diff --git a/frontend/index.html b/frontend/index.html
index cdbc8a69d..5e4f3933f 100644
--- a/frontend/index.html
+++ b/frontend/index.html
@@ -1,4 +1,5 @@
 <!--
+Copyright 2025, 2026 Element Creations Ltd.
 Copyright 2024, 2025 New Vector Ltd.
 Copyright 2022-2024 The Matrix.org Foundation C.I.C.
 
@@ -14,15 +15,10 @@ Please see LICENSE files in the repository root for full details.
     <meta charset="UTF-8" />
     <meta name="viewport" content="width=device-width, initial-scale=1.0" />
     <title>matrix-authentication-service</title>
-    <script type="application/javascript">
-      window.APP_CONFIG = JSON.parse(
-        '{"root": "/account/", "graphqlEndpoint": "/graphql"}',
-      );
-    </script>
   </head>
 
   <body>
-    <div id="root"></div>
+    <div id="root" data-root="/account/" data-graphql-endpoint="/graphql"></div>
     <script type="module" src="/src/entrypoints/main.tsx"></script>
   </body>
 </html>
diff --git a/frontend/src/config.ts b/frontend/src/config.ts
deleted file mode 100644
index 2019620c6..000000000
--- a/frontend/src/config.ts
+++ /dev/null
@@ -1,22 +0,0 @@
-// Copyright 2024, 2025 New Vector Ltd.
-// Copyright 2022-2024 The Matrix.org Foundation C.I.C.
-//
-// SPDX-License-Identifier: AGPL-3.0-only OR LicenseRef-Element-Commercial
-// Please see LICENSE files in the repository root for full details.
-
-type AppConfig = {
-  root: string;
-  graphqlEndpoint: string;
-};
-
-interface IWindow {
-  APP_CONFIG?: AppConfig;
-}
-
-const config: AppConfig = (typeof window !== "undefined" &&
-  (window as IWindow).APP_CONFIG) || {
-  root: "/",
-  graphqlEndpoint: "/graphql",
-};
-
-export default config;
diff --git a/frontend/src/entrypoints/main.tsx b/frontend/src/entrypoints/main.tsx
index 0c24e9110..0635b09ab 100644
--- a/frontend/src/entrypoints/main.tsx
+++ b/frontend/src/entrypoints/main.tsx
@@ -1,33 +1,55 @@
+// Copyright 2025, 2026 Element Creations Ltd.
 // Copyright 2024, 2025 New Vector Ltd.
 // Copyright 2022-2024 The Matrix.org Foundation C.I.C.
 //
 // SPDX-License-Identifier: AGPL-3.0-only OR LicenseRef-Element-Commercial
 // Please see LICENSE files in the repository root for full details.
 
-import { QueryClientProvider } from "@tanstack/react-query";
+import { QueryClient, QueryClientProvider } from "@tanstack/react-query";
 import { RouterProvider } from "@tanstack/react-router";
 import { TooltipProvider } from "@vector-im/compound-web";
 import { StrictMode, Suspense } from "react";
 import { createRoot } from "react-dom/client";
 import { I18nextProvider } from "react-i18next";
+import * as v from "valibot";
 import ErrorBoundary from "../components/ErrorBoundary";
 import LoadingScreen from "../components/LoadingScreen";
-import { queryClient } from "../graphql";
+import { setGraphqlEndpoint } from "../graphql";
 import i18n, { setupI18n } from "../i18n";
-import { router } from "../router";
+import { makeRouter } from "../router";
 import "./vendor.css";
 import "./shared.css";
 
 setupI18n();
 
-createRoot(document.getElementById("root") as HTMLElement).render(
+const configSchema = v.object({
+  root: v.optional(v.string(), "/"),
+  graphqlEndpoint: v.optional(v.string(), "/graphql"),
+});
+
+const queryClient = new QueryClient({
+  defaultOptions: {
+    mutations: {
+      throwOnError: true,
+    },
+  },
+});
+
+const rootElement = document.getElementById("root");
+if (!rootElement) throw new Error("#root element not found");
+
+const config = v.parse(configSchema, rootElement.dataset);
+setGraphqlEndpoint(config.graphqlEndpoint);
+const router = makeRouter(config.root, queryClient);
+
+createRoot(rootElement).render(
   <StrictMode>
     <QueryClientProvider client={queryClient}>
       <ErrorBoundary>
         <TooltipProvider>
           <Suspense fallback={<LoadingScreen />}>
             <I18nextProvider i18n={i18n}>
-              <RouterProvider router={router} context={{ queryClient }} />
+              <RouterProvider router={router} />
             </I18nextProvider>
           </Suspense>
         </TooltipProvider>
diff --git a/frontend/src/entrypoints/swagger.ts b/frontend/src/entrypoints/swagger.ts
index 7ec3d78d9..20975ec5b 100644
--- a/frontend/src/entrypoints/swagger.ts
+++ b/frontend/src/entrypoints/swagger.ts
@@ -1,3 +1,4 @@
+// Copyright 2025, 2026 Element Creations Ltd.
 // Copyright 2024, 2025 New Vector Ltd.
 // Copyright 2024 The Matrix.org Foundation C.I.C.
 //
@@ -6,21 +7,18 @@
 
