diff --git a/CHANGELOG.md b/CHANGELOG.md
new file mode 100644
index 00000000..4d87cc2c
--- /dev/null
+++ b/CHANGELOG.md
@@ -0,0 +1,6 @@
+# Changelog
+
+## [Unreleased]
+
+### Fixed
+- Expressed explicit shared implementation wiring between `/api/v1/lottery` and `/api/v2/lottery` in `backend/src/routes/api.js`.
diff --git a/backend/src/index.ts b/backend/src/index.ts
index 2a7ed23b..46041765 100644
--- a/backend/src/index.ts
+++ b/backend/src/index.ts
@@ -23,6 +23,7 @@ import { requestLogger } from './middleware/requestLogger.js';
 import { requireWorkspaceMiddleware } from './middleware/WorkspaceContext.js';
 import freelanceRoute from './routes/freelance.js';
 import routes from './routes/index.js';
+import apiRouter from './routes/api.js';
 import { startWebhookWorker, stopWebhookWorker } from './services/webhooks/index.js';
 import { startBackupWorker, stopBackupWorker, scheduleBackupCron } from './jobs/backup.worker.js';
 import logger from './utils/logger.js';
@@ -184,6 +185,7 @@ setupGraphQL().catch(() => {});
 
 // API Routes - with workspace isolation
 app.use('/api/v1', requireWorkspaceMiddleware, createI18nMiddleware(), routes);
+app.use('/api', requireWorkspaceMiddleware, createI18nMiddleware(), apiRouter);
 
 // Swagger Documentation
 app.use('/api-docs', swaggerUi.serve, swaggerUi.setup(swaggerSpec, {
diff --git a/backend/src/routes/api.ts b/backend/src/routes/api.ts
new file mode 100644
index 00000000..71a72839
--- /dev/null
+++ b/backend/src/routes/api.ts
@@ -0,0 +1,28 @@
+import { Router } from 'express';
+import v2Lottery from './lottery.routes.js';
+
+const apiRouter = Router();
+const v1Router = Router();
+const v2Router = Router();
+
+/**
+ * Version 2 API Routes
+ */
+v2Router.use('/lottery', v2Lottery);
+
+/**
+ * Version 1 API Routes
+ *
+ * NOTE / EXPLICIT SPECIFICATION (Option 2 Fix):
+ * The v1 lottery router intentionally shares the v2Lottery router implementation.
+ * Both /api/v1/lottery and /api/v2/lottery maintain an identical contract and behavior.
+ * This shared mounting is deliberate to maintain backwards-compatibility for v1 consumers
+ * without maintaining redundant code until v1/v2 requirements diverge.
+ */
+v1Router.use('/lottery', v2Lottery);
+
+apiRouter.use('/v1', v1Router);
+apiRouter.use('/v2', v2Router);
+
+export default apiRouter;
+export { v1Router, v2Router };
diff --git a/backend/src/routes/index.ts b/backend/src/routes/index.ts
index e94446f4..5d2b323c 100644
--- a/backend/src/routes/index.ts
+++ b/backend/src/routes/index.ts
@@ -39,6 +39,7 @@ import simulatorRouter from '../simulator/simulator.routes.js';
 
 import webhooksRouter from './webhooks.js';
 import adminDLQRouter from './admin/dlq.routes.js';
+import apiRouter from './api.js';
 
 const router = Router();
 
@@ -79,5 +80,6 @@ router.use('/roadmap/tos', termsOfServiceRouter);
 router.use('/playground', playgroundRouter);
 router.use('/playground/privacy-policy', privacyPolicyRouter);
 router.use('/oauth', oauthRouter);
+router.use('/', apiRouter);
 
