diff --git a/spec/unit/interactive-auth.spec.ts b/spec/unit/interactive-auth.spec.ts
index 554d747352d..ea11fc4c900 100644
--- a/spec/unit/interactive-auth.spec.ts
+++ b/spec/unit/interactive-auth.spec.ts
@@ -94,7 +94,6 @@ describe("InteractiveAuth", () => {
             authData: {
                 session: "sessionId",
                 flows: [{ stages: [AuthType.Password] }],
-                errcode: "MockError0",
                 params: {
                     [AuthType.Password]: { param: "aa" },
                 },
diff --git a/src/@types/auth.ts b/src/@types/auth.ts
index f34e45bf130..ac0f6c9d4af 100644
--- a/src/@types/auth.ts
+++ b/src/@types/auth.ts
@@ -15,6 +15,7 @@ limitations under the License.
 */
 
 import { UnstableValue } from "../NamespacedValue";
+import { IClientWellKnown } from "../client";
 
 // disable lint because these are wire responses
 /* eslint-disable camelcase */
@@ -79,25 +80,166 @@ export interface IIdentityProvider {
     brand?: IdentityProviderBrand | string;
 }
 
+export enum SSOAction {
+    /** The user intends to login to an existing account */
+    LOGIN = "login",
+
+    /** The user intends to register for a new account */
+    REGISTER = "register",
+}
+
 /**
- * Parameters to login request as per https://spec.matrix.org/v1.3/client-server-api/#login
+ * A client can identify a user using their Matrix ID.
+ * This can either be the fully qualified Matrix user ID, or just the localpart of the user ID.
+ * @see https://spec.matrix.org/v1.7/client-server-api/#matrix-user-id
  */
-/* eslint-disable camelcase */
-export interface ILoginParams {
-    identifier?: object;
-    password?: string;
-    token?: string;
+type UserLoginIdentifier = {
+    type: "m.id.user";
+    user: string;
+};
+
+/**
+ * A client can identify a user using a 3PID associated with the user’s account on the homeserver,
+ * where the 3PID was previously associated using the /account/3pid API.
+ * See the 3PID Types Appendix for a list of Third-party ID media.
+ * @see https://spec.matrix.org/v1.7/client-server-api/#third-party-id
+ */
+type ThirdPartyLoginIdentifier = {
+    type: "m.id.thirdparty";
+    medium: string;
+    address: string;
+};
+
+/**
+ * A client can identify a user using a phone number associated with the user’s account,
+ * where the phone number was previously associated using the /account/3pid API.
+ * The phone number can be passed in as entered by the user; the homeserver will be responsible for canonicalising it.
+ * If the client wishes to canonicalise the phone number,
+ * then it can use the m.id.thirdparty identifier type with a medium of msisdn instead.
+ *
+ * The country is the two-letter uppercase ISO-3166-1 alpha-2 country code that the number in phone should be parsed as if it were dialled from.
+ *
+ * @see https://spec.matrix.org/v1.7/client-server-api/#phone-number
+ */
+type PhoneLoginIdentifier = {
+    type: "m.id.phone";
+    country: string;
+    phone: string;
+};
+
+type SpecUserIdentifier = UserLoginIdentifier | ThirdPartyLoginIdentifier | PhoneLoginIdentifier;
+
+/**
+ * User Identifiers usable for login & user-interactive authentication.
+ *
+ * Extensibly allows more than Matrix specified identifiers.
+ */
+export type UserIdentifier =
+    | SpecUserIdentifier
+    | { type: Exclude<string, SpecUserIdentifier["type"]>; [key: string]: any };
+
+/**
+ * Request body for POST /login request
+ * @see https://spec.matrix.org/v1.7/client-server-api/#post_matrixclientv3login
+ */
+export interface LoginRequest {
+    /**
+     * The login type being used.
+     */
+    type: "m.login.password" | "m.login.token" | string;
+    /**
+     * Third-party identifier for the user.
+     * @deprecated in favour of `identifier`.
+     */
+    address?: string;
+    /**
+     * ID of the client device.
+     * If this does not correspond to a known client device, a new device will be created.
+     * The given device ID must not be the same as a cross-signing key ID.
+     * The server will auto-generate a device_id if this is not specified.
+     */
     device_id?: string;
+    /**
+     * Identification information for a user
+     */
+    identifier?: UserIdentifier;
+    /**
+     * A display name to assign to the newly-created device.
+     * Ignored if device_id corresponds to a known device.
+     */
     initial_device_display_name?: string;
+    /**
+     * When logging in using a third-party identifier, the medium of the identifier.
+     * Must be `email`.
+     * @deprecated in favour of `identifier`.
+     */
+    medium?: "email";
+    /**
+     * Required when type is `m.login.password`. The user’s password.
+     */
+    password?: string;
+    /**
+     * If true, the client supports refresh tokens.
+     */
+    refresh_token?: boolean;
+    /**
+     * Required when type is `m.login.token`. Part of Token-based login.
+     */
+    token?: string;
+    /**
+     * The fully qualified user ID or just local part of the user ID, to log in.
+     * @deprecated in favour of identifier.
+     */
+    user?: string;
+    // Extensible
+    [key: string]: any;
 }
-/* eslint-enable camelcase */
 
