returns 403 when shelf belongs to another user', async () => {
+    prismaMock.goodreadsShelf.findUnique.mockResolvedValueOnce({ ...SHELF, userId: 'other-user' });
+
+    const { PATCH } = await import('@/app/api/user/goodreads-shelves/[id]/route');
+    const response = await PATCH(
+      { json: vi.fn().mockResolvedValue({ rssUrl: NEW_RSS }) } as any,
+      { params: Promise.resolve({ id: 'shelf-1' }) }
+    );
+    const payload = await response.json();
+
+    expect(response.status).toBe(403);
+    expect(payload.error).toBe('Forbidden');
+  });
+
+  it('returns 400 for an invalid (non-URL) rssUrl', async () => {
+    prismaMock.goodreadsShelf.findUnique.mockResolvedValueOnce(SHELF);
+
+    const { PATCH } = await import('@/app/api/user/goodreads-shelves/[id]/route');
+    const response = await PATCH(
+      { json: vi.fn().mockResolvedValue({ rssUrl: 'not-a-url' }) } as any,
+      { params: Promise.resolve({ id: 'shelf-1' }) }
+    );
+    const payload = await response.json();
+
+    expect(response.status).toBe(400);
+    expect(payload.error).toBe('ValidationError');
+  });
+
+  it('updates the shelf, clears sync metadata, and triggers a sync job', async () => {
+    prismaMock.goodreadsShelf.findUnique.mockResolvedValueOnce(SHELF);
+    const updatedShelf = { ...SHELF, rssUrl: NEW_RSS, lastSyncAt: null };
+    prismaMock.goodreadsShelf.update.mockResolvedValueOnce(updatedShelf);
+
+    const { PATCH } = await import('@/app/api/user/goodreads-shelves/[id]/route');
+    const response = await PATCH(
+      { json: vi.fn().mockResolvedValue({ rssUrl: NEW_RSS }) } as any,
+      { params: Promise.resolve({ id: 'shelf-1' }) }
+    );
+    const payload = await response.json();
+
+    expect(response.status).toBe(200);
+    expect(payload.success).toBe(true);
+    expect(prismaMock.goodreadsShelf.update).toHaveBeenCalledWith({
+      where: { id: 'shelf-1' },
+      data: { rssUrl: NEW_RSS, lastSyncAt: null, bookCount: null, coverUrls: null },
+    });
+    expect(jobQueueMock.addSyncShelvesJob).toHaveBeenCalledWith(undefined, updatedShelf.id, 'goodreads', 0);
+  });
+
+  it('still returns 200 even when the sync job fails to enqueue', async () => {
+    prismaMock.goodreadsShelf.findUnique.mockResolvedValueOnce(SHELF);
+    prismaMock.goodreadsShelf.update.mockResolvedValueOnce({ ...SHELF, rssUrl: NEW_RSS });
+    jobQueueMock.addSyncShelvesJob.mockRejectedValueOnce(new Error('queue down'));
+
+    const { PATCH } = await import('@/app/api/user/goodreads-shelves/[id]/route');
+    const response = await PATCH(
+      { json: vi.fn().mockResolvedValue({ rssUrl: NEW_RSS }) } as any,
+      { params: Promise.resolve({ id: 'shelf-1' }) }
+    );
+    const payload = await response.json();
+
+    // Sync job failure is swallowed; shelf update should still succeed
+    expect(response.status).toBe(200);
+    expect(payload.success).toBe(true);
+  });
+});
diff --git a/tests/api/hardcover-shelves-id.routes.test.ts b/tests/api/hardcover-shelves-id.routes.test.ts
new file mode 100644
index 0000000..338ce2d
--- /dev/null
+++ b/tests/api/hardcover-shelves-id.routes.test.ts
@@ -0,0 +1,222 @@
+/**
+ * Component: Hardcover Shelves [id] API Route Tests
+ * Documentation: documentation/backend/services/hardcover-sync.md
+ */
+
+import { beforeEach, describe, expect, it, vi } from 'vitest';
+import { createPrismaMock } from '../helpers/prisma';
+
