diff --git a/packages/backend/src/routes/cards.ts b/packages/backend/src/routes/cards.ts
index 425eb67..c759910 100644
--- a/packages/backend/src/routes/cards.ts
+++ b/packages/backend/src/routes/cards.ts
@@ -3,7 +3,7 @@ import multer from 'multer';
 import { cardCreateSchema, cardUpdateSchema } from '@flashcard/shared';
 import type { Db } from '../db/client.js';
 import { ApiError } from '../lib/errors.js';
-import { createCard, deleteCard, listCardsByLesson, updateCard } from '../services/cards.js';
+import { createCard, deleteCard, getCard, listCardsByLesson, updateCard } from '../services/cards.js';
 import { exportCardsToBuffer, importCardsFromBuffer } from '../services/import.js';
 
 export function cardsRouter(db: Db): Router {
@@ -21,6 +21,10 @@ export function cardsRouter(db: Db): Router {
     } catch (e) { next(e); }
   });
 
+  r.get('/cards/:id', async (req, res, next) => {
+    try { res.json(await getCard(db, Number(req.params.id))); } catch (e) { next(e); }
+  });
+
   r.patch('/cards/:id', async (req, res, next) => {
     try {
       const input = cardUpdateSchema.parse(req.body);
diff --git a/packages/frontend/src/api/cards.ts b/packages/frontend/src/api/cards.ts
new file mode 100644
index 0000000..a9e4cb4
--- /dev/null
+++ b/packages/frontend/src/api/cards.ts
@@ -0,0 +1,23 @@
+import type { Card, CardCreateInput, CardUpdateInput } from '@flashcard/shared';
+import { api } from './client.js';
+
+export interface ImportResult {
+  inserted: number; updated: number; skipped: number; errors: { row: number; message: string }[];
+}
+
+export const cardsApi = {
+  list: (lessonId: number) => api.get<Card[]>(`/lessons/${lessonId}/cards`),
+  get: (id: number) => api.get<Card>(`/cards/${id}`),
+  create: (lessonId: number, input: CardCreateInput) => api.post<Card>(`/lessons/${lessonId}/cards`, input),
+  update: (id: number, input: CardUpdateInput) => api.patch<Card>(`/cards/${id}`, input),
+  remove: (id: number) => api.delete<void>(`/cards/${id}`),
+  importXlsx: (lessonId: number, file: File, opts: { updateExisting: boolean; createMissingLessons: boolean }) => {
+    const fd = new FormData();
+    fd.append('file', file);
+    fd.append('updateExisting', String(opts.updateExisting));
+    fd.append('createMissingLessons', String(opts.createMissingLessons));
+    return api.postForm<ImportResult>(`/lessons/${lessonId}/cards/import`, fd);
+  },
+  exportUrl: (lessonId: number, includeDescendants: boolean) =>
+    `/api/lessons/${lessonId}/cards/export?include_descendants=${includeDescendants}`,
+};
diff --git a/packages/frontend/src/api/client.ts b/packages/frontend/src/api/client.ts
new file mode 100644
index 0000000..4d044c0
--- /dev/null
+++ b/packages/frontend/src/api/client.ts
@@ -0,0 +1,38 @@
+export class ApiClientError extends Error {
+  constructor(public status: number, public code: string, message: string, public details?: unknown) {
+    super(message);
+  }
+}
+
+async function request<T>(method: string, path: string, body?: unknown, opts?: { isFormData?: boolean }): Promise<T> {
+  const headers: Record<string, string> = {};
+  let payload: BodyInit | undefined;
+  if (opts?.isFormData) {
+    payload = body as FormData;
+  } else if (body !== undefined) {
+    headers['Content-Type'] = 'application/json';
+    payload = JSON.stringify(body);
+  }
+  const res = await fetch(`/api${path}`, { method, headers, body: payload });
+  if (res.status === 204) return undefined as T;
+  const isJson = res.headers.get('content-type')?.includes('application/json');
+  const data = isJson ? await res.json() : await res.blob();
+  if (!res.ok) {
+    const e = (data as { error?: { code: string; message: string; details?: unknown } }).error;
+    throw new ApiClientError(res.status, e?.code ?? 'UNKNOWN', e?.message ?? 'Request failed', e?.details);
+  }
+  return data as T;
+}
+
+export const api = {
