diff --git a/lib/reducers/keyserver-reducer.test.js b/lib/reducers/keyserver-reducer.test.js
index ba1809dab..6462f4495 100644
--- a/lib/reducers/keyserver-reducer.test.js
+++ b/lib/reducers/keyserver-reducer.test.js
@@ -1,129 +1,126 @@
 // @flow
 
 import reduceKeyserverStore from './keyserver-reducer.js';
 import { deleteKeyserverAccountActionTypes } from '../actions/user-actions.js';
-import {
-  defaultKeyserverInfo,
-  type KeyserverStore,
-} from '../types/keyserver-types.js';
+import { defaultKeyserverInfo } from '../types/keyserver-types.js';
 import { authoritativeKeyserverID } from '../utils/authoritative-keyserver.js';
 
 jest.mock('../utils/config.js');
 
 describe('reduceKeyserverStore', () => {
   it('removes from the store keyservers the user has disconnected from', () => {
     const oldKeyserverStore = {
       keyserverInfos: {
         ['0']: defaultKeyserverInfo('url1'),
         ['100']: defaultKeyserverInfo('url2'),
         ['200']: defaultKeyserverInfo('url3'),
       },
     };
 
     const deleteAccountAction = {
       type: deleteKeyserverAccountActionTypes.success,
       payload: {
         currentUserInfo: { anonymous: true },
         preRequestUserState: {
           cookiesAndSessions: {},
           currentUserInfo: {
             id: '1000',
             username: 'test',
           },
         },
         keyserverIDs: ['100', '200'],
       },
       loadingInfo: {
         fetchIndex: 1,
         trackMultipleRequests: false,
         customKeyName: undefined,
       },
     };
 
     expect(
       reduceKeyserverStore(oldKeyserverStore, deleteAccountAction)
         .keyserverStore,
     ).toEqual({ keyserverInfos: { ['0']: defaultKeyserverInfo('url1') } });
   });
   it('update keyserverInfo with authoritativeKeyserverID', () => {
     const defaultAshoatKeyserverInfo = defaultKeyserverInfo('url1');
-    const oldKeyserverStore: KeyserverStore = ({
+    const oldKeyserverStore = {
       keyserverInfos: {
         [authoritativeKeyserverID()]: {
           ...defaultAshoatKeyserverInfo,
           connection: {
             ...defaultAshoatKeyserverInfo.connection,
-            connectionIssue: 'blah',
+            connectionIssue: 'client_version_unsupported',
           },
         },
       },
-    }: any);
+    };
 
     const deleteAccountAction = {
       type: deleteKeyserverAccountActionTypes.success,
       payload: {
         currentUserInfo: { anonymous: true },
         preRequestUserState: {
           cookiesAndSessions: {},
           currentUserInfo: {
             id: '1000',
             username: 'test',
           },
         },
         keyserverIDs: [authoritativeKeyserverID()],
       },
       loadingInfo: {
         fetchIndex: 1,
         trackMultipleRequests: false,
         customKeyName: undefined,
       },
     };
 
     expect(
       reduceKeyserverStore(oldKeyserverStore, deleteAccountAction)
         .keyserverStore.keyserverInfos[authoritativeKeyserverID()].connection
         .connectionIssue,
     ).toEqual(null);
   });
 
   it('return the same keyserverInfo with authoritativeKeyserverID()', () => {
     const defaultAshoatKeyserverInfo = defaultKeyserverInfo('url1');
-    const oldKeyserverStore: KeyserverStore = ({
+    const oldKeyserverStore = {
       keyserverInfos: {
         [authoritativeKeyserverID()]: {
           ...defaultAshoatKeyserverInfo,
           connection: {
             ...defaultAshoatKeyserverInfo.connection,
-            connectionIssue: 'blah',
+            connectionIssue: 'client_version_unsupported',
           },
         },
       },
-    }: any);
+    };
 
     const deleteAccountAction = {
       type: deleteKeyserverAccountActionTypes.success,
       payload: {
         currentUserInfo: { anonymous: true },
         preRequestUserState: {
           cookiesAndSessions: {},
           currentUserInfo: {
             id: '1000',
             username: 'test',
           },
         },
         keyserverIDs: ['100', '200'],
       },
       loadingInfo: {
         fetchIndex: 1,
         trackMultipleRequests: false,
         customKeyName: undefined,
       },
     };
 
