diff --git a/playwright/tsconfig.json b/playwright/tsconfig.json
index cea25ebab7..55f979f3ce 100644
--- a/playwright/tsconfig.json
+++ b/playwright/tsconfig.json
@@ -10,6 +10,7 @@
     },
     "include": [
         "**/*.ts",
+        "../src/@types/matrix-js-sdk.d.ts",
         "../node_modules/matrix-js-sdk/src/@types/*.d.ts",
         "../node_modules/matrix-js-sdk/node_modules/@matrix-org/olm/index.d.ts"
     ]
diff --git a/src/@types/matrix-js-sdk.d.ts b/src/@types/matrix-js-sdk.d.ts
index 1ce1702f1f..4a32ee0f37 100644
--- a/src/@types/matrix-js-sdk.d.ts
+++ b/src/@types/matrix-js-sdk.d.ts
@@ -14,14 +14,40 @@ See the License for the specific language governing permissions and
 limitations under the License.
 */
 
-import { BLURHASH_FIELD } from "../utils/image-media";
+import type { IWidget } from "matrix-widget-api";
+import type { BLURHASH_FIELD } from "../utils/image-media";
+import type { JitsiCallMemberEventType, JitsiCallMemberContent } from "../call-types";
+import type { ILayoutStateEvent, WIDGET_LAYOUT_EVENT_TYPE } from "../stores/widgets/types";
+import type { VoiceBroadcastInfoEventContent, VoiceBroadcastInfoEventType } from "../voice-broadcast/types";
 
 // Matrix JS SDK extensions
-declare module "matrix-js-sdk" {
+declare module "matrix-js-sdk/src/types" {
     export interface FileInfo {
         /**
          * @see https://github.com/matrix-org/matrix-spec-proposals/pull/2448
          */
         [BLURHASH_FIELD]?: string;
     }
+
+    export interface StateEvents {
+        // Jitsi-backed video room state events
+        [JitsiCallMemberEventType]: JitsiCallMemberContent;
+
+        // Unstable widgets state events
+        "im.vector.modular.widgets": IWidget | {};
+        [WIDGET_LAYOUT_EVENT_TYPE]: ILayoutStateEvent;
+
+        // Unstable voice broadcast state events
+        [VoiceBroadcastInfoEventType]: VoiceBroadcastInfoEventContent;
+
+        // Element custom state events
+        "im.vector.web.settings": Record<string, any>;
+        "org.matrix.room.preview_urls": { disable: boolean };
+
+        // XXX unspecced usages of `m.room.*` events
+        "m.room.plumbing": {
+            status: string;
+        };
+        "m.room.bot.options": unknown;
+    }
 }
diff --git a/src/call-types.ts b/src/call-types.ts
index d042faaaf3..40cd006dcc 100644
--- a/src/call-types.ts
+++ b/src/call-types.ts
@@ -17,3 +17,12 @@ limitations under the License.
 // Event type for room account data and room creation content used to mark rooms as virtual rooms
 // (and store the ID of their native room)
 export const VIRTUAL_ROOM_EVENT_TYPE = "im.vector.is_virtual_room";
+
+export const JitsiCallMemberEventType = "io.element.video.member";
+
+export interface JitsiCallMemberContent {
+    // Connected device IDs
+    devices: string[];
+    // Time at which this state event should be considered stale
+    expires_ts: number;
+}
diff --git a/src/models/Call.ts b/src/models/Call.ts
index 369f712534..eeae614bd8 100644
--- a/src/models/Call.ts
+++ b/src/models/Call.ts
@@ -57,6 +57,7 @@ import { UPDATE_EVENT } from "../stores/AsyncStore";
 import { getJoinedNonFunctionalMembers } from "../utils/room/getJoinedNonFunctionalMembers";
 import { isVideoRoom } from "../utils/video-rooms";
 import { FontWatcher } from "../settings/watchers/FontWatcher";
+import { JitsiCallMemberContent, JitsiCallMemberEventType } from "../call-types";
 
 const TIMEOUT_MS = 16000;
 
@@ -321,18 +322,13 @@ export abstract class Call extends TypedEventEmitter<CallEvent, CallEventHandler
     private beforeUnload = (): void => this.setDisconnected();
 }
 
-export interface JitsiCallMemberContent {
-    // Connected device IDs
-    devices: string[];
-    // Time at which this state event should be considered stale
-    expires_ts: number;
-}
+export type { JitsiCallMemberContent };
 
