diff --git a/src/UrlParams.test.ts b/src/UrlParams.test.ts
index 75bf9bfb8..05c5f7ba1 100644
--- a/src/UrlParams.test.ts
+++ b/src/UrlParams.test.ts
@@ -123,6 +123,28 @@ describe("UrlParams", () => {
     });
   });
 
+  describe("enableClientWellKnownLookups", () => {
+    it("is undefined when not set (so the config value applies)", () => {
+      expect(
+        computeUrlParams().enableClientWellKnownLookups,
+      ).toBeUndefined();
+    });
+
+    it("is false when set to false", () => {
+      expect(
+        computeUrlParams("?enableClientWellKnownLookups=false")
+          .enableClientWellKnownLookups,
+      ).toBe(false);
+    });
+
+    it("is true when set to true", () => {
+      expect(
+        computeUrlParams("?enableClientWellKnownLookups=true")
+          .enableClientWellKnownLookups,
+      ).toBe(true);
+    });
+  });
+
   describe("returnToLobby", () => {
     it("is false in SPA mode", () => {
       expect(computeUrlParams("?returnToLobby=true").returnToLobby).toBe(false);
diff --git a/src/UrlParams.ts b/src/UrlParams.ts
index 0212c50fe..abde3f38b 100644
--- a/src/UrlParams.ts
+++ b/src/UrlParams.ts
@@ -190,9 +190,10 @@ export interface UrlConfiguration {
   /**
    * Whether the app may make client `.well-known` lookups against the user's
    * homeserver `server_name` (the post-login well-known poll and the legacy
-   * MatrixRTC foci `.well-known` fallback). Defaults to true.
+   * MatrixRTC foci `.well-known` fallback). Set by the embedder in widget mode;
+   * when unset the `enable_client_well_known_lookups` config value applies.
    */
-  enableClientWellKnownLookups: boolean;
+  enableClientWellKnownLookups?: boolean;
 
   /**
    * Whether the app should use per participant keys for E2EE.
@@ -378,7 +379,6 @@ export const computeUrlParams = (search = "", hash = ""): UrlParams => {
     showControls: true,
     hideScreensharing: false,
     allowIceFallback: true,
-    enableClientWellKnownLookups: true,
     perParticipantE2EE: true,
     controlledAudioDevices: platform === "desktop" ? false : true,
     skipLobby: true,
@@ -434,7 +434,6 @@ export const computeUrlParams = (search = "", hash = ""): UrlParams => {
         showControls: true,
         hideScreensharing: false,
         allowIceFallback: false,
-        enableClientWellKnownLookups: true,
         perParticipantE2EE: false,
         controlledAudioDevices: false,
         skipLobby: false,
diff --git a/src/config/Config.ts b/src/config/Config.ts
index f52b28fde..e40e1dfb5 100644
--- a/src/config/Config.ts
+++ b/src/config/Config.ts
@@ -90,6 +90,19 @@ export class Config {
     return Config.get().default_server_config?.["m.homeserver"].server_name;
   }
 
+  /**
+   * Whether the app may make client `.well-known` lookups against the
+   * homeserver `server_name`. The embedded (widget) deployment sets this via
+   * the `enableClientWellKnownLookups` URL parameter; the standalone (SPA)
+   * deployment sets it via `enable_client_well_known_lookups` in config.json.
+   */
+  public static clientWellKnownLookupsEnabled(): boolean {
+    return (
+      getUrlParams().enableClientWellKnownLookups ??
+      Config.get().enable_client_well_known_lookups
+    );
+  }
+
   public config?: ResolvedConfigOptions;
   private initPromise?: Promise<void>;
 }
diff --git a/src/config/ConfigOptions.ts b/src/config/ConfigOptions.ts
index 3d9fcfb50..1f0effbb6 100644
--- a/src/config/ConfigOptions.ts
+++ b/src/config/ConfigOptions.ts
@@ -70,6 +70,16 @@ export interface ConfigOptions {
     };
   };
 
