diff --git a/modules/rcart/mod.ts b/modules/rcart/mod.ts
index 02d10bd..8aa401b 100644
--- a/modules/rcart/mod.ts
+++ b/modules/rcart/mod.ts
@@ -30,7 +30,7 @@ import {
 	type CartItem, type CartStatus,
 } from './schemas';
 import { extractProductFromUrl } from './extract';
-import { createTransakWidgetUrl } from '../../shared/transak';
+import { createTransakWidgetUrl, extractRootDomain } from '../../shared/transak';
 import QRCode from 'qrcode';
 
 let _syncServer: SyncServer | null = null;
@@ -1368,9 +1368,11 @@ routes.post("/api/payments/:id/transak-session", async (c) => {
 
 	const networkMap: Record<number, string> = { 8453: 'base', 84532: 'base', 1: 'ethereum' };
 
+	const host = new URL(c.req.url).hostname;
+
 	const widgetUrl = createTransakWidgetUrl({
 		apiKey: transakApiKey,
-		referrerDomain: 'rspace.online',
+		referrerDomain: extractRootDomain(host),
 		cryptoCurrencyCode: p.token,
 		network: networkMap[p.chainId] || 'base',
 		defaultCryptoCurrency: p.token,
diff --git a/modules/rflows/lib/onramp-provider.ts b/modules/rflows/lib/onramp-provider.ts
index b6f6294..7593f6f 100644
--- a/modules/rflows/lib/onramp-provider.ts
+++ b/modules/rflows/lib/onramp-provider.ts
@@ -14,6 +14,7 @@ export interface OnrampSessionRequest {
 	fiatCurrency: string;
 	sessionId: string;
 	returnUrl?: string;
+	hostname?: string;
 }
 
 export interface OnrampSessionResult {
diff --git a/modules/rflows/lib/transak-onramp.ts b/modules/rflows/lib/transak-onramp.ts
index 6895a93..6eeee37 100644
--- a/modules/rflows/lib/transak-onramp.ts
+++ b/modules/rflows/lib/transak-onramp.ts
@@ -4,7 +4,7 @@
  */
 
 import type { OnrampProvider, OnrampSessionRequest, OnrampSessionResult } from './onramp-provider';
-import { createTransakWidgetUrl } from '../../../shared/transak';
+import { createTransakWidgetUrl, extractRootDomain } from '../../../shared/transak';
 
 export class TransakOnrampAdapter implements OnrampProvider {
 	id = 'transak' as const;
@@ -20,7 +20,7 @@ export class TransakOnrampAdapter implements OnrampProvider {
 
 		const widgetParams: Record<string, string> = {
 			apiKey,
-			referrerDomain: 'rspace.online',
+			referrerDomain: req.hostname ? extractRootDomain(req.hostname) : 'rspace.online',
 			cryptoCurrencyCode: 'USDC',
 			network: 'base',
 			defaultCryptoCurrency: 'USDC',
diff --git a/modules/rflows/mod.ts b/modules/rflows/mod.ts
index 6cd3622..7732cea 100644
--- a/modules/rflows/mod.ts
+++ b/modules/rflows/mod.ts
@@ -233,6 +233,7 @@ routes.post("/api/flows/user-onramp", async (c) => {
 			fiatCurrency,
 			sessionId,
 			returnUrl,
+			hostname: new URL(c.req.url).hostname,
 		});
 
 		console.log(`[rflows] On-ramp session created: provider=${provider} session=${sessionId} wallet=${wallet.address}`);
diff --git a/shared/transak.ts b/shared/transak.ts
index 5f304ce..0d8e9ff 100644
--- a/shared/transak.ts
+++ b/shared/transak.ts
@@ -9,6 +9,12 @@
 const TRANSAK_WIDGET_BASE = 'https://global.transak.com';
 const TRANSAK_WIDGET_BASE_STG = 'https://global-stg.transak.com';
 
+/** Extract root domain from a hostname (e.g. "demo.rspace.online" → "rspace.online") */
+export function extractRootDomain(host: string): string {
+	const parts = host.replace(/:\d+$/, '').split('.');
+	return parts.length > 2 ? parts.slice(-2).join('.') : parts.join('.');
+}
+
 export function createTransakWidgetUrl(params: Record<string, string>): string {
 	const env = process.env.TRANSAK_ENV || 'PRODUCTION';
 	const base = env === 'PRODUCTION' ? TRANSAK_WIDGET_BASE : TRANSAK_WIDGET_BASE_STG;