diff --git a/apps/api/src/app.ts b/apps/api/src/app.ts
index 147dcc2e..c3acc678 100644
--- a/apps/api/src/app.ts
+++ b/apps/api/src/app.ts
@@ -1,6 +1,7 @@
 import 'dotenv/config';
 
-import { API_SERVER_URL, TRUSTED_ORIGINS } from '@api/constants';
+import { API_SERVER_URL } from '@api/constants';
+import { resolveTrustedBrowserOriginForCors } from '@api/utils/origins';
 
 import { Hono } from '@api/utils/hono';
 import { accountRouter } from '@api/routes/account';
@@ -44,7 +45,7 @@ export const app = new Hono()
   .use(
     '*',
     cors({
-      origin: TRUSTED_ORIGINS,
+      origin: (origin) => resolveTrustedBrowserOriginForCors(origin),
       allowMethods: ['GET', 'POST', 'PUT', 'PATCH', 'DELETE', 'OPTIONS'],
       allowHeaders: ['Content-Type', 'Authorization', 'Cio-org-id'],
       exposeHeaders: ['Content-Length', 'X-Kuma-Revision'],
diff --git a/apps/api/src/constants/index.ts b/apps/api/src/constants/index.ts
index 666be2f1..50ffa991 100644
--- a/apps/api/src/constants/index.ts
+++ b/apps/api/src/constants/index.ts
@@ -6,7 +6,7 @@ export const API_PORT = env.PORT ? parseInt(env.PORT) : 3002;
 export const API_SERVER_URL = env.PUBLIC_SERVER_URL || `http://localhost:${API_PORT}`;
 export const TRUSTED_ORIGINS = env.TRUSTED_ORIGINS
   ? env.TRUSTED_ORIGINS.split(',')
-  : ['http://localhost:5173', 'http://localhost:5180', 'http://*.classroomio.*'];
+  : ['http://localhost:5173', 'http://localhost:5180', 'https://*.classroomio.com'];
 
 const {
   CLOUDFLARE_BUCKET_DOMAIN,
diff --git a/apps/api/src/index.ts b/apps/api/src/index.ts
index 8b197d20..b781d6a5 100644
--- a/apps/api/src/index.ts
+++ b/apps/api/src/index.ts
@@ -2,9 +2,10 @@ import 'dotenv/config';
 
 import { API_PORT } from '@api/constants';
 import { app } from '@api/app';
-import { env } from '@api/config/env';
 import { configureOpenAPI } from '@api/utils/openapi';
 import { connectRedis } from '@api/utils/redis/redis';
+import { env } from '@api/config/env';
+import { preloadVerifiedCustomDomainOriginsRegistry } from '@api/utils/origins';
 import { serve } from '@hono/node-server';
 import { showRoutes } from 'hono/dev';
 
@@ -15,6 +16,10 @@ async function startServer() {
   // Connect to Redis (non-blocking: API starts even if Redis fails)
   await connectRedis();
 
+  preloadVerifiedCustomDomainOriginsRegistry().then(() => {
+    console.log('Verified custom domain origins preloaded');
+  });
+
   serve({ fetch: app.fetch, port: API_PORT });
 
   if (env.NODE_ENV !== 'production') {
diff --git a/apps/api/src/services/organization.ts b/apps/api/src/services/organization.ts
index a6d3db8e..2fbaee3e 100644
--- a/apps/api/src/services/organization.ts
+++ b/apps/api/src/services/organization.ts
@@ -13,6 +13,7 @@ import {
   getOrgIdBySiteName,
   getOrganizationAudience,
   getOrganizationAudienceMember,
+  getOrganizationById,
   getOrganizationBySiteName,
   getOrganizationTeam,
   getOrganizations,
@@ -42,6 +43,7 @@ import { createOrganizationWithOwner } from '@api/services/onboarding';
 import { deriveAudienceMemberStatus } from '@api/utils/audience-member-status';
 import { getProfileById } from '@cio/db/queries/auth';
 import { inviteTeamMembers as inviteTeamMembersSecure } from './organization/invite';
+import { trustCustomDomainHostname, untrustCustomDomainHostname } from '@cio/db/utils';
 
 const PUBLIC_ORG_LANDING_PAGE_COURSE_LIMIT = 4;
 
@@ -572,10 +574,32 @@ export async function updateOrg(orgId: string, data: Partial<TOrganization>) {
       }
     }
 
