diff --git a/spec/integ/crypto/crypto.spec.ts b/spec/integ/crypto/crypto.spec.ts
index 0d348caef..55c513a3a 100644
--- a/spec/integ/crypto/crypto.spec.ts
+++ b/spec/integ/crypto/crypto.spec.ts
@@ -50,6 +50,7 @@ import {
     ClientEvent,
     createClient,
     CryptoEvent,
+    HistoryVisibility,
     IClaimOTKsResult,
     IContent,
     IDownloadKeyResult,
@@ -59,11 +60,11 @@ import {
     MatrixClient,
     MatrixEvent,
     MatrixEventEvent,
+    MsgType,
     PendingEventOrdering,
     Room,
     RoomMember,
     RoomStateEvent,
-    HistoryVisibility,
 } from "../../../src/matrix";
 import { DeviceInfo } from "../../../src/crypto/deviceinfo";
 import { E2EKeyReceiver } from "../../test-utils/E2EKeyReceiver";
@@ -1925,7 +1926,7 @@ describe.each(Object.entries(CRYPTO_BACKENDS))("crypto (%s)", (backend: string,
         expectAliceKeyQuery({ device_keys: { "@other:user": {} }, failures: {} });
         aliceClient.on(RoomStateEvent.NewMember, (_e, _s, member: RoomMember) => {
             if (member.userId == "@other:user") {
-                aliceClient.sendMessage(testRoomId, { msgtype: "m.text", body: "Hello, World" });
+                aliceClient.sendMessage(testRoomId, { msgtype: MsgType.Text, body: "Hello, World" });
             }
         });
 
diff --git a/spec/integ/crypto/olm-encryption-spec.ts b/spec/integ/crypto/olm-encryption-spec.ts
index ff79bf28b..5977bda74 100644
--- a/spec/integ/crypto/olm-encryption-spec.ts
+++ b/spec/integ/crypto/olm-encryption-spec.ts
@@ -34,7 +34,7 @@ import { logger } from "../../../src/logger";
 import * as testUtils from "../../test-utils/test-utils";
 import { TestClient } from "../../TestClient";
 import { CRYPTO_ENABLED, IClaimKeysRequest, IQueryKeysRequest, IUploadKeysRequest } from "../../../src/client";
-import { ClientEvent, IContent, ISendEventResponse, MatrixClient, MatrixEvent } from "../../../src/matrix";
+import { ClientEvent, IContent, ISendEventResponse, MatrixClient, MatrixEvent, MsgType } from "../../../src/matrix";
 import { DeviceInfo } from "../../../src/crypto/deviceinfo";
 import { KnownMembership } from "../../../src/@types/membership";
 
@@ -217,7 +217,7 @@ async function expectBobSendMessageRequest(): Promise<OlmPayload> {
 }
 
 function sendMessage(client: MatrixClient): Promise<ISendEventResponse> {
-    return client.sendMessage(roomId, { msgtype: "m.text", body: "Hello, World" });
+    return client.sendMessage(roomId, { msgtype: MsgType.Text, body: "Hello, World" });
 }
 
 async function expectSendMessageRequest(httpBackend: TestClient["httpBackend"]): Promise<IContent> {
diff --git a/spec/integ/matrix-client-retrying.spec.ts b/spec/integ/matrix-client-retrying.spec.ts
index d62e968a0..b78e3c7b4 100644
--- a/spec/integ/matrix-client-retrying.spec.ts
+++ b/spec/integ/matrix-client-retrying.spec.ts
@@ -16,7 +16,7 @@ limitations under the License.
 
 import HttpBackend from "matrix-mock-request";
 
-import { EventStatus, RoomEvent, MatrixClient, MatrixScheduler } from "../../src/matrix";
+import { EventStatus, MatrixClient, MatrixScheduler, MsgType, RoomEvent } from "../../src/matrix";
 import { Room } from "../../src/models/room";
 import { TestClient } from "../TestClient";
 
