diff --git a/lib/types/message-types.js b/lib/types/message-types.js
index d74971194..d57bbd495 100644
--- a/lib/types/message-types.js
+++ b/lib/types/message-types.js
@@ -1,606 +1,678 @@
 // @flow
 
 import invariant from 'invariant';
+import t, { type TUnion, type TInterface } from 'tcomb';
 
 import { type ClientDBMediaInfo } from './media-types.js';
 import { messageTypes, type MessageType } from './message-types-enum.js';
-import type {
-  AddMembersMessageData,
-  AddMembersMessageInfo,
-  RawAddMembersMessageInfo,
+import {
+  type AddMembersMessageData,
+  type AddMembersMessageInfo,
+  type RawAddMembersMessageInfo,
+  rawAddMembersMessageInfoValidator,
 } from './messages/add-members.js';
-import type {
-  ChangeRoleMessageData,
-  ChangeRoleMessageInfo,
-  RawChangeRoleMessageInfo,
+import {
+  type ChangeRoleMessageData,
+  type ChangeRoleMessageInfo,
+  type RawChangeRoleMessageInfo,
+  rawChangeRoleMessageInfoValidator,
 } from './messages/change-role.js';
-import type {
-  ChangeSettingsMessageData,
-  ChangeSettingsMessageInfo,
-  RawChangeSettingsMessageInfo,
+import {
+  type ChangeSettingsMessageData,
+  type ChangeSettingsMessageInfo,
+  type RawChangeSettingsMessageInfo,
+  rawChangeSettingsMessageInfoValidator,
 } from './messages/change-settings.js';
-import type {
-  CreateEntryMessageData,
-  CreateEntryMessageInfo,
-  RawCreateEntryMessageInfo,
+import {
+  type CreateEntryMessageData,
+  type CreateEntryMessageInfo,
+  type RawCreateEntryMessageInfo,
+  rawCreateEntryMessageInfoValidator,
 } from './messages/create-entry.js';
-import type {
-  CreateSidebarMessageData,
-  CreateSidebarMessageInfo,
-  RawCreateSidebarMessageInfo,
+import {
+  type CreateSidebarMessageData,
+  type CreateSidebarMessageInfo,
+  type RawCreateSidebarMessageInfo,
+  rawCreateSidebarMessageInfoValidator,
 } from './messages/create-sidebar.js';
-import type {
-  CreateSubthreadMessageData,
-  CreateSubthreadMessageInfo,
-  RawCreateSubthreadMessageInfo,
+import {
+  type CreateSubthreadMessageData,
+  type CreateSubthreadMessageInfo,
+  type RawCreateSubthreadMessageInfo,
+  rawCreateSubthreadMessageInfoValidator,
 } from './messages/create-subthread.js';
-import type {
-  CreateThreadMessageData,
-  CreateThreadMessageInfo,
-  RawCreateThreadMessageInfo,
+import {
+  type CreateThreadMessageData,
+  type CreateThreadMessageInfo,
+  type RawCreateThreadMessageInfo,
+  rawCreateThreadMessageInfoValidator,
 } from './messages/create-thread.js';
-import type {
-  DeleteEntryMessageData,
-  DeleteEntryMessageInfo,
-  RawDeleteEntryMessageInfo,
+import {
+  type DeleteEntryMessageData,
+  type DeleteEntryMessageInfo,
+  type RawDeleteEntryMessageInfo,
+  rawDeleteEntryMessageInfoValidator,
 } from './messages/delete-entry.js';
-import type {
-  EditEntryMessageData,
-  EditEntryMessageInfo,
-  RawEditEntryMessageInfo,
+import {
+  type EditEntryMessageData,
+  type EditEntryMessageInfo,
+  type RawEditEntryMessageInfo,
+  rawEditEntryMessageInfoValidator,
 } from './messages/edit-entry.js';
-import type {
-  RawEditMessageInfo,
-  EditMessageData,
-  EditMessageInfo,
+import {
+  type RawEditMessageInfo,
+  rawEditMessageInfoValidator,
+  type EditMessageData,
+  type EditMessageInfo,
 } from './messages/edit.js';