 import { SwaggerUIBundle } from "swagger-ui-dist";
 import "swagger-ui-dist/swagger-ui.css";
-
-type ApiConfig = {
-  openapiUrl: string;
-  callbackUrl: string;
-};
+import * as v from "valibot";
 
 interface IWindow {
-  API_CONFIG?: ApiConfig;
   ui?: SwaggerUIBundle;
 }
 
-const config = typeof window !== "undefined" && (window as IWindow).API_CONFIG;
-if (!config) {
-  throw new Error("API_CONFIG is not defined");
-}
+const el = document.getElementById("swagger-ui");
+if (!el) throw new Error("swagger-ui element not found");
+const config = v.parse(
+  v.object({ openapiUrl: v.string(), callbackUrl: v.string() }),
+  el.dataset,
+);
 
 (window as IWindow).ui = SwaggerUIBundle({
   url: config.openapiUrl,
diff --git a/frontend/src/graphql.ts b/frontend/src/graphql.ts
index 7401a7220..c1e92a3db 100644
--- a/frontend/src/graphql.ts
+++ b/frontend/src/graphql.ts
@@ -1,26 +1,22 @@
+// Copyright 2025, 2026 Element Creations Ltd.
 // Copyright 2024, 2025 New Vector Ltd.
 // Copyright 2023, 2024 The Matrix.org Foundation C.I.C.
 //
 // SPDX-License-Identifier: AGPL-3.0-only OR LicenseRef-Element-Commercial
 // Please see LICENSE files in the repository root for full details.
 
-import { QueryClient } from "@tanstack/react-query";
 import type { ExecutionResult } from "graphql";
-import appConfig from "./config";
 import type { TypedDocumentString } from "./gql/graphql";
 
-let graphqlEndpoint: string;
-if (import.meta.env.TEST && typeof window === "undefined") {
-  graphqlEndpoint = new URL(
-    appConfig.graphqlEndpoint,
-    "http:://localhost/",
-  ).toString();
-} else {
-  graphqlEndpoint = new URL(
-    appConfig.graphqlEndpoint,
-    window.location.toString(),
-  ).toString();
-}
+let graphqlEndpoint = "/graphql";
+
+/**
+ * Sets the GraphQL endpoint to use for requests.
+ * This is called during initialization, once config has been loaded.
+ */
+export const setGraphqlEndpoint = (endpoint: string): void => {
+  graphqlEndpoint = endpoint;
+};
 
 type RequestOptions<TData, TVariables> = {
   query: TypedDocumentString<TData, TVariables>;
@@ -35,9 +31,14 @@ export const graphqlRequest = async <TData, TVariables>({
   variables,
   signal,
 }: RequestOptions<TData, TVariables>): Promise<TData> => {
+  const endpoint =
+    import.meta.env.TEST && typeof window === "undefined"
+      ? new URL(graphqlEndpoint, "http://localhost/").toString()
+      : new URL(graphqlEndpoint, window.location.toString()).toString();
+
   let response: Response;
   try {
-    response = await fetch(graphqlEndpoint, {
+    response = await fetch(endpoint, {
       method: "POST",
       headers: {
         "Content-Type": "application/json",
@@ -49,14 +50,14 @@ export const graphqlRequest = async <TData, TVariables>({
       signal,
     });
   } catch (cause) {
-    throw new Error(`GraphQL request to ${graphqlEndpoint} request failed`, {
+    throw new Error(`GraphQL request to ${endpoint} request failed`, {
       cause,
     });
   }
 
   if (!response.ok) {
     throw new Error(
-      `GraphQL request to ${graphqlEndpoint} failed: ${response.status}`,
+      `GraphQL request to ${endpoint} failed: ${response.status}`,
     );
   }
 
@@ -66,16 +67,8 @@ export const graphqlRequest = async <TData, TVariables>({
   }
 
   if (!json.data) {
-    throw new Error(`GraphQL request to ${graphqlEndpoint} returned no data`);
+    throw new Error(`GraphQL request to ${endpoint} returned no data`);
   }
 
   return json.data;
 };
-
-export const queryClient = new QueryClient({
-  defaultOptions: {
-    mutations: {
-      throwOnError: true,
-    },
-  },
-});
diff --git a/frontend/src/router.tsx b/frontend/src/router.tsx
index d9d3ca2ac..8ab118e0a 100644
--- a/frontend/src/router.tsx
+++ b/frontend/src/router.tsx
@@ -1,28 +1,28 @@
+// Copyright 2025, 2026 Element Creations Ltd.
 // Copyright 2024, 2025 New Vector Ltd.
 // Copyright 2022-2024 The Matrix.org Foundation C.I.C.
 //
 // SPDX-License-Identifier: AGPL-3.0-only OR LicenseRef-Element-Commercial
 // Please see LICENSE files in the repository root for full details.
 