@@ -60,7 +60,7 @@ describe("MatrixClient retrying", function () {
         // send a couple of events; the second will be queued
         const p1 = client!
             .sendMessage(roomId, {
-                msgtype: "m.text",
+                msgtype: MsgType.Text,
                 body: "m1",
             })
             .then(
@@ -77,7 +77,7 @@ describe("MatrixClient retrying", function () {
         // never gets resolved.
         // https://github.com/matrix-org/matrix-js-sdk/issues/496
         client!.sendMessage(roomId, {
-            msgtype: "m.text",
+            msgtype: MsgType.Text,
             body: "m2",
         });
 
diff --git a/spec/integ/matrix-client-unread-notifications.spec.ts b/spec/integ/matrix-client-unread-notifications.spec.ts
index 7b35cbbf5..8518d0864 100644
--- a/spec/integ/matrix-client-unread-notifications.spec.ts
+++ b/spec/integ/matrix-client-unread-notifications.spec.ts
@@ -152,7 +152,7 @@ describe("MatrixClient syncing", () => {
         await client!.sendEvent(roomId, EventType.Reaction, {
             "m.relates_to": {
                 rel_type: RelationType.Annotation,
-                event_id: threadReply.getId(),
+                event_id: threadReply.getId()!,
                 key: "",
             },
         });
diff --git a/spec/unit/embedded.spec.ts b/spec/unit/embedded.spec.ts
index b42acfff1..d9ac5a62f 100644
--- a/spec/unit/embedded.spec.ts
+++ b/spec/unit/embedded.spec.ts
@@ -81,6 +81,12 @@ declare module "../../src/types" {
             hello: string;
         };
     }
+
+    interface TimelineEvents {
+        "org.matrix.rageshake_request": {
+            request_id: number;
+        };
+    }
 }
 
 describe("RoomWidgetClient", () => {
diff --git a/spec/unit/matrix-client.spec.ts b/spec/unit/matrix-client.spec.ts
index 5f0cddda3..62b479f89 100644
--- a/spec/unit/matrix-client.spec.ts
+++ b/spec/unit/matrix-client.spec.ts
@@ -22,6 +22,7 @@ import { Filter } from "../../src/filter";
 import { DEFAULT_TREE_POWER_LEVELS_TEMPLATE } from "../../src/models/MSC3089TreeSpace";
 import {
     EventType,
+    MsgType,
     RelationType,
     RoomCreateTypeField,
     RoomType,
@@ -73,6 +74,7 @@ import { StubStore } from "../../src/store/stub";
 import { SecretStorageKeyDescriptionAesV1, ServerSideSecretStorageImpl } from "../../src/secret-storage";
 import { CryptoBackend } from "../../src/common-crypto/CryptoBackend";
 import { KnownMembership } from "../../src/@types/membership";
+import { RoomMessageEventContent } from "../../src/@types/events";
 
 jest.useFakeTimers();
 
@@ -567,7 +569,7 @@ describe("MatrixClient", function () {
     describe("sendEvent", () => {
         const roomId = "!room:example.org";
         const body = "This is the body";
-        const content = { body };
+        const content = { body, msgtype: MsgType.Text } satisfies RoomMessageEventContent;
 
         it("overload without threadId works", async () => {
             const eventId = "$eventId:example.org";
@@ -662,12 +664,13 @@ describe("MatrixClient", function () {
 
             const content = {
                 body,
+                "msgtype": MsgType.Text,
                 "m.relates_to": {
                     "m.in_reply_to": {
                         event_id: "$other:event",
                     },
                 },
-            };
+            } satisfies RoomMessageEventContent;
 
             const room = new Room(roomId, client, userId);
             mocked(store.getRoom).mockReturnValue(room);
diff --git a/spec/unit/models/MSC3089TreeSpace.spec.ts b/spec/unit/models/MSC3089TreeSpace.spec.ts
index 8f000d844..5a63c282c 100644
--- a/spec/unit/models/MSC3089TreeSpace.spec.ts
+++ b/spec/unit/models/MSC3089TreeSpace.spec.ts
@@ -26,6 +26,7 @@ import {
 import { DEFAULT_ALPHABET } from "../../../src/utils";
 import { MatrixError } from "../../../src/http-api";
 import { KnownMembership } from "../../../src/@types/membership";
+import { EncryptedFile } from "../../../src/@types/media";
 