-export enum SSOAction {
-    /** The user intends to login to an existing account */
-    LOGIN = "login",
+// Export for backwards compatibility
+export type ILoginParams = LoginRequest;
 
-    /** The user intends to register for a new account */
-    REGISTER = "register",
+/**
+ * Response body for POST /login request
+ * @see https://spec.matrix.org/v1.7/client-server-api/#post_matrixclientv3login
+ */
+export interface LoginResponse {
+    /**
+     * An access token for the account.
+     * This access token can then be used to authorize other requests.
+     */
+    access_token: string;
+    /**
+     * ID of the logged-in device.
+     * Will be the same as the corresponding parameter in the request, if one was specified.
+     */
+    device_id: string;
+    /**
+     * The fully-qualified Matrix ID for the account.
+     */
+    user_id: string;
+    /**
+     * The lifetime of the access token, in milliseconds.
+     * Once the access token has expired a new access token can be obtained by using the provided refresh token.
+     * If no refresh token is provided, the client will need to re-log in to obtain a new access token.
+     * If not given, the client can assume that the access token will not expire.
+     */
+    expires_in_ms?: number;
+    /**
+     * A refresh token for the account.
+     * This token can be used to obtain a new access token when it expires by calling the /refresh endpoint.
+     */
+    refresh_token?: string;
+    /**
+     * Optional client configuration provided by the server.
+     * If present, clients SHOULD use the provided object to reconfigure themselves, optionally validating the URLs within.
+     * This object takes the same form as the one returned from .well-known autodiscovery.
+     */
+    well_known?: IClientWellKnown;
+    /**
+     * The server_name of the homeserver on which the account has been registered.
+     * @deprecated Clients should extract the server_name from user_id (by splitting at the first colon) if they require it.
+     */
+    home_server?: string;
 }
 
 /**
diff --git a/src/@types/registration.ts b/src/@types/registration.ts
new file mode 100644
index 00000000000..98eb1977eb6
--- /dev/null
+++ b/src/@types/registration.ts
@@ -0,0 +1,116 @@
+/*
+Copyright 2023 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 { AuthDict } from "../interactive-auth";
+
+/**
+ * The request body of a call to `POST /_matrix/client/v3/register`.
+ *
+ * @see https://spec.matrix.org/v1.7/client-server-api/#post_matrixclientv3register
+ */
+export interface RegisterRequest {
+    /**
+     * Additional authentication information for the user-interactive authentication API.
+     * Note that this information is not used to define how the registered user should be authenticated,
+     * but is instead used to authenticate the register call itself.
+     */
+    auth?: AuthDict;
+    /**
+     * The basis for the localpart of the desired Matrix ID.
+     * If omitted, the homeserver MUST generate a Matrix ID local part.
+     */
+    username?: string;
+    /**
+     * The desired password for the account.
+     */
+    password?: string;
+    /**
+     * If true, the client supports refresh tokens.
+     */
+    refresh_token?: boolean;
+    /**
+     * If true, an access_token and device_id should not be returned from this call, therefore preventing an automatic login.
+     * Defaults to false.
+     */
+    inhibit_login?: boolean;
+    /**
+     * A display name to assign to the newly-created device.
+     * Ignored if device_id corresponds to a known device.
+     */
+    initial_device_display_name?: string;
+    /**
+     * @deprecated missing in the spec
+     */
+    guest_access_token?: string;
+    /**
+     * @deprecated missing in the spec
+     */
+    x_show_msisdn?: boolean;
+    /**
+     * @deprecated missing in the spec
+     */
+    bind_msisdn?: boolean;
+    /**
+     * @deprecated missing in the spec
+     */
+    bind_email?: boolean;
+}
+
+/**
+ * The result of a successful call to `POST /_matrix/client/v3/register`.
+ *
+ * @see https://spec.matrix.org/v1.7/client-server-api/#post_matrixclientv3register
+ */
+export interface RegisterResponse {
+    /**
+     * The fully-qualified Matrix user ID (MXID) that has been registered.
+     */
+    user_id: string;
+    /**
+     * An access token for the account.
+     * This access token can then be used to authorize other requests.
+     * Required if the inhibit_login option is false.
+     */
+    access_token?: string;
+    /**
+     * ID of the registered device.
+     * Will be the same as the corresponding parameter in the request, if one was specified.
+     * Required if the inhibit_login option is false.
+     */
+    device_id?: string;
+    /**
+     * The lifetime of the access token, in milliseconds.
+     * Once the access token has expired a new access token can be obtained by using the provided refresh token.
+     * If no refresh token is provided, the client will need to re-log in to obtain a new access token.
+     * If not given, the client can assume that the access token will not expire.
+     *
+     * Omitted if the inhibit_login option is true.
+     */
+    expires_in_ms?: number;
+    /**
+     * A refresh token for the account.
+     * This token can be used to obtain a new access token when it expires by calling the /refresh endpoint.
+     *
+     * Omitted if the inhibit_login option is true.
+     */
+    refresh_token?: string;
+    /**
+     * The server_name of the homeserver on which the account has been registered.
+     *
+     * @deprecated Clients should extract the server_name from user_id (by splitting at the first colon) if they require it.
+     */
+    home_server?: string;
+}
diff --git a/src/client.ts b/src/client.ts
index 85d35db1002..87464cf640e 100644
--- a/src/client.ts
+++ b/src/client.ts
@@ -101,7 +101,7 @@ import {
 import { IIdentityServerProvider } from "./@types/IIdentityServerProvider";
 import { MatrixScheduler } from "./scheduler";
 import { BeaconEvent, BeaconEventHandlerMap } from "./models/beacon";
-import { IAuthData, IAuthDict } from "./interactive-auth";
+import { AuthDict } from "./interactive-auth";
 import { IMinimalEvent, IRoomEvent, IStateEvent } from "./sync-accumulator";
 import { CrossSigningKey, ICreateSecretStorageOpts, IEncryptedEventInfo, IRecoveryKey } from "./crypto/api";
 import { EventTimelineSet } from "./models/event-timeline-set";
@@ -178,7 +178,14 @@ import { IThreepid } from "./@types/threepids";
 import { CryptoStore, OutgoingRoomKeyRequest } from "./crypto/store/base";
 import { GroupCall, IGroupCallDataChannelOptions, GroupCallIntent, GroupCallType } from "./webrtc/groupCall";
 import { MediaHandler } from "./webrtc/mediaHandler";
-import { LoginTokenPostResponse, ILoginFlowsResponse, IRefreshTokenResponse, SSOAction } from "./@types/auth";
+import {
+    LoginTokenPostResponse,
+    ILoginFlowsResponse,
+    IRefreshTokenResponse,
+    SSOAction,
+    LoginResponse,
+    LoginRequest,
+} from "./@types/auth";
 import { TypedEventEmitter } from "./models/typed-event-emitter";
 import { MAIN_ROOM_TIMELINE, ReceiptType } from "./@types/read_receipts";
 import { MSC3575SlidingSyncRequest, MSC3575SlidingSyncResponse, SlidingSync } from "./sliding-sync";
@@ -209,6 +216,7 @@ import {
     ServerSideSecretStorage,
     ServerSideSecretStorageImpl,
 } from "./secret-storage";
+import { RegisterRequest, RegisterResponse } from "./@types/registration";
 
