diff --git a/src/test/audit-outbox.spec.ts b/src/test/audit-outbox.spec.ts
new file mode 100644
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--- /dev/null
+++ b/src/test/audit-outbox.spec.ts
@@ -0,0 +1,118 @@
+/**
+ * Audit, Outbox and Transaction Integration Tests
+ *
+ * Verifies that:
+ * 1. audit_log rows are created for mutations
+ * 2. outbox_events rows are created atomically
+ * 3. Transactions store amounts in minor units (no float drift)
+ *
+ * Runs against real DB via DATABASE_URL. Skip if not set.
+ */
+import { eq, desc } from 'drizzle-orm';
+import { db } from '../db/client';
+import { auditLog, outboxEvents, transactions } from '../db/schema';
+
+const HAS_DB = !!process.env.DATABASE_URL;
+
+const TENANT = '00000000-0000-0000-0000-000000000c01';
+const USER = '00000000-0000-0000-0000-000000000c02';
+const ORG = '00000000-0000-0000-0000-000000000c03';
+
+(HAS_DB ? describe : describe.skip)('Audit Log', () => {
+  it('audit record is written with correct tenant and actor', async () => {
+    // Arrange
+    const resource = `test:audit-${Date.now()}`;
+
+    // Act
+    await db.insert(auditLog).values({
+      tenantId: TENANT,
+      actorId: USER,
+      action: 'test.audit_integration',
+      resource,
+    });
+
+    // Assert
+    const row = await db.query.auditLog.findFirst({
+      where: eq(auditLog.resource, resource),
+    });
+    expect(row).toBeDefined();
+    expect(row!.tenantId).toBe(TENANT);
+    expect(row!.actorId).toBe(USER);
+    expect(row!.action).toBe('test.audit_integration');
+
+    // Cleanup
+    await db.delete(auditLog).where(eq(auditLog.resource, resource));
+  });
+});
+
+(HAS_DB ? describe : describe.skip)('Outbox Events', () => {
+  it('outbox event is persisted with correct aggregate info', async () => {
+    // Arrange
+    const subjectId = '00000000-0000-0000-0000-aabbccddeeff';
+    const correlationId = `test-${Date.now()}`;
+
+    // Act
+    const [row] = await db
+      .insert(outboxEvents)
+      .values({
+        tenantId: TENANT,
+        actorId: USER,
+        eventType: 'test.integration_event',
+        aggregateType: 'test',
+        subjectId,
+        correlationId,
+        payload: { test: true } as unknown,
+      })
+      .returning();
+
+    // Assert
+    expect(row.tenantId).toBe(TENANT);
+    expect(row.eventType).toBe('test.integration_event');
+    expect(row.processedAt).toBeNull();
+
+    // Cleanup
+    await db.delete(outboxEvents).where(eq(outboxEvents.id, row.id));
+  });
+});
+
+(HAS_DB ? describe : describe.skip)('Transactions - minor units integrity', () => {
+  let txId: string;
+
+  afterAll(async () => {
+    if (txId) await db.delete(transactions).where(eq(transactions.id, txId));
+  });
+
+  it('stores amount as integer string (no float drift)', async () => {
+    // Arrange — 1234 EUR = 123400 eurocenti
+    const amountCents = 123400;
+
+    // Act
+    const [row] = await db
+      .insert(transactions)
+      .values({
+        tenantId: TENANT,
+        organizationId: ORG,
+        type: 'invoice',
+        amountMinorUnits: String(amountCents),
+        currency: 'EUR',
+        transactionDate: new Date('2026-07-31'),
+        evidenceStatus: 'missing',
+      })
+      .returning();
+    txId = row.id;
+
+    // Assert — no float conversion artifacts
+    expect(row.amountMinorUnits).toBe('123400');
+    expect(parseFloat(row.amountMinorUnits)).toBe(123400);
+    expect(Number.isInteger(parseFloat(row.amountMinorUnits))).toBe(true);
+  });
+
+  it('tenant isolation: other tenant cannot see this transaction', async () => {
+    const OTHER_TENANT = '00000000-0000-0000-0000-000000000d99';
+    const rows = await db.query.transactions.findMany({
+      where: eq(transactions.tenantId, OTHER_TENANT),
+    });
+    const leaked = rows.filter((t) => t.id === txId);
+    expect(leaked).toHaveLength(0);
+  });
+});