 describe("MSC3089TreeSpace", () => {
     let client: MatrixClient;
@@ -947,7 +948,7 @@ describe("MSC3089TreeSpace", () => {
         const fileInfo = {
             mimetype: "text/plain",
             // other fields as required by encryption, but ignored here
-        };
+        } as unknown as EncryptedFile;
         const fileEventId = "$file";
         const fileName = "My File.txt";
         const fileContents = "This is a test file";
@@ -1007,7 +1008,7 @@ describe("MSC3089TreeSpace", () => {
         const fileInfo = {
             mimetype: "text/plain",
             // other fields as required by encryption, but ignored here
-        };
+        } as unknown as EncryptedFile;
         const fileEventId = "$file";
         const fileName = "My File.txt";
         const fileContents = "This is a test file";
diff --git a/src/@types/event.ts b/src/@types/event.ts
index 6f11720a2..0a144a352 100644
--- a/src/@types/event.ts
+++ b/src/@types/event.ts
@@ -41,8 +41,23 @@ import {
     IGroupCallRoomState,
 } from "../webrtc/groupCall";
 import { MSC3089EventContent } from "../models/MSC3089Branch";
-import { M_BEACON_INFO, MBeaconInfoEventContent } from "./beacon";
+import { M_BEACON, M_BEACON_INFO, MBeaconEventContent, MBeaconInfoEventContent } from "./beacon";
 import { XOR } from "./common";
+import { ReactionEventContent, RoomMessageEventContent, StickerEventContent } from "./events";
+import {
+    MCallAnswer,
+    MCallBase,
+    MCallCandidates,
+    MCallHangupReject,
+    MCallInviteNegotiate,
+    MCallReplacesEvent,
+    MCallSelectAnswer,
+    SDPStreamMetadata,
+    SDPStreamMetadataKey,
+} from "../webrtc/callEventTypes";
+import { EncryptionKeysEventContent, ICallNotifyContent } from "../matrixrtc/types";
+import { EncryptedFile } from "./media";
+import { M_POLL_END, M_POLL_START, PollEndEventContent, PollStartEventContent } from "./polls";
 
 export enum EventType {
     // Room state events
@@ -283,21 +298,37 @@ export const LOCAL_NOTIFICATION_SETTINGS_PREFIX = new UnstableValue(
  */
 export const UNSIGNED_THREAD_ID_FIELD = new UnstableValue("thread_id", "org.matrix.msc4023.thread_id");
 
-export interface IEncryptedFile {
-    url: string;
-    mimetype?: string;
-    key: {
-        alg: string;
-        key_ops: string[]; // eslint-disable-line camelcase
-        kty: string;
-        k: string;
-        ext: boolean;
-    };
-    iv: string;
-    hashes: { [alg: string]: string };
-    v: string;
+/**
+ * @deprecated in favour of {@link EncryptedFile}
+ */
+export type IEncryptedFile = EncryptedFile;
+
+/**
+ * Mapped type from event type to content type for all specified non-state room events.
+ */
+export interface TimelineEvents {
+    [EventType.RoomMessage]: RoomMessageEventContent;
+    [EventType.Sticker]: StickerEventContent;
+    [EventType.Reaction]: ReactionEventContent;
+    [EventType.CallReplaces]: MCallReplacesEvent;
+    [EventType.CallAnswer]: MCallAnswer;
+    [EventType.CallSelectAnswer]: MCallSelectAnswer;
+    [EventType.CallNegotiate]: Omit<MCallInviteNegotiate, "offer">;
+    [EventType.CallInvite]: MCallInviteNegotiate;
+    [EventType.CallCandidates]: MCallCandidates;
+    [EventType.CallHangup]: MCallHangupReject;
+    [EventType.CallReject]: MCallHangupReject;
+    [EventType.CallSDPStreamMetadataChangedPrefix]: MCallBase & { [SDPStreamMetadataKey]: SDPStreamMetadata };
+    [EventType.CallEncryptionKeysPrefix]: EncryptionKeysEventContent;
+    [EventType.CallNotify]: ICallNotifyContent;
+    [M_BEACON.name]: MBeaconEventContent;
+    [M_POLL_START.name]: PollStartEventContent;
+    [M_POLL_END.name]: PollEndEventContent;
 }
 