 export type Store = IStore;
 
@@ -717,18 +725,8 @@ interface IJoinedMembersResponse {
     };
 }
 
-export interface IRegisterRequestParams {
-    auth?: IAuthDict;
-    username?: string;
-    password?: string;
-    refresh_token?: boolean;
-    guest_access_token?: string;
-    x_show_msisdn?: boolean;
-    bind_msisdn?: boolean;
-    bind_email?: boolean;
-    inhibit_login?: boolean;
-    initial_device_display_name?: string;
-}
+// Re-export for backwards compatibility
+export type IRegisterRequestParams = RegisterRequest;
 
 export interface IPublicRoomsChunkRoom {
     room_id: string;
@@ -7653,7 +7651,7 @@ export class MatrixClient extends TypedEventEmitter<EmittedEvents, ClientEventHa
      * @param bindThreepids - Set key 'email' to true to bind any email
      *     threepid uses during registration in the identity server. Set 'msisdn' to
      *     true to bind msisdn.
-     * @returns Promise which resolves: TODO
+     * @returns Promise which resolves to a RegisterResponse object
      * @returns Rejects: with an error response.
      */
     public register(
@@ -7664,7 +7662,7 @@ export class MatrixClient extends TypedEventEmitter<EmittedEvents, ClientEventHa
         bindThreepids?: boolean | null | { email?: boolean; msisdn?: boolean },
         guestAccessToken?: string,
         inhibitLogin?: boolean,
-    ): Promise<IAuthData> {
+    ): Promise<RegisterResponse> {
         // backwards compat
         if (bindThreepids === true) {
             bindThreepids = { email: true };
@@ -7675,7 +7673,7 @@ export class MatrixClient extends TypedEventEmitter<EmittedEvents, ClientEventHa
             auth.session = sessionId;
         }
 
-        const params: IRegisterRequestParams = {
+        const params: RegisterRequest = {
             auth: auth,
             refresh_token: true, // always ask for a refresh token - does nothing if unsupported
         };
@@ -7731,8 +7729,7 @@ export class MatrixClient extends TypedEventEmitter<EmittedEvents, ClientEventHa
      *                   `{ user_id, device_id, access_token, home_server }`
      * @returns Rejects: with an error response.
      */
-    public registerGuest({ body }: { body?: any } = {}): Promise<any> {
-        // TODO: Types
+    public registerGuest({ body }: { body?: RegisterRequest } = {}): Promise<RegisterResponse> {
         return this.registerRequest(body || {}, "guest");
     }
 