-import type {
-  ImagesMessageData,
-  ImagesMessageInfo,
-  RawImagesMessageInfo,
+import {
+  type ImagesMessageData,
+  type ImagesMessageInfo,
+  type RawImagesMessageInfo,
+  rawImagesMessageInfoValidator,
 } from './messages/images.js';
-import type {
-  JoinThreadMessageData,
-  JoinThreadMessageInfo,
-  RawJoinThreadMessageInfo,
+import {
+  type JoinThreadMessageData,
+  type JoinThreadMessageInfo,
+  type RawJoinThreadMessageInfo,
+  rawJoinThreadMessageInfoValidator,
 } from './messages/join-thread.js';
-import type {
-  LeaveThreadMessageData,
-  LeaveThreadMessageInfo,
-  RawLeaveThreadMessageInfo,
+import {
+  type LeaveThreadMessageData,
+  type LeaveThreadMessageInfo,
+  type RawLeaveThreadMessageInfo,
+  rawLeaveThreadMessageInfoValidator,
 } from './messages/leave-thread.js';
-import type {
-  MediaMessageData,
-  MediaMessageInfo,
-  MediaMessageServerDBContent,
-  RawMediaMessageInfo,
+import {
+  type MediaMessageData,
+  type MediaMessageInfo,
+  type MediaMessageServerDBContent,
+  type RawMediaMessageInfo,
+  rawMediaMessageInfoValidator,
 } from './messages/media.js';
-import type {
-  ReactionMessageData,
-  RawReactionMessageInfo,
-  ReactionMessageInfo,
+import {
+  type ReactionMessageData,
+  type RawReactionMessageInfo,
+  rawReactionMessageInfoValidator,
+  type ReactionMessageInfo,
 } from './messages/reaction.js';
-import type {
-  RawRemoveMembersMessageInfo,
-  RemoveMembersMessageData,
-  RemoveMembersMessageInfo,
+import {
+  type RawRemoveMembersMessageInfo,
+  rawRemoveMembersMessageInfoValidator,
+  type RemoveMembersMessageData,
+  type RemoveMembersMessageInfo,
 } from './messages/remove-members.js';
-import type {
-  RawRestoreEntryMessageInfo,
-  RestoreEntryMessageData,
-  RestoreEntryMessageInfo,
+import {
+  type RawRestoreEntryMessageInfo,
+  rawRestoreEntryMessageInfoValidator,
+  type RestoreEntryMessageData,
+  type RestoreEntryMessageInfo,
 } from './messages/restore-entry.js';
-import type {
-  RawTextMessageInfo,
-  TextMessageData,
-  TextMessageInfo,
+import {
+  type RawTextMessageInfo,
+  rawTextMessageInfoValidator,
+  type TextMessageData,
+  type TextMessageInfo,
 } from './messages/text.js';
-import type {
-  TogglePinMessageData,
-  TogglePinMessageInfo,
-  RawTogglePinMessageInfo,
+import {
+  type TogglePinMessageData,
+  type TogglePinMessageInfo,
+  type RawTogglePinMessageInfo,
+  rawTogglePinMessageInfoValidator,
 } from './messages/toggle-pin.js';
-import type {
-  RawUnsupportedMessageInfo,
-  UnsupportedMessageInfo,
+import {
+  type RawUnsupportedMessageInfo,
+  rawUnsupportedMessageInfoValidator,
+  type UnsupportedMessageInfo,
 } from './messages/unsupported.js';
-import type {
-  RawUpdateRelationshipMessageInfo,
-  UpdateRelationshipMessageData,
-  UpdateRelationshipMessageInfo,
+import {
+  type RawUpdateRelationshipMessageInfo,
+  rawUpdateRelationshipMessageInfoValidator,
+  type UpdateRelationshipMessageData,
+  type UpdateRelationshipMessageInfo,
 } from './messages/update-relationship.js';
 import { type RelativeUserInfo, type UserInfos } from './user-types.js';
 import type { CallServerEndpointResultInfoInterface } from '../utils/call-server-endpoint.js';
+import { tNumber, tShape, tID } from '../utils/validation-utils.js';
 