+/**
+ * Mapped type from event type to content type for all specified room state events.
+ */
 export interface StateEvents {
     [EventType.RoomCanonicalAlias]: RoomCanonicalAliasEventContent;
     [EventType.RoomCreate]: RoomCreateEventContent;
diff --git a/src/@types/events.ts b/src/@types/events.ts
new file mode 100644
index 000000000..59c41d201
--- /dev/null
+++ b/src/@types/events.ts
@@ -0,0 +1,119 @@
+/*
+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.
+*/
+
+import { MsgType, RelationType } from "./event";
+import { FileInfo, ImageInfo, MediaEventContent } from "./media";
+import { XOR } from "./common";
+
+interface BaseTimelineEvent {
+    "body": string;
+    "m.mentions"?: {
+        user_ids?: string[];
+        room?: boolean;
+    };
+}
+
+interface ReplyEvent {
+    "m.relates_to"?: {
+        "m.in_reply_to"?: {
+            event_id: string;
+        };
+    };
+}
+
+interface NoRelationEvent {
+    "m.new_content"?: never;
+    "m.relates_to"?: never;
+}
+
+/**
+ * Partial content format of timeline events with rel_type `m.replace`
+ *
+ * @see https://spec.matrix.org/v1.9/client-server-api/#event-replacements
+ */
+export interface ReplacementEvent<T> {
+    "m.new_content": T;
+    "m.relates_to": {
+        event_id: string;
+        rel_type: RelationType.Replace;
+    };
+}
+
+/**
+ * Partial content format of timeline events with rel_type other than `m.replace`
+ *
+ * @see https://spec.matrix.org/v1.9/client-server-api/#forming-relationships-between-events
+ */
+export interface RelationEvent {
+    "m.new_content"?: never;
+    "m.relates_to": {
+        event_id: string;
+        rel_type: Exclude<RelationType, RelationType.Replace>;
+    };
+}
+
+/**
+ * Content format of timeline events with type `m.room.message` and `msgtype` `m.text`, `m.emote`, or `m.notice`
+ *
+ * @see https://spec.matrix.org/v1.9/client-server-api/#mroommessage
+ */
+export interface RoomMessageTextEventContent extends BaseTimelineEvent {
+    msgtype: MsgType.Text | MsgType.Emote | MsgType.Notice;
+    format?: "org.matrix.custom.html";
+    formatted_body?: string;
+}
+
+/**
+ * Content format of timeline events with type `m.room.message` and `msgtype` `m.location`
+ *
+ * @see https://spec.matrix.org/v1.9/client-server-api/#mlocation
+ */
+export interface RoomMessageLocationEventContent extends BaseTimelineEvent {
+    body: string;
+    geo_uri: string;
+    info: Pick<FileInfo, "thumbnail_info" | "thumbnail_file" | "thumbnail_url">;
+    msgtype: MsgType.Location;
+}
+
+type MessageEventContent = RoomMessageTextEventContent | RoomMessageLocationEventContent | MediaEventContent;
+
+export type RoomMessageEventContent = BaseTimelineEvent &
+    XOR<XOR<ReplacementEvent<MessageEventContent>, RelationEvent>, XOR<ReplyEvent, NoRelationEvent>> &
+    MessageEventContent;
+
+/**
+ * Content format of timeline events with type `m.sticker`
+ *
+ * @see https://spec.matrix.org/v1.9/client-server-api/#msticker
+ */
+export interface StickerEventContent extends BaseTimelineEvent {
+    body: string;
+    info: ImageInfo;
+    url: string;
+}
+
+/**
+ * Content format of timeline events with type `m.reaction`
+ *
+ * @see https://spec.matrix.org/v1.9/client-server-api/#mreaction
+ */
+export interface ReactionEventContent {
+    "m.relates_to": {
+        event_id: string;
+        key: string;
+        rel_type: RelationType.Annotation;
+    };
+}
diff --git a/src/client.ts b/src/client.ts
index 8bf277071..6de5cd5d7 100644
--- a/src/client.ts
+++ b/src/client.ts
@@ -145,6 +145,7 @@ import {
     RoomCreateTypeField,
     RoomType,
     StateEvents,
+    TimelineEvents,
     UNSTABLE_MSC3088_ENABLED,
     UNSTABLE_MSC3088_PURPOSE,
     UNSTABLE_MSC3089_TREE_SUBTYPE,
@@ -223,6 +224,7 @@ import { RegisterRequest, RegisterResponse } from "./@types/registration";
 import { MatrixRTCSessionManager } from "./matrixrtc/MatrixRTCSessionManager";
 import { getRelationsThreadFilter } from "./thread-utils";
 import { KnownMembership, Membership } from "./@types/membership";
+import { RoomMessageEventContent, StickerEventContent } from "./@types/events";
 import { ImageInfo } from "./@types/media";
 
 export type Store = IStore;
@@ -4551,12 +4553,17 @@ export class MatrixClient extends TypedEventEmitter<EmittedEvents, ClientEventHa
         return this.sendStateEvent(roomId, M_BEACON_INFO.name, beaconInfoContent, this.getUserId()!);
     }
 