     expect(
       reduceKeyserverStore(oldKeyserverStore, deleteAccountAction)
         .keyserverStore.keyserverInfos[authoritativeKeyserverID()].connection
         .connectionIssue,
-    ).toEqual('blah');
+    ).toEqual('client_version_unsupported');
   });
 });
diff --git a/lib/types/socket-types.js b/lib/types/socket-types.js
index 35de9af36..fbfbb361c 100644
--- a/lib/types/socket-types.js
+++ b/lib/types/socket-types.js
@@ -1,549 +1,549 @@
 // @flow
 
 import invariant from 'invariant';
 import t, { type TInterface, type TUnion } from 'tcomb';
 
 import {
   type RecoveryActionSource,
   recoveryActionSources,
 } from './account-types.js';
 import {
   type ActivityUpdate,
   activityUpdateValidator,
   type UpdateActivityResult,
   updateActivityResultValidator,
 } from './activity-types.js';
 import {
   type CompressedData,
   compressedDataValidator,
 } from './compression-types.js';
 import type { APIRequest } from './endpoints.js';
 import {
   type RawEntryInfo,
   rawEntryInfoValidator,
   type CalendarQuery,
 } from './entry-types.js';
 import {
   type MessagesResponse,
   messagesResponseValidator,
   type NewMessagesPayload,
   newMessagesPayloadValidator,
 } from './message-types.js';
 import {
   type ServerServerRequest,
   serverServerRequestValidator,
   type ClientServerRequest,
   type ClientResponse,
   type ClientClientResponse,
 } from './request-types.js';
 import type { SessionState, SessionIdentification } from './session-types.js';
 import type { MixedRawThreadInfos, RawThreadInfos } from './thread-types.js';
 import {
   type ClientUpdatesResult,
   type ClientUpdatesResultWithUserInfos,
   type ServerUpdatesResult,
   serverUpdatesResultValidator,
   type ServerUpdatesResultWithUserInfos,
   serverUpdatesResultWithUserInfosValidator,
 } from './update-types.js';
 import {
   type UserInfo,
   userInfoValidator,
   type CurrentUserInfo,
   currentUserInfoValidator,
   type LoggedOutUserInfo,
   loggedOutUserInfoValidator,
 } from './user-types.js';
 import { mixedRawThreadInfoValidator } from '../permissions/minimally-encoded-raw-thread-info-validators.js';
 import { values } from '../utils/objects.js';
 import { tShape, tNumber, tID } from '../utils/validation-utils.js';
 
 // The types of messages that the client sends across the socket
 export const clientSocketMessageTypes = Object.freeze({
   INITIAL: 0,
   RESPONSES: 1,
   //ACTIVITY_UPDATES: 2, (DEPRECATED)
   PING: 3,
   ACK_UPDATES: 4,
   API_REQUEST: 5,
 });
 export type ClientSocketMessageType = $Values<typeof clientSocketMessageTypes>;
 export function assertClientSocketMessageType(
   ourClientSocketMessageType: number,
 ): ClientSocketMessageType {
   invariant(
     ourClientSocketMessageType === 0 ||
       ourClientSocketMessageType === 1 ||
       ourClientSocketMessageType === 3 ||
       ourClientSocketMessageType === 4 ||
       ourClientSocketMessageType === 5,
     'number is not ClientSocketMessageType enum',
   );
   return ourClientSocketMessageType;
 }
 
 export type InitialClientSocketMessage = {
   +type: 0,
   +id: number,
   +payload: {
     +sessionIdentification: SessionIdentification,
     +sessionState: SessionState,
     +clientResponses: $ReadOnlyArray<ClientResponse>,
   },
 };
 export type ResponsesClientSocketMessage = {
   +type: 1,
   +id: number,
   +payload: {
     +clientResponses: $ReadOnlyArray<ClientResponse>,
   },
 };
 export type PingClientSocketMessage = {
   +type: 3,
   +id: number,
 };
 export type AckUpdatesClientSocketMessage = {
   +type: 4,
   +id: number,
   +payload: {
     +currentAsOf: number,
   },
 };
 export type APIRequestClientSocketMessage = {
   +type: 5,
   +id: number,
   +payload: APIRequest,
 };
 export type ClientSocketMessage =
   | InitialClientSocketMessage
   | ResponsesClientSocketMessage
   | PingClientSocketMessage
   | AckUpdatesClientSocketMessage
   | APIRequestClientSocketMessage;
 
