diff --git a/src/app/components/Account/AccountHeader/index.test.tsx b/src/app/components/Account/AccountHeader/index.test.tsx
index 21be09c88a0..2b4fcd25839 100644
--- a/src/app/components/Account/AccountHeader/index.test.tsx
+++ b/src/app/components/Account/AccountHeader/index.test.tsx
@@ -17,9 +17,6 @@ const idctaConfig: IdctaConfig = {
   signout_url: 'https://example.com/signout',
   foryou_url: 'https://example.com/foryou',
   initialIsSignedIn: false,
-  identity: {
-    idSignedInCookieName: 'ckns_id',
-  },
 };
 
 const renderWithProviders = (overrides = {}) =>
diff --git a/src/app/components/Account/AccountPromotionalBanner/index.test.tsx b/src/app/components/Account/AccountPromotionalBanner/index.test.tsx
index b255465d1e6..5a27f3bd7c3 100644
--- a/src/app/components/Account/AccountPromotionalBanner/index.test.tsx
+++ b/src/app/components/Account/AccountPromotionalBanner/index.test.tsx
@@ -15,9 +15,6 @@ const idctaConfig: IdctaConfig = {
   settings_url: 'https://example.com/settings',
   signout_url: 'https://example.com/signout',
   foryou_url: 'https://example.com/foryou',
-  identity: {
-    idSignedInCookieName: 'ckns_id',
-  },
 } as unknown as IdctaConfig;
 
 jest.mock('#app/hooks/useToggle');
diff --git a/src/app/contexts/AccountContext/index.test.tsx b/src/app/contexts/AccountContext/index.test.tsx
index 493f3bdf69e..71ea094b444 100644
--- a/src/app/contexts/AccountContext/index.test.tsx
+++ b/src/app/contexts/AccountContext/index.test.tsx
@@ -1,8 +1,6 @@
 /* eslint-disable @typescript-eslint/no-explicit-any */
 import { use } from 'react';
-import onClient from '#app/lib/utilities/onClient';
 import { IdctaConfig } from '#app/models/types/account';
-import Cookie from 'js-cookie';
 import { AccountContext } from '.';
 import {
   render,
@@ -10,8 +8,6 @@ import {
   waitFor,
 } from '../../components/react-testing-library-with-providers';
 
-jest.mock('#app/lib/utilities/onClient');
-
 const mockIdctaConfig = {
   'id-availability': 'GREEN',
   signin_url: 'https://example.com/signin',
@@ -21,15 +17,11 @@ const mockIdctaConfig = {
   foryou_url: 'https://example.com/foryou',
   unavailable_url: 'https://example.com/unavailable',
   initialIsSignedIn: true,
-  identity: {
-    idSignedInCookieName: 'ckns_id',
-  },
 } as IdctaConfig;
 
 describe('AccountContext', () => {
   beforeEach(() => {
     jest.clearAllMocks();
-    (onClient as jest.Mock).mockReturnValue(true);
 
     delete (window as any).location;
     window.location = { href: 'https://example.com/current-page' } as any;
@@ -176,21 +168,6 @@ describe('AccountContext', () => {
     expect(context.isSignedIn).toBe(false);
   });
 
-  it('should set isSignedIn to true when ckns_id cookie is present', () => {
-    jest.spyOn(Cookie, 'get').mockReturnValue('ckns_id_cookie_value' as any);
-
-    render(<TestComponent />, {
-      idctaConfig: { ...mockIdctaConfig, initialIsSignedIn: false },
-      service: 'hindi',
-    });
-
-    const testEl = screen.getByTestId('test-component');
-    const context = JSON.parse(testEl.textContent as string);
-
-    expect(Cookie.get).toHaveBeenCalledWith('ckns_id');
-    expect(context.isSignedIn).toBe(true);
-  });
-
   it('should handle null initialConfig gracefully', () => {
     render(<TestComponent />, {
       idctaConfig: null,
diff --git a/src/app/contexts/AccountContext/index.tsx b/src/app/contexts/AccountContext/index.tsx
index 60718814dda..19a2e54ec93 100644
--- a/src/app/contexts/AccountContext/index.tsx
+++ b/src/app/contexts/AccountContext/index.tsx
@@ -10,8 +10,6 @@ import { AccountContextProps, IdctaConfig } from '#app/models/types/account';
 import appendCtaQueryParams from '#app/lib/idcta/appendCtaQueryParams';
 import { ServiceContext } from '#app/contexts/ServiceContext';
 import { RequestContext } from '#app/contexts/RequestContext';
-import onClient from '#app/lib/utilities/onClient';
-import Cookie from 'js-cookie';
 import { getIdctaUserOrigin } from '#app/lib/idcta/getIDCTAUserOrigin';
 
 export const AccountContext = createContext<AccountContextProps>(
@@ -22,10 +20,6 @@ type AccountProviderProps = {
   initialConfig: IdctaConfig | null;
 };
 
-const getSignedInCookie = (cookieName = 'ckns_id') => {
-  return onClient() ? Cookie.get(cookieName) : false;
-};
-
 export const AccountProvider = ({
   children,
   initialConfig,
@@ -62,15 +56,8 @@ export const AccountProvider = ({
   const signOutUrl = buildAccountUrl(initialConfig?.signout_url);
   const forYouUrl = buildAccountUrl(initialConfig?.foryou_url);
 