-    public sendEvent(roomId: string, eventType: string, content: IContent, txnId?: string): Promise<ISendEventResponse>;
-    public sendEvent(
+    public sendEvent<K extends keyof TimelineEvents>(
+        roomId: string,
+        eventType: K,
+        content: TimelineEvents[K],
+        txnId?: string,
+    ): Promise<ISendEventResponse>;
+    public sendEvent<K extends keyof TimelineEvents>(
         roomId: string,
         threadId: string | null,
-        eventType: string,
-        content: IContent,
+        eventType: K,
+        content: TimelineEvents[K],
         txnId?: string,
     ): Promise<ISendEventResponse>;
     public sendEvent(
@@ -4943,27 +4950,27 @@ export class MatrixClient extends TypedEventEmitter<EmittedEvents, ClientEventHa
      * @returns Promise which resolves: to an ISendEventResponse object
      * @returns Rejects: with an error response.
      */
-    public sendMessage(roomId: string, content: IContent, txnId?: string): Promise<ISendEventResponse>;
+    public sendMessage(roomId: string, content: RoomMessageEventContent, txnId?: string): Promise<ISendEventResponse>;
     public sendMessage(
         roomId: string,
         threadId: string | null,
-        content: IContent,
+        content: RoomMessageEventContent,
         txnId?: string,
     ): Promise<ISendEventResponse>;
     public sendMessage(
         roomId: string,
-        threadId: string | null | IContent,
-        content?: IContent | string,
+        threadId: string | null | RoomMessageEventContent,
+        content?: RoomMessageEventContent | string,
         txnId?: string,
     ): Promise<ISendEventResponse> {
         if (typeof threadId !== "string" && threadId !== null) {
             txnId = content as string;
-            content = threadId as IContent;
+            content = threadId as RoomMessageEventContent;
             threadId = null;
         }
 
-        const eventType: string = EventType.RoomMessage;
-        const sendContent: IContent = content as IContent;
+        const eventType = EventType.RoomMessage;
+        const sendContent = content as RoomMessageEventContent;
 
         return this.sendEvent(roomId, threadId as string | null, eventType, sendContent, txnId);
     }
@@ -5076,10 +5083,10 @@ export class MatrixClient extends TypedEventEmitter<EmittedEvents, ClientEventHa
         }
         const content = {
             msgtype: MsgType.Image,
-            url: url,
-            info: info,
+            url: url as string,
+            info: info as ImageInfo,
             body: text,
-        };
+        } satisfies RoomMessageEventContent;
         return this.sendMessage(roomId, threadId, content);
     }
 
@@ -5114,10 +5121,10 @@ export class MatrixClient extends TypedEventEmitter<EmittedEvents, ClientEventHa
             threadId = null;
         }
         const content = {
-            url: url,
-            info: info,
+            url: url as string,
+            info: info as ImageInfo,
             body: text,
-        };
+        } satisfies StickerEventContent;
 
         return this.sendEvent(roomId, threadId, EventType.Sticker, content);
     }
diff --git a/src/content-helpers.ts b/src/content-helpers.ts
index 6790886f2..3f611e369 100644
--- a/src/content-helpers.ts
+++ b/src/content-helpers.ts
@@ -30,7 +30,7 @@ import {
     LegacyLocationEventContent,
 } from "./@types/location";
 import { MRoomTopicEventContent, MTopicContent, M_TOPIC } from "./@types/topic";
-import { IContent } from "./models/event";
+import { RoomMessageEventContent } from "./@types/events";
 