+    let previousCustomDomainHostname: string | undefined;
+
+    if (data.customDomain !== undefined || data.isCustomDomainVerified !== undefined) {
+      const previousOrg = await getOrganizationById(orgId);
+      const oldHost = previousOrg?.customDomain?.trim().toLowerCase();
+
+      if (oldHost) {
+        previousCustomDomainHostname = oldHost;
+      }
+    }
+
     const organization = await updateOrganization(orgId, data);
     if (!organization) {
       throw new AppError('Organization not found', ErrorCodes.ORGANIZATION_NOT_FOUND, 404);
     }
+
+    if (previousCustomDomainHostname) {
+      untrustCustomDomainHostname(previousCustomDomainHostname);
+    }
+
+    const newCustomDomainHostname = organization.customDomain?.trim().toLowerCase();
+
+    if (newCustomDomainHostname && organization.isCustomDomainVerified) {
+      trustCustomDomainHostname(newCustomDomainHostname);
+    }
+
     return organization;
   } catch (error) {
     if (error instanceof AppError) {
diff --git a/apps/api/src/utils/origins.ts b/apps/api/src/utils/origins.ts
new file mode 100644
index 00000000..393ac063
--- /dev/null
+++ b/apps/api/src/utils/origins.ts
@@ -0,0 +1,21 @@
+import {
+  preloadVerifiedCustomDomainOrigins,
+  resolveTrustedBrowserOrigin,
+  trustCustomDomainHostname,
+  untrustCustomDomainHostname
+} from '@cio/db/utils';
+
+import { TRUSTED_ORIGINS } from '@api/constants';
+
+const staticTrustedOriginEntries = TRUSTED_ORIGINS.map((entry) => entry.trim()).filter(Boolean) as readonly string[];
+
+export async function preloadVerifiedCustomDomainOriginsRegistry(): Promise<void> {
+  await preloadVerifiedCustomDomainOrigins();
+}
+
+export function resolveTrustedBrowserOriginForCors(origin: string): string | undefined {
+  console.log('check origin', origin);
+  return resolveTrustedBrowserOrigin(origin, staticTrustedOriginEntries);
+}
+
+export { trustCustomDomainHostname, untrustCustomDomainHostname };
diff --git a/apps/website/src/lib/components/hero.svelte b/apps/website/src/lib/components/hero.svelte
index eb70abcd..0bc20405 100644
--- a/apps/website/src/lib/components/hero.svelte
+++ b/apps/website/src/lib/components/hero.svelte
@@ -82,7 +82,7 @@
   </div>
 
   <!-- Particle cloud — same component used in the footer at lower intensity -->
-  <ParticleField class="absolute inset-0 z-[2] h-full w-full" />
+  <ParticleField class="pointer-events-none absolute inset-0 z-[2] hidden h-full w-full md:block" />
 
   <!-- Bottom fade to next section -->
   <div
diff --git a/packages/db/package.json b/packages/db/package.json
index fe623be4..602aa550 100644
--- a/packages/db/package.json
+++ b/packages/db/package.json
@@ -25,6 +25,10 @@
       "types": "./dist/auth.d.ts",
       "default": "./dist/auth.js"
     },
+    "./utils": {
+      "types": "./dist/utils/index.d.ts",
+      "default": "./dist/utils/index.js"
+    },
     "./queries": {
       "types": "./dist/queries/index.d.ts",
       "default": "./dist/queries/index.js"
diff --git a/packages/db/src/auth.ts b/packages/db/src/auth.ts
index 033bcdee..9c4f98be 100644
--- a/packages/db/src/auth.ts
+++ b/packages/db/src/auth.ts
@@ -1,4 +1,5 @@
 import * as CONSTANTS from './constants';
+import { resolveTrustedBrowserOrigin } from './utils';
 import * as schema from '@db/schema';
 
 import { admin, anonymous } from 'better-auth/plugins';
@@ -43,7 +44,17 @@ export const auth: ReturnType<typeof betterAuth> = betterAuth({
       prompt: 'select_account consent'
     }
   },
-  trustedOrigins: CONSTANTS.TRUSTED_ORIGINS,
+  trustedOrigins: (request) => {
+    const origins = [...CONSTANTS.TRUSTED_ORIGINS];
+    const originHeader = request?.headers.get('origin');
+    const resolved = resolveTrustedBrowserOrigin(originHeader, CONSTANTS.TRUSTED_ORIGINS);
+
+    if (resolved && !origins.includes(resolved)) {
+      origins.push(resolved);
+    }
+
+    return origins;
+  },
   advanced: {
     cookiePrefix: 'classroomio',
     crossSubDomainCookies: {
diff --git a/packages/db/src/constants.ts b/packages/db/src/constants.ts
index cf3f027c..cb10bcb6 100644
--- a/packages/db/src/constants.ts
+++ b/packages/db/src/constants.ts
@@ -6,7 +6,7 @@ const {
 
 const DEFAULT_TRUSTED_ORIGINS = [
   'http://localhost:5173',
-  'http://*.classroomio.*',
+  'https://*.classroomio.com',
   // Common OIDC IdP discovery origins (SSO registration fetches .well-known/openid-configuration)
   'https://accounts.google.com',
   'https://account.google.com', // common typo for Google
diff --git a/packages/db/src/queries/organization/organization.ts b/packages/db/src/queries/organization/organization.ts
index 1304eb03..b765c843 100644
--- a/packages/db/src/queries/organization/organization.ts
+++ b/packages/db/src/queries/organization/organization.ts
@@ -8,7 +8,7 @@ import type {
   TOrganization,
   TOrganizationPlan
 } from '@db/types';
-import { and, asc, count, desc, eq, ilike, inArray, or, sql } from 'drizzle-orm';
+import { and, asc, count, desc, eq, ilike, inArray, isNotNull, or, sql } from 'drizzle-orm';
 
 import { ROLE } from '@cio/utils/constants';
 import { db, type DbOrTxClient } from '@db/drizzle';
@@ -18,6 +18,26 @@ export function getOrgIdBySiteName(siteName: string) {
   return db.select().from(schema.organization).where(eq(schema.organization.siteName, siteName)).limit(1);
 }
 
