diff --git a/babel.config.js b/babel.config.js
index a9e4b5c137b..541c567770a 100644
--- a/babel.config.js
+++ b/babel.config.js
@@ -10,15 +10,15 @@ module.exports = {
                     "last 2 Safari versions",
                     "last 2 Edge versions",
                 ],
+                include: ["@babel/plugin-transform-class-properties"],
             },
         ],
-        "@babel/preset-typescript",
+        ["@babel/preset-typescript", { allowDeclareFields: true }],
         "@babel/preset-react",
     ],
     plugins: [
         "@babel/plugin-proposal-export-default-from",
         "@babel/plugin-transform-numeric-separator",
-        "@babel/plugin-transform-class-properties",
         "@babel/plugin-transform-object-rest-spread",
         "@babel/plugin-syntax-dynamic-import",
         "@babel/plugin-transform-runtime",
diff --git a/playwright/plugins/homeserver/dendrite/index.ts b/playwright/plugins/homeserver/dendrite/index.ts
index 603bd360a8c..0ddaecc1b7d 100644
--- a/playwright/plugins/homeserver/dendrite/index.ts
+++ b/playwright/plugins/homeserver/dendrite/index.ts
@@ -29,7 +29,6 @@ const dendriteConfigFile = "dendrite.yaml";
 
 // Surprisingly, Dendrite implements the same register user Admin API Synapse, so we can just extend it
 export class Dendrite extends Synapse implements Homeserver, HomeserverInstance {
-    public config: HomeserverConfig & { serverId: string };
     protected image = "matrixdotorg/dendrite-monolith:main";
     protected entrypoint = "/usr/bin/dendrite";
 
diff --git a/playwright/tsconfig.json b/playwright/tsconfig.json
index 48ff1f8c02e..5f3083fd57b 100644
--- a/playwright/tsconfig.json
+++ b/playwright/tsconfig.json
@@ -1,8 +1,8 @@
 {
     "compilerOptions": {
-        "target": "es2018",
+        "target": "es2022",
         "jsx": "react",
-        "lib": ["ESNext", "es2021", "dom", "dom.iterable"],
+        "lib": ["ESNext", "es2022", "dom", "dom.iterable"],
         "resolveJsonModule": true,
         "esModuleInterop": true,
         "moduleResolution": "node",
diff --git a/src/@types/global.d.ts b/src/@types/global.d.ts
index e42e83d58db..fab9791ada1 100644
--- a/src/@types/global.d.ts
+++ b/src/@types/global.d.ts
@@ -144,69 +144,14 @@ declare global {
         usageDetails?: { [key: string]: number };
     }
 
-    // https://developer.mozilla.org/en-US/docs/Web/API/OffscreenCanvas
-    interface OffscreenCanvas {
-        convertToBlob(opts?: { type?: string; quality?: number }): Promise<Blob>;
-    }
-
-    interface HTMLAudioElement {
-        type?: string;
-    }
-
-    interface HTMLVideoElement {
-        type?: string;
-    }
-
-    // Add Chrome-specific `instant` ScrollBehaviour
-    type _ScrollBehavior = ScrollBehavior | "instant";
-
-    interface _ScrollOptions {
-        behavior?: _ScrollBehavior;
-    }
-
-    interface _ScrollIntoViewOptions extends _ScrollOptions {
-        block?: ScrollLogicalPosition;
-        inline?: ScrollLogicalPosition;
-    }
-
     interface Element {
         // Safari & IE11 only have this prefixed: we used prefixed versions
         // previously so let's continue to support them for now
         webkitRequestFullScreen(options?: FullscreenOptions): Promise<void>;
         msRequestFullscreen(options?: FullscreenOptions): Promise<void>;
-        scrollIntoView(arg?: boolean | _ScrollIntoViewOptions): void;
-    }
-
-    interface Error {
-        // Standard
-        // https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Error/cause
-        cause?: unknown;
-
-        // Non-standard
-        // https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Error/fileName
-        fileName?: string;
-        // https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Error/lineNumber
-        lineNumber?: number;
-        // https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Error/columnNumber
-        columnNumber?: number;
-    }
-
-    // We can remove these pieces if we ever update to `target: "es2022"` in our
-    // TypeScript config which supports the new `cause` property, see
-    // https://github.com/vector-im/element-web/issues/24913
-    interface ErrorOptions {
-        // https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Error/cause
-        cause?: unknown;
-    }
-
-    interface ErrorConstructor {
-        new (message?: string, options?: ErrorOptions): Error;
-        (message?: string, options?: ErrorOptions): Error;
+        // scrollIntoView(arg?: boolean | _ScrollIntoViewOptions): void;
     }
 
-    // eslint-disable-next-line no-var
-    var Error: ErrorConstructor;
-
     // https://github.com/microsoft/TypeScript/issues/28308#issuecomment-650802278
     interface AudioWorkletProcessor {
         readonly port: MessagePort;
diff --git a/src/components/structures/EmbeddedPage.tsx b/src/components/structures/EmbeddedPage.tsx
index 4c36412cb62..2a37e53859a 100644
--- a/src/components/structures/EmbeddedPage.tsx
+++ b/src/components/structures/EmbeddedPage.tsx
@@ -45,7 +45,7 @@ interface IState {
 
 export default class EmbeddedPage extends React.PureComponent<IProps, IState> {
     public static contextType = MatrixClientContext;
-    public context!: React.ContextType<typeof MatrixClientContext>;
+    public declare context: React.ContextType<typeof MatrixClientContext>;
     private unmounted = false;
     private dispatcherRef: string | null = null;
 
diff --git a/src/components/structures/FilePanel.tsx b/src/components/structures/FilePanel.tsx
index 77448627035..86a3e1cf833 100644
--- a/src/components/structures/FilePanel.tsx
+++ b/src/components/structures/FilePanel.tsx
@@ -59,7 +59,7 @@ interface IState {
  */
 class FilePanel extends React.Component<IProps, IState> {
     public static contextType = RoomContext;
-    public context!: React.ContextType<typeof RoomContext>;
+    public declare context: React.ContextType<typeof RoomContext>;
 
