diff --git a/src/Login.ts b/src/Login.ts
index cbaab1cb34..d5992af2ab 100644
--- a/src/Login.ts
+++ b/src/Login.ts
@@ -15,6 +15,7 @@ import {
     type ILoginFlow,
     type LoginRequest,
     type OidcClientConfig,
+    type ISSOFlow,
 } from "matrix-js-sdk/src/matrix";
 import { logger } from "matrix-js-sdk/src/logger";
 
@@ -127,7 +128,7 @@ export default class Login {
         // If an m.login.sso flow is present which is also flagged as being for MSC3824 OIDC compatibility then we only
         // return that flow as (per MSC3824) it is the only one that the user should be offered to give the best experience
         const oidcCompatibilityFlow = flows.find(
-            (f) => f.type === "m.login.sso" && DELEGATED_OIDC_COMPATIBILITY.findIn(f),
+            (f) => f.type === "m.login.sso" && DELEGATED_OIDC_COMPATIBILITY.findIn(f as ISSOFlow),
         );
         this.flows = oidcCompatibilityFlow ? [oidcCompatibilityFlow] : flows;
         return this.flows;
diff --git a/src/components/views/dialogs/ForwardDialog.tsx b/src/components/views/dialogs/ForwardDialog.tsx
index 19c84bc108..f97ccd61a2 100644
--- a/src/components/views/dialogs/ForwardDialog.tsx
+++ b/src/components/views/dialogs/ForwardDialog.tsx
@@ -213,7 +213,7 @@ const transformEvent = (event: MatrixEvent, cli: MatrixClient): { type: string;
         // beacon pulses get transformed into static locations on forward
         M_BEACON.matches(event.getType())
     ) {
-        const timestamp = M_TIMESTAMP.findIn<number>(content);
+        const timestamp = M_TIMESTAMP.findIn<number>(content as ILocationContent);
         const geoUri = locationEventGeoUri(event);
         return {
             type,
diff --git a/src/components/views/dialogs/devtools/AccountData.tsx b/src/components/views/dialogs/devtools/AccountData.tsx
index 6900a7097e..e4e1ffe769 100644
--- a/src/components/views/dialogs/devtools/AccountData.tsx
+++ b/src/components/views/dialogs/devtools/AccountData.tsx
@@ -8,7 +8,12 @@ Please see LICENSE files in the repository root for full details.
 */
 
 import React, { useContext, useMemo, useState } from "react";
-import { type AccountDataEvents, type IContent, type MatrixEvent } from "matrix-js-sdk/src/matrix";
+import {
+    type AccountDataEvents,
+    type IContent,
+    type MatrixEvent,
+    type RoomAccountDataEvents,
+} from "matrix-js-sdk/src/matrix";
 
 import BaseTool, { DevtoolsContext, type IDevtoolsProps } from "./BaseTool";
 import MatrixClientContext from "../../../../contexts/MatrixClientContext";
@@ -35,7 +40,7 @@ export const RoomAccountDataEventEditor: React.FC<IEditorProps> = ({ mxEvent, on
 
     const fields = useMemo(() => [eventTypeField(mxEvent?.getType())], [mxEvent]);
 
-    const onSend = async ([eventType]: string[], content?: IContent): Promise<void> => {
+    const onSend = async ([eventType]: Array<keyof RoomAccountDataEvents>, content?: IContent): Promise<void> => {
         await cli.setRoomAccountData(context.room.roomId, eventType, content || {});
     };
 
diff --git a/src/components/views/right_panel/types.ts b/src/components/views/right_panel/types.ts
index 09965a2a10..da48795aca 100644
--- a/src/components/views/right_panel/types.ts
+++ b/src/components/views/right_panel/types.ts
@@ -7,3 +7,9 @@ Please see LICENSE files in the repository root for full details.
 */
 
 export const ReadPinsEventId = "im.vector.room.read_pins";
+
+declare module "matrix-js-sdk/src/types" {
+    interface RoomAccountDataEvents {
+        [ReadPinsEventId]: { event_ids: string[] };
+    }
+}
diff --git a/src/settings/controllers/MediaPreviewConfigController.ts b/src/settings/controllers/MediaPreviewConfigController.ts
index cb8b9b34aa..d349ef33fa 100644
--- a/src/settings/controllers/MediaPreviewConfigController.ts
+++ b/src/settings/controllers/MediaPreviewConfigController.ts
@@ -16,6 +16,12 @@ import {
 import { type SettingLevel } from "../SettingLevel.ts";
 import MatrixClientBackedController from "./MatrixClientBackedController.ts";
 
