diff --git a/src/routes/links.test.ts b/src/routes/links.test.ts
index 4b579b0..eb17457 100644
--- a/src/routes/links.test.ts
+++ b/src/routes/links.test.ts
@@ -1,6 +1,8 @@
 import { beforeEach, describe, expect, it, vi } from 'vitest';
 
-const dbQueryMock = vi.fn();
+const { dbQueryMock } = vi.hoisted(() => ({
+  dbQueryMock: vi.fn(),
+}));
 
 vi.mock('../lib/database.js', () => ({
   db: {
@@ -15,17 +17,25 @@ describe('resolveLinkTemplateId', () => {
     dbQueryMock.mockReset();
   });
 
-  it('returns null when the provided template id does not exist', async () => {
-    dbQueryMock.mockResolvedValueOnce({ rows: [] });
-
-    await expect(resolveLinkTemplateId('00000000-0000-0000-0000-000000000000', null)).resolves.toBeNull();
-  });
-
-  it('falls back to template slug when the provided id is not usable', async () => {
+  it('falls back to the default template when the provided id does not exist', async () => {
     dbQueryMock.mockResolvedValueOnce({ rows: [] });
     dbQueryMock.mockResolvedValueOnce({ rows: [{ id: '11111111-1111-1111-1111-111111111111' }] });
 
+    await expect(resolveLinkTemplateId('00000000-0000-0000-0000-000000000000', null)).resolves.toBe('11111111-1111-1111-1111-111111111111');
+    expect(dbQueryMock).toHaveBeenNthCalledWith(2, 'SELECT id FROM link_templates WHERE is_default = true LIMIT 1');
+  });
+
+  it('uses the template slug when it can be resolved', async () => {
+    dbQueryMock.mockResolvedValueOnce({ rows: [{ id: '11111111-1111-1111-1111-111111111111' }] });
+
     await expect(resolveLinkTemplateId(null, 'default')).resolves.toBe('11111111-1111-1111-1111-111111111111');
-    expect(dbQueryMock).toHaveBeenNthCalledWith(2, 'SELECT id FROM link_templates WHERE slug = $1 LIMIT 1', ['default']);
+    expect(dbQueryMock).toHaveBeenCalledWith('SELECT id FROM link_templates WHERE slug = $1 LIMIT 1', ['default']);
+  });
+
+  it('falls back to the default template when the provided template id is invalid', async () => {
+    dbQueryMock.mockResolvedValueOnce({ rows: [{ id: '22222222-2222-2222-2222-222222222222' }] });
+
+    await expect(resolveLinkTemplateId('not-a-uuid', null)).resolves.toBe('22222222-2222-2222-2222-222222222222');
+    expect(dbQueryMock).toHaveBeenCalledWith('SELECT id FROM link_templates WHERE is_default = true LIMIT 1');
   });
 });
diff --git a/src/routes/links.ts b/src/routes/links.ts
index 58fa46d..01ebd71 100644
--- a/src/routes/links.ts
+++ b/src/routes/links.ts
@@ -13,6 +13,43 @@ async function getTemplateSlug(templateId: string | null): Promise<string | null
   return result.rows[0]?.slug ?? null;
 }
 
+export async function resolveLinkTemplateId(
+  templateId: string | null | undefined,
+  templateSlug: string | null | undefined
+): Promise<string | null> {
+  const normalizedTemplateId = templateId?.trim();
+  const normalizedSlug = templateSlug?.trim();
+
+  if (normalizedTemplateId) {
+    const parsed = z.string().uuid().safeParse(normalizedTemplateId);
+    if (parsed.success) {
+      const result = await db.query(
+        'SELECT id FROM link_templates WHERE id = $1 LIMIT 1',
+        [normalizedTemplateId]
+      );
+      if (result.rows[0]?.id) {
+        return result.rows[0].id;
+      }
+    }
+  }
+
+  if (normalizedSlug) {
+    const result = await db.query(
+      'SELECT id FROM link_templates WHERE slug = $1 LIMIT 1',
+      [normalizedSlug]
+    );
+    if (result.rows[0]?.id) {
+      return result.rows[0].id;
+    }
+  }
+
+  const defaultResult = await db.query(
+    'SELECT id FROM link_templates WHERE is_default = true LIMIT 1'
+  );
+
+  return defaultResult.rows[0]?.id ?? null;
+}
+
 const createLinkSchema = z.object({
   userId: z.string().uuid().optional(),
   templateId: z.string().uuid().optional(),
@@ -182,6 +219,7 @@ export async function linkRoutes(fastify: FastifyInstance) {
     }
 
     const originalUrl = data.originalUrl || 'https://angkorlifes.com';
+    const resolvedTemplateId = await resolveLinkTemplateId(data.templateId, null);
 
     const result = await db.query(
       `INSERT INTO links (
@@ -195,7 +233,7 @@ export async function linkRoutes(fastify: FastifyInstance) {
          RETURNING *`,
       [
         data.userId || null,
-        data.templateId || null,
+        resolvedTemplateId,
         shortCode,
         originalUrl,
         data.title || null,
@@ -238,6 +276,10 @@ export async function linkRoutes(fastify: FastifyInstance) {
     const { userId } = request.query;
 
     const data = updateLinkSchema.parse(request.body);
+    const resolvedData = {
+      ...data,
+      templateId: data.templateId === undefined ? undefined : await resolveLinkTemplateId(data.templateId, null),
+    };
 
     // Capture current identifiers for cache invalidation after the update
     const oldLinkResult = await db.query(
@@ -250,7 +292,7 @@ export async function linkRoutes(fastify: FastifyInstance) {
     const values: any[] = [];
     let paramIndex = 1;
 
-    Object.entries(data).forEach(([key, value]) => {
+    Object.entries(resolvedData).forEach(([key, value]) => {
       if (value !== undefined) {
         if (key === 'utmParameters' || key === 'targetingRules' || key === 'deepLinkParameters') {
           updates.push(`${key.replace(/([A-Z])/g, '_$1').toLowerCase()} = $${paramIndex}`);
diff --git a/src/routes/sdk.ts b/src/routes/sdk.ts
index 4146d04..7d0bd27 100644
--- a/src/routes/sdk.ts
+++ b/src/routes/sdk.ts
@@ -12,6 +12,7 @@ import { triggerWebhooks } from '../lib/webhook.js';
 import { parseUserAgent, getLocationFromIP, detectDevice } from '../lib/utils.js';
 import { emitClickEvent } from '../lib/event-emitter.js';
 import { classifyBot, edgeBotSignal } from '../lib/bot-detection.js';
+import { resolveLinkTemplateId } from './links.js';
 
 /**
  * SDK Routes - Mobile SDK endpoints for deferred deep linking
@@ -66,6 +67,7 @@ export async function sdkRoutes(fastify: FastifyInstance) {
     const originalUrl = body.originalUrl || 'https://angkorlifes.com';
 
     const shortCode = body.customCode || 'sdk-link';
+    const resolvedTemplateId = await resolveLinkTemplateId(body.templateId, null);
 
     const result = await db.query(
       `INSERT INTO links (
@@ -79,7 +81,7 @@ export async function sdkRoutes(fastify: FastifyInstance) {
       RETURNING *`,
       [
         body.userId || null,
-        body.templateId || null,
+        resolvedTemplateId,
         shortCode,
         originalUrl,
         body.title || null,