+  /**
+   * Whether the app may make client `.well-known` lookups against the user's
+   * homeserver `server_name` (the post-login well-known poll and the legacy
+   * MatrixRTC foci `.well-known` fallback). Set to false to keep the app on the
+   * homeserver base URL. This is the standalone (SPA) deployment control;
+   * embedded deployments set it via the `enableClientWellKnownLookups` URL
+   * parameter instead. Defaults to true.
+   */
+  enable_client_well_known_lookups?: boolean;
+
   // Describes the LiveKit configuration to be used.
   livekit?: {
     // The link to the service that returns a livekit url and token to use it.
@@ -189,6 +199,7 @@ export interface ResolvedConfigOptions extends ConfigOptions {
       server_name: string;
     };
   };
+  enable_client_well_known_lookups: boolean;
   sync_disconnect_grace_period_ms: number;
   ssla: string;
   matrix_rtc_session: {
@@ -211,6 +222,7 @@ export const DEFAULT_CONFIG: ResolvedConfigOptions = {
   features: {
     feature_use_device_session_member_events: true,
   },
+  enable_client_well_known_lookups: true,
   sync_disconnect_grace_period_ms: 10000,
   ssla: "https://static.element.io/legal/element-software-and-services-license-agreement-uk-1.pdf",
   matrix_rtc_session: {
diff --git a/src/state/CallViewModel/localMember/LocalTransport.ts b/src/state/CallViewModel/localMember/LocalTransport.ts
index 91eae4fc8..aacd76b09 100644
--- a/src/state/CallViewModel/localMember/LocalTransport.ts
+++ b/src/state/CallViewModel/localMember/LocalTransport.ts
@@ -44,7 +44,6 @@ import {
 } from "../../../livekit/openIDSFU.ts";
 import { areLivekitTransportsEqual } from "../remoteMembers/MatrixLivekitMembers.ts";
 import { customLivekitUrl } from "../../../settings/settings.ts";
-import { getUrlParams } from "../../../UrlParams.ts";
 import { RtcTransportAutoDiscovery } from "./RtcTransportAutoDiscovery.ts";
 
 const logger = rootLogger.getChild("[LocalTransport]");
@@ -148,7 +147,7 @@ export const createLocalTransport$ = ({
   const transportDiscovery = new RtcTransportAutoDiscovery({
     client: client,
     resolvedConfig: Config.get(),
-    enableClientWellKnownLookups: getUrlParams().enableClientWellKnownLookups,
+    enableClientWellKnownLookups: Config.clientWellKnownLookupsEnabled(),
     wellKnownFetcher: AutoDiscovery.getRawClientConfig.bind(AutoDiscovery),
     logger: logger,
   });
diff --git a/src/utils/matrix.ts b/src/utils/matrix.ts
index 2ea7aea76..4cac5cba3 100644
--- a/src/utils/matrix.ts
+++ b/src/utils/matrix.ts
@@ -112,7 +112,7 @@ export async function initClient(
   // the values around, but we initialise the matrix client in
   // many different places so we'd have to pass it into all of
   // them.
-  const { e2eEnabled, enableClientWellKnownLookups } = getUrlParams();
+  const { e2eEnabled } = getUrlParams();
   if (!e2eEnabled) {
     logger.info("Disabling E2E: group call signalling will NOT be encrypted.");
   }
@@ -169,7 +169,9 @@ export async function initClient(
   // Leaving `clientWellKnownPollPeriod` unset stops the SDK polling the
   // homeserver's `server_name` `.well-known` after login.
   await client.startClient({
-    clientWellKnownPollPeriod: enableClientWellKnownLookups ? 60 * 10 : undefined,
+    clientWellKnownPollPeriod: Config.clientWellKnownLookupsEnabled()
+      ? 60 * 10
+      : undefined,
   });
   await syncPromise;
 
diff --git a/src/widget.ts b/src/widget.ts
index 6c4c80903..9d62b4b20 100644
--- a/src/widget.ts
+++ b/src/widget.ts
@@ -82,7 +82,6 @@ export const initializeWidget = (
       baseUrl,
       e2eEnabled,
       allowIceFallback,
-      enableClientWellKnownLookups,
     } = getUrlParams();
 
     if (!roomId) throw new Error("Room ID must be supplied");
@@ -199,7 +198,7 @@ export const initializeWidget = (
         // Leaving `clientWellKnownPollPeriod` unset stops the SDK polling the
         // homeserver's `server_name` `.well-known` after login.
         await client.startClient({
-          clientWellKnownPollPeriod: enableClientWellKnownLookups
+          clientWellKnownPollPeriod: Config.clientWellKnownLookupsEnabled()
             ? 60 * 10
             : undefined,
         });