 export type ClientInitialClientSocketMessage = {
   +type: 0,
   +id: number,
   +payload: {
     +sessionIdentification: SessionIdentification,
     +sessionState: SessionState,
     +clientResponses: $ReadOnlyArray<ClientClientResponse>,
   },
 };
 export type ClientResponsesClientSocketMessage = {
   +type: 1,
   +id: number,
   +payload: {
     +clientResponses: $ReadOnlyArray<ClientClientResponse>,
   },
 };
 export type ClientClientSocketMessage =
   | ClientInitialClientSocketMessage
   | ClientResponsesClientSocketMessage
   | PingClientSocketMessage
   | AckUpdatesClientSocketMessage
   | APIRequestClientSocketMessage;
 export type ClientSocketMessageWithoutID = $Diff<
   ClientClientSocketMessage,
   { id: number },
 >;
 
 // The types of messages that the server sends across the socket
 export const serverSocketMessageTypes = Object.freeze({
   STATE_SYNC: 0,
   REQUESTS: 1,
   ERROR: 2,
   AUTH_ERROR: 3,
   ACTIVITY_UPDATE_RESPONSE: 4,
   PONG: 5,
   UPDATES: 6,
   MESSAGES: 7,
   API_RESPONSE: 8,
   COMPRESSED_MESSAGE: 9,
 });
 export type ServerSocketMessageType = $Values<typeof serverSocketMessageTypes>;
 export function assertServerSocketMessageType(
   ourServerSocketMessageType: number,
 ): ServerSocketMessageType {
   invariant(
     ourServerSocketMessageType === 0 ||
       ourServerSocketMessageType === 1 ||
       ourServerSocketMessageType === 2 ||
       ourServerSocketMessageType === 3 ||
       ourServerSocketMessageType === 4 ||
       ourServerSocketMessageType === 5 ||
       ourServerSocketMessageType === 6 ||
       ourServerSocketMessageType === 7 ||
       ourServerSocketMessageType === 8 ||
       ourServerSocketMessageType === 9,
     'number is not ServerSocketMessageType enum',
   );
   return ourServerSocketMessageType;
 }
 
 export const stateSyncPayloadTypes = Object.freeze({
   FULL: 0,
   INCREMENTAL: 1,
 });
 
 export const fullStateSyncActionType = 'FULL_STATE_SYNC';
 export type BaseFullStateSync = {
   +messagesResult: MessagesResponse,
   +rawEntryInfos: $ReadOnlyArray<RawEntryInfo>,
   +userInfos: $ReadOnlyArray<UserInfo>,
   +updatesCurrentAsOf: number,
 };
 const baseFullStateSyncValidator = tShape<BaseFullStateSync>({
   messagesResult: messagesResponseValidator,
   rawEntryInfos: t.list(rawEntryInfoValidator),
   userInfos: t.list(userInfoValidator),
   updatesCurrentAsOf: t.Number,
 });
 
 export type ClientFullStateSync = $ReadOnly<{
   ...BaseFullStateSync,
   +threadInfos: RawThreadInfos,
   +currentUserInfo: CurrentUserInfo,
 }>;
 export type StateSyncFullActionPayload = $ReadOnly<{
   ...ClientFullStateSync,
   +calendarQuery: CalendarQuery,
   +keyserverID: string,
 }>;
 export type ClientStateSyncFullSocketPayload = $ReadOnly<{
   ...ClientFullStateSync,
   +type: 0,
   // Included iff client is using sessionIdentifierTypes.BODY_SESSION_ID
   +sessionID?: string,
 }>;
 
 export type ServerFullStateSync = $ReadOnly<{
   ...BaseFullStateSync,
   +threadInfos: MixedRawThreadInfos,
   +currentUserInfo: CurrentUserInfo,
 }>;
 const serverFullStateSyncValidator = tShape<ServerFullStateSync>({
   ...baseFullStateSyncValidator.meta.props,
   threadInfos: t.dict(tID, mixedRawThreadInfoValidator),
   currentUserInfo: currentUserInfoValidator,
 });
 