@@ -7742,7 +7739,7 @@ export class MatrixClient extends TypedEventEmitter<EmittedEvents, ClientEventHa
      * @returns Promise which resolves: to the /register response
      * @returns Rejects: with an error response.
      */
-    public registerRequest(data: IRegisterRequestParams, kind?: string): Promise<IAuthData> {
+    public registerRequest(data: RegisterRequest, kind?: string): Promise<RegisterResponse> {
         const params: { kind?: string } = {};
         if (kind) {
             params.kind = kind;
@@ -7795,23 +7792,15 @@ export class MatrixClient extends TypedEventEmitter<EmittedEvents, ClientEventHa
     }
 
     /**
-     * @returns Promise which resolves: TODO
+     * @returns Promise which resolves to a LoginResponse object
      * @returns Rejects: with an error response.
      */
-    public login(loginType: string, data: any): Promise<any> {
-        // TODO: Types
-        const loginData = {
-            type: loginType,
-        };
-
-        // merge data into loginData
-        Object.assign(loginData, data);
-
+    public login(loginType: LoginRequest["type"], data: Omit<LoginRequest, "type">): Promise<LoginResponse> {
         return this.http
-            .authedRequest<{
-                access_token?: string;
-                user_id?: string;
-            }>(Method.Post, "/login", undefined, loginData)
+            .authedRequest<LoginResponse>(Method.Post, "/login", undefined, {
+                ...data,
+                type: loginType,
+            })
             .then((response) => {
                 if (response.access_token && response.user_id) {
                     this.http.opts.accessToken = response.access_token;
@@ -7824,11 +7813,10 @@ export class MatrixClient extends TypedEventEmitter<EmittedEvents, ClientEventHa
     }
 
     /**
-     * @returns Promise which resolves: TODO
+     * @returns Promise which resolves to a LoginResponse object
      * @returns Rejects: with an error response.
      */
-    public loginWithPassword(user: string, password: string): Promise<any> {
-        // TODO: Types
+    public loginWithPassword(user: string, password: string): Promise<LoginResponse> {
         return this.login("m.login.password", {
             user: user,
             password: password,
@@ -7837,11 +7825,11 @@ export class MatrixClient extends TypedEventEmitter<EmittedEvents, ClientEventHa
 
     /**
      * @param relayState - URL Callback after SAML2 Authentication
-     * @returns Promise which resolves: TODO
+     * @returns Promise which resolves to a LoginResponse object
      * @returns Rejects: with an error response.
+     * @deprecated this isn't in the Matrix spec anymore
      */
-    public loginWithSAML2(relayState: string): Promise<any> {
-        // TODO: Types
+    public loginWithSAML2(relayState: string): Promise<LoginResponse> {
         return this.login("m.login.saml2", {
             relay_state: relayState,
         });
@@ -7881,11 +7869,10 @@ export class MatrixClient extends TypedEventEmitter<EmittedEvents, ClientEventHa
 
     /**
      * @param token - Login token previously received from homeserver
-     * @returns Promise which resolves: TODO
+     * @returns Promise which resolves to a LoginResponse object
      * @returns Rejects: with an error response.
      */
-    public loginWithToken(token: string): Promise<any> {
-        // TODO: Types
+    public loginWithToken(token: string): Promise<LoginResponse> {
         return this.login("m.login.token", {
             token: token,
         });
@@ -7929,7 +7916,7 @@ export class MatrixClient extends TypedEventEmitter<EmittedEvents, ClientEventHa
      * to false.
      * @returns Promise which resolves: On success, the empty object
      */
-    public deactivateAccount(auth?: any, erase?: boolean): Promise<{}> {
+    public deactivateAccount(auth?: any, erase?: boolean): Promise<{ id_server_unbind_result: IdServerUnbindResult }> {
         const body: any = {};
         if (auth) {
             body.auth = auth;
@@ -7950,7 +7937,7 @@ export class MatrixClient extends TypedEventEmitter<EmittedEvents, ClientEventHa
      * @returns Promise which resolves: On success, the token response
      * or UIA auth data.
      */
-    public async requestLoginToken(auth?: IAuthDict): Promise<UIAResponse<LoginTokenPostResponse>> {
+    public async requestLoginToken(auth?: AuthDict): Promise<UIAResponse<LoginTokenPostResponse>> {
         // use capabilities to determine which revision of the MSC is being used
         const capabilities = await this.getCapabilities();
         // use r1 endpoint if capability is exposed otherwise use old r0 endpoint
@@ -8590,7 +8577,7 @@ export class MatrixClient extends TypedEventEmitter<EmittedEvents, ClientEventHa
      * @returns Promise which resolves: to an empty object `{}`
      * @returns Rejects: with an error response.
      */
-    public setPassword(authDict: IAuthDict, newPassword: string, logoutDevices?: boolean): Promise<{}> {
+    public setPassword(authDict: AuthDict, newPassword: string, logoutDevices?: boolean): Promise<{}> {
         const path = "/account/password";
         const data = {
             auth: authDict,
@@ -8648,7 +8635,7 @@ export class MatrixClient extends TypedEventEmitter<EmittedEvents, ClientEventHa
      * @returns Promise which resolves: result object
      * @returns Rejects: with an error response.
      */
-    public deleteDevice(deviceId: string, auth?: IAuthDict): Promise<IAuthData | {}> {
+    public deleteDevice(deviceId: string, auth?: AuthDict): Promise<{}> {
         const path = utils.encodeUri("/devices/$device_id", {
             $device_id: deviceId,
         });
@@ -8670,7 +8657,7 @@ export class MatrixClient extends TypedEventEmitter<EmittedEvents, ClientEventHa
      * @returns Promise which resolves: result object
      * @returns Rejects: with an error response.
      */
-    public deleteMultipleDevices(devices: string[], auth?: IAuthDict): Promise<IAuthData | {}> {
+    public deleteMultipleDevices(devices: string[], auth?: AuthDict): Promise<{}> {
         const body: any = { devices };
 