 const composableMessageTypes = new Set([
   messageTypes.TEXT,
   messageTypes.IMAGES,
   messageTypes.MULTIMEDIA,
 ]);
 export function isComposableMessageType(ourMessageType: MessageType): boolean {
   return composableMessageTypes.has(ourMessageType);
 }
 export function assertComposableMessageType(
   ourMessageType: MessageType,
 ): MessageType {
   invariant(
     isComposableMessageType(ourMessageType),
     'MessageType is not composed',
   );
   return ourMessageType;
 }
 export function assertComposableRawMessage(
   message: RawMessageInfo,
 ): RawComposableMessageInfo {
   invariant(
     message.type === messageTypes.TEXT ||
       message.type === messageTypes.IMAGES ||
       message.type === messageTypes.MULTIMEDIA,
     'Message is not composable',
   );
   return message;
 }
 export function messageDataLocalID(messageData: MessageData): ?string {
   if (
     messageData.type !== messageTypes.TEXT &&
     messageData.type !== messageTypes.IMAGES &&
     messageData.type !== messageTypes.MULTIMEDIA &&
     messageData.type !== messageTypes.REACTION
   ) {
     return null;
   }
   return messageData.localID;
 }
 
 export function isMessageSidebarSourceReactionOrEdit(
   message: RawMessageInfo | MessageInfo,
 ): boolean %checks {
   return (
     message.type === messageTypes.SIDEBAR_SOURCE ||
     message.type === messageTypes.REACTION ||
     message.type === messageTypes.EDIT_MESSAGE
   );
 }
 
 const mediaMessageTypes = new Set([
   messageTypes.IMAGES,
   messageTypes.MULTIMEDIA,
 ]);
 export function isMediaMessageType(ourMessageType: MessageType): boolean {
   return mediaMessageTypes.has(ourMessageType);
 }
 export function assertMediaMessageType(
   ourMessageType: MessageType,
 ): MessageType {
   invariant(isMediaMessageType(ourMessageType), 'MessageType is not media');
   return ourMessageType;
 }
 
 // *MessageData = passed to createMessages function to insert into database
 // Raw*MessageInfo = used by server, and contained in client's local store
 // *MessageInfo = used by client in UI code
 
 export type SidebarSourceMessageData = {
   +type: 17,
   +threadID: string,
   +creatorID: string,
   +time: number,
   +sourceMessage?: RawComposableMessageInfo | RawRobotextMessageInfo,
 };
 
 export type MessageData =
   | TextMessageData
   | CreateThreadMessageData
   | AddMembersMessageData
   | CreateSubthreadMessageData
   | ChangeSettingsMessageData
   | RemoveMembersMessageData
   | ChangeRoleMessageData
   | LeaveThreadMessageData
   | JoinThreadMessageData
   | CreateEntryMessageData
   | EditEntryMessageData
   | DeleteEntryMessageData
   | RestoreEntryMessageData
   | ImagesMessageData
   | MediaMessageData
   | UpdateRelationshipMessageData
   | SidebarSourceMessageData
   | CreateSidebarMessageData
   | ReactionMessageData
   | EditMessageData
   | TogglePinMessageData;
 
 export type MultimediaMessageData = ImagesMessageData | MediaMessageData;
 
 export type RawMultimediaMessageInfo =
   | RawImagesMessageInfo
   | RawMediaMessageInfo;
+const rawMultimediaMessageInfoValidator = t.union([
+  rawImagesMessageInfoValidator,
+  rawMediaMessageInfoValidator,
+]);
+
 export type RawComposableMessageInfo =
   | RawTextMessageInfo
   | RawMultimediaMessageInfo;
+const rawComposableMessageInfoValidator = t.union([
+  rawTextMessageInfoValidator,
+  rawMultimediaMessageInfoValidator,
+]);
 