 export type ServerStateSyncFullSocketPayload = {
   ...ServerFullStateSync,
   +type: 0,
   // Included iff client is using sessionIdentifierTypes.BODY_SESSION_ID
   +sessionID?: string,
 };
 const serverStateSyncFullSocketPayloadValidator =
   tShape<ServerStateSyncFullSocketPayload>({
     ...serverFullStateSyncValidator.meta.props,
     type: tNumber(stateSyncPayloadTypes.FULL),
     sessionID: t.maybe(t.String),
   });
 
 export const incrementalStateSyncActionType = 'INCREMENTAL_STATE_SYNC';
 export type BaseIncrementalStateSync = {
   +messagesResult: MessagesResponse,
   +deltaEntryInfos: $ReadOnlyArray<RawEntryInfo>,
   +deletedEntryIDs: $ReadOnlyArray<string>,
   +userInfos: $ReadOnlyArray<UserInfo>,
 };
 const baseIncrementalStateSyncValidator = tShape<BaseIncrementalStateSync>({
   messagesResult: messagesResponseValidator,
   deltaEntryInfos: t.list(rawEntryInfoValidator),
   deletedEntryIDs: t.list(tID),
   userInfos: t.list(userInfoValidator),
 });
 
 export type ClientIncrementalStateSync = {
   ...BaseIncrementalStateSync,
   +updatesResult: ClientUpdatesResult,
 };
 export type StateSyncIncrementalActionPayload = {
   ...ClientIncrementalStateSync,
   +calendarQuery: CalendarQuery,
   +keyserverID: string,
 };
 type ClientStateSyncIncrementalSocketPayload = {
   +type: 1,
   ...ClientIncrementalStateSync,
 };
 
 export type ServerIncrementalStateSync = {
   ...BaseIncrementalStateSync,
   +updatesResult: ServerUpdatesResult,
 };
 const serverIncrementalStateSyncValidator = tShape<ServerIncrementalStateSync>({
   ...baseIncrementalStateSyncValidator.meta.props,
   updatesResult: serverUpdatesResultValidator,
 });
 
 type ServerStateSyncIncrementalSocketPayload = {
   +type: 1,
   ...ServerIncrementalStateSync,
 };
 const serverStateSyncIncrementalSocketPayloadValidator =
   tShape<ServerStateSyncIncrementalSocketPayload>({
     type: tNumber(stateSyncPayloadTypes.INCREMENTAL),
     ...serverIncrementalStateSyncValidator.meta.props,
   });
 
 export type ClientStateSyncSocketPayload =
   | ClientStateSyncFullSocketPayload
   | ClientStateSyncIncrementalSocketPayload;
 export type ServerStateSyncSocketPayload =
   | ServerStateSyncFullSocketPayload
   | ServerStateSyncIncrementalSocketPayload;
 const serverStateSyncSocketPayloadValidator = t.union([
   serverStateSyncFullSocketPayloadValidator,
   serverStateSyncIncrementalSocketPayloadValidator,
 ]);
 
 export type ServerStateSyncServerSocketMessage = {
   +type: 0,
   +responseTo: number,
   +payload: ServerStateSyncSocketPayload,
 };
 export const serverStateSyncServerSocketMessageValidator: TInterface<ServerStateSyncServerSocketMessage> =
   tShape<ServerStateSyncServerSocketMessage>({
     type: tNumber(serverSocketMessageTypes.STATE_SYNC),
     responseTo: t.Number,
     payload: serverStateSyncSocketPayloadValidator,
   });
 
 type ServerRequestsServerSocketMessagePayload = {
   +serverRequests: $ReadOnlyArray<ServerServerRequest>,
 };
 export type ServerRequestsServerSocketMessage = {
   +type: 1,
   +responseTo?: number,
   +payload: ServerRequestsServerSocketMessagePayload,
 };
 export const serverRequestsServerSocketMessageValidator: TInterface<ServerRequestsServerSocketMessage> =
   tShape<ServerRequestsServerSocketMessage>({
     type: tNumber(serverSocketMessageTypes.REQUESTS),
     responseTo: t.maybe(t.Number),
     payload: tShape<ServerRequestsServerSocketMessagePayload>({
       serverRequests: t.list(serverServerRequestValidator),
     }),
   });
 