+import type { QueryClient } from "@tanstack/react-query";
 import { createRouter } from "@tanstack/react-router";
 import LoadingScreen from "./components/LoadingScreen";
-import config from "./config";
-import { queryClient } from "./graphql";
 import { routeTree } from "./routeTree.gen";
 
-// Create a new router instance
-export const router = createRouter({
-  routeTree,
-  scrollRestoration: true,
-  basepath: config.root,
-  defaultPendingComponent: LoadingScreen,
-  defaultPreload: "intent",
-  context: { queryClient },
-});
+export const makeRouter = (basepath: string, queryClient: QueryClient) =>
+  createRouter({
+    routeTree,
+    scrollRestoration: true,
+    basepath,
+    defaultPendingComponent: LoadingScreen,
+    defaultPreload: "intent",
+    context: { queryClient },
+  });
 
 // Register the router instance for type safety
 declare module "@tanstack/react-router" {
   interface Register {
-    router: typeof router;
+    router: ReturnType<typeof makeRouter>;
   }
 }
diff --git a/templates/app.html b/templates/app.html
index d43416f9a..0763b8d12 100644
--- a/templates/app.html
+++ b/templates/app.html
@@ -1,4 +1,5 @@
 {#
+Copyright 2025, 2026 Element Creations Ltd.
 Copyright 2024, 2025 New Vector Ltd.
 Copyright 2023, 2024 The Matrix.org Foundation C.I.C.
 
@@ -15,19 +16,12 @@ Please see LICENSE files in the repository root for full details.
     <meta charset="UTF-8" />
     <meta name="viewport" content="width=device-width, initial-scale=1.0" />
     <title>{{ _("app.name") }}</title>
-    {% set config = {
-      'graphqlEndpoint': app_config.graphqlEndpoint,
-      'root': app_config.root,
-    } -%}
-    <script>
-      window.APP_CONFIG = JSON.parse("{{ config | tojson | add_slashes | safe }}");
-    </script>
     {{ include_asset('src/entrypoints/main.tsx') | indent(4) | safe }}
     {# Pre-load the locale data for the current language #}
     {{ include_asset('locales/' ~ lang ~ '.json') | indent(4) | safe }}
   </head>
 
   <body>
-    <div id="root"></div>
+    <div id="root" data-root="{{ app_config.root }}" data-graphql-endpoint="{{ app_config.graphqlEndpoint }}"></div>
   </body>
 </html>
diff --git a/templates/swagger/doc.html b/templates/swagger/doc.html
index 454ca04e5..f85c99d6c 100644
--- a/templates/swagger/doc.html
+++ b/templates/swagger/doc.html
@@ -1,4 +1,5 @@
 {#
+Copyright 2025, 2026 Element Creations Ltd.
 Copyright 2024, 2025 New Vector Ltd.
 Copyright 2024 The Matrix.org Foundation C.I.C.
 
@@ -12,16 +13,10 @@ Please see LICENSE files in the repository root for full details.
     <meta charset="UTF-8" />
     <meta name="viewport" content="width=device-width, initial-scale=1.0" />
     <title>API documentation</title>
-    <script>
-      window.API_CONFIG = {
-        openapiUrl: "{{ openapi_url | add_slashes | safe }}",
-        callbackUrl: "{{ callback_url | add_slashes | safe }}",
-      };
-    </script>
     {{ include_asset('src/entrypoints/swagger.ts') | indent(4) | safe }}
   </head>
 
   <body>
-    <div id="swagger-ui"></div>
+    <div id="swagger-ui" data-openapi-url="{{ openapi_url }}" data-callback-url="{{ callback_url }}"></div>
   </body>
 </html>
diff --git a/translations/en.json b/translations/en.json
index e09768a7e..320fed5e0 100644
--- a/translations/en.json
+++ b/translations/en.json
@@ -41,7 +41,7 @@
     },
     "name": "matrix-authentication-service",
     "@name": {
-      "context": "app.html:17:14-27, base.html:24:31-44",
+      "context": "app.html:18:14-27, base.html:24:31-44",
       "description": "Name of the application"
     },
     "technical_description": "OpenID Connect discovery document: <a class=\"cpd-link\" data-kind=\"primary\" href=\"%(discovery_url)s\">%(discovery_url)s</a>",