     // This is used to track if a decrypted event was a live event and should be
     // added to the timeline.
diff --git a/src/components/structures/MessagePanel.tsx b/src/components/structures/MessagePanel.tsx
index 3a97f27b381..07b600484ac 100644
--- a/src/components/structures/MessagePanel.tsx
+++ b/src/components/structures/MessagePanel.tsx
@@ -205,7 +205,7 @@ interface IReadReceiptForUser {
  */
 export default class MessagePanel extends React.Component<IProps, IState> {
     public static contextType = RoomContext;
-    public context!: React.ContextType<typeof RoomContext>;
+    public declare context: React.ContextType<typeof RoomContext>;
 
     public static defaultProps = {
         disableGrouping: false,
diff --git a/src/components/structures/NotificationPanel.tsx b/src/components/structures/NotificationPanel.tsx
index 1f9fb4c57f6..7c8fd71b791 100644
--- a/src/components/structures/NotificationPanel.tsx
+++ b/src/components/structures/NotificationPanel.tsx
@@ -42,7 +42,7 @@ interface IState {
  */
 export default class NotificationPanel extends React.PureComponent<IProps, IState> {
     public static contextType = RoomContext;
-    public context!: React.ContextType<typeof RoomContext>;
+    public declare context: React.ContextType<typeof RoomContext>;
 
     private card = React.createRef<HTMLDivElement>();
 
diff --git a/src/components/structures/RightPanel.tsx b/src/components/structures/RightPanel.tsx
index 1d6bf101b6e..9e228de611b 100644
--- a/src/components/structures/RightPanel.tsx
+++ b/src/components/structures/RightPanel.tsx
@@ -73,7 +73,7 @@ interface IState {
 
 export default class RightPanel extends React.Component<Props, IState> {
     public static contextType = MatrixClientContext;
-    public context!: React.ContextType<typeof MatrixClientContext>;
+    public declare context: React.ContextType<typeof MatrixClientContext>;
 
     public constructor(props: Props, context: React.ContextType<typeof MatrixClientContext>) {
         super(props, context);
diff --git a/src/components/structures/RoomStatusBar.tsx b/src/components/structures/RoomStatusBar.tsx
index ce489a5019d..e98785aa7e7 100644
--- a/src/components/structures/RoomStatusBar.tsx
+++ b/src/components/structures/RoomStatusBar.tsx
@@ -97,11 +97,10 @@ interface IState {
 export default class RoomStatusBar extends React.PureComponent<IProps, IState> {
     private unmounted = false;
     public static contextType = MatrixClientContext;
-    public context!: React.ContextType<typeof MatrixClientContext>;
+    public declare context: React.ContextType<typeof MatrixClientContext>;
 
     public constructor(props: IProps, context: React.ContextType<typeof MatrixClientContext>) {
         super(props, context);
-        this.context = context; // XXX: workaround for lack of `declare` support on `public context!:` definition
 
         this.state = {
             syncState: this.context.getSyncState(),
diff --git a/src/components/structures/RoomView.tsx b/src/components/structures/RoomView.tsx
index a0555abbf78..9c6ffb857f9 100644
--- a/src/components/structures/RoomView.tsx
+++ b/src/components/structures/RoomView.tsx
@@ -417,7 +417,7 @@ export class RoomView extends React.Component<IRoomProps, IRoomState> {
     private roomViewBody = createRef<HTMLDivElement>();
 
     public static contextType = SDKContext;
-    public context!: React.ContextType<typeof SDKContext>;
+    public declare context: React.ContextType<typeof SDKContext>;
 
     public constructor(props: IRoomProps, context: React.ContextType<typeof SDKContext>) {
         super(props, context);
diff --git a/src/components/structures/SpaceRoomView.tsx b/src/components/structures/SpaceRoomView.tsx
index 4564741a290..1c188f8f73b 100644
--- a/src/components/structures/SpaceRoomView.tsx
+++ b/src/components/structures/SpaceRoomView.tsx
@@ -605,7 +605,7 @@ const SpaceSetupPrivateInvite: React.FC<{
 
 export default class SpaceRoomView extends React.PureComponent<IProps, IState> {
     public static contextType = MatrixClientContext;
-    public context!: React.ContextType<typeof MatrixClientContext>;
+    public declare context: React.ContextType<typeof MatrixClientContext>;
 
     private readonly dispatcherRef: string;
 
diff --git a/src/components/structures/ThreadView.tsx b/src/components/structures/ThreadView.tsx
index dbe2c59551e..f2d775464ed 100644
--- a/src/components/structures/ThreadView.tsx
+++ b/src/components/structures/ThreadView.tsx
@@ -83,7 +83,7 @@ interface IState {
 
 export default class ThreadView extends React.Component<IProps, IState> {
     public static contextType = RoomContext;
-    public context!: React.ContextType<typeof RoomContext>;
+    public declare context: React.ContextType<typeof RoomContext>;
 
     private dispatcherRef: string | null = null;
     private readonly layoutWatcherRef: string;
diff --git a/src/components/structures/TimelinePanel.tsx b/src/components/structures/TimelinePanel.tsx
index b193403695c..976c00e2fdc 100644
--- a/src/components/structures/TimelinePanel.tsx
+++ b/src/components/structures/TimelinePanel.tsx
@@ -241,7 +241,7 @@ interface IEventIndexOpts {
  */
 class TimelinePanel extends React.Component<IProps, IState> {
     public static contextType = RoomContext;
-    public context!: React.ContextType<typeof RoomContext>;
+    public declare context: React.ContextType<typeof RoomContext>;
 
     // a map from room id to read marker event timestamp
     public static roomReadMarkerTsMap: Record<string, number> = {};
@@ -273,7 +273,6 @@ class TimelinePanel extends React.Component<IProps, IState> {
 
     public constructor(props: IProps, context: React.ContextType<typeof RoomContext>) {
         super(props, context);
-        this.context = context;
 
         debuglog("mounting");
 
diff --git a/src/components/structures/UserMenu.tsx b/src/components/structures/UserMenu.tsx
index 6921c262645..ca949f46d08 100644
--- a/src/components/structures/UserMenu.tsx
+++ b/src/components/structures/UserMenu.tsx
@@ -90,7 +90,7 @@ const below = (rect: PartialDOMRect): MenuProps => {
 
 export default class UserMenu extends React.Component<IProps, IState> {
     public static contextType = SDKContext;
-    public context!: React.ContextType<typeof SDKContext>;
+    public declare context: React.ContextType<typeof SDKContext>;
 
     private dispatcherRef?: string;
     private themeWatcherRef?: string;
@@ -100,7 +100,6 @@ export default class UserMenu extends React.Component<IProps, IState> {
     public constructor(props: IProps, context: React.ContextType<typeof SDKContext>) {
         super(props, context);
 
-        this.context = context;
         this.state = {
             contextMenuPosition: null,
             isDarkTheme: this.isUserOnDarkTheme(),
diff --git a/src/components/structures/UserView.tsx b/src/components/structures/UserView.tsx
index 4398af851a9..7aa2d92d0ca 100644
--- a/src/components/structures/UserView.tsx
+++ b/src/components/structures/UserView.tsx
@@ -41,7 +41,7 @@ interface IState {
 
 export default class UserView extends React.Component<IProps, IState> {
     public static contextType = MatrixClientContext;
-    public context!: React.ContextType<typeof MatrixClientContext>;
+    public declare context: React.ContextType<typeof MatrixClientContext>;
 
     public constructor(props: IProps, context: React.ContextType<typeof MatrixClientContext>) {
         super(props, context);
diff --git a/src/components/structures/auth/SoftLogout.tsx b/src/components/structures/auth/SoftLogout.tsx
index f623ae7dcbb..ca34e3830aa 100644
--- a/src/components/structures/auth/SoftLogout.tsx
+++ b/src/components/structures/auth/SoftLogout.tsx
@@ -72,13 +72,11 @@ interface IState {
 
 export default class SoftLogout extends React.Component<IProps, IState> {
     public static contextType = SDKContext;
-    public context!: React.ContextType<typeof SDKContext>;
+    public declare context: React.ContextType<typeof SDKContext>;
 
     public constructor(props: IProps, context: React.ContextType<typeof SDKContext>) {
         super(props, context);
 