 export type RawRobotextMessageInfo =
   | RawCreateThreadMessageInfo
   | RawAddMembersMessageInfo
   | RawCreateSubthreadMessageInfo
   | RawChangeSettingsMessageInfo
   | RawRemoveMembersMessageInfo
   | RawChangeRoleMessageInfo
   | RawLeaveThreadMessageInfo
   | RawJoinThreadMessageInfo
   | RawCreateEntryMessageInfo
   | RawEditEntryMessageInfo
   | RawDeleteEntryMessageInfo
   | RawRestoreEntryMessageInfo
   | RawUpdateRelationshipMessageInfo
   | RawCreateSidebarMessageInfo
   | RawUnsupportedMessageInfo
   | RawTogglePinMessageInfo;
+const rawRobotextMessageInfoValidator = t.union([
+  rawCreateThreadMessageInfoValidator,
+  rawAddMembersMessageInfoValidator,
+  rawCreateSubthreadMessageInfoValidator,
+  rawChangeSettingsMessageInfoValidator,
+  rawRemoveMembersMessageInfoValidator,
+  rawChangeRoleMessageInfoValidator,
+  rawLeaveThreadMessageInfoValidator,
+  rawJoinThreadMessageInfoValidator,
+  rawCreateEntryMessageInfoValidator,
+  rawEditEntryMessageInfoValidator,
+  rawDeleteEntryMessageInfoValidator,
+  rawRestoreEntryMessageInfoValidator,
+  rawUpdateRelationshipMessageInfoValidator,
+  rawCreateSidebarMessageInfoValidator,
+  rawUnsupportedMessageInfoValidator,
+  rawTogglePinMessageInfoValidator,
+]);
+
 export type RawSidebarSourceMessageInfo = {
   ...SidebarSourceMessageData,
   id: string,
 };
+export const rawSidebarSourceMessageInfoValidator: TInterface<RawSidebarSourceMessageInfo> =
+  tShape<RawSidebarSourceMessageInfo>({
+    type: tNumber(messageTypes.SIDEBAR_SOURCE),
+    threadID: tID,
+    creatorID: t.String,
+    time: t.Number,
+    sourceMessage: t.maybe(
+      t.union([
+        rawComposableMessageInfoValidator,
+        rawRobotextMessageInfoValidator,
+      ]),
+    ),
+    id: tID,
+  });
 
 export type RawMessageInfo =
   | RawComposableMessageInfo
   | RawRobotextMessageInfo
   | RawSidebarSourceMessageInfo
   | RawReactionMessageInfo
   | RawEditMessageInfo;
+export const rawMessageInfoValidator: TUnion<RawMessageInfo> = t.union([
+  rawComposableMessageInfoValidator,
+  rawRobotextMessageInfoValidator,
+  rawSidebarSourceMessageInfoValidator,
+  rawReactionMessageInfoValidator,
+  rawEditMessageInfoValidator,
+]);
 
 export type LocallyComposedMessageInfo =
   | ({
       ...RawImagesMessageInfo,
       +localID: string,
     } & RawImagesMessageInfo)
   | ({
       ...RawMediaMessageInfo,
       +localID: string,
     } & RawMediaMessageInfo)
   | ({
       ...RawTextMessageInfo,
       +localID: string,
     } & RawTextMessageInfo)
   | ({
       ...RawReactionMessageInfo,
       +localID: string,
     } & RawReactionMessageInfo);
 
 export type MultimediaMessageInfo = ImagesMessageInfo | MediaMessageInfo;
 export type ComposableMessageInfo = TextMessageInfo | MultimediaMessageInfo;
 