 /**
  * Generates the content for a HTML Message event
@@ -38,7 +38,7 @@ import { IContent } from "./models/event";
  * @param htmlBody - the HTML representation of the message
  * @returns
  */
-export function makeHtmlMessage(body: string, htmlBody: string): IContent {
+export function makeHtmlMessage(body: string, htmlBody: string): RoomMessageEventContent {
     return {
         msgtype: MsgType.Text,
         format: "org.matrix.custom.html",
@@ -53,7 +53,7 @@ export function makeHtmlMessage(body: string, htmlBody: string): IContent {
  * @param htmlBody - the HTML representation of the notice
  * @returns
  */
-export function makeHtmlNotice(body: string, htmlBody: string): IContent {
+export function makeHtmlNotice(body: string, htmlBody: string): RoomMessageEventContent {
     return {
         msgtype: MsgType.Notice,
         format: "org.matrix.custom.html",
@@ -68,7 +68,7 @@ export function makeHtmlNotice(body: string, htmlBody: string): IContent {
  * @param htmlBody - the HTML representation of the emote
  * @returns
  */
-export function makeHtmlEmote(body: string, htmlBody: string): IContent {
+export function makeHtmlEmote(body: string, htmlBody: string): RoomMessageEventContent {
     return {
         msgtype: MsgType.Emote,
         format: "org.matrix.custom.html",
@@ -82,7 +82,7 @@ export function makeHtmlEmote(body: string, htmlBody: string): IContent {
  * @param body - the plaintext body of the emote
  * @returns
  */
-export function makeTextMessage(body: string): IContent {
+export function makeTextMessage(body: string): RoomMessageEventContent {
     return {
         msgtype: MsgType.Text,
         body: body,
@@ -94,7 +94,7 @@ export function makeTextMessage(body: string): IContent {
  * @param body - the plaintext body of the notice
  * @returns
  */
-export function makeNotice(body: string): IContent {
+export function makeNotice(body: string): RoomMessageEventContent {
     return {
         msgtype: MsgType.Notice,
         body: body,
@@ -106,7 +106,7 @@ export function makeNotice(body: string): IContent {
  * @param body - the plaintext body of the emote
  * @returns
  */
-export function makeEmoteMessage(body: string): IContent {
+export function makeEmoteMessage(body: string): RoomMessageEventContent {
     return {
         msgtype: MsgType.Emote,
         body: body,
diff --git a/src/crypto/verification/request/InRoomChannel.ts b/src/crypto/verification/request/InRoomChannel.ts
index 59b90a17d..59df11d78 100644
--- a/src/crypto/verification/request/InRoomChannel.ts
+++ b/src/crypto/verification/request/InRoomChannel.ts
@@ -18,7 +18,7 @@ limitations under the License.
 import { VerificationRequest, REQUEST_TYPE, READY_TYPE, START_TYPE } from "./VerificationRequest";
 import { logger } from "../../../logger";
 import { IVerificationChannel } from "./Channel";
-import { EventType } from "../../../@types/event";
+import { EventType, TimelineEvents } from "../../../@types/event";
 import { MatrixClient } from "../../../client";
 import { MatrixEvent } from "../../../models/event";
 import { IRequestsMap } from "../..";
@@ -299,7 +299,11 @@ export class InRoomChannel implements IVerificationChannel {
         if (type === REQUEST_TYPE) {
             sendType = MESSAGE_TYPE;
         }
-        const response = await this.client.sendEvent(this.roomId, sendType, content);
+        const response = await this.client.sendEvent(
+            this.roomId,
+            sendType as keyof TimelineEvents,
+            content as TimelineEvents[keyof TimelineEvents],
+        );
         if (type === REQUEST_TYPE) {
             this.requestEventId = response.event_id;
         }
diff --git a/src/models/MSC3089Branch.ts b/src/models/MSC3089Branch.ts
index 3a294ebc2..ebae391e3 100644
--- a/src/models/MSC3089Branch.ts
+++ b/src/models/MSC3089Branch.ts
@@ -15,12 +15,20 @@ limitations under the License.
 */
 
 import { MatrixClient } from "../client";
-import { IEncryptedFile, RelationType, UNSTABLE_MSC3089_BRANCH } from "../@types/event";
+import { RelationType, UNSTABLE_MSC3089_BRANCH } from "../@types/event";
 import { IContent, MatrixEvent } from "./event";
 import { MSC3089TreeSpace } from "./MSC3089TreeSpace";
 import { EventTimeline } from "./event-timeline";
 import { FileType } from "../http-api";
 import type { ISendEventResponse } from "../@types/requests";
+import { EncryptedFile } from "../@types/media";
+
+export interface MSC3089EventContent {
+    active?: boolean;
+    name?: string;
+    locked?: boolean;
+    version?: number;
+}
 
 export interface MSC3089EventContent {
     active?: boolean;
@@ -138,7 +146,7 @@ export class MSC3089Branch {
      * Gets information about the file needed to download it.
      * @returns Information about the file.
      */
-    public async getFileInfo(): Promise<{ info: IEncryptedFile; httpUrl: string }> {
+    public async getFileInfo(): Promise<{ info: EncryptedFile; httpUrl: string }> {
         const event = await this.getFileEvent();
 
         const file = event.getOriginalContent()["file"];
@@ -186,7 +194,7 @@ export class MSC3089Branch {
     public async createNewVersion(
         name: string,
         encryptedContents: FileType,
-        info: Partial<IEncryptedFile>,
+        info: EncryptedFile,
         additionalContent?: IContent,
     ): Promise<ISendEventResponse> {
         const fileEventResponse = await this.directory.createFile(name, encryptedContents, info, {
diff --git a/src/models/MSC3089TreeSpace.ts b/src/models/MSC3089TreeSpace.ts
index 3890afeb7..76aae6558 100644
--- a/src/models/MSC3089TreeSpace.ts
+++ b/src/models/MSC3089TreeSpace.ts
@@ -17,7 +17,7 @@ limitations under the License.
 import promiseRetry from "p-retry";
 
 import { MatrixClient } from "../client";
-import { EventType, IEncryptedFile, MsgType, UNSTABLE_MSC3089_BRANCH, UNSTABLE_MSC3089_LEAF } from "../@types/event";
+import { EventType, MsgType, UNSTABLE_MSC3089_BRANCH, UNSTABLE_MSC3089_LEAF } from "../@types/event";
 import { Room } from "./room";
 import { logger } from "../logger";
 import { IContent, MatrixEvent } from "./event";
@@ -35,6 +35,7 @@ import { ISendEventResponse } from "../@types/requests";
 import { FileType } from "../http-api";
 import { KnownMembership } from "../@types/membership";
 import { RoomPowerLevelsEventContent, SpaceChildEventContent } from "../@types/state_events";
+import { EncryptedFile, FileContent } from "../@types/media";
 