 export default router;
diff --git a/backend/src/routes/lottery.routes.ts b/backend/src/routes/lottery.routes.ts
new file mode 100644
index 00000000..b20fdb62
--- /dev/null
+++ b/backend/src/routes/lottery.routes.ts
@@ -0,0 +1,46 @@
+import { Router, Request, Response } from 'express';
+
+const lotteryRouter = Router();
+
+/**
+ * @openapi
+ * /api/v2/lottery:
+ *   get:
+ *     summary: Get current lottery details
+ *     tags: [Lottery]
+ *     responses:
+ *       200:
+ *         description: Current lottery status
+ */
+lotteryRouter.get('/', (_req: Request, res: Response) => {
+  res.json({
+    status: 'success',
+    data: {
+      lotteryId: 'lottery-active',
+      prizePool: '10000 XLM',
+      ticketPrice: '10 XLM',
+      status: 'open',
+    },
+  });
+});
+
+/**
+ * @openapi
+ * /api/v2/lottery/tickets:
+ *   post:
+ *     summary: Buy lottery tickets
+ *     tags: [Lottery]
+ */
+lotteryRouter.post('/tickets', (req: Request, res: Response) => {
+  const { amount } = req.body || {};
+  res.status(201).json({
+    status: 'success',
+    data: {
+      ticketsPurchased: amount || 1,
+      transactionHash: '0xmocklotterytxhash',
+    },
+  });
+});
+
+export default lotteryRouter;
+export { lotteryRouter as v2Lottery };
diff --git a/backend/tests/lottery.routes.test.ts b/backend/tests/lottery.routes.test.ts
new file mode 100644
index 00000000..8b3e4857
--- /dev/null
+++ b/backend/tests/lottery.routes.test.ts
@@ -0,0 +1,66 @@
+import request from 'supertest';
+import { app } from '../src/index';
+
+describe('Lottery Router API Versioning Integration Tests', () => {
+  describe('GET /api/v1/lottery and GET /api/v2/lottery', () => {
+    it('should respond to v1 lottery endpoint with valid lottery details', async () => {
+      const response = await request(app)
+        .get('/api/v1/lottery')
+        .set('x-workspace-id', 'test-workspace');
+
+      expect(response.status).toBe(200);
+      expect(response.body).toHaveProperty('status', 'success');
+      expect(response.body).toHaveProperty('data');
+      expect(response.body.data).toHaveProperty('lotteryId');
+    });
+
+    it('should respond to v2 lottery endpoint with valid lottery details', async () => {
+      const response = await request(app)
+        .get('/api/v2/lottery')
+        .set('x-workspace-id', 'test-workspace');
+
+      expect(response.status).toBe(200);
+      expect(response.body).toHaveProperty('status', 'success');
+      expect(response.body).toHaveProperty('data');
+      expect(response.body.data).toHaveProperty('lotteryId');
+    });
+
+    it('should return identical data contract for v1 and v2 shared router', async () => {
+      const responseV1 = await request(app)
+        .get('/api/v1/lottery')
+        .set('x-workspace-id', 'test-workspace');
+
+      const responseV2 = await request(app)
+        .get('/api/v2/lottery')
+        .set('x-workspace-id', 'test-workspace');
+
+      expect(responseV1.status).toBe(200);
+      expect(responseV2.status).toBe(200);
+      expect(responseV1.body).toEqual(responseV2.body);
+    });
+  });
+
+  describe('POST /api/v1/lottery/tickets and POST /api/v2/lottery/tickets', () => {
+    it('should allow purchasing tickets via v1 lottery endpoint', async () => {
+      const response = await request(app)
+        .post('/api/v1/lottery/tickets')
+        .set('x-workspace-id', 'test-workspace')
+        .send({ amount: 3 });
+
+      expect(response.status).toBe(201);
+      expect(response.body).toHaveProperty('status', 'success');
+      expect(response.body.data).toHaveProperty('ticketsPurchased', 3);
+    });
+
+    it('should allow purchasing tickets via v2 lottery endpoint', async () => {
+      const response = await request(app)
+        .post('/api/v2/lottery/tickets')
+        .set('x-workspace-id', 'test-workspace')
+        .send({ amount: 5 });
+
+      expect(response.status).toBe(201);
+      expect(response.body).toHaveProperty('status', 'success');
+      expect(response.body.data).toHaveProperty('ticketsPurchased', 5);
+    });
+  });
+});