+let authRequest: any;
+
+const requireAuthMock = vi.hoisted(() => vi.fn());
+const prismaMock = createPrismaMock();
+const jobQueueMock = vi.hoisted(() => ({
+  addSyncShelvesJob: vi.fn(() => Promise.resolve()),
+}));
+const encryptionMock = vi.hoisted(() => ({
+  encrypt: vi.fn((s: string) => `enc:${s}`),
+  decrypt: vi.fn((s: string) => s.replace('enc:', '')),
+}));
+
+vi.mock('@/lib/middleware/auth', () => ({
+  requireAuth: requireAuthMock,
+}));
+
+vi.mock('@/lib/db', () => ({
+  prisma: prismaMock,
+}));
+
+vi.mock('@/lib/services/job-queue.service', () => ({
+  getJobQueueService: () => jobQueueMock,
+}));
+
+vi.mock('@/lib/services/encryption.service', () => ({
+  getEncryptionService: () => encryptionMock,
+}));
+
+const SHELF = {
+  id: 'hc-shelf-1',
+  userId: 'user-1',
+  name: 'Currently Reading',
+  listId: 'status-2',
+  apiToken: 'enc:secret-token',
+  lastSyncAt: null,
+  bookCount: 3,
+  coverUrls: null,
+  createdAt: new Date().toISOString(),
+};
+
+describe('DELETE /api/user/hardcover-shelves/[id]', () => {
+  beforeEach(() => {
+    vi.clearAllMocks();
+    authRequest = { user: { id: 'user-1', role: 'user' } };
+    requireAuthMock.mockImplementation((_req: any, handler: any) => handler(authRequest));
+  });
+
+  it('returns 404 when list does not exist', async () => {
+    prismaMock.hardcoverShelf.findUnique.mockResolvedValueOnce(null);
+
+    const { DELETE } = await import('@/app/api/user/hardcover-shelves/[id]/route');
+    const response = await DELETE({} as any, { params: Promise.resolve({ id: 'hc-shelf-1' }) });
+    const payload = await response.json();
+
+    expect(response.status).toBe(404);
+    expect(payload.error).toBe('List not found');
+  });
+
+  it('returns 403 when list belongs to another user', async () => {
+    prismaMock.hardcoverShelf.findUnique.mockResolvedValueOnce({ ...SHELF, userId: 'other-user' });
+
+    const { DELETE } = await import('@/app/api/user/hardcover-shelves/[id]/route');
+    const response = await DELETE({} as any, { params: Promise.resolve({ id: 'hc-shelf-1' }) });
+    const payload = await response.json();
+
+    expect(response.status).toBe(403);
+    expect(payload.error).toBe('Forbidden');
+  });
+
+  it('deletes the list and returns success', async () => {
+    prismaMock.hardcoverShelf.findUnique.mockResolvedValueOnce(SHELF);
+    prismaMock.hardcoverShelf.delete.mockResolvedValueOnce({});
+
+    const { DELETE } = await import('@/app/api/user/hardcover-shelves/[id]/route');
+    const response = await DELETE({} as any, { params: Promise.resolve({ id: 'hc-shelf-1' }) });
+    const payload = await response.json();
+
+    expect(response.status).toBe(200);
+    expect(payload.success).toBe(true);
+    expect(prismaMock.hardcoverShelf.delete).toHaveBeenCalledWith({ where: { id: 'hc-shelf-1' } });
+  });
+
+  it('returns 500 when deletion throws', async () => {
+    prismaMock.hardcoverShelf.findUnique.mockResolvedValueOnce(SHELF);
+    prismaMock.hardcoverShelf.delete.mockRejectedValueOnce(new Error('db error'));
+
+    const { DELETE } = await import('@/app/api/user/hardcover-shelves/[id]/route');
+    const response = await DELETE({} as any, { params: Promise.resolve({ id: 'hc-shelf-1' }) });
+    const payload = await response.json();
+
+    expect(response.status).toBe(500);
+    expect(payload.error).toBe('Failed to delete list');
+  });
+});
+