-        this.context = context;
-
         this.state = {
             loginView: LoginView.Loading,
             busy: false,
diff --git a/src/components/views/context_menus/MessageContextMenu.tsx b/src/components/views/context_menus/MessageContextMenu.tsx
index 77fc7215ebf..801ab0b023e 100644
--- a/src/components/views/context_menus/MessageContextMenu.tsx
+++ b/src/components/views/context_menus/MessageContextMenu.tsx
@@ -133,7 +133,7 @@ interface IState {
 
 export default class MessageContextMenu extends React.Component<IProps, IState> {
     public static contextType = RoomContext;
-    public context!: React.ContextType<typeof RoomContext>;
+    public declare context: React.ContextType<typeof RoomContext>;
 
     private reactButtonRef = createRef<any>(); // XXX Ref to a functional component
 
diff --git a/src/components/views/elements/AppTile.tsx b/src/components/views/elements/AppTile.tsx
index 1612154c943..6d326b09007 100644
--- a/src/components/views/elements/AppTile.tsx
+++ b/src/components/views/elements/AppTile.tsx
@@ -120,7 +120,7 @@ interface IState {
 
 export default class AppTile extends React.Component<IProps, IState> {
     public static contextType = MatrixClientContext;
-    public context!: ContextType<typeof MatrixClientContext>;
+    public declare context: ContextType<typeof MatrixClientContext>;
 
     public static defaultProps: Partial<IProps> = {
         waitForIframeLoad: true,
@@ -144,7 +144,6 @@ export default class AppTile extends React.Component<IProps, IState> {
 
     public constructor(props: IProps, context: ContextType<typeof MatrixClientContext>) {
         super(props, context);
-        this.context = context; // XXX: workaround for lack of `declare` support on `public context!:` definition
 
         // Tiles in miniMode are floating, and therefore not docked
         if (!this.props.miniMode) {
diff --git a/src/components/views/elements/EventListSummary.tsx b/src/components/views/elements/EventListSummary.tsx
index a1270427ccd..4f5817e4c74 100644
--- a/src/components/views/elements/EventListSummary.tsx
+++ b/src/components/views/elements/EventListSummary.tsx
@@ -81,7 +81,7 @@ export default class EventListSummary extends React.Component<
     IProps & Required<Pick<IProps, "summaryLength" | "threshold" | "avatarsMaxLength" | "layout">>
 > {
     public static contextType = RoomContext;
-    public context!: React.ContextType<typeof RoomContext>;
+    public declare context: React.ContextType<typeof RoomContext>;
 
     public static defaultProps = {
         summaryLength: 1,
diff --git a/src/components/views/elements/PersistentApp.tsx b/src/components/views/elements/PersistentApp.tsx
index 812d3432498..dfed54a3ba0 100644
--- a/src/components/views/elements/PersistentApp.tsx
+++ b/src/components/views/elements/PersistentApp.tsx
@@ -32,7 +32,7 @@ interface IProps {
 
 export default class PersistentApp extends React.Component<IProps> {
     public static contextType = MatrixClientContext;
-    public context!: ContextType<typeof MatrixClientContext>;
+    public declare context: ContextType<typeof MatrixClientContext>;
     private room: Room;
 
     public constructor(props: IProps, context: ContextType<typeof MatrixClientContext>) {
diff --git a/src/components/views/elements/ReplyChain.tsx b/src/components/views/elements/ReplyChain.tsx
index b7e833a629b..621a360bc54 100644
--- a/src/components/views/elements/ReplyChain.tsx
+++ b/src/components/views/elements/ReplyChain.tsx
@@ -73,7 +73,7 @@ interface IState {
 // be low as each event being loaded (after the first) is triggered by an explicit user action.
 export default class ReplyChain extends React.Component<IProps, IState> {
     public static contextType = RoomContext;
-    public context!: React.ContextType<typeof RoomContext>;
+    public declare context: React.ContextType<typeof RoomContext>;
 
     private unmounted = false;
     private room: Room;
diff --git a/src/components/views/elements/RoomAliasField.tsx b/src/components/views/elements/RoomAliasField.tsx
index d5353dcabc3..1ec057fff10 100644
--- a/src/components/views/elements/RoomAliasField.tsx
+++ b/src/components/views/elements/RoomAliasField.tsx
@@ -41,7 +41,7 @@ interface IState {
 // Controlled form component wrapping Field for inputting a room alias scoped to a given domain
 export default class RoomAliasField extends React.PureComponent<IProps, IState> {
     public static contextType = MatrixClientContext;
-    public context!: React.ContextType<typeof MatrixClientContext>;
+    public declare context: React.ContextType<typeof MatrixClientContext>;
 
     private fieldRef = createRef<Field>();
 
diff --git a/src/components/views/emojipicker/ReactionPicker.tsx b/src/components/views/emojipicker/ReactionPicker.tsx
index 075a6e6cee7..8265331a3cd 100644
--- a/src/components/views/emojipicker/ReactionPicker.tsx
+++ b/src/components/views/emojipicker/ReactionPicker.tsx
@@ -37,7 +37,7 @@ interface IState {
 
 class ReactionPicker extends React.Component<IProps, IState> {
     public static contextType = RoomContext;
-    public context!: React.ContextType<typeof RoomContext>;
+    public declare context: React.ContextType<typeof RoomContext>;
 
     public constructor(props: IProps, context: React.ContextType<typeof RoomContext>) {
         super(props, context);
diff --git a/src/components/views/emojipicker/Search.tsx b/src/components/views/emojipicker/Search.tsx
index 33549b7489a..d7077f0591a 100644
--- a/src/components/views/emojipicker/Search.tsx
+++ b/src/components/views/emojipicker/Search.tsx
@@ -31,7 +31,7 @@ interface IProps {
 
 class Search extends React.PureComponent<IProps> {
     public static contextType = RovingTabIndexContext;
-    public context!: React.ContextType<typeof RovingTabIndexContext>;
+    public declare context: React.ContextType<typeof RovingTabIndexContext>;
 
     private inputRef = React.createRef<HTMLInputElement>();
 
diff --git a/src/components/views/location/LocationPicker.tsx b/src/components/views/location/LocationPicker.tsx
index 75437296d97..d4739935c76 100644
--- a/src/components/views/location/LocationPicker.tsx
+++ b/src/components/views/location/LocationPicker.tsx
@@ -50,7 +50,7 @@ const isSharingOwnLocation = (shareType: LocationShareType): boolean =>
 