 export type RobotextMessageInfo =
   | CreateThreadMessageInfo
   | AddMembersMessageInfo
   | CreateSubthreadMessageInfo
   | ChangeSettingsMessageInfo
   | RemoveMembersMessageInfo
   | ChangeRoleMessageInfo
   | LeaveThreadMessageInfo
   | JoinThreadMessageInfo
   | CreateEntryMessageInfo
   | EditEntryMessageInfo
   | DeleteEntryMessageInfo
   | RestoreEntryMessageInfo
   | UnsupportedMessageInfo
   | UpdateRelationshipMessageInfo
   | CreateSidebarMessageInfo
   | TogglePinMessageInfo;
 export type PreviewableMessageInfo =
   | RobotextMessageInfo
   | MultimediaMessageInfo
   | ReactionMessageInfo;
 
 export type SidebarSourceMessageInfo = {
   +type: 17,
   +id: string,
   +threadID: string,
   +creator: RelativeUserInfo,
   +time: number,
   +sourceMessage: ComposableMessageInfo | RobotextMessageInfo,
 };
 
 export type MessageInfo =
   | ComposableMessageInfo
   | RobotextMessageInfo
   | SidebarSourceMessageInfo
   | ReactionMessageInfo
   | EditMessageInfo;
 
 export type ThreadMessageInfo = {
   messageIDs: string[],
   startReached: boolean,
   lastNavigatedTo: number, // millisecond timestamp
   lastPruned: number, // millisecond timestamp
 };
 
 // Tracks client-local information about a message that hasn't been assigned an
 // ID by the server yet. As soon as the client gets an ack from the server for
 // this message, it will clear the LocalMessageInfo.
 export type LocalMessageInfo = {
   +sendFailed?: boolean,
 };
 
 export type MessageStoreThreads = {
   +[threadID: string]: ThreadMessageInfo,
 };
 
 export type MessageStore = {
   +messages: { +[id: string]: RawMessageInfo },
   +threads: MessageStoreThreads,
   +local: { +[id: string]: LocalMessageInfo },
   +currentAsOf: number,
 };
 
 // MessageStore messages ops
 export type RemoveMessageOperation = {
   +type: 'remove',
   +payload: { +ids: $ReadOnlyArray<string> },
 };
 
 export type RemoveMessagesForThreadsOperation = {
   +type: 'remove_messages_for_threads',
   +payload: { +threadIDs: $ReadOnlyArray<string> },
 };
 
 export type ReplaceMessageOperation = {
   +type: 'replace',
   +payload: { +id: string, +messageInfo: RawMessageInfo },
 };
 
 export type RekeyMessageOperation = {
   +type: 'rekey',
   +payload: { +from: string, +to: string },
 };
 
 export type RemoveAllMessagesOperation = {
   +type: 'remove_all',
 };
 
 // MessageStore threads ops
 export type ReplaceMessageStoreThreadsOperation = {
   +type: 'replace_threads',
   +payload: { +threads: MessageStoreThreads },
 };
 
 export type RemoveMessageStoreThreadsOperation = {
   +type: 'remove_threads',
   +payload: { +ids: $ReadOnlyArray<string> },
 };
 
 export type RemoveMessageStoreAllThreadsOperation = {
   +type: 'remove_all_threads',
 };
 
 // We were initially using `number`s` for `thread`, `type`, `future_type`, etc.
 // However, we ended up changing `thread` to `string` to account for thread IDs
 // including information about the keyserver (eg 'GENESIS|123') in the future.
 //
 // At that point we discussed whether we should switch the remaining `number`
 // fields to `string`s for consistency and flexibility. We researched whether
 // there was any performance cost to using `string`s instead of `number`s and
 // found the differences to be negligible. We also concluded using `string`s
 // may be safer after considering `jsi::Number` and the various C++ number
 // representations on the CommCoreModule side.
 export type ClientDBMessageInfo = {
   +id: string,
   +local_id: ?string,
   +thread: string,
   +user: string,
   +type: string,
   +future_type: ?string,
   +content: ?string,
   +time: string,
   +media_infos: ?$ReadOnlyArray<ClientDBMediaInfo>,
 };
 