 export type ErrorServerSocketMessage = {
   type: 2,
   responseTo?: number,
   message: string,
   payload?: Object,
 };
 export const errorServerSocketMessageValidator: TInterface<ErrorServerSocketMessage> =
   tShape<ErrorServerSocketMessage>({
     type: tNumber(serverSocketMessageTypes.ERROR),
     responseTo: t.maybe(t.Number),
     message: t.String,
     payload: t.maybe(t.Object),
   });
 
 type SessionChange = {
   +cookie: string,
   +currentUserInfo: LoggedOutUserInfo,
 };
 
 export type AuthErrorServerSocketMessage = {
   +type: 3,
   +responseTo: number,
   +message: string,
   +sessionChange: SessionChange,
 };
 export const authErrorServerSocketMessageValidator: TInterface<AuthErrorServerSocketMessage> =
   tShape<AuthErrorServerSocketMessage>({
     type: tNumber(serverSocketMessageTypes.AUTH_ERROR),
     responseTo: t.Number,
     message: t.String,
     sessionChange: t.maybe(
       tShape<SessionChange>({
         cookie: t.String,
         currentUserInfo: loggedOutUserInfoValidator,
       }),
     ),
   });
 
 export type ActivityUpdateResponseServerSocketMessage = {
   +type: 4,
   +responseTo: number,
   +payload: UpdateActivityResult,
 };
 export const activityUpdateResponseServerSocketMessageValidator: TInterface<ActivityUpdateResponseServerSocketMessage> =
   tShape<ActivityUpdateResponseServerSocketMessage>({
     type: tNumber(serverSocketMessageTypes.ACTIVITY_UPDATE_RESPONSE),
     responseTo: t.Number,
     payload: updateActivityResultValidator,
   });
 
 export type PongServerSocketMessage = {
   +type: 5,
   +responseTo: number,
 };
 export const pongServerSocketMessageValidator: TInterface<PongServerSocketMessage> =
   tShape<PongServerSocketMessage>({
     type: tNumber(serverSocketMessageTypes.PONG),
     responseTo: t.Number,
   });
 
 export type ServerUpdatesServerSocketMessage = {
   +type: 6,
   +payload: ServerUpdatesResultWithUserInfos,
 };
 export const serverUpdatesServerSocketMessageValidator: TInterface<ServerUpdatesServerSocketMessage> =
   tShape<ServerUpdatesServerSocketMessage>({
     type: tNumber(serverSocketMessageTypes.UPDATES),
     payload: serverUpdatesResultWithUserInfosValidator,
   });
 
 export type MessagesServerSocketMessage = {
   +type: 7,
   +payload: NewMessagesPayload,
 };
 export const messagesServerSocketMessageValidator: TInterface<MessagesServerSocketMessage> =
   tShape<MessagesServerSocketMessage>({
     type: tNumber(serverSocketMessageTypes.MESSAGES),
     payload: newMessagesPayloadValidator,
   });
 
 export type APIResponseServerSocketMessage = {
   +type: 8,
   +responseTo: number,
   +payload?: Object,
 };
 export const apiResponseServerSocketMessageValidator: TInterface<APIResponseServerSocketMessage> =
   tShape<APIResponseServerSocketMessage>({
     type: tNumber(serverSocketMessageTypes.API_RESPONSE),
     responseTo: t.Number,
     payload: t.maybe(t.Object),
   });
 
 export type CompressedMessageServerSocketMessage = {
   +type: 9,
   +payload: CompressedData,
 };
 export const compressedMessageServerSocketMessageValidator: TInterface<CompressedMessageServerSocketMessage> =
   tShape<CompressedMessageServerSocketMessage>({
     type: tNumber(serverSocketMessageTypes.COMPRESSED_MESSAGE),
     payload: compressedDataValidator,
   });
 