+declare module "matrix-js-sdk/src/types" {
+    interface RoomAccountDataEvents {
+        [MEDIA_PREVIEW_ACCOUNT_DATA_TYPE]: MediaPreviewConfig;
+    }
+}
+
 /**
  * Handles media preview settings provided by MSC4278.
  * This uses both account-level and room-level account data.
diff --git a/src/settings/handlers/RoomAccountSettingsHandler.ts b/src/settings/handlers/RoomAccountSettingsHandler.ts
index 6ed09a9801..939c267a15 100644
--- a/src/settings/handlers/RoomAccountSettingsHandler.ts
+++ b/src/settings/handlers/RoomAccountSettingsHandler.ts
@@ -7,7 +7,13 @@ SPDX-License-Identifier: AGPL-3.0-only OR GPL-3.0-only OR LicenseRef-Element-Com
 Please see LICENSE files in the repository root for full details.
 */
 
-import { type MatrixClient, type MatrixEvent, type Room, RoomEvent } from "matrix-js-sdk/src/matrix";
+import {
+    type RoomAccountDataEvents,
+    type MatrixClient,
+    type MatrixEvent,
+    type Room,
+    RoomEvent,
+} from "matrix-js-sdk/src/matrix";
 
 import MatrixClientBackedSettingsHandler from "./MatrixClientBackedSettingsHandler";
 import { objectClone, objectKeyChanges } from "../../utils/objects";
@@ -18,6 +24,14 @@ import { MEDIA_PREVIEW_ACCOUNT_DATA_TYPE } from "../../@types/media_preview";
 const ALLOWED_WIDGETS_EVENT_TYPE = "im.vector.setting.allowed_widgets";
 const DEFAULT_SETTINGS_EVENT_TYPE = "im.vector.web.settings";
 
+declare module "matrix-js-sdk/src/types" {
+    interface RoomAccountDataEvents {
+        [ALLOWED_WIDGETS_EVENT_TYPE]: { [eventId: string]: boolean };
+        [DEFAULT_SETTINGS_EVENT_TYPE]: Record<string, any>;
+        "org.matrix.room.preview_urls": { disable: boolean };
+    }
+}
+
 /**
  * Gets and sets settings at the "room-account" level for the current user.
  */
@@ -81,11 +95,11 @@ export default class RoomAccountSettingsHandler extends MatrixClientBackedSettin
     }
 
     // helper function to send room account data then await it being echoed back
-    private async setRoomAccountData(
+    private async setRoomAccountData<K extends keyof RoomAccountDataEvents, F extends keyof RoomAccountDataEvents[K]>(
         roomId: string,
-        eventType: string,
-        field: string | null,
-        value: any,
+        eventType: K,
+        field: F | null,
+        value: RoomAccountDataEvents[K][F],
     ): Promise<void> {
         let content: ReturnType<RoomAccountSettingsHandler["getSettings"]>;
 
@@ -101,7 +115,7 @@ export default class RoomAccountSettingsHandler extends MatrixClientBackedSettin
         const deferred = Promise.withResolvers<void>();
         const handler = (event: MatrixEvent, room: Room): void => {
             if (room.roomId !== roomId || event.getType() !== eventType) return;
-            if (field !== null && event.getContent()[field] !== value) return;
+            if (field !== null && event.getContent<Record<F, RoomAccountDataEvents[K][F]>>()[field] !== value) return;
             this.client.off(RoomEvent.AccountData, handler);
             deferred.resolve();
         };
diff --git a/src/stores/spaces/SpaceStore.ts b/src/stores/spaces/SpaceStore.ts
index c0b9a92159..98006ac905 100644
--- a/src/stores/spaces/SpaceStore.ts
+++ b/src/stores/spaces/SpaceStore.ts
@@ -1406,7 +1406,7 @@ export class SpaceStoreClass extends AsyncStoreWithClient<EmptyObject> {
         return sortBy(spaces, [this.getSpaceTagOrdering, "roomId"]);
     }
 