+/**
+ * Hostnames (lowercase) for organizations with a verified custom domain.
+ * Used by the API to warm an in-memory CORS / trusted-origin registry at startup.
+ */
+export async function getVerifiedCustomDomainHostnames(): Promise<string[]> {
+  try {
+    const rows = await db
+      .select({ customDomain: schema.organization.customDomain })
+      .from(schema.organization)
+      .where(and(eq(schema.organization.isCustomDomainVerified, true), isNotNull(schema.organization.customDomain)));
+
+    return [...new Set(rows.map((row) => row.customDomain?.trim().toLowerCase()).filter(Boolean) as string[])];
+  } catch (error) {
+    console.error('getVerifiedCustomDomainHostnames error:', error);
+    throw new Error(
+      `Failed to load verified custom domains: ${error instanceof Error ? error.message : 'Unknown error'}`
+    );
+  }
+}
+
 export const getOrganizationByProfileId = async (profileId: string): Promise<OrganizationWithMemberAndPlans[]> => {
   const result = await db
     .select({
diff --git a/packages/db/src/utils/custom-domain/trusted-origin.ts b/packages/db/src/utils/custom-domain/trusted-origin.ts
new file mode 100644
index 00000000..5ed787e5
--- /dev/null
+++ b/packages/db/src/utils/custom-domain/trusted-origin.ts
@@ -0,0 +1,94 @@
+import { getVerifiedCustomDomainHostnames } from '../../queries/organization/organization';
+
+const CLASSROOMIO_ROOT = 'classroomio.com';
+
+/** Lowercase hostnames with verified custom domains ( warmed at API boot + updated on domain routes ). */
+const verifiedCustomDomainHostnames = new Set<string>();
+
+function originMatchesStaticEntry(origin: string, entry: string): boolean {
+  const trimmedEntry = entry.trim();
+
+  if (!trimmedEntry.includes('*')) {
+    return origin === trimmedEntry;
+  }
+
+  const regex = new RegExp(
+    `^${trimmedEntry
+      .split('*')
+      .map((part) => part.replace(/[.+?^${}()|[\]\\]/g, '\\$&'))
+      .join('.*')}$`
+  );
+
+  return regex.test(origin);
+}
+
+function isClassroomioHost(hostname: string): boolean {
+  const host = hostname.toLowerCase();
+
+  return host === CLASSROOMIO_ROOT || host.endsWith(`.${CLASSROOMIO_ROOT}`);
+}
+
+export function trustCustomDomainHostname(hostname: string): void {
+  const normalized = hostname.trim().toLowerCase();
+
+  if (normalized) {
+    verifiedCustomDomainHostnames.add(normalized);
+  }
+}
+
+export function untrustCustomDomainHostname(hostname: string): void {
+  verifiedCustomDomainHostnames.delete(hostname.trim().toLowerCase());
+}
+
+export async function preloadVerifiedCustomDomainOrigins(): Promise<void> {
+  const hostnames = await getVerifiedCustomDomainHostnames();
+
+  verifiedCustomDomainHostnames.clear();
+
+  for (const hostname of hostnames) {
+    verifiedCustomDomainHostnames.add(hostname);
+  }
+}
+
+/**
+ * Resolves whether a browser `Origin` header value is allowed for CORS / Better Auth.
+ * `staticTrustedOriginEntries` may include exact origins or `*` patterns (e.g. https://*.classroomio.com).
+ */
+export function resolveTrustedBrowserOrigin(
+  origin: string | undefined | null,
+  staticTrustedOriginEntries: readonly string[]
+): string | undefined {
+  if (!origin || origin === 'null') {
+    return undefined;
+  }
+
+  let parsed: URL;
+
+  try {
+    parsed = new URL(origin);
+  } catch {
+    return undefined;
+  }
+
+  if (parsed.protocol !== 'http:' && parsed.protocol !== 'https:') {
+    return undefined;
+  }
+
+  for (const entry of staticTrustedOriginEntries) {
+    if (originMatchesStaticEntry(origin, entry)) {
+      return origin;
+    }
+  }
+
+  const hostname = parsed.hostname;
+
+  if (isClassroomioHost(hostname)) {
+    return origin;
+  }
+
+  if (verifiedCustomDomainHostnames.has(hostname.toLowerCase())) {
+    return origin;
+  }
+
+  return undefined;
+}
diff --git a/packages/db/src/utils/index.ts b/packages/db/src/utils/index.ts
new file mode 100644
index 00000000..5ad88428
--- /dev/null
+++ b/packages/db/src/utils/index.ts
@@ -0,0 +1 @@
+export * from './custom-domain/trusted-origin';