 export type ClientDBReplaceMessageOperation = {
   +type: 'replace',
   +payload: ClientDBMessageInfo,
 };
 
 export type ClientDBThreadMessageInfo = {
   +id: string,
   +start_reached: string,
   +last_navigated_to: string,
   +last_pruned: string,
 };
 
 export type ClientDBReplaceThreadsOperation = {
   +type: 'replace_threads',
   +payload: { +threads: $ReadOnlyArray<ClientDBThreadMessageInfo> },
 };
 
 export type MessageStoreOperation =
   | RemoveMessageOperation
   | ReplaceMessageOperation
   | RekeyMessageOperation
   | RemoveMessagesForThreadsOperation
   | RemoveAllMessagesOperation
   | ReplaceMessageStoreThreadsOperation
   | RemoveMessageStoreThreadsOperation
   | RemoveMessageStoreAllThreadsOperation;
 
 export type ClientDBMessageStoreOperation =
   | RemoveMessageOperation
   | ClientDBReplaceMessageOperation
   | RekeyMessageOperation
   | RemoveMessagesForThreadsOperation
   | RemoveAllMessagesOperation
   | ClientDBReplaceThreadsOperation
   | RemoveMessageStoreThreadsOperation
   | RemoveMessageStoreAllThreadsOperation;
 
 export const messageTruncationStatus = Object.freeze({
   // EXHAUSTIVE means we've reached the start of the thread. Either the result
   // set includes the very first message for that thread, or there is nothing
   // behind the cursor you queried for. Given that the client only ever issues
   // ranged queries whose range, when unioned with what is in state, represent
   // the set of all messages for a given thread, we can guarantee that getting
   // EXHAUSTIVE means the start has been reached.
   EXHAUSTIVE: 'exhaustive',
   // TRUNCATED is rare, and means that the server can't guarantee that the
   // result set for a given thread is contiguous with what the client has in its
   // state. If the client can't verify the contiguousness itself, it needs to
   // replace its Redux store's contents with what it is in this payload.
   //  1) getMessageInfosSince: Result set for thread is equal to max, and the
   //     truncation status isn't EXHAUSTIVE (ie. doesn't include the very first
   //     message).
   //  2) getMessageInfos: MessageSelectionCriteria does not specify cursors, the
   //     result set for thread is equal to max, and the truncation status isn't
   //     EXHAUSTIVE. If cursors are specified, we never return truncated, since
   //     the cursor given us guarantees the contiguousness of the result set.
   // Note that in the reducer, we can guarantee contiguousness if there is any
   // intersection between messageIDs in the result set and the set currently in
   // the Redux store.
   TRUNCATED: 'truncated',
   // UNCHANGED means the result set is guaranteed to be contiguous with what the
   // client has in its state, but is not EXHAUSTIVE. Basically, it's anything
   // that isn't either EXHAUSTIVE or TRUNCATED.
   UNCHANGED: 'unchanged',
 });
 export type MessageTruncationStatus = $Values<typeof messageTruncationStatus>;
 export function assertMessageTruncationStatus(
   ourMessageTruncationStatus: string,
 ): MessageTruncationStatus {
   invariant(
     ourMessageTruncationStatus === 'truncated' ||
       ourMessageTruncationStatus === 'unchanged' ||
       ourMessageTruncationStatus === 'exhaustive',
     'string is not ourMessageTruncationStatus enum',
   );
   return ourMessageTruncationStatus;
 }
 export type MessageTruncationStatuses = {
   [threadID: string]: MessageTruncationStatus,
 };
 
 export type ThreadCursors = { +[threadID: string]: ?string };
 
 export type MessageSelectionCriteria = {
   +threadCursors?: ?ThreadCursors,
   +joinedThreads?: ?boolean,
   +newerThan?: ?number,
 };
 
