diff --git a/src/core/schema.ts b/src/core/schema.ts
new file mode 100644
index 0000000..a211652
--- /dev/null
+++ b/src/core/schema.ts
@@ -0,0 +1,34 @@
+export const TOPICS_TABLE = 'topics';
+export const FACTS_TABLE = 'facts';
+export const FACT_TOPICS_TABLE = 'fact_topics';
+
+export const TOPIC_COLUMNS = [
+  'id',
+  'name',
+  'normalized_name',
+  'category',
+  'granularity',
+  'description',
+  'metadata',
+  'created_at',
+  'updated_at',
+] as const;
+
+export const FACT_COLUMNS = [
+  'id',
+  'statement',
+  'summary',
+  'source',
+  'confidence',
+  'metadata',
+  'created_at',
+  'updated_at',
+] as const;
+
+export const FACT_TOPIC_COLUMNS = [
+  'fact_id',
+  'topic_id',
+  'role',
+  'position',
+  'created_at',
+] as const;
diff --git a/src/types/api.ts b/src/types/api.ts
new file mode 100644
index 0000000..06ea540
--- /dev/null
+++ b/src/types/api.ts
@@ -0,0 +1,22 @@
+import type { JsonValue, TopicCategory, TopicGranularity } from './domain';
+
+export interface UpsertTopicInput {
+  name: string;
+  category?: TopicCategory;
+  granularity?: TopicGranularity;
+  description?: string | null;
+  metadata?: JsonValue | null;
+}
+
+export interface TopicLinkInput extends UpsertTopicInput {
+  role?: string | null;
+}
+
+export interface AddFactInput {
+  statement: string;
+  summary?: string | null;
+  source?: string | null;
+  confidence?: number | null;
+  metadata?: JsonValue | null;
+  topics: TopicLinkInput[];
+}
diff --git a/src/types/database.ts b/src/types/database.ts
new file mode 100644
index 0000000..2ce0ea2
--- /dev/null
+++ b/src/types/database.ts
@@ -0,0 +1,7 @@
+import type { FactRecord, FactTopicRecord, TopicRecord } from './domain';
+
+export interface IdentityDatabaseSchema {
+  topics: TopicRecord;
+  facts: FactRecord;
+  fact_topics: FactTopicRecord;
+}
diff --git a/src/types/domain.ts b/src/types/domain.ts
new file mode 100644
index 0000000..8ffcc13
--- /dev/null
+++ b/src/types/domain.ts
@@ -0,0 +1,37 @@
+export type TopicCategory = 'entity' | 'concept' | 'temporal' | 'custom';
+
+export type TopicGranularity = 'abstract' | 'concrete' | 'mixed';
+
+export type JsonPrimitive = string | number | boolean | null;
+export type JsonValue = JsonPrimitive | JsonValue[] | { [key: string]: JsonValue };
+
+export interface TopicRecord {
+  id: string;
+  name: string;
+  normalized_name: string;
+  category: TopicCategory;
+  granularity: TopicGranularity;
+  description: string | null;
+  metadata: string | null;
+  created_at: string;
+  updated_at: string;
+}
+
+export interface FactRecord {
+  id: string;
+  statement: string;
+  summary: string | null;
+  source: string | null;
+  confidence: number | null;
+  metadata: string | null;
+  created_at: string;
+  updated_at: string;
+}
+
+export interface FactTopicRecord {
+  fact_id: string;
+  topic_id: string;
+  role: string | null;
+  position: number;
+  created_at: string;
+}
diff --git a/tests/migrations.test.ts b/tests/migrations.test.ts
new file mode 100644
index 0000000..cafb721
--- /dev/null
+++ b/tests/migrations.test.ts
@@ -0,0 +1,88 @@
+import { sql } from 'kysely';
+import { afterEach, describe, expect, it } from 'vitest';
+
+import { createDatabase } from '../src/adapters/dialect';
+import { initializeSchema } from '../src/core/migrations';
+
+const openConnections: Array<() => Promise<void>> = [];
+
+afterEach(async () => {
+  while (openConnections.length > 0) {
+    const close = openConnections.pop();
+    if (close) {
+      await close();
+    }
+  }
+});
+
+describe('initializeSchema', () => {
+  it('creates the topics, facts, and fact_topics tables', async () => {
+    const connection = await createDatabase({ client: 'sqlite', filename: ':memory:' });
+    openConnections.push(connection.destroy);
+
+    await initializeSchema(connection.db);
+
+    const tables = await sql<{ name: string }>`
+      SELECT name
+      FROM sqlite_master
+      WHERE type = 'table'
+      ORDER BY name
+    `.execute(connection.db);
+
+    const tableNames = tables.rows.map((row) => row.name);
+
+    expect(tableNames).toContain('topics');
+    expect(tableNames).toContain('facts');
+    expect(tableNames).toContain('fact_topics');
+  });
+
+  it('creates the expected columns for each table', async () => {
+    const connection = await createDatabase({ client: 'sqlite', filename: ':memory:' });
+    openConnections.push(connection.destroy);
+
+    await initializeSchema(connection.db);
+
+    const topicsColumns = await sql<{ name: string }>`PRAGMA table_info(topics)`.execute(connection.db);
+    const factsColumns = await sql<{ name: string }>`PRAGMA table_info(facts)`.execute(connection.db);
+    const factTopicsColumns = await sql<{ name: string }>`PRAGMA table_info(fact_topics)`.execute(connection.db);
+
+    expect(topicsColumns.rows.map((row) => row.name)).toEqual([
+      'id',
+      'name',
+      'normalized_name',
+      'category',
+      'granularity',
+      'description',
+      'metadata',
+      'created_at',
+      'updated_at',
+    ]);
+
+    expect(factsColumns.rows.map((row) => row.name)).toEqual([
+      'id',
+      'statement',
+      'summary',
+      'source',
+      'confidence',
+      'metadata',
+      'created_at',
+      'updated_at',
+    ]);
+
+    expect(factTopicsColumns.rows.map((row) => row.name)).toEqual([
+      'fact_id',
+      'topic_id',
+      'role',
+      'position',
+      'created_at',
+    ]);
+  });
+
+  it('is idempotent when called more than once', async () => {
+    const connection = await createDatabase({ client: 'sqlite', filename: ':memory:' });
+    openConnections.push(connection.destroy);
+
+    await initializeSchema(connection.db);
+    await expect(initializeSchema(connection.db)).resolves.toBeUndefined();
+  });
+});