 /**
  * The recommended defaults for a tree space's power levels. Note that this
@@ -79,6 +80,12 @@ export enum TreePermissions {
     Owner = "owner", // "Admin" or PL100
 }
 
+declare module "../@types/media" {
+    interface FileContent {
+        [UNSTABLE_MSC3089_LEAF.name]?: {};
+    }
+}
+
 /**
  * Represents a [MSC3089](https://github.com/matrix-org/matrix-doc/pull/3089)
  * file tree Space. Note that this is UNSTABLE and subject to breaking changes
@@ -502,7 +509,7 @@ export class MSC3089TreeSpace {
     public async createFile(
         name: string,
         encryptedContents: FileType,
-        info: Partial<IEncryptedFile>,
+        info: EncryptedFile,
         additionalContent?: IContent,
     ): Promise<ISendEventResponse> {
         const { content_uri: mxc } = await this.client.uploadContent(encryptedContents, {
@@ -510,7 +517,7 @@ export class MSC3089TreeSpace {
         });
         info.url = mxc;
 
-        const fileContent = {
+        const fileContent: FileContent = {
             msgtype: MsgType.File,
             body: name,
             url: mxc,
@@ -529,7 +536,7 @@ export class MSC3089TreeSpace {
             ...additionalContent,
             ...fileContent,
             [UNSTABLE_MSC3089_LEAF.name]: {},
-        });
+        } as FileContent);
 
         await this.client.sendStateEvent(
             this.roomId,
diff --git a/src/types.ts b/src/types.ts
index adfd4e5b3..c1469b170 100644
--- a/src/types.ts
+++ b/src/types.ts
@@ -24,6 +24,7 @@ limitations under the License.
 export type * from "./@types/media";
 export * from "./@types/membership";
 export type * from "./@types/event";
+export type * from "./@types/events";
 export type * from "./@types/state_events";
 
 /** The different methods for device and user verification */
diff --git a/src/webrtc/call.ts b/src/webrtc/call.ts
index 92b4862de..45d35f60c 100644
--- a/src/webrtc/call.ts
+++ b/src/webrtc/call.ts
@@ -26,8 +26,8 @@ import { parse as parseSdp, write as writeSdp } from "sdp-transform";
 
 import { logger } from "../logger";
 import { checkObjectHasKeys, isNullOrUndefined, recursivelyAssign } from "../utils";
-import { IContent, MatrixEvent } from "../models/event";
-import { EventType, ToDeviceMessageId } from "../@types/event";
+import { MatrixEvent } from "../models/event";
+import { EventType, TimelineEvents, ToDeviceMessageId } from "../@types/event";
 import { RoomMember } from "../models/room-member";
 import { randomString } from "../randomstring";
 import {
@@ -293,13 +293,24 @@ function getCodecParamMods(isPtt: boolean): CodecParamsMod[] {
     return mods;
 }
 
+type CallEventType =
+    | EventType.CallReplaces
+    | EventType.CallAnswer
+    | EventType.CallSelectAnswer
+    | EventType.CallNegotiate
+    | EventType.CallInvite
+    | EventType.CallCandidates
+    | EventType.CallHangup
+    | EventType.CallReject
+    | EventType.CallSDPStreamMetadataChangedPrefix;
+
 export interface VoipEvent {
     type: "toDevice" | "sendEvent";
     eventType: string;
     userId?: string;
     opponentDeviceId?: string;
     roomId?: string;
-    content: Record<string, unknown>;
+    content: TimelineEvents[CallEventType];
 }
 