 export type FetchMessageInfosRequest = {
   +cursors: ThreadCursors,
   +numberPerThread?: ?number,
 };
 export type FetchMessageInfosResponse = {
   +rawMessageInfos: $ReadOnlyArray<RawMessageInfo>,
   +truncationStatuses: MessageTruncationStatuses,
   +userInfos: UserInfos,
 };
 export type FetchMessageInfosResult = {
   +rawMessageInfos: $ReadOnlyArray<RawMessageInfo>,
   +truncationStatuses: MessageTruncationStatuses,
 };
 export type FetchMessageInfosPayload = {
   +threadID: string,
   +rawMessageInfos: $ReadOnlyArray<RawMessageInfo>,
   +truncationStatus: MessageTruncationStatus,
 };
 export type MessagesResponse = {
   +rawMessageInfos: $ReadOnlyArray<RawMessageInfo>,
   +truncationStatuses: MessageTruncationStatuses,
   +currentAsOf: number,
 };
 export type SimpleMessagesPayload = {
   +rawMessageInfos: $ReadOnlyArray<RawMessageInfo>,
   +truncationStatuses: MessageTruncationStatuses,
 };
 export const defaultNumberPerThread = 20;
 export const defaultMaxMessageAge = 14 * 24 * 60 * 60 * 1000; // 2 weeks
 
 export type SendMessageResponse = {
   +newMessageInfo: RawMessageInfo,
 };
 export type SendMessageResult = {
   +id: string,
   +time: number,
   +interface: CallServerEndpointResultInfoInterface,
 };
 
 export type SendMessagePayload = {
   +localID: string,
   +serverID: string,
   +threadID: string,
   +time: number,
   +interface: CallServerEndpointResultInfoInterface,
 };
 
 export type SendTextMessageRequest = {
   +threadID: string,
   +localID?: string,
   +text: string,
   +sidebarCreation?: boolean,
 };
 export type SendMultimediaMessageRequest =
   // This option is only used for messageTypes.IMAGES
   | {
       +threadID: string,
       +localID: string,
       +sidebarCreation?: boolean,
       +mediaIDs: $ReadOnlyArray<string>,
     }
   | {
       +threadID: string,
       +localID: string,
       +sidebarCreation?: boolean,
       +mediaMessageContents: $ReadOnlyArray<MediaMessageServerDBContent>,
     };
 
 export type SendReactionMessageRequest = {
   +threadID: string,
   +localID?: string,
   +targetMessageID: string,
   +reaction: string,
   +action: 'add_reaction' | 'remove_reaction',
 };
 
 export type SendEditMessageRequest = {
   +targetMessageID: string,
   +text: string,
 };
 
 export type SendEditMessageResponse = {
   +newMessageInfos: $ReadOnlyArray<RawMessageInfo>,
 };
 
 export type EditMessagePayload = SendEditMessageResponse;
 export type SendEditMessageResult = SendEditMessageResponse;
 
 export type EditMessageContent = {
   +text: string,
 };
 
 // Used for the message info included in log-in type actions
 export type GenericMessagesResult = {
   +messageInfos: RawMessageInfo[],
   +truncationStatus: MessageTruncationStatuses,
   +watchedIDsAtRequestTime: $ReadOnlyArray<string>,
   +currentAsOf: number,
 };
 
 export type SaveMessagesPayload = {
   +rawMessageInfos: $ReadOnlyArray<RawMessageInfo>,
   +updatesCurrentAsOf: number,
 };
 
 export type NewMessagesPayload = {
   +messagesResult: MessagesResponse,
 };
 
 export type MessageStorePrunePayload = {
   +threadIDs: $ReadOnlyArray<string>,
 };
 
 export type FetchPinnedMessagesRequest = {
   +threadID: string,
 };
 
 export type FetchPinnedMessagesResult = {
   +pinnedMessages: $ReadOnlyArray<RawMessageInfo>,
 };
diff --git a/lib/types/messages/add-members.js b/lib/types/messages/add-members.js
index 25d60b5a3..ab2e1d6f8 100644
--- a/lib/types/messages/add-members.js
+++ b/lib/types/messages/add-members.js
@@ -1,25 +1,39 @@
 // @flow
 