 class LocationPicker extends React.Component<ILocationPickerProps, IState> {
     public static contextType = MatrixClientContext;
-    public context!: React.ContextType<typeof MatrixClientContext>;
+    public declare context: React.ContextType<typeof MatrixClientContext>;
     private map?: maplibregl.Map;
     private geolocate?: maplibregl.GeolocateControl;
     private marker?: maplibregl.Marker;
diff --git a/src/components/views/messages/EditHistoryMessage.tsx b/src/components/views/messages/EditHistoryMessage.tsx
index bd7eccba3e9..de2ba8a1b4b 100644
--- a/src/components/views/messages/EditHistoryMessage.tsx
+++ b/src/components/views/messages/EditHistoryMessage.tsx
@@ -52,7 +52,7 @@ interface IState {
 
 export default class EditHistoryMessage extends React.PureComponent<IProps, IState> {
     public static contextType = MatrixClientContext;
-    public context!: React.ContextType<typeof MatrixClientContext>;
+    public declare context: React.ContextType<typeof MatrixClientContext>;
 
     private content = createRef<HTMLDivElement>();
     private pills: Element[] = [];
@@ -60,7 +60,6 @@ export default class EditHistoryMessage extends React.PureComponent<IProps, ISta
 
     public constructor(props: IProps, context: React.ContextType<typeof MatrixClientContext>) {
         super(props, context);
-        this.context = context;
 
         const cli = this.context;
         const userId = cli.getSafeUserId();
diff --git a/src/components/views/messages/MAudioBody.tsx b/src/components/views/messages/MAudioBody.tsx
index 5e8d9f2436c..13c97d32020 100644
--- a/src/components/views/messages/MAudioBody.tsx
+++ b/src/components/views/messages/MAudioBody.tsx
@@ -38,7 +38,7 @@ interface IState {
 
 export default class MAudioBody extends React.PureComponent<IBodyProps, IState> {
     public static contextType = RoomContext;
-    public context!: React.ContextType<typeof RoomContext>;
+    public declare context: React.ContextType<typeof RoomContext>;
 
     public state: IState = {};
 
diff --git a/src/components/views/messages/MFileBody.tsx b/src/components/views/messages/MFileBody.tsx
index 1da3cafc65b..d7542b97407 100644
--- a/src/components/views/messages/MFileBody.tsx
+++ b/src/components/views/messages/MFileBody.tsx
@@ -106,7 +106,7 @@ interface IState {
 
 export default class MFileBody extends React.Component<IProps, IState> {
     public static contextType = RoomContext;
-    public context!: React.ContextType<typeof RoomContext>;
+    public declare context: React.ContextType<typeof RoomContext>;
 
     public state: IState = {};
 
diff --git a/src/components/views/messages/MImageBody.tsx b/src/components/views/messages/MImageBody.tsx
index 547972cdb02..82f03519087 100644
--- a/src/components/views/messages/MImageBody.tsx
+++ b/src/components/views/messages/MImageBody.tsx
@@ -65,7 +65,7 @@ interface IState {
 
 export default class MImageBody extends React.Component<IBodyProps, IState> {
     public static contextType = RoomContext;
-    public context!: React.ContextType<typeof RoomContext>;
+    public declare context: React.ContextType<typeof RoomContext>;
 
     private unmounted = true;
     private image = createRef<HTMLImageElement>();
diff --git a/src/components/views/messages/MLocationBody.tsx b/src/components/views/messages/MLocationBody.tsx
index 276b22eeed7..f3f1a3d9d3a 100644
--- a/src/components/views/messages/MLocationBody.tsx
+++ b/src/components/views/messages/MLocationBody.tsx
@@ -38,7 +38,7 @@ interface IState {
 
 export default class MLocationBody extends React.Component<IBodyProps, IState> {
     public static contextType = MatrixClientContext;
-    public context!: React.ContextType<typeof MatrixClientContext>;
+    public declare context: React.ContextType<typeof MatrixClientContext>;
 
     private unmounted = false;
     private mapId: string;
diff --git a/src/components/views/messages/MPollBody.tsx b/src/components/views/messages/MPollBody.tsx
index fadab6e2a5c..5fad5acd5fc 100644
--- a/src/components/views/messages/MPollBody.tsx
+++ b/src/components/views/messages/MPollBody.tsx
@@ -147,7 +147,7 @@ export function launchPollEditor(mxEvent: MatrixEvent, getRelationsForEvent?: Ge
 
 export default class MPollBody extends React.Component<IBodyProps, IState> {
     public static contextType = MatrixClientContext;
-    public context!: React.ContextType<typeof MatrixClientContext>;
+    public declare context: React.ContextType<typeof MatrixClientContext>;
     private seenEventIds: string[] = []; // Events we have already seen
 
     public constructor(props: IBodyProps, context: React.ContextType<typeof MatrixClientContext>) {
diff --git a/src/components/views/messages/MVideoBody.tsx b/src/components/views/messages/MVideoBody.tsx
index 143176a1550..1309a034ad2 100644
--- a/src/components/views/messages/MVideoBody.tsx
+++ b/src/components/views/messages/MVideoBody.tsx
@@ -42,7 +42,7 @@ interface IState {
 
 export default class MVideoBody extends React.PureComponent<IBodyProps, IState> {
     public static contextType = RoomContext;
-    public context!: React.ContextType<typeof RoomContext>;
+    public declare context: React.ContextType<typeof RoomContext>;
 
     private videoRef = React.createRef<HTMLVideoElement>();
     private sizeWatcher?: string;
diff --git a/src/components/views/messages/MessageActionBar.tsx b/src/components/views/messages/MessageActionBar.tsx
index f6e01dcd100..25547c78363 100644
--- a/src/components/views/messages/MessageActionBar.tsx
+++ b/src/components/views/messages/MessageActionBar.tsx
@@ -261,7 +261,7 @@ interface IMessageActionBarProps {
 
 export default class MessageActionBar extends React.PureComponent<IMessageActionBarProps> {
     public static contextType = RoomContext;
-    public context!: React.ContextType<typeof RoomContext>;
+    public declare context: React.ContextType<typeof RoomContext>;
 
     public componentDidMount(): void {
         if (this.props.mxEvent.status && this.props.mxEvent.status !== EventStatus.SENT) {
diff --git a/src/components/views/messages/MessageEvent.tsx b/src/components/views/messages/MessageEvent.tsx
index db0016de7b0..fb700579bea 100644
--- a/src/components/views/messages/MessageEvent.tsx
+++ b/src/components/views/messages/MessageEvent.tsx
@@ -90,7 +90,7 @@ export default class MessageEvent extends React.Component<IProps> implements IMe
     private evTypes = new Map<string, React.ComponentType<IBodyProps>>(baseEvTypes.entries());
 
     public static contextType = MatrixClientContext;
-    public context!: React.ContextType<typeof MatrixClientContext>;
+    public declare context: React.ContextType<typeof MatrixClientContext>;
 