 export type ServerServerSocketMessage =
   | ServerStateSyncServerSocketMessage
   | ServerRequestsServerSocketMessage
   | ErrorServerSocketMessage
   | AuthErrorServerSocketMessage
   | ActivityUpdateResponseServerSocketMessage
   | PongServerSocketMessage
   | ServerUpdatesServerSocketMessage
   | MessagesServerSocketMessage
   | APIResponseServerSocketMessage
   | CompressedMessageServerSocketMessage;
 export const serverServerSocketMessageValidator: TUnion<ServerServerSocketMessage> =
   t.union([
     serverStateSyncServerSocketMessageValidator,
     serverRequestsServerSocketMessageValidator,
     errorServerSocketMessageValidator,
     authErrorServerSocketMessageValidator,
     activityUpdateResponseServerSocketMessageValidator,
     pongServerSocketMessageValidator,
     serverUpdatesServerSocketMessageValidator,
     messagesServerSocketMessageValidator,
     apiResponseServerSocketMessageValidator,
     compressedMessageServerSocketMessageValidator,
   ]);
 
 export type ClientRequestsServerSocketMessage = {
   +type: 1,
   +responseTo?: number,
   +payload: {
     +serverRequests: $ReadOnlyArray<ClientServerRequest>,
   },
 };
 export type ClientStateSyncServerSocketMessage = {
   +type: 0,
   +responseTo: number,
   +payload: ClientStateSyncSocketPayload,
 };
 export type ClientUpdatesServerSocketMessage = {
   +type: 6,
   +payload: ClientUpdatesResultWithUserInfos,
 };
 export type ClientServerSocketMessage =
   | ClientStateSyncServerSocketMessage
   | ClientRequestsServerSocketMessage
   | ErrorServerSocketMessage
   | AuthErrorServerSocketMessage
   | ActivityUpdateResponseServerSocketMessage
   | PongServerSocketMessage
   | ClientUpdatesServerSocketMessage
   | MessagesServerSocketMessage
   | APIResponseServerSocketMessage
   | CompressedMessageServerSocketMessage;
 
 export type SocketListener = (message: ClientServerSocketMessage) => void;
 
 export type ConnectionStatus =
   | 'connecting'
   | 'connected'
   | 'reconnecting'
   | 'disconnecting'
   | 'forcedDisconnecting'
   | 'disconnected';
 
-export type ConnectionIssue = empty;
+export type ConnectionIssue = 'client_version_unsupported';
 
 export type ConnectionInfo = {
   +status: ConnectionStatus,
   +queuedActivityUpdates: $ReadOnlyArray<ActivityUpdate>,
   +lateResponses: $ReadOnlyArray<number>,
   +unreachable: boolean,
   +connectionIssue: ?ConnectionIssue,
   // When this is flipped to truthy, a session recovery is attempted
   // This can happen when the keyserver invalidates the session
   +activeSessionRecovery: null | RecoveryActionSource,
 };
 export const connectionInfoValidator: TInterface<ConnectionInfo> =
   tShape<ConnectionInfo>({
     status: t.enums.of([
       'connecting',
       'connected',
       'reconnecting',
       'disconnecting',
       'forcedDisconnecting',
       'disconnected',
     ]),
     queuedActivityUpdates: t.list(activityUpdateValidator),
     lateResponses: t.list(t.Number),
     unreachable: t.Boolean,
     connectionIssue: t.maybe(t.enums.of([])),
     activeSessionRecovery: t.maybe(t.enums.of(values(recoveryActionSources))),
   });
 export const defaultConnectionInfo: ConnectionInfo = {
   status: 'connecting',
   queuedActivityUpdates: [],
   lateResponses: [],
   unreachable: false,
   connectionIssue: null,
   activeSessionRecovery: null,
 };
 
 export type SetActiveSessionRecoveryPayload = {
   +activeSessionRecovery: null | RecoveryActionSource,
   +keyserverID: string,
 };
 
 export type OneTimeKeyGenerator = (inc: number) => string;
 
 export type GRPCStream = {
   readyState: number,
   onopen: (ev: any) => mixed,
   onmessage: (ev: MessageEvent) => mixed,
   onclose: (ev: CloseEvent) => mixed,
   close(code?: number, reason?: string): void,
   send(data: string | Blob | ArrayBuffer | $ArrayBufferView): void,
 };
 
 export type CommTransportLayer = GRPCStream | WebSocket;