+describe('PATCH /api/user/hardcover-shelves/[id]', () => {
+  beforeEach(() => {
+    vi.clearAllMocks();
+    authRequest = { user: { id: 'user-1', role: 'user' } };
+    requireAuthMock.mockImplementation((_req: any, handler: any) => handler(authRequest));
+  });
+
+  it('returns 404 when list does not exist', async () => {
+    prismaMock.hardcoverShelf.findUnique.mockResolvedValueOnce(null);
+
+    const { PATCH } = await import('@/app/api/user/hardcover-shelves/[id]/route');
+    const response = await PATCH(
+      { json: vi.fn().mockResolvedValue({ listId: 'status-3' }) } as any,
+      { params: Promise.resolve({ id: 'hc-shelf-1' }) }
+    );
+    const payload = await response.json();
+
+    expect(response.status).toBe(404);
+    expect(payload.error).toBe('List not found');
+  });
+
+  it('returns 403 when list belongs to another user', async () => {
+    prismaMock.hardcoverShelf.findUnique.mockResolvedValueOnce({ ...SHELF, userId: 'other-user' });
+
+    const { PATCH } = await import('@/app/api/user/hardcover-shelves/[id]/route');
+    const response = await PATCH(
+      { json: vi.fn().mockResolvedValue({ listId: 'status-3' }) } as any,
+      { params: Promise.resolve({ id: 'hc-shelf-1' }) }
+    );
+    const payload = await response.json();
+
+    expect(response.status).toBe(403);
+    expect(payload.error).toBe('Forbidden');
+  });
+
+  it('does not trigger a sync when no fields changed', async () => {
+    // listId is the same as existing; no apiToken provided
+    prismaMock.hardcoverShelf.findUnique.mockResolvedValueOnce(SHELF);
+    prismaMock.hardcoverShelf.update.mockResolvedValueOnce(SHELF);
+
+    const { PATCH } = await import('@/app/api/user/hardcover-shelves/[id]/route');
+    const response = await PATCH(
+      { json: vi.fn().mockResolvedValue({ listId: SHELF.listId }) } as any,
+      { params: Promise.resolve({ id: 'hc-shelf-1' }) }
+    );
+    const payload = await response.json();
+
+    expect(response.status).toBe(200);
+    expect(payload.success).toBe(true);
+    expect(jobQueueMock.addSyncShelvesJob).not.toHaveBeenCalled();
+  });
+
+  it('updates listId, clears metadata, and triggers a sync job', async () => {
+    prismaMock.hardcoverShelf.findUnique.mockResolvedValueOnce(SHELF);
+    const updated = { ...SHELF, listId: 'status-3', lastSyncAt: null };
+    prismaMock.hardcoverShelf.update.mockResolvedValueOnce(updated);
+
+    const { PATCH } = await import('@/app/api/user/hardcover-shelves/[id]/route');
+    const response = await PATCH(
+      { json: vi.fn().mockResolvedValue({ listId: 'status-3' }) } as any,
+      { params: Promise.resolve({ id: 'hc-shelf-1' }) }
+    );
+    const payload = await response.json();
+
+    expect(response.status).toBe(200);
+    expect(payload.success).toBe(true);
+    expect(prismaMock.hardcoverShelf.update).toHaveBeenCalledWith({
+      where: { id: 'hc-shelf-1' },
+      data: expect.objectContaining({ listId: 'status-3', lastSyncAt: null }),
+    });
+    expect(jobQueueMock.addSyncShelvesJob).toHaveBeenCalledWith(undefined, updated.id, 'hardcover', 0);
+  });
+
+  it('encrypts the apiToken before persisting', async () => {
+    prismaMock.hardcoverShelf.findUnique.mockResolvedValueOnce(SHELF);
+    prismaMock.hardcoverShelf.update.mockResolvedValueOnce(SHELF);
+
+    const { PATCH } = await import('@/app/api/user/hardcover-shelves/[id]/route');
+    await PATCH(