 /**
  * A group call using Jitsi as a backend.
  */
 export class JitsiCall extends Call {
-    public static readonly MEMBER_EVENT_TYPE = "io.element.video.member";
+    public static readonly MEMBER_EVENT_TYPE = JitsiCallMemberEventType;
     public readonly STUCK_DEVICE_TIMEOUT_MS = 1000 * 60 * 60; // 1 hour
 
     private resendDevicesTimer: number | null = null;
diff --git a/src/stores/widgets/WidgetLayoutStore.ts b/src/stores/widgets/WidgetLayoutStore.ts
index c965836c8b..eef5d84d0d 100644
--- a/src/stores/widgets/WidgetLayoutStore.ts
+++ b/src/stores/widgets/WidgetLayoutStore.ts
@@ -28,55 +28,10 @@ import { ReadyWatchingStore } from "../ReadyWatchingStore";
 import { SettingLevel } from "../../settings/SettingLevel";
 import { arrayFastClone } from "../../utils/arrays";
 import { UPDATE_EVENT } from "../AsyncStore";
+import { Container, IStoredLayout, ILayoutStateEvent, WIDGET_LAYOUT_EVENT_TYPE, IWidgetLayouts } from "./types";
 
-export const WIDGET_LAYOUT_EVENT_TYPE = "io.element.widgets.layout";
-
-export enum Container {
-    // "Top" is the app drawer, and currently the only sensible value.
-    Top = "top",
-
-    // "Right" is the right panel, and the default for widgets. Setting
-    // this as a container on a widget is essentially like saying "no
-    // changes needed", though this may change in the future.
-    Right = "right",
-
-    Center = "center",
-}
-
-export interface IStoredLayout {
-    // Where to store the widget. Required.
-    container: Container;
-
-    // The index (order) to position the widgets in. Only applies for
-    // ordered containers (like the top container). Smaller numbers first,
-    // and conflicts resolved by comparing widget IDs.
-    index?: number;
-
-    // Percentage (integer) for relative width of the container to consume.
-    // Clamped to 0-100 and may have minimums imposed upon it. Only applies
-    // to containers which support inner resizing (currently only the top
-    // container).
-    width?: number;
-
-    // Percentage (integer) for relative height of the container. Note that
-    // this only applies to the top container currently, and that container
-    // will take the highest value among widgets in the container. Clamped
-    // to 0-100 and may have minimums imposed on it.
-    height?: number | null;
-
-    // TODO: [Deferred] Maximizing (fullscreen) widgets by default.
-}
-
-interface IWidgetLayouts {
-    [widgetId: string]: IStoredLayout;
-}
-
-interface ILayoutStateEvent {
-    // TODO: [Deferred] Forced layout (fixed with no changes)
-
-    // The widget layouts.
-    widgets: IWidgetLayouts;
-}
+export type { IStoredLayout, ILayoutStateEvent };
+export { Container, WIDGET_LAYOUT_EVENT_TYPE };
 
 interface ILayoutSettings extends ILayoutStateEvent {
     overrides?: string; // event ID for layout state event, if present
diff --git a/src/stores/widgets/types.ts b/src/stores/widgets/types.ts
new file mode 100644
index 0000000000..36d5d86472
--- /dev/null
+++ b/src/stores/widgets/types.ts
@@ -0,0 +1,64 @@
+/*
+Copyright 2024 The Matrix.org Foundation C.I.C.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+export interface IStoredLayout {
+    // Where to store the widget. Required.
+    container: Container;
+
+    // The index (order) to position the widgets in. Only applies for
+    // ordered containers (like the top container). Smaller numbers first,
+    // and conflicts resolved by comparing widget IDs.
+    index?: number;
+
+    // Percentage (integer) for relative width of the container to consume.
+    // Clamped to 0-100 and may have minimums imposed upon it. Only applies
+    // to containers which support inner resizing (currently only the top
+    // container).
+    width?: number;
+
+    // Percentage (integer) for relative height of the container. Note that
+    // this only applies to the top container currently, and that container
+    // will take the highest value among widgets in the container. Clamped
+    // to 0-100 and may have minimums imposed on it.
+    height?: number | null;
+
+    // TODO: [Deferred] Maximizing (fullscreen) widgets by default.
+}
+
+export interface IWidgetLayouts {
+    [widgetId: string]: IStoredLayout;
+}
+
+export interface ILayoutStateEvent {
+    // TODO: [Deferred] Forced layout (fixed with no changes)
+
+    // The widget layouts.
+    widgets: IWidgetLayouts;
+}
+
+export const WIDGET_LAYOUT_EVENT_TYPE = "io.element.widgets.layout";
+
+export enum Container {
+    // "Top" is the app drawer, and currently the only sensible value.
+    Top = "top",
+
+    // "Right" is the right panel, and the default for widgets. Setting
+    // this as a container on a widget is essentially like saying "no
+    // changes needed", though this may change in the future.
+    Right = "right",
+
+    Center = "center",
+}