     public constructor(props: IProps, context: React.ContextType<typeof MatrixClientContext>) {
         super(props, context);
diff --git a/src/components/views/messages/ReactionsRow.tsx b/src/components/views/messages/ReactionsRow.tsx
index e57326edd73..c5d004b12b0 100644
--- a/src/components/views/messages/ReactionsRow.tsx
+++ b/src/components/views/messages/ReactionsRow.tsx
@@ -83,11 +83,10 @@ interface IState {
 
 export default class ReactionsRow extends React.PureComponent<IProps, IState> {
     public static contextType = RoomContext;
-    public context!: React.ContextType<typeof RoomContext>;
+    public declare context: React.ContextType<typeof RoomContext>;
 
     public constructor(props: IProps, context: React.ContextType<typeof RoomContext>) {
         super(props, context);
-        this.context = context;
 
         this.state = {
             myReactions: this.getMyReactions(),
diff --git a/src/components/views/messages/ReactionsRowButton.tsx b/src/components/views/messages/ReactionsRowButton.tsx
index 1dbd1bd7bf1..7c4dcc8b3cb 100644
--- a/src/components/views/messages/ReactionsRowButton.tsx
+++ b/src/components/views/messages/ReactionsRowButton.tsx
@@ -46,7 +46,7 @@ export interface IProps {
 
 export default class ReactionsRowButton extends React.PureComponent<IProps> {
     public static contextType = MatrixClientContext;
-    public context!: React.ContextType<typeof MatrixClientContext>;
+    public declare context: React.ContextType<typeof MatrixClientContext>;
 
     public onClick = (): void => {
         const { mxEvent, myReactionEvent, content } = this.props;
diff --git a/src/components/views/messages/ReactionsRowButtonTooltip.tsx b/src/components/views/messages/ReactionsRowButtonTooltip.tsx
index 5b4db10ed6b..f9a5c2d66f6 100644
--- a/src/components/views/messages/ReactionsRowButtonTooltip.tsx
+++ b/src/components/views/messages/ReactionsRowButtonTooltip.tsx
@@ -36,7 +36,7 @@ interface IProps {
 
 export default class ReactionsRowButtonTooltip extends React.PureComponent<PropsWithChildren<IProps>> {
     public static contextType = MatrixClientContext;
-    public context!: React.ContextType<typeof MatrixClientContext>;
+    public declare context: React.ContextType<typeof MatrixClientContext>;
 
     public render(): React.ReactNode {
         const { content, reactionEvents, mxEvent, children } = this.props;
diff --git a/src/components/views/messages/TextualBody.tsx b/src/components/views/messages/TextualBody.tsx
index 2133eb5fe82..5dba3e42b77 100644
--- a/src/components/views/messages/TextualBody.tsx
+++ b/src/components/views/messages/TextualBody.tsx
@@ -66,7 +66,7 @@ export default class TextualBody extends React.Component<IBodyProps, IState> {
     private tooltips: Element[] = [];
 
     public static contextType = RoomContext;
-    public context!: React.ContextType<typeof RoomContext>;
+    public declare context: React.ContextType<typeof RoomContext>;
 
     public state = {
         links: [],
diff --git a/src/components/views/right_panel/TimelineCard.tsx b/src/components/views/right_panel/TimelineCard.tsx
index 67aca930909..97f5aabc320 100644
--- a/src/components/views/right_panel/TimelineCard.tsx
+++ b/src/components/views/right_panel/TimelineCard.tsx
@@ -77,7 +77,7 @@ interface IState {
 
 export default class TimelineCard extends React.Component<IProps, IState> {
     public static contextType = RoomContext;
-    public context!: React.ContextType<typeof RoomContext>;
+    public declare context: React.ContextType<typeof RoomContext>;
 
     private dispatcherRef?: string;
     private layoutWatcherRef?: string;
diff --git a/src/components/views/room_settings/AliasSettings.tsx b/src/components/views/room_settings/AliasSettings.tsx
index 3b2f294e5c1..a8fe6cdbe95 100644
--- a/src/components/views/room_settings/AliasSettings.tsx
+++ b/src/components/views/room_settings/AliasSettings.tsx
@@ -102,7 +102,7 @@ interface IState {
 
 export default class AliasSettings extends React.Component<IProps, IState> {
     public static contextType = MatrixClientContext;
-    public context!: ContextType<typeof MatrixClientContext>;
+    public declare context: ContextType<typeof MatrixClientContext>;
 
     public static defaultProps = {
         canSetAliases: false,
diff --git a/src/components/views/rooms/Autocomplete.tsx b/src/components/views/rooms/Autocomplete.tsx
index 840fd098da3..eb7c42ee7c8 100644
--- a/src/components/views/rooms/Autocomplete.tsx
+++ b/src/components/views/rooms/Autocomplete.tsx
@@ -56,7 +56,7 @@ export default class Autocomplete extends React.PureComponent<IProps, IState> {
     private containerRef = createRef<HTMLDivElement>();
 
     public static contextType = RoomContext;
-    public context!: React.ContextType<typeof RoomContext>;
+    public declare context: React.ContextType<typeof RoomContext>;
 
     public constructor(props: IProps, context: React.ContextType<typeof RoomContext>) {
         super(props, context);
diff --git a/src/components/views/rooms/EditMessageComposer.tsx b/src/components/views/rooms/EditMessageComposer.tsx
index b379da2ea64..9b33f42914e 100644
--- a/src/components/views/rooms/EditMessageComposer.tsx
+++ b/src/components/views/rooms/EditMessageComposer.tsx
@@ -129,7 +129,7 @@ interface IState {
 
 class EditMessageComposer extends React.Component<IEditMessageComposerProps, IState> {
     public static contextType = RoomContext;
-    public context!: React.ContextType<typeof RoomContext>;
+    public declare context: React.ContextType<typeof RoomContext>;
 
     private readonly editorRef = createRef<BasicMessageComposer>();
     private readonly dispatcherRef: string;
@@ -138,7 +138,6 @@ class EditMessageComposer extends React.Component<IEditMessageComposerProps, ISt
 
     public constructor(props: IEditMessageComposerProps, context: React.ContextType<typeof RoomContext>) {
         super(props, context);
-        this.context = context; // otherwise React will only set it prior to render due to type def above
 
         const isRestored = this.createEditorModel();
         const ev = this.props.editState.getEvent();
diff --git a/src/components/views/rooms/EventTile.tsx b/src/components/views/rooms/EventTile.tsx
index 669e57a06a4..e0f8ab1161c 100644
--- a/src/components/views/rooms/EventTile.tsx
+++ b/src/components/views/rooms/EventTile.tsx
@@ -297,7 +297,7 @@ export class UnwrappedEventTile extends React.Component<EventTileProps, IState>
     };
 
     public static contextType = RoomContext;
-    public context!: React.ContextType<typeof RoomContext>;
+    public declare context: React.ContextType<typeof RoomContext>;
 
     private unmounted = false;
 
diff --git a/src/components/views/rooms/LegacyRoomHeader.tsx b/src/components/views/rooms/LegacyRoomHeader.tsx
index f16e324d80c..20c8357473b 100644
--- a/src/components/views/rooms/LegacyRoomHeader.tsx
+++ b/src/components/views/rooms/LegacyRoomHeader.tsx
@@ -493,7 +493,7 @@ export default class RoomHeader extends React.Component<IProps, IState> {
     };
 