         if (auth) {
@@ -8955,7 +8942,7 @@ export class MatrixClient extends TypedEventEmitter<EmittedEvents, ClientEventHa
         return this.http.authedRequest(Method.Get, "/keys/changes", qps);
     }
 
-    public uploadDeviceSigningKeys(auth?: IAuthDict, keys?: CrossSigningKeys): Promise<{}> {
+    public uploadDeviceSigningKeys(auth?: AuthDict, keys?: CrossSigningKeys): Promise<{}> {
         // API returns empty object
         const data = Object.assign({}, keys);
         if (auth) Object.assign(data, { auth });
@@ -9168,8 +9155,17 @@ export class MatrixClient extends TypedEventEmitter<EmittedEvents, ClientEventHa
      * @param identityAccessToken - The access token for the identity server.
      * @returns The hashing information for the identity server.
      */
-    public getIdentityHashDetails(identityAccessToken: string): Promise<any> {
-        // TODO: Types
+    public getIdentityHashDetails(identityAccessToken: string): Promise<{
+        /**
+         * The algorithms the server supports. Must contain at least sha256.
+         */
+        algorithms: string[];
+        /**
+         * The pepper the client MUST use in hashing identifiers,
+         * and MUST supply to the /lookup endpoint when performing lookups.
+         */
+        lookup_pepper: string;
+    }> {
         return this.http.idServerRequest(
             Method.Get,
             "/hash_details",
@@ -9277,8 +9273,18 @@ export class MatrixClient extends TypedEventEmitter<EmittedEvents, ClientEventHa
      *                                 exists
      * @returns Rejects: with an error response.
      */
-    public async lookupThreePid(medium: string, address: string, identityAccessToken: string): Promise<any> {
-        // TODO: Types
+    public async lookupThreePid(
+        medium: string,
+        address: string,
+        identityAccessToken: string,
+    ): Promise<
+        | {
+              address: string;
+              medium: string;
+              mxid: string;
+          }
+        | {}
+    > {
         // Note: we're using the V2 API by calling this function, but our
         // function contract requires a V1 response. We therefore have to
         // convert it manually.
@@ -9314,8 +9320,12 @@ export class MatrixClient extends TypedEventEmitter<EmittedEvents, ClientEventHa
      * @returns Promise which resolves: Lookup results from IS.
      * @returns Rejects: with an error response.
      */
-    public async bulkLookupThreePids(query: [string, string][], identityAccessToken: string): Promise<any> {
-        // TODO: Types
+    public async bulkLookupThreePids(
+        query: [string, string][],
+        identityAccessToken: string,
+    ): Promise<{
+        threepids: [medium: string, address: string, mxid: string][];
+    }> {
         // Note: we're using the V2 API by calling this function, but our
         // function contract requires a V1 response. We therefore have to
         // convert it manually.
@@ -9353,8 +9363,7 @@ export class MatrixClient extends TypedEventEmitter<EmittedEvents, ClientEventHa
      * @returns Promise which resolves: an object with account info.
      * @returns Rejects: with an error response.
      */
-    public getIdentityAccount(identityAccessToken: string): Promise<any> {
-        // TODO: Types
+    public getIdentityAccount(identityAccessToken: string): Promise<{ user_id: string }> {
         return this.http.idServerRequest(Method.Get, "/account", undefined, IdentityPrefix.V2, identityAccessToken);
     }
 
