diff --git a/packages/shared/src/index.ts b/packages/shared/src/index.ts
index cb0ff5c..e903b98 100644
--- a/packages/shared/src/index.ts
+++ b/packages/shared/src/index.ts
@@ -1 +1,2 @@
-export {};
+export * from './types.js';
+export * from './schemas.js';
diff --git a/packages/shared/src/schemas.ts b/packages/shared/src/schemas.ts
new file mode 100644
index 0000000..ab250dd
--- /dev/null
+++ b/packages/shared/src/schemas.ts
@@ -0,0 +1,45 @@
+import { z } from 'zod';
+
+export const lessonCreateSchema = z.object({
+  parentId: z.number().int().nullable().optional(),
+  name: z.string().min(1).max(200),
+  description: z.string().max(2000).optional().nullable(),
+  bidirectional: z.boolean().optional(),
+});
+
+export const lessonUpdateSchema = lessonCreateSchema.partial();
+
+export const lessonMoveSchema = z.object({
+  parentId: z.number().int().nullable(),
+  position: z.number().int().min(0),
+});
+
+export const cardCreateSchema = z.object({
+  question: z.string().min(1).max(2000),
+  answer: z.string().min(1).max(2000),
+  hint: z.string().max(2000).optional().nullable(),
+});
+
+export const cardUpdateSchema = cardCreateSchema.partial();
+
+export const sessionStartSchema = z.object({
+  lessonId: z.number().int().positive(),
+  maxCards: z.number().int().min(1).max(500).nullable().optional(),
+  shuffle: z.boolean().optional(),
+  direction: z.enum(['forward', 'backward', 'both']).optional(),
+});
+
+export const attemptCreateSchema = z.object({
+  cardId: z.number().int().positive(),
+  direction: z.enum(['forward', 'backward']),
+  result: z.enum(['correct', 'incorrect']),
+  timeToAnswerMs: z.number().int().min(0).nullable().optional(),
+});
+
+export type LessonCreateInput = z.infer<typeof lessonCreateSchema>;
+export type LessonUpdateInput = z.infer<typeof lessonUpdateSchema>;
+export type LessonMoveInput = z.infer<typeof lessonMoveSchema>;
+export type CardCreateInput = z.infer<typeof cardCreateSchema>;
+export type CardUpdateInput = z.infer<typeof cardUpdateSchema>;
+export type SessionStartInput = z.infer<typeof sessionStartSchema>;
+export type AttemptCreateInput = z.infer<typeof attemptCreateSchema>;
diff --git a/packages/shared/src/types.ts b/packages/shared/src/types.ts
new file mode 100644
index 0000000..1cc1220
--- /dev/null
+++ b/packages/shared/src/types.ts
@@ -0,0 +1,73 @@
+export type Direction = 'forward' | 'backward';
+export type AttemptResult = 'correct' | 'incorrect';
+export type SessionStatus = 'active' | 'completed' | 'abandoned';
+
+export interface Lesson {
+  id: number;
+  parentId: number | null;
+  name: string;
+  description: string | null;
+  position: number;
+  bidirectional: boolean;
+  createdAt: number;
+  updatedAt: number;
+}
+
+export interface LessonTreeNode extends Lesson {
+  children: LessonTreeNode[];
+  cardCount: number;
+}
+
+export interface Card {
+  id: number;
+  lessonId: number;
+  question: string;
+  answer: string;
+  hint: string | null;
+  position: number;
+  createdAt: number;
+  updatedAt: number;
+}
+
+export interface CardProgress {
+  cardId: number;
+  direction: Direction;
+  box: number;
+  correctCount: number;
+  incorrectCount: number;
+  lastShownAt: number | null;
+  nextDueAt: number;
+}
+
+export interface SessionRow {
+  id: number;
+  lessonId: number;
+  startedAt: number;
+  endedAt: number | null;
+  durationSeconds: number | null;
+  cardsShown: number;
+  cardsCorrect: number;
+  cardsIncorrect: number;
+  status: SessionStatus;
+}
+
+export interface Attempt {
+  id: number;
+  sessionId: number;
+  cardId: number;
+  direction: Direction;
+  shownAt: number;
+  result: AttemptResult;
+  timeToAnswerMs: number | null;
+}
+
+export interface QueueItem {
+  cardId: number;
+  direction: Direction;
+}
+
+export interface SessionSettings {
+  maxCards: number | null;
+  shuffle: boolean;
+  direction: 'forward' | 'backward' | 'both';
+}