     public static contextType = RoomContext;
-    public context!: React.ContextType<typeof RoomContext>;
+    public declare context: React.ContextType<typeof RoomContext>;
     private readonly client = this.props.room.client;
     private readonly featureAskToJoinWatcher: string;
 
diff --git a/src/components/views/rooms/MemberList.tsx b/src/components/views/rooms/MemberList.tsx
index 1ffca0821cb..cb671035359 100644
--- a/src/components/views/rooms/MemberList.tsx
+++ b/src/components/views/rooms/MemberList.tsx
@@ -82,7 +82,7 @@ export default class MemberList extends React.Component<IProps, IState> {
     private mounted = false;
 
     public static contextType = SDKContext;
-    public context!: React.ContextType<typeof SDKContext>;
+    public declare context: React.ContextType<typeof SDKContext>;
     private tiles: Map<string, MemberTile> = new Map();
 
     public constructor(props: IProps, context: React.ContextType<typeof SDKContext>) {
diff --git a/src/components/views/rooms/MessageComposer.tsx b/src/components/views/rooms/MessageComposer.tsx
index d1a72a6988b..a4a73b495f1 100644
--- a/src/components/views/rooms/MessageComposer.tsx
+++ b/src/components/views/rooms/MessageComposer.tsx
@@ -119,7 +119,7 @@ export class MessageComposer extends React.Component<IProps, IState> {
     private _voiceRecording: Optional<VoiceMessageRecording>;
 
     public static contextType = RoomContext;
-    public context!: React.ContextType<typeof RoomContext>;
+    public declare context: React.ContextType<typeof RoomContext>;
 
     public static defaultProps = {
         compact: false,
diff --git a/src/components/views/rooms/MessageComposerButtons.tsx b/src/components/views/rooms/MessageComposerButtons.tsx
index 77d809d1f8d..dc5c14517b6 100644
--- a/src/components/views/rooms/MessageComposerButtons.tsx
+++ b/src/components/views/rooms/MessageComposerButtons.tsx
@@ -298,7 +298,7 @@ interface IPollButtonProps {
 
 class PollButton extends React.PureComponent<IPollButtonProps> {
     public static contextType = OverflowMenuContext;
-    public context!: React.ContextType<typeof OverflowMenuContext>;
+    public declare context: React.ContextType<typeof OverflowMenuContext>;
 
     private onCreateClick = (): void => {
         this.context?.(); // close overflow menu
diff --git a/src/components/views/rooms/PinnedEventTile.tsx b/src/components/views/rooms/PinnedEventTile.tsx
index 581583d1d5a..6c63efc3520 100644
--- a/src/components/views/rooms/PinnedEventTile.tsx
+++ b/src/components/views/rooms/PinnedEventTile.tsx
@@ -40,7 +40,7 @@ const AVATAR_SIZE = "24px";
 
 export default class PinnedEventTile extends React.Component<IProps> {
     public static contextType = MatrixClientContext;
-    public context!: React.ContextType<typeof MatrixClientContext>;
+    public declare context: React.ContextType<typeof MatrixClientContext>;
 
     private onTileClicked = (): void => {
         dis.dispatch<ViewRoomPayload>({
diff --git a/src/components/views/rooms/ReplyPreview.tsx b/src/components/views/rooms/ReplyPreview.tsx
index 009d8d21a50..431af5ce6ff 100644
--- a/src/components/views/rooms/ReplyPreview.tsx
+++ b/src/components/views/rooms/ReplyPreview.tsx
@@ -39,7 +39,7 @@ interface IProps {
 
 export default class ReplyPreview extends React.Component<IProps> {
     public static contextType = RoomContext;
-    public context!: React.ContextType<typeof RoomContext>;
+    public declare context: React.ContextType<typeof RoomContext>;
 
     public render(): JSX.Element | null {
         if (!this.props.replyToEvent) return null;
diff --git a/src/components/views/rooms/RoomList.tsx b/src/components/views/rooms/RoomList.tsx
index 10fcca7709a..7d47748de80 100644
--- a/src/components/views/rooms/RoomList.tsx
+++ b/src/components/views/rooms/RoomList.tsx
@@ -432,7 +432,7 @@ export default class RoomList extends React.PureComponent<IProps, IState> {
     private treeRef = createRef<HTMLDivElement>();
 
     public static contextType = MatrixClientContext;
-    public context!: React.ContextType<typeof MatrixClientContext>;
+    public declare context: React.ContextType<typeof MatrixClientContext>;
 
     public constructor(props: IProps, context: React.ContextType<typeof MatrixClientContext>) {
         super(props, context);
diff --git a/src/components/views/rooms/RoomUpgradeWarningBar.tsx b/src/components/views/rooms/RoomUpgradeWarningBar.tsx
index 99ae4f7ba4b..ab374108e9d 100644
--- a/src/components/views/rooms/RoomUpgradeWarningBar.tsx
+++ b/src/components/views/rooms/RoomUpgradeWarningBar.tsx
@@ -33,7 +33,7 @@ interface IState {
 
 export default class RoomUpgradeWarningBar extends React.PureComponent<IProps, IState> {
     public static contextType = MatrixClientContext;
-    public context!: React.ContextType<typeof MatrixClientContext>;
+    public declare context: React.ContextType<typeof MatrixClientContext>;
 
     public constructor(props: IProps, context: React.ContextType<typeof MatrixClientContext>) {
         super(props, context);
diff --git a/src/components/views/rooms/SearchResultTile.tsx b/src/components/views/rooms/SearchResultTile.tsx
index 99b5f0805c3..52977901cf9 100644
--- a/src/components/views/rooms/SearchResultTile.tsx
+++ b/src/components/views/rooms/SearchResultTile.tsx
@@ -44,7 +44,7 @@ interface IProps {
 
 export default class SearchResultTile extends React.Component<IProps> {
     public static contextType = RoomContext;
-    public context!: React.ContextType<typeof RoomContext>;
+    public declare context: React.ContextType<typeof RoomContext>;
 