@@ -9447,7 +9456,6 @@ export class MatrixClient extends TypedEventEmitter<EmittedEvents, ClientEventHa
      * @returns Promise which resolves to the result object
      */
     public getThirdpartyUser(protocol: string, params: any): Promise<IThirdPartyUser[]> {
-        // TODO: Types
         const path = utils.encodeUri("/thirdparty/user/$protocol", {
             $protocol: protocol,
         });
diff --git a/src/interactive-auth.ts b/src/interactive-auth.ts
index 4d3f643f0d7..e85ac9c2770 100644
--- a/src/interactive-auth.ts
+++ b/src/interactive-auth.ts
@@ -21,6 +21,7 @@ import { MatrixClient } from "./client";
 import { defer, IDeferred } from "./utils";
 import { MatrixError } from "./http-api";
 import { UIAResponse } from "./@types/uia";
+import { UserIdentifier } from "./@types/auth";
 
 const EMAIL_STAGE_TYPE = "m.login.email.identity";
 const MSISDN_STAGE_TYPE = "m.login.msisdn";
@@ -51,22 +52,25 @@ export interface IStageStatus {
  * @see https://spec.matrix.org/v1.6/client-server-api/#user-interactive-api-in-the-rest-api
  */
 export interface IAuthData {
-    // XXX: many of the fields here (`type`, `available_flows`, `required_stages`, etc) look like they
-    // shouldn't be here. They aren't in the spec and it's unclear what they are supposed to do. Be wary of using them.
+    /**
+     * This is a session identifier that the client must pass back to the home server,
+     * if one is provided, in subsequent attempts to authenticate in the same API call.
+     */
     session?: string;
-    type?: string;
+    /**
+     * A list of the stages the client has completed successfully
+     */
     completed?: string[];
+    /**
+     * A list of the login flows supported by the server for this API.
+     */
     flows?: UIAFlow[];
-    available_flows?: UIAFlow[];
-    stages?: string[];
-    required_stages?: AuthType[];
+    /**
+     * Contains any information that the client will need to know in order to use a given type of authentication.
+     * For each login type presented, that type may be present as a key in this dictionary.
+     * For example, the public part of an OAuth client ID could be given here.
+     */
     params?: Record<string, Record<string, any>>;
-    data?: Record<string, string>;
-    errcode?: string;
-    error?: string;
-    user_id?: string;
-    device_id?: string;
-    access_token?: string;
 }
 
 export enum AuthType {
@@ -85,30 +89,62 @@ export enum AuthType {
     UnstableRegistrationToken = "org.matrix.msc3231.login.registration_token",
 }
 
+/**
+ * https://spec.matrix.org/v1.7/client-server-api/#password-based
+ */
+type PasswordDict = {
+    type: AuthType.Password;
+    identifier: UserIdentifier;
+    password: string;
+    session: string;
+};
+
+/**
+ * https://spec.matrix.org/v1.7/client-server-api/#google-recaptcha
+ */
+type RecaptchaDict = {
+    type: AuthType.Recaptcha;
+    response: string;
+    session: string;
+};
+
+interface ThreepidCreds {
+    sid: string;
+    client_secret: string;
+    id_server: string;
+    id_access_token: string;
+}
+
+/**
+ * https://spec.matrix.org/v1.7/client-server-api/#email-based-identity--homeserver
+ */
+type EmailIdentityDict = {
+    type: AuthType.Email;
+    threepid_creds: ThreepidCreds;
+    /**
+     * @deprecated in favour of `threepid_creds` - kept for backwards compatibility
+     */
+    threepidCreds?: ThreepidCreds;
+    session: string;
+};
+
 /**
  * The parameters which are submitted as the `auth` dict in a UIA request
  *
  * @see https://spec.matrix.org/v1.6/client-server-api/#authentication-types
  */
-export interface IAuthDict {
-    // [key: string]: any;
-    type?: string;
-    session?: string;
-    // TODO: Remove `user` once servers support proper UIA
-    // See https://github.com/vector-im/element-web/issues/10312
-    user?: string;
-    identifier?: any;
-    password?: string;
-    response?: string;
-    // TODO: Remove `threepid_creds` once servers support proper UIA
-    // See https://github.com/vector-im/element-web/issues/10312
-    // See https://github.com/matrix-org/matrix-doc/issues/2220
-    // eslint-disable-next-line camelcase
-    threepid_creds?: any;
-    threepidCreds?: any;
-    // For m.login.registration_token type
-    token?: string;
-}
+export type AuthDict =
+    | PasswordDict
+    | RecaptchaDict
+    | EmailIdentityDict
+    | { type: Exclude<string, AuthType>; [key: string]: any }
+    | {};
+
+/**
+ * Backwards compatible export
+ * @deprecated in favour of AuthDict
+ */
+export type IAuthDict = AuthDict;
 
 export class NoAuthFlowFoundError extends Error {
     public name = "NoAuthFlowFoundError";
@@ -129,7 +165,7 @@ export class NoAuthFlowFoundError extends Error {
  */
 export type UIAuthCallback<T> = (makeRequest: (authData: IAuthDict) => Promise<UIAResponse<T>>) => Promise<T>;
 