+      { json: vi.fn().mockResolvedValue({ apiToken: 'my-raw-token' }) } as any,
+      { params: Promise.resolve({ id: 'hc-shelf-1' }) }
+    );
+
+    expect(encryptionMock.encrypt).toHaveBeenCalledWith('my-raw-token');
+    expect(prismaMock.hardcoverShelf.update).toHaveBeenCalledWith({
+      where: { id: 'hc-shelf-1' },
+      data: expect.objectContaining({ apiToken: 'enc:my-raw-token' }),
+    });
+  });
+
+  it('strips the Bearer prefix before encrypting the token', async () => {
+    prismaMock.hardcoverShelf.findUnique.mockResolvedValueOnce(SHELF);
+    prismaMock.hardcoverShelf.update.mockResolvedValueOnce(SHELF);
+
+    const { PATCH } = await import('@/app/api/user/hardcover-shelves/[id]/route');
+    await PATCH(
+      { json: vi.fn().mockResolvedValue({ apiToken: 'Bearer my-raw-token' }) } as any,
+      { params: Promise.resolve({ id: 'hc-shelf-1' }) }
+    );
+
+    expect(encryptionMock.encrypt).toHaveBeenCalledWith('my-raw-token');
+  });
+
+  it('still returns 200 even when the sync job fails to enqueue', async () => {
+    prismaMock.hardcoverShelf.findUnique.mockResolvedValueOnce(SHELF);
+    prismaMock.hardcoverShelf.update.mockResolvedValueOnce({ ...SHELF, listId: 'status-3' });
+    jobQueueMock.addSyncShelvesJob.mockRejectedValueOnce(new Error('queue down'));
+
+    const { PATCH } = await import('@/app/api/user/hardcover-shelves/[id]/route');
+    const response = await PATCH(
+      { json: vi.fn().mockResolvedValue({ listId: 'status-3' }) } as any,
+      { params: Promise.resolve({ id: 'hc-shelf-1' }) }
+    );
+    const payload = await response.json();
+
+    expect(response.status).toBe(200);
+    expect(payload.success).toBe(true);
+  });
+});
diff --git a/tests/api/hardcover-shelves.routes.test.ts b/tests/api/hardcover-shelves.routes.test.ts
new file mode 100644
index 0000000..fae8242
--- /dev/null
+++ b/tests/api/hardcover-shelves.routes.test.ts
@@ -0,0 +1,216 @@
+/**
+ * Component: Hardcover Shelves API Route Tests (POST / GET)
+ * Documentation: documentation/backend/services/hardcover-sync.md
+ */
+
+import { beforeEach, describe, expect, it, vi } from 'vitest';
+import { createPrismaMock } from '../helpers/prisma';
+
+let authRequest: any;
+
+const requireAuthMock = vi.hoisted(() => vi.fn());
+const prismaMock = createPrismaMock();
+const jobQueueMock = vi.hoisted(() => ({
+  addSyncShelvesJob: vi.fn(() => Promise.resolve()),
+}));
+const encryptionMock = vi.hoisted(() => ({
+  encrypt: vi.fn((s: string) => `enc:${s}`),
+  decrypt: vi.fn((s: string) => s.replace('enc:', '')),
+}));
+const fetchHardcoverListMock = vi.hoisted(() => vi.fn());
+
+vi.mock('@/lib/middleware/auth', () => ({
+  requireAuth: requireAuthMock,
+}));
+
+vi.mock('@/lib/db', () => ({
+  prisma: prismaMock,
+}));
+
+vi.mock('@/lib/services/job-queue.service', () => ({
+  getJobQueueService: () => jobQueueMock,
+}));
+
+vi.mock('@/lib/services/encryption.service', () => ({
+  getEncryptionService: () => encryptionMock,
+}));
+
+vi.mock('@/lib/services/hardcover-sync.service', () => ({
+  fetchHardcoverList: fetchHardcoverListMock,
+}));
+
+const FETCHED_LIST = {
+  listName: 'Currently Reading',
+  books: [
+    { title: 'Dune', author: 'Frank Herbert', coverUrl: 'https://example.com/dune.jpg' },
+    { title: 'Foundation', author: 'Isaac Asimov', coverUrl: null },
+  ],
+};
+
+describe('POST /api/user/hardcover-shelves', () => {