     // A map of <callId, LegacyCallEventGrouper>
     private callEventGroupers = new Map<string, LegacyCallEventGrouper>();
diff --git a/src/components/views/rooms/SendMessageComposer.tsx b/src/components/views/rooms/SendMessageComposer.tsx
index c5972ee86ac..eee2a476a7e 100644
--- a/src/components/views/rooms/SendMessageComposer.tsx
+++ b/src/components/views/rooms/SendMessageComposer.tsx
@@ -254,7 +254,7 @@ interface ISendMessageComposerProps extends MatrixClientProps {
 
 export class SendMessageComposer extends React.Component<ISendMessageComposerProps> {
     public static contextType = RoomContext;
-    public context!: React.ContextType<typeof RoomContext>;
+    public declare context: React.ContextType<typeof RoomContext>;
 
     private readonly prepareToEncrypt?: DebouncedFunc<() => void>;
     private readonly editorRef = createRef<BasicMessageComposer>();
@@ -269,7 +269,6 @@ export class SendMessageComposer extends React.Component<ISendMessageComposerPro
 
     public constructor(props: ISendMessageComposerProps, context: React.ContextType<typeof RoomContext>) {
         super(props, context);
-        this.context = context; // otherwise React will only set it prior to render due to type def above
 
         if (this.props.mxClient.isCryptoEnabled() && this.props.mxClient.isRoomEncrypted(this.props.room.roomId)) {
             this.prepareToEncrypt = throttle(
diff --git a/src/components/views/rooms/VoiceRecordComposerTile.tsx b/src/components/views/rooms/VoiceRecordComposerTile.tsx
index 333bd248e10..4010adf283f 100644
--- a/src/components/views/rooms/VoiceRecordComposerTile.tsx
+++ b/src/components/views/rooms/VoiceRecordComposerTile.tsx
@@ -63,7 +63,7 @@ interface IState {
  */
 export default class VoiceRecordComposerTile extends React.PureComponent<IProps, IState> {
     public static contextType = RoomContext;
-    public context!: React.ContextType<typeof RoomContext>;
+    public declare context: React.ContextType<typeof RoomContext>;
     private voiceRecordingId: string;
 
     public constructor(props: IProps, context: React.ContextType<typeof RoomContext>) {
diff --git a/src/components/views/settings/tabs/room/BridgeSettingsTab.tsx b/src/components/views/settings/tabs/room/BridgeSettingsTab.tsx
index cfe6b3ccd32..1f44f06323e 100644
--- a/src/components/views/settings/tabs/room/BridgeSettingsTab.tsx
+++ b/src/components/views/settings/tabs/room/BridgeSettingsTab.tsx
@@ -36,7 +36,7 @@ interface IProps {
 
 export default class BridgeSettingsTab extends React.Component<IProps> {
     public static contextType = MatrixClientContext;
-    public context!: React.ContextType<typeof MatrixClientContext>;
+    public declare context: React.ContextType<typeof MatrixClientContext>;
 
     private renderBridgeCard(event: MatrixEvent, room: Room | null): ReactNode {
         const content = event.getContent();
diff --git a/src/components/views/settings/tabs/room/GeneralRoomSettingsTab.tsx b/src/components/views/settings/tabs/room/GeneralRoomSettingsTab.tsx
index 7b260e3a7e6..97503ef50a7 100644
--- a/src/components/views/settings/tabs/room/GeneralRoomSettingsTab.tsx
+++ b/src/components/views/settings/tabs/room/GeneralRoomSettingsTab.tsx
@@ -42,7 +42,7 @@ interface IState {
 
 export default class GeneralRoomSettingsTab extends React.Component<IProps, IState> {
     public static contextType = MatrixClientContext;
-    public context!: ContextType<typeof MatrixClientContext>;
+    public declare context: ContextType<typeof MatrixClientContext>;
 
     public constructor(props: IProps, context: ContextType<typeof MatrixClientContext>) {
         super(props, context);
diff --git a/src/components/views/settings/tabs/room/NotificationSettingsTab.tsx b/src/components/views/settings/tabs/room/NotificationSettingsTab.tsx
index 1c536ed6d64..1b0dbfdf1a9 100644
--- a/src/components/views/settings/tabs/room/NotificationSettingsTab.tsx
+++ b/src/components/views/settings/tabs/room/NotificationSettingsTab.tsx
@@ -50,7 +50,7 @@ export default class NotificationsSettingsTab extends React.Component<IProps, IS
     private soundUpload = createRef<HTMLInputElement>();
 
     public static contextType = MatrixClientContext;
-    public context!: React.ContextType<typeof MatrixClientContext>;
+    public declare context: React.ContextType<typeof MatrixClientContext>;
 
     public constructor(props: IProps, context: React.ContextType<typeof MatrixClientContext>) {
         super(props, context);
diff --git a/src/components/views/settings/tabs/room/RolesRoomSettingsTab.tsx b/src/components/views/settings/tabs/room/RolesRoomSettingsTab.tsx
index 2197cad3dff..3105ba961a3 100644
--- a/src/components/views/settings/tabs/room/RolesRoomSettingsTab.tsx
+++ b/src/components/views/settings/tabs/room/RolesRoomSettingsTab.tsx
@@ -89,7 +89,7 @@ interface IBannedUserProps {
 
 export class BannedUser extends React.Component<IBannedUserProps> {
     public static contextType = MatrixClientContext;
-    public context!: React.ContextType<typeof MatrixClientContext>;
+    public declare context: React.ContextType<typeof MatrixClientContext>;
 
     private onUnbanClick = (): void => {
         this.context.unban(this.props.member.roomId, this.props.member.userId).catch((err) => {
@@ -137,7 +137,7 @@ interface IProps {
 
 export default class RolesRoomSettingsTab extends React.Component<IProps> {
     public static contextType = MatrixClientContext;
-    public context!: React.ContextType<typeof MatrixClientContext>;
+    public declare context: React.ContextType<typeof MatrixClientContext>;
 
     public componentDidMount(): void {
         this.context.on(RoomStateEvent.Update, this.onRoomStateUpdate);
diff --git a/src/components/views/settings/tabs/room/SecurityRoomSettingsTab.tsx b/src/components/views/settings/tabs/room/SecurityRoomSettingsTab.tsx
index 01fcbd1abb0..adbf1b72d96 100644
--- a/src/components/views/settings/tabs/room/SecurityRoomSettingsTab.tsx
+++ b/src/components/views/settings/tabs/room/SecurityRoomSettingsTab.tsx
@@ -67,7 +67,7 @@ interface IState {
 
 export default class SecurityRoomSettingsTab extends React.Component<IProps, IState> {
     public static contextType = MatrixClientContext;
-    public context!: React.ContextType<typeof MatrixClientContext>;
+    public declare context: React.ContextType<typeof MatrixClientContext>;
 
     public constructor(props: IProps, context: React.ContextType<typeof MatrixClientContext>) {
         super(props, context);
diff --git a/src/components/views/settings/tabs/user/HelpUserSettingsTab.tsx b/src/components/views/settings/tabs/user/HelpUserSettingsTab.tsx
index eace2caa8de..867b986c820 100644
--- a/src/components/views/settings/tabs/user/HelpUserSettingsTab.tsx
+++ b/src/components/views/settings/tabs/user/HelpUserSettingsTab.tsx
@@ -40,7 +40,7 @@ interface IState {
 
 export default class HelpUserSettingsTab extends React.Component<IProps, IState> {
     public static contextType = MatrixClientContext;
-    public context!: React.ContextType<typeof MatrixClientContext>;
+    public declare context: React.ContextType<typeof MatrixClientContext>;
 