-  // TODO: initialIsSignedIn is always false in test/live env due to filtered cookie header,
-  // it will be improved to detect signed-in status server side in the future
-  // Ticket: https://bbc.atlassian.net/browse/WS-2388
-  const clientSignedInState = getSignedInCookie(
-    initialConfig?.identity?.idSignedInCookieName,
-  );
   const isSignedIn =
-    isIdctaAvailable &&
-    Boolean(initialConfig?.initialIsSignedIn || clientSignedInState);
+    isIdctaAvailable && Boolean(initialConfig?.initialIsSignedIn);
 
   const value = useMemo(
     () => ({
diff --git a/src/app/lib/idcta/getIdctaConfig/index.test.ts b/src/app/lib/idcta/getIdctaConfig/index.test.ts
index 1cc52c54921..3d2b4ecb9d9 100644
--- a/src/app/lib/idcta/getIdctaConfig/index.test.ts
+++ b/src/app/lib/idcta/getIdctaConfig/index.test.ts
@@ -102,4 +102,36 @@ describe('getIdctaConfig', () => {
 
     expect(result).toBeNull();
   });
+
+  it('should set initialIsSignedIn to true when x-id-oidc-signedin header is "1"', async () => {
+    mockFetchIdctaConfig.mockResolvedValue(mockIdctaConfig);
+
+    const result = await getIdctaConfig(mockToggles, mockService, '1');
+
+    expect(result?.initialIsSignedIn).toBe(true);
+  });
+
+  it('should set initialIsSignedIn to false when x-id-oidc-signedin header is "0"', async () => {
+    mockFetchIdctaConfig.mockResolvedValue(mockIdctaConfig);
+
+    const result = await getIdctaConfig(mockToggles, mockService, '0');
+
+    expect(result?.initialIsSignedIn).toBe(false);
+  });
+
+  it('should set initialIsSignedIn to false when x-id-oidc-signedin header is absent', async () => {
+    mockFetchIdctaConfig.mockResolvedValue(mockIdctaConfig);
+
+    const result = await getIdctaConfig(mockToggles, mockService);
+
+    expect(result?.initialIsSignedIn).toBe(false);
+  });
+
+  it('should set initialIsSignedIn to false when x-id-oidc-signedin header has an invalid value', async () => {
+    mockFetchIdctaConfig.mockResolvedValue(mockIdctaConfig);
+
+    const result = await getIdctaConfig(mockToggles, mockService, 'invalid');
+
+    expect(result?.initialIsSignedIn).toBe(false);
+  });
 });
diff --git a/src/app/lib/idcta/getIdctaConfig/index.ts b/src/app/lib/idcta/getIdctaConfig/index.ts
index 6d946a7d5f5..1e1532ee77c 100644
--- a/src/app/lib/idcta/getIdctaConfig/index.ts
+++ b/src/app/lib/idcta/getIdctaConfig/index.ts
@@ -3,7 +3,6 @@ import getToggleDefinitions from '#app/lib/utilities/getToggleDefinition';
 import isLocal from '#app/lib/utilities/isLocal';
 import { IdctaConfig } from '#app/models/types/account';
 import { Toggles, Services } from '#app/models/types/global';
-import hasCookie from '#app/lib/utilities/hasCookie';
 import fetchIdctaConfig from '../fetchIdctaConfig';
 
 const logger = nodeLogger(__filename);
@@ -12,13 +11,13 @@ const logger = nodeLogger(__filename);
  * Gets IDCTA config with toggle validation and config verification
  * @param toggles - Feature toggles
  * @param service - Service name
- * @param cookieHeader - Cookie header from request
+ * @param signedInHeader - Value of x-id-oidc-signedin header forwarded by Belfrage
  * @returns Validated IdctaConfig with initialIsSignedIn or null
  */
 export default async function getIdctaConfig(
   toggles: Toggles,
   service: Services,
-  cookieHeader?: string,
+  signedInHeader?: string,
 ): Promise<IdctaConfig | null> {
   const toggleDefinitions = getToggleDefinitions(toggles);
   const { enabled: isAccountEnabled, value: accountService = '' } =
@@ -47,12 +46,6 @@ export default async function getIdctaConfig(
     return null;
   }
 
-  const cookieName = config?.identity?.idSignedInCookieName;
-  const initialIsSignedIn = Boolean(
-    cookieHeader && cookieName
-      ? hasCookie(cookieHeader, cookieName)
-      : undefined,
-  );
-
+  const initialIsSignedIn = signedInHeader === '1';
   return { ...config, initialIsSignedIn };
 }
diff --git a/src/app/models/types/account.ts b/src/app/models/types/account.ts
index c7dd6d9a285..2f7665a5c4b 100644
--- a/src/app/models/types/account.ts
+++ b/src/app/models/types/account.ts
@@ -10,9 +10,6 @@ export type IdctaConfig = {
   signout_url: string;
   foryou_url: string;
   initialIsSignedIn?: boolean;
-  identity: {
-    idSignedInCookieName: string;
-  };
 };
 
 export type AccountContextProps = {
diff --git a/ws-nextjs-app/pages/_app.page.tsx b/ws-nextjs-app/pages/_app.page.tsx
index a9d32bfb211..8a0c3d16cf2 100644
--- a/ws-nextjs-app/pages/_app.page.tsx
+++ b/ws-nextjs-app/pages/_app.page.tsx
@@ -96,11 +96,12 @@ export default class CustomApp extends App<Props> {
         ? (navResult.value?.data?.items ?? null)
         : null;
 
-    const cookieHeader = ctx.req?.headers?.cookie;
-    const idctaResult = await getIdctaConfig(toggles, service, cookieHeader);
+    const signedInHeader = ctx.req?.headers?.['x-id-oidc-signedin'] as
+      | string
+      | undefined;
+    const idctaResult = await getIdctaConfig(toggles, service, signedInHeader);
     const pageType =
       (ctx.req?.headers['page-type'] as PageTypes) || derivePageType(asPath);
-
     const serverSideExperiments = getServerExperiments({
       headers: ctx.req?.headers || {},
       service,