-    private async setRootSpaceOrder(space: Room, order?: string): Promise<void> {
+    private async setRootSpaceOrder(space: Room, order: string): Promise<void> {
         this.spaceOrderLocalEchoMap.set(space.roomId, order);
         try {
             await this.matrixClient?.setRoomAccountData(space.roomId, EventType.SpaceOrder, { order });
diff --git a/src/utils/location/locationEventGeoUri.ts b/src/utils/location/locationEventGeoUri.ts
index 7648120102..f4d206712e 100644
--- a/src/utils/location/locationEventGeoUri.ts
+++ b/src/utils/location/locationEventGeoUri.ts
@@ -6,7 +6,9 @@ SPDX-License-Identifier: AGPL-3.0-only OR GPL-3.0-only OR LicenseRef-Element-Com
 Please see LICENSE files in the repository root for full details.
 */
 
-import { type MatrixEvent, M_LOCATION } from "matrix-js-sdk/src/matrix";
+import { type MatrixEvent, M_LOCATION, type MLocationEvent } from "matrix-js-sdk/src/matrix";
+
+type LocationEvent = { geo_uri: string } & MLocationEvent;
 
 /**
  * Find the geo-URI contained within a location event.
@@ -16,7 +18,7 @@ export const locationEventGeoUri = (mxEvent: MatrixEvent): string => {
     // events until the end of days, or until we figure out mutable
     // events - so folks can read their old chat history correctly.
     // https://github.com/matrix-org/matrix-doc/issues/3516
-    const content = mxEvent.getContent();
-    const loc = M_LOCATION.findIn(content) as { uri?: string };
+    const content = mxEvent.getContent<LocationEvent>();
+    const loc = M_LOCATION.findIn(content);
     return loc?.uri ?? content["geo_uri"];
 };
diff --git a/src/utils/notifications.ts b/src/utils/notifications.ts
index ebfd7e90f6..9fab246a55 100644
--- a/src/utils/notifications.ts
+++ b/src/utils/notifications.ts
@@ -15,6 +15,7 @@ import {
     ReceiptType,
     type IMarkedUnreadEvent,
     type EmptyObject,
+    EventType,
 } from "matrix-js-sdk/src/matrix";
 import { type IndicatorIcon } from "@vector-im/compound-web";
 
@@ -34,7 +35,13 @@ export const MARKED_UNREAD_TYPE_UNSTABLE = "com.famedly.marked_unread";
 /**
  * Stable identifier for the marked_unread event
  */
-export const MARKED_UNREAD_TYPE_STABLE = "m.marked_unread";
+export const MARKED_UNREAD_TYPE_STABLE = EventType.MarkedUnread;
+
+declare module "matrix-js-sdk/src/types" {
+    interface RoomAccountDataEvents {
+        [MARKED_UNREAD_TYPE_UNSTABLE]: { [eventId: string]: boolean };
+    }
+}
 
 export const deviceNotificationSettingsKeys: SettingKey[] = [
     "notificationsEnabled",
@@ -157,7 +164,7 @@ export async function setMarkedUnreadState(room: Room, client: MatrixClient, unr
     const currentState = getMarkedUnreadState(room);
 
     if (Boolean(currentState) !== unread) {
-        await client.setRoomAccountData(room.roomId, MARKED_UNREAD_TYPE_STABLE, { unread });
+        await client.setRoomAccountData(room.roomId, EventType.MarkedUnread, { unread });
     }
 }
 
diff --git a/src/utils/stringOrderField.ts b/src/utils/stringOrderField.ts
index b6ba8410e3..e8e3d18cfb 100644
--- a/src/utils/stringOrderField.ts
+++ b/src/utils/stringOrderField.ts
@@ -54,7 +54,7 @@ export const reorderLexicographically = (
     fromIndex: number,
     toIndex: number,
     maxLen = 50,
-): IEntry[] => {
+): Required<IEntry>[] => {
     // sanity check inputs
     if (fromIndex < 0 || toIndex < 0 || fromIndex > orders.length || toIndex > orders.length || fromIndex === toIndex) {
         return [];