     public constructor(props: IProps, context: React.ContextType<typeof MatrixClientContext>) {
         super(props, context);
diff --git a/src/components/views/settings/tabs/user/VoiceUserSettingsTab.tsx b/src/components/views/settings/tabs/user/VoiceUserSettingsTab.tsx
index ad8de753384..c3d21205ff0 100644
--- a/src/components/views/settings/tabs/user/VoiceUserSettingsTab.tsx
+++ b/src/components/views/settings/tabs/user/VoiceUserSettingsTab.tsx
@@ -59,7 +59,7 @@ const mapDeviceKindToHandlerValue = (deviceKind: MediaDeviceKindEnum): string |
 
 export default class VoiceUserSettingsTab extends React.Component<{}, IState> {
     public static contextType = MatrixClientContext;
-    public context!: React.ContextType<typeof MatrixClientContext>;
+    public declare context: React.ContextType<typeof MatrixClientContext>;
 
     public constructor(props: {}, context: React.ContextType<typeof MatrixClientContext>) {
         super(props, context);
diff --git a/src/models/Call.ts b/src/models/Call.ts
index 7935025e5b2..658cb780487 100644
--- a/src/models/Call.ts
+++ b/src/models/Call.ts
@@ -126,8 +126,8 @@ interface CallEventHandlerMap {
  * A group call accessed through a widget.
  */
 export abstract class Call extends TypedEventEmitter<CallEvent, CallEventHandlerMap> {
-    protected readonly widgetUid = WidgetUtils.getWidgetUid(this.widget);
-    protected readonly room = this.client.getRoom(this.roomId)!;
+    protected readonly widgetUid: string;
+    protected readonly room: Room;
 
     /**
      * The time after which device member state should be considered expired.
@@ -184,6 +184,8 @@ export abstract class Call extends TypedEventEmitter<CallEvent, CallEventHandler
         protected readonly client: MatrixClient,
     ) {
         super();
+        this.widgetUid = WidgetUtils.getWidgetUid(this.widget);
+        this.room = this.client.getRoom(this.roomId)!;
     }
 
     /**
diff --git a/src/stores/room-list/previews/PollStartEventPreview.ts b/src/stores/room-list/previews/PollStartEventPreview.ts
index 793a8230716..728256101d4 100644
--- a/src/stores/room-list/previews/PollStartEventPreview.ts
+++ b/src/stores/room-list/previews/PollStartEventPreview.ts
@@ -26,7 +26,7 @@ import MatrixClientContext from "../../../contexts/MatrixClientContext";
 
 export class PollStartEventPreview implements IPreview {
     public static contextType = MatrixClientContext;
-    public context!: React.ContextType<typeof MatrixClientContext>;
+    public declare context: React.ContextType<typeof MatrixClientContext>;
 
     public getTextFor(event: MatrixEvent, tagId?: TagID, isThread?: boolean): string | null {
         let eventContent = event.getContent();
diff --git a/src/utils/MegolmExportEncryption.ts b/src/utils/MegolmExportEncryption.ts
index de6ffea5f1c..fc0958c1795 100644
--- a/src/utils/MegolmExportEncryption.ts
+++ b/src/utils/MegolmExportEncryption.ts
@@ -20,7 +20,7 @@ import { logger } from "matrix-js-sdk/src/logger";
 import { _t } from "../languageHandler";
 import SdkConfig from "../SdkConfig";
 
-const subtleCrypto = window.crypto.subtle || window.crypto.webkitSubtle;
+const subtleCrypto = window.crypto.subtle;
 
 /**
  * Make an Error object which has a friendlyText property which is already
diff --git a/test/TestSdkContext.ts b/test/TestSdkContext.ts
index 5aad5bcfa51..154881db530 100644
--- a/test/TestSdkContext.ts
+++ b/test/TestSdkContext.ts
@@ -35,18 +35,18 @@ import {
  * replace individual stores. This is useful for tests which need to mock out stores.
  */
 export class TestSdkContext extends SdkContextClass {
-    public _RightPanelStore?: RightPanelStore;
-    public _RoomNotificationStateStore?: RoomNotificationStateStore;
-    public _RoomViewStore?: RoomViewStore;
-    public _WidgetPermissionStore?: WidgetPermissionStore;
-    public _WidgetLayoutStore?: WidgetLayoutStore;
-    public _WidgetStore?: WidgetStore;
-    public _PosthogAnalytics?: PosthogAnalytics;
-    public _SlidingSyncManager?: SlidingSyncManager;
-    public _SpaceStore?: SpaceStoreClass;
-    public _VoiceBroadcastRecordingsStore?: VoiceBroadcastRecordingsStore;
-    public _VoiceBroadcastPreRecordingStore?: VoiceBroadcastPreRecordingStore;
-    public _VoiceBroadcastPlaybacksStore?: VoiceBroadcastPlaybacksStore;
+    public declare _RightPanelStore?: RightPanelStore;
+    public declare _RoomNotificationStateStore?: RoomNotificationStateStore;
+    public declare _RoomViewStore?: RoomViewStore;
+    public declare _WidgetPermissionStore?: WidgetPermissionStore;
+    public declare _WidgetLayoutStore?: WidgetLayoutStore;
+    public declare _WidgetStore?: WidgetStore;
+    public declare _PosthogAnalytics?: PosthogAnalytics;
+    public declare _SlidingSyncManager?: SlidingSyncManager;
+    public declare _SpaceStore?: SpaceStoreClass;
+    public declare _VoiceBroadcastRecordingsStore?: VoiceBroadcastRecordingsStore;
+    public declare _VoiceBroadcastPreRecordingStore?: VoiceBroadcastPreRecordingStore;
+    public declare _VoiceBroadcastPlaybacksStore?: VoiceBroadcastPlaybacksStore;
 
     constructor() {
         super();
diff --git a/test/test-utils/call.ts b/test/test-utils/call.ts
index e97c7a59e9b..21672b98867 100644
--- a/test/test-utils/call.ts
+++ b/test/test-utils/call.ts
@@ -43,6 +43,7 @@ export class MockedCall extends Call {
             },
             room.client,
         );
+        this.groupCall = { creationTs: this.event.getTs() } as unknown as GroupCall;
     }
 
     public static get(room: Room): MockedCall | null {
@@ -67,7 +68,7 @@ export class MockedCall extends Call {
         CallStore.instance.updateRoom(room);
     }
 
-    public readonly groupCall = { creationTs: this.event.getTs() } as unknown as GroupCall;
+    public readonly groupCall: GroupCall;
 
     public get participants(): Map<RoomMember, Set<string>> {
         return super.participants;
diff --git a/tsconfig.json b/tsconfig.json
index 3118f598c4c..55e83d95b97 100644
--- a/tsconfig.json
+++ b/tsconfig.json
@@ -4,9 +4,10 @@
         "emitDecoratorMetadata": false,
         "resolveJsonModule": true,
         "esModuleInterop": true,
+        "useDefineForClassFields": true,
         "module": "es2022",
         "moduleResolution": "node",
-        "target": "es2018",
+        "target": "es2022",
         "noUnusedLocals": true,
         "sourceMap": false,
         "outDir": "./lib",