+  get: <T>(path: string) => request<T>('GET', path),
+  post: <T>(path: string, body?: unknown) => request<T>('POST', path, body),
+  postForm: <T>(path: string, form: FormData) => request<T>('POST', path, form, { isFormData: true }),
+  patch: <T>(path: string, body: unknown) => request<T>('PATCH', path, body),
+  delete: <T>(path: string) => request<T>('DELETE', path),
+  getBlob: async (path: string): Promise<Blob> => {
+    const res = await fetch(`/api${path}`);
+    if (!res.ok) throw new ApiClientError(res.status, 'UNKNOWN', 'Request failed');
+    return res.blob();
+  },
+};
diff --git a/packages/frontend/src/api/lessons.ts b/packages/frontend/src/api/lessons.ts
new file mode 100644
index 0000000..f531dca
--- /dev/null
+++ b/packages/frontend/src/api/lessons.ts
@@ -0,0 +1,10 @@
+import type { Lesson, LessonCreateInput, LessonMoveInput, LessonTreeNode, LessonUpdateInput } from '@flashcard/shared';
+import { api } from './client.js';
+
+export const lessonsApi = {
+  tree: () => api.get<LessonTreeNode[]>('/lessons/tree'),
+  create: (input: LessonCreateInput) => api.post<Lesson>('/lessons', input),
+  update: (id: number, input: LessonUpdateInput) => api.patch<Lesson>(`/lessons/${id}`, input),
+  remove: (id: number) => api.delete<void>(`/lessons/${id}`),
+  move: (id: number, input: LessonMoveInput) => api.post<Lesson>(`/lessons/${id}/move`, input),
+};
diff --git a/packages/frontend/src/api/sessions.ts b/packages/frontend/src/api/sessions.ts
new file mode 100644
index 0000000..85f4b0c
--- /dev/null
+++ b/packages/frontend/src/api/sessions.ts
@@ -0,0 +1,15 @@
+import type { QueueItem, SessionRow, SessionStartInput, AttemptCreateInput } from '@flashcard/shared';
+import { api } from './client.js';
+
+export interface StartedSession { session: SessionRow; queue: QueueItem[]; }
+export interface SessionState { session: SessionRow; queue: QueueItem[]; index: number; }
+
+export const sessionsApi = {
+  start: (input: SessionStartInput) => api.post<StartedSession>('/sessions', input),
+  active: () => api.get<SessionRow | null>('/sessions/active'),
+  state: (id: number) => api.get<SessionState>(`/sessions/${id}`),
+  next: (id: number) => api.get<{ done: true } | { done: false; item: QueueItem }>(`/sessions/${id}/next`),
+  attempt: (id: number, input: AttemptCreateInput) => api.post<void>(`/sessions/${id}/attempts`, input),
+  end: (id: number) => api.post<SessionRow>(`/sessions/${id}/end`),
+  abandon: (id: number) => api.post<SessionRow>(`/sessions/${id}/abandon`),
+};
diff --git a/packages/frontend/src/api/stats.ts b/packages/frontend/src/api/stats.ts
new file mode 100644
index 0000000..a396083
--- /dev/null
+++ b/packages/frontend/src/api/stats.ts
@@ -0,0 +1,23 @@
+import { api } from './client.js';
+
+export interface Overview {
+  totalSessions: number; totalDurationSeconds: number; totalAttempts: number; streakDays: number;
+  recentSessions: { id: number; lessonId: number; startedAt: number; durationSeconds: number | null; cardsShown: number; cardsCorrect: number }[];
+}
+export interface LessonStats {
+  lessonId: number; totalCards: number; mastered: number; score: number;
+  sessions: number; totalDurationSeconds: number; attempts: number; correct: number; incorrect: number;
+}
+export interface CardStats {
+  cardId: number; attempts: number; correct: number; incorrect: number;
+  box: { forward: number; backward: number | null };
+  lastShownAt: number | null; nextDueAt: number;
+  history: { shownAt: number; result: 'correct' | 'incorrect'; direction: 'forward' | 'backward' }[];
+}
+
+export const statsApi = {
+  overview: () => api.get<Overview>('/stats/overview'),
+  lesson: (id: number) => api.get<LessonStats>(`/stats/lessons/${id}`),
+  card: (id: number) => api.get<CardStats>(`/stats/cards/${id}`),
+  heatmap: (weeks = 12) => api.get<{ day: string; sessions: number; attempts: number }[]>(`/stats/heatmap?weeks=${weeks}`),
+};