+  beforeEach(() => {
+    vi.clearAllMocks();
+    authRequest = {
+      user: { id: 'user-1', role: 'user' },
+      json: vi.fn().mockResolvedValue({ listId: 'status-2', apiToken: 'raw-token' }),
+    };
+    requireAuthMock.mockImplementation((_req: any, handler: any) => handler(authRequest));
+  });
+
+  it('returns 400 when apiToken is missing', async () => {
+    authRequest.json.mockResolvedValueOnce({ listId: 'status-2' });
+
+    const { POST } = await import('@/app/api/user/hardcover-shelves/route');
+    const response = await POST({} as any);
+    const payload = await response.json();
+
+    expect(response.status).toBe(400);
+    expect(payload.error).toBe('ValidationError');
+  });
+
+  it('returns 400 when listId is missing', async () => {
+    authRequest.json.mockResolvedValueOnce({ apiToken: 'raw-token' });
+
+    const { POST } = await import('@/app/api/user/hardcover-shelves/route');
+    const response = await POST({} as any);
+    const payload = await response.json();
+
+    expect(response.status).toBe(400);
+    expect(payload.error).toBe('ValidationError');
+  });
+
+  it('returns 409 when the list is already subscribed', async () => {
+    prismaMock.hardcoverShelf.findUnique.mockResolvedValueOnce({ id: 'existing-shelf' });
+
+    const { POST } = await import('@/app/api/user/hardcover-shelves/route');
+    const response = await POST({} as any);
+    const payload = await response.json();
+
+    expect(response.status).toBe(409);
+    expect(payload.error).toBe('DuplicateShelf');
+  });
+
+  it('returns 400 when Hardcover API fetch fails', async () => {
+    prismaMock.hardcoverShelf.findUnique.mockResolvedValueOnce(null);
+    fetchHardcoverListMock.mockRejectedValueOnce(new Error('Invalid token'));
+
+    const { POST } = await import('@/app/api/user/hardcover-shelves/route');
+    const response = await POST({} as any);
+    const payload = await response.json();
+
+    expect(response.status).toBe(400);
+    expect(payload.error).toBe('InvalidHardcoverList');
+    expect(payload.message).toContain('Invalid token');
+  });
+
+  it('creates the shelf with an encrypted token and triggers sync', async () => {
+    prismaMock.hardcoverShelf.findUnique.mockResolvedValueOnce(null);
+    fetchHardcoverListMock.mockResolvedValueOnce(FETCHED_LIST);
+    prismaMock.hardcoverShelf.create.mockResolvedValueOnce({
+      id: 'new-shelf',
+      name: 'Currently Reading',
+      listId: 'status-2',
+      lastSyncAt: null,
+      createdAt: new Date().toISOString(),
+      bookCount: 2,
+      coverUrls: null,
+    });
+
+    const { POST } = await import('@/app/api/user/hardcover-shelves/route');
+    const response = await POST({} as any);
+    const payload = await response.json();
+
+    expect(response.status).toBe(201);
+    expect(payload.success).toBe(true);
+    expect(payload.shelf.name).toBe('Currently Reading');
+
+    // Token must have been encrypted before storage
+    expect(encryptionMock.encrypt).toHaveBeenCalledWith('raw-token');
+    expect(prismaMock.hardcoverShelf.create).toHaveBeenCalledWith(
+      expect.objectContaining({
+        data: expect.objectContaining({
+          apiToken: 'enc:raw-token',
+          listId: 'status-2',
+          userId: 'user-1',
+        }),
+      })
+    );
+
+    // Immediate background sync must have been triggered