-interface IOpts {
+interface IOpts<T> {
     /**
      * A matrix client to use for the auth process
      */
@@ -170,7 +206,7 @@ interface IOpts {
      * The busyChanged callback should be used instead of the background flag.
      * Should return a promise which resolves to the successful response or rejects with a MatrixError.
      */
-    doRequest(auth: IAuthDict | null, background: boolean): Promise<IAuthData>;
+    doRequest(auth: AuthDict | null, background: boolean): Promise<T>;
     /**
      * Called when the status of the UI auth changes,
      * ie. when the state of an auth stage changes of when the auth flow moves to a new stage.
@@ -215,21 +251,23 @@ interface IOpts {
  * submitAuthDict.
  *
  * @param opts - options object
+ * @typeParam T - the return type of the request when it is successful
  */
-export class InteractiveAuth {
+export class InteractiveAuth<T> {
     private readonly matrixClient: MatrixClient;
     private readonly inputs: IInputs;
     private readonly clientSecret: string;
-    private readonly requestCallback: IOpts["doRequest"];
-    private readonly busyChangedCallback?: IOpts["busyChanged"];
-    private readonly stateUpdatedCallback: IOpts["stateUpdated"];
-    private readonly requestEmailTokenCallback: IOpts["requestEmailToken"];
+    private readonly requestCallback: IOpts<T>["doRequest"];
+    private readonly busyChangedCallback?: IOpts<T>["busyChanged"];
+    private readonly stateUpdatedCallback: IOpts<T>["stateUpdated"];
+    private readonly requestEmailTokenCallback: IOpts<T>["requestEmailToken"];
     private readonly supportedStages?: Set<string>;
 
+    // The current latest data received from the server during the user interactive auth flow.
     private data: IAuthData;
     private emailSid?: string;
     private requestingEmailToken = false;
-    private attemptAuthDeferred: IDeferred<IAuthData> | null = null;
+    private attemptAuthDeferred: IDeferred<T> | null = null;
     private chosenFlow: UIAFlow | null = null;
     private currentStage: string | null = null;
 
@@ -239,9 +277,9 @@ export class InteractiveAuth {
     // the promise the will resolve/reject when it completes
     private submitPromise: Promise<void> | null = null;
 
-    public constructor(opts: IOpts) {
+    public constructor(opts: IOpts<T>) {
         this.matrixClient = opts.matrixClient;
-        this.data = opts.authData || {};
+        this.data = opts.authData || { flows: [] };
         this.requestCallback = opts.doRequest;
         this.busyChangedCallback = opts.busyChanged;
         // startAuthStage included for backwards compat
@@ -262,7 +300,7 @@ export class InteractiveAuth {
      * or rejects with the error on failure. Rejects with NoAuthFlowFoundError if
      *     no suitable authentication flow can be found
      */
-    public attemptAuth(): Promise<IAuthData> {
+    public async attemptAuth(): Promise<T> {
         // This promise will be quite long-lived and will resolve when the
         // request is authenticated and completes successfully.
         this.attemptAuthDeferred = defer();
@@ -270,10 +308,10 @@ export class InteractiveAuth {
         const promise = this.attemptAuthDeferred.promise;
 
         // if we have no flows, try a request to acquire the flows
-        if (!this.data?.flows) {
+        if (!(this.data as IAuthData)?.flows?.length) {
             this.busyChangedCallback?.(true);
             // use the existing sessionId, if one is present.
-            const auth = this.data.session ? { session: this.data.session } : null;
+            const auth = (this.data as IAuthData).session ? { session: (this.data as IAuthData).session } : null;
             this.doRequest(auth).finally(() => {
                 this.busyChangedCallback?.(false);
             });
@@ -290,7 +328,7 @@ export class InteractiveAuth {
      * be resolved.
      */
     public async poll(): Promise<void> {
-        if (!this.data.session) return;
+        if (!(this.data as IAuthData).session) return;
         // likewise don't poll if there is no auth session in progress
         if (!this.attemptAuthDeferred) return;
         // if we currently have a request in flight, there's no point making
@@ -330,7 +368,7 @@ export class InteractiveAuth {
      * @returns session id
      */
     public getSessionId(): string | undefined {
-        return this.data?.session;
+        return (this.data as IAuthData)?.session;
     }
 
     /**
@@ -350,7 +388,7 @@ export class InteractiveAuth {
      * @returns any parameters from the server for this stage
      */
     public getStageParams(loginType: string): Record<string, any> | undefined {
-        return this.data.params?.[loginType];
+        return (this.data as IAuthData)?.params?.[loginType];
     }
 
     public getChosenFlow(): UIAFlow | null {
@@ -391,9 +429,9 @@ export class InteractiveAuth {
 