 /**
@@ -406,7 +417,7 @@ export class MatrixCall extends TypedEventEmitter<CallEvent, CallEventHandlerMap
     // If candidates arrive before we've picked an opponent (which, in particular,
     // will happen if the opponent sends candidates eagerly before the user answers
     // the call) we buffer them up here so we can then add the ones from the party we pick
-    private remoteCandidateBuffer = new Map<string, RTCIceCandidate[]>();
+    private remoteCandidateBuffer = new Map<string, MCallCandidates["candidates"]>();
 
     private remoteAssertedIdentity?: AssertedIdentity;
     private remoteSDPStreamMetadata?: SDPStreamMetadata;
@@ -1156,7 +1167,7 @@ export class MatrixCall extends TypedEventEmitter<CallEvent, CallEventHandlerMap
         this.terminate(CallParty.Local, reason, !suppressEvent);
         // We don't want to send hangup here if we didn't even get to sending an invite
         if ([CallState.Fledgling, CallState.WaitLocalMedia].includes(this.state)) return;
-        const content: IContent = {};
+        const content: Omit<MCallHangupReject, "version" | "call_id" | "party_id" | "conf_id"> = {};
         // Don't send UserHangup reason to older clients
         if ((this.opponentVersion && this.opponentVersion !== 0) || reason !== CallErrorCode.UserHangup) {
             content["reason"] = reason;
@@ -1916,7 +1927,7 @@ export class MatrixCall extends TypedEventEmitter<CallEvent, CallEventHandlerMap
         if (this.opponentPartyId !== null) {
             try {
                 await this.sendVoipEvent(EventType.CallSelectAnswer, {
-                    selected_party_id: this.opponentPartyId,
+                    selected_party_id: this.opponentPartyId!,
                 });
             } catch (err) {
                 // This isn't fatal, and will just mean that if another party has raced to answer
@@ -2012,6 +2023,7 @@ export class MatrixCall extends TypedEventEmitter<CallEvent, CallEventHandlerMap
                 logger.debug(`Call ${this.callId} onNegotiateReceived() create an answer`);
 
                 this.sendVoipEvent(EventType.CallNegotiate, {
+                    lifetime: CALL_TIMEOUT_MS,
                     description: this.peerConn!.localDescription?.toJSON(),
                     [SDPStreamMetadataKey]: this.getLocalSDPStreamMetadata(true),
                 });
@@ -2444,13 +2456,17 @@ export class MatrixCall extends TypedEventEmitter<CallEvent, CallEventHandlerMap
     /**
      * @internal
      */
-    private async sendVoipEvent(eventType: string, content: object): Promise<void> {
-        const realContent = Object.assign({}, content, {
+    private async sendVoipEvent<K extends keyof Pick<TimelineEvents, CallEventType>>(
+        eventType: K,
+        content: Omit<TimelineEvents[K], "version" | "call_id" | "party_id" | "conf_id">,
+    ): Promise<void> {
+        const realContent = {
+            ...content,
             version: VOIP_PROTO_VERSION,
             call_id: this.callId,
             party_id: this.ourPartyId,
             conf_id: this.groupCallId,
-        });
+        } as TimelineEvents[K];
 
         if (this.opponentDeviceId) {
             const toDeviceSeq = this.toDeviceSeq++;
@@ -2729,7 +2745,9 @@ export class MatrixCall extends TypedEventEmitter<CallEvent, CallEventHandlerMap
         const candidates = this.candidateSendQueue;
         this.candidateSendQueue = [];
         ++this.candidateSendTries;
-        const content = { candidates: candidates.map((candidate) => candidate.toJSON()) };
+        const content: Pick<MCallCandidates, "candidates"> = {
+            candidates: candidates.map((candidate) => candidate.toJSON()),
+        };
         if (this.candidatesEnded) {
             // If there are no more candidates, signal this by adding an empty string candidate
             content.candidates.push({
@@ -2923,7 +2941,7 @@ export class MatrixCall extends TypedEventEmitter<CallEvent, CallEventHandlerMap
         this.remoteCandidateBuffer.clear();
     }
 
-    private async addIceCandidates(candidates: RTCIceCandidate[]): Promise<void> {
+    private async addIceCandidates(candidates: RTCIceCandidate[] | MCallCandidates["candidates"]): Promise<void> {
         for (const candidate of candidates) {
             if (
                 (candidate.sdpMid === null || candidate.sdpMid === undefined) &&
diff --git a/src/webrtc/callEventTypes.ts b/src/webrtc/callEventTypes.ts
index f06ed5b0d..0be2b2d4d 100644
--- a/src/webrtc/callEventTypes.ts
+++ b/src/webrtc/callEventTypes.ts
@@ -34,6 +34,7 @@ export interface CallReplacesTarget {
 
 export interface MCallBase {
     call_id: string;
+    conf_id?: string;
     version: string | number;
     party_id?: string;
     sender_session_id?: string;
@@ -82,7 +83,7 @@ export interface MCAllAssertedIdentity extends MCallBase {
 }
 
 export interface MCallCandidates extends MCallBase {
-    candidates: RTCIceCandidate[];
+    candidates: Omit<RTCIceCandidateInit, "usernameFragment">[];
 }
 
 export interface MCallHangupReject extends MCallBase {