+    expect(jobQueueMock.addSyncShelvesJob).toHaveBeenCalledWith(undefined, 'new-shelf', 'hardcover', 0);
+  });
+
+  it('strips Bearer prefix from apiToken before encrypting', async () => {
+    authRequest.json.mockResolvedValueOnce({ listId: 'status-2', apiToken: 'Bearer raw-token' });
+    prismaMock.hardcoverShelf.findUnique.mockResolvedValueOnce(null);
+    fetchHardcoverListMock.mockResolvedValueOnce(FETCHED_LIST);
+    prismaMock.hardcoverShelf.create.mockResolvedValueOnce({
+      id: 'new-shelf-2',
+      name: 'Currently Reading',
+      listId: 'status-2',
+      lastSyncAt: null,
+      createdAt: new Date().toISOString(),
+      bookCount: 2,
+      coverUrls: null,
+    });
+
+    const { POST } = await import('@/app/api/user/hardcover-shelves/route');
+    await POST({} as any);
+
+    // "Bearer " prefix must have been stripped before encrypt was called
+    expect(encryptionMock.encrypt).toHaveBeenCalledWith('raw-token');
+  });
+
+  it('returns 201 even when the sync job fails to enqueue', async () => {
+    prismaMock.hardcoverShelf.findUnique.mockResolvedValueOnce(null);
+    fetchHardcoverListMock.mockResolvedValueOnce(FETCHED_LIST);
+    prismaMock.hardcoverShelf.create.mockResolvedValueOnce({
+      id: 'new-shelf-3',
+      name: 'Currently Reading',
+      listId: 'status-2',
+      lastSyncAt: null,
+      createdAt: new Date().toISOString(),
+      bookCount: 2,
+      coverUrls: null,
+    });
+    jobQueueMock.addSyncShelvesJob.mockRejectedValueOnce(new Error('queue down'));
+
+    const { POST } = await import('@/app/api/user/hardcover-shelves/route');
+    const response = await POST({} as any);
+    const payload = await response.json();
+
+    expect(response.status).toBe(201);
+    expect(payload.success).toBe(true);
+  });
+
+  it('only includes books with cover URLs in the initial shelf preview', async () => {
+    prismaMock.hardcoverShelf.findUnique.mockResolvedValueOnce(null);
+    fetchHardcoverListMock.mockResolvedValueOnce(FETCHED_LIST); // only 1 of 2 books has coverUrl
+    prismaMock.hardcoverShelf.create.mockResolvedValueOnce({
+      id: 'new-shelf-4',
+      name: 'Currently Reading',
+      listId: 'status-2',
+      lastSyncAt: null,
+      createdAt: new Date().toISOString(),
+      bookCount: 2,
+      coverUrls: null,
+    });
+
+    const { POST } = await import('@/app/api/user/hardcover-shelves/route');
+    const response = await POST({} as any);
+    const payload = await response.json();
+
+    expect(response.status).toBe(201);
+    // The coverUrls stored should only include books with non-null coverUrl
+    expect(prismaMock.hardcoverShelf.create).toHaveBeenCalledWith(
+      expect.objectContaining({
+        data: expect.objectContaining({
+          // 1 book has cover, 1 doesn't → only 1 stored
+          coverUrls: JSON.stringify([
+            { coverUrl: 'https://example.com/dune.jpg', asin: null, title: 'Dune', author: 'Frank Herbert' },
+          ]),
+        }),
+      })
+    );
+  });
+});
diff --git a/tests/helpers/prisma.ts b/tests/helpers/prisma.ts
index fc551c1..6dfc5a1 100644
--- a/tests/helpers/prisma.ts
+++ b/tests/helpers/prisma.ts
@@ -47,6 +47,7 @@ export const createPrismaMock = () => ({
   bookDateSwipe: createModelMock(),
   goodreadsShelf: createModelMock(),
   goodreadsBookMapping: createModelMock(),
+  hardcoverShelf: createModelMock(),
   $queryRaw: vi.fn(),
   $disconnect: vi.fn(),
 });