         // use the sessionid from the last request, if one is present.
         let auth: IAuthDict;
-        if (this.data.session) {
+        if ((this.data as IAuthData)?.session) {
             auth = {
-                session: this.data.session,
+                session: (this.data as IAuthData).session,
             };
             Object.assign(auth, authData);
         } else {
@@ -451,7 +489,7 @@ export class InteractiveAuth {
                     this.inputs.emailAddress!,
                     this.clientSecret,
                     this.emailAttempt++,
-                    this.data.session!,
+                    (this.data as IAuthData).session!,
                 );
                 this.emailSid = requestTokenResult.sid;
                 logger.trace("Email token request succeeded");
@@ -480,10 +518,12 @@ export class InteractiveAuth {
             this.attemptAuthDeferred!.resolve(result);
             this.attemptAuthDeferred = null;
         } catch (error) {
+            const matrixError = error instanceof MatrixError ? error : null;
+
             // sometimes UI auth errors don't come with flows
-            const errorFlows = (<MatrixError>error).data?.flows ?? null;
-            const haveFlows = this.data.flows || Boolean(errorFlows);
-            if ((<MatrixError>error).httpStatus !== 401 || !(<MatrixError>error).data || !haveFlows) {
+            const errorFlows = matrixError?.data?.flows ?? null;
+            const haveFlows = (this.data as IAuthData)?.flows || Boolean(errorFlows);
+            if (!matrixError || matrixError.httpStatus !== 401 || !matrixError.data || !haveFlows) {
                 // doesn't look like an interactive-auth failure.
                 if (!background) {
                     this.attemptAuthDeferred?.reject(error);
@@ -494,24 +534,22 @@ export class InteractiveAuth {
                     logger.log("Background poll request failed doing UI auth: ignoring", error);
                 }
             }
-            if (!(<MatrixError>error).data) {
-                (<MatrixError>error).data = {};
+            if (matrixError && !matrixError.data) {
+                matrixError.data = {};
             }
             // if the error didn't come with flows, completed flows or session ID,
             // copy over the ones we have. Synapse sometimes sends responses without
             // any UI auth data (eg. when polling for email validation, if the email
             // has not yet been validated). This appears to be a Synapse bug, which
             // we workaround here.
-            if (
-                !(<MatrixError>error).data.flows &&
-                !(<MatrixError>error).data.completed &&
-                !(<MatrixError>error).data.session
-            ) {
-                (<MatrixError>error).data.flows = this.data.flows;
-                (<MatrixError>error).data.completed = this.data.completed;
-                (<MatrixError>error).data.session = this.data.session;
+            if (matrixError && !matrixError.data.flows && !matrixError.data.completed && !matrixError.data.session) {
+                matrixError.data.flows = (this.data as IAuthData).flows;
+                matrixError.data.completed = (this.data as IAuthData).completed;
+                matrixError.data.session = (this.data as IAuthData).session;
+            }
+            if (matrixError) {
+                this.data = matrixError.data as IAuthData;
             }
-            this.data = (<MatrixError>error).data;
             try {
                 this.startNextAuthStage();
             } catch (e) {
@@ -563,14 +601,6 @@ export class InteractiveAuth {
             return;
         }
 
-        if (this.data?.errcode || this.data?.error) {
-            this.stateUpdatedCallback(nextStage, {
-                errcode: this.data?.errcode || "",
-                error: this.data?.error || "",
-            });
-            return;
-        }
-
         this.stateUpdatedCallback(nextStage, nextStage === EMAIL_STAGE_TYPE ? { emailSid: this.emailSid } : {});
     }
 
@@ -618,7 +648,7 @@ export class InteractiveAuth {
      * @throws {@link NoAuthFlowFoundError} If no suitable authentication flow can be found
      */
     private chooseFlow(): UIAFlow {
-        const flows = this.data.flows || [];
+        const flows = (this.data as IAuthData)?.flows || [];
 
         // we've been given an email or we've already done an email part
         const haveEmail = Boolean(this.inputs.emailAddress) || Boolean(this.emailSid);
@@ -659,7 +689,7 @@ export class InteractiveAuth {
      * @returns login type
      */
     private firstUncompletedStage(flow: UIAFlow): AuthType | string | undefined {
-        const completed = this.data.completed || [];
+        const completed = (this.data as IAuthData)?.completed || [];
         return flow.stages.find((stageType) => !completed.includes(stageType));
     }
 }
diff --git a/src/models/event.ts b/src/models/event.ts
index 378d37b2811..992044f9fba 100644
--- a/src/models/event.ts
+++ b/src/models/event.ts
@@ -1376,10 +1376,10 @@ export class MatrixEvent extends TypedEventEmitter<MatrixEventEmittedEvents, Mat
         const relation = this.getWireContent()?.["m.relates_to"];
         if (
             this.isState() &&
-            relation?.rel_type &&
+            !!relation?.rel_type &&
             ([RelationType.Replace, RelationType.Thread] as string[]).includes(relation.rel_type)
         ) {
-            // State events cannot be m.replace relations
+            // State events cannot be m.replace or m.thread relations
             return false;
         }
         return !!(relation?.rel_type && relation.event_id && (relType ? relation.rel_type === relType : true));