+import t, { type TInterface } from 'tcomb';
+
+import { tShape, tID, tNumber } from '../../utils/validation-utils.js';
+import { messageTypes } from '../message-types-enum.js';
 import type { RelativeUserInfo } from '../user-types.js';
 
 export type AddMembersMessageData = {
   type: 2,
   threadID: string,
   creatorID: string,
   time: number,
   addedUserIDs: string[],
 };
 
 export type RawAddMembersMessageInfo = {
   ...AddMembersMessageData,
   id: string,
 };
 
+export const rawAddMembersMessageInfoValidator: TInterface<RawAddMembersMessageInfo> =
+  tShape<RawAddMembersMessageInfo>({
+    type: tNumber(messageTypes.ADD_MEMBERS),
+    threadID: tID,
+    creatorID: t.String,
+    time: t.Number,
+    addedUserIDs: t.list(t.String),
+    id: tID,
+  });
+
 export type AddMembersMessageInfo = {
   type: 2,
   id: string,
   threadID: string,
   creator: RelativeUserInfo,
   time: number,
   addedMembers: RelativeUserInfo[],
 };
diff --git a/lib/types/messages/change-role.js b/lib/types/messages/change-role.js
index 0196a6c11..2df53fa02 100644
--- a/lib/types/messages/change-role.js
+++ b/lib/types/messages/change-role.js
@@ -1,27 +1,42 @@
 // @flow
 
+import t, { type TInterface } from 'tcomb';
+
+import { tID, tNumber, tShape } from '../../utils/validation-utils.js';
+import { messageTypes } from '../message-types-enum.js';
 import type { RelativeUserInfo } from '../user-types.js';
 
 export type ChangeRoleMessageData = {
   type: 6,
   threadID: string,
   creatorID: string,
   time: number,
   userIDs: string[],
   newRole: string,
 };
 
 export type RawChangeRoleMessageInfo = {
   ...ChangeRoleMessageData,
   id: string,
 };
 
+export const rawChangeRoleMessageInfoValidator: TInterface<RawChangeRoleMessageInfo> =
+  tShape<RawChangeRoleMessageInfo>({
+    type: tNumber(messageTypes.CHANGE_ROLE),
+    threadID: tID,
+    creatorID: t.String,
+    time: t.Number,
+    userIDs: t.list(t.String),
+    newRole: tID,
+    id: tID,
+  });
+
 export type ChangeRoleMessageInfo = {
   type: 6,
   id: string,
   threadID: string,
   creator: RelativeUserInfo,
   time: number,
   members: RelativeUserInfo[],
   newRole: string,
 };
diff --git a/lib/types/messages/change-settings.js b/lib/types/messages/change-settings.js
index 7c926358a..03bd1e954 100644
--- a/lib/types/messages/change-settings.js
+++ b/lib/types/messages/change-settings.js
@@ -1,27 +1,42 @@
 // @flow
 
+import t, { type TInterface } from 'tcomb';
+
+import { tID, tNumber, tShape } from '../../utils/validation-utils.js';
+import { messageTypes } from '../message-types-enum.js';
 import type { RelativeUserInfo } from '../user-types.js';
 
 export type ChangeSettingsMessageData = {
   type: 4,
   threadID: string,
   creatorID: string,
   time: number,
   field: string,
   value: string | number,
 };
 
 export type RawChangeSettingsMessageInfo = {
   ...ChangeSettingsMessageData,
   id: string,
 };
 
+export const rawChangeSettingsMessageInfoValidator: TInterface<RawChangeSettingsMessageInfo> =
+  tShape<RawChangeSettingsMessageInfo>({
+    type: tNumber(messageTypes.CHANGE_SETTINGS),
+    threadID: tID,
+    creatorID: t.String,
+    time: t.Number,
+    field: t.String,
+    value: t.union([t.String, t.Number]),
+    id: tID,
+  });
+
 export type ChangeSettingsMessageInfo = {
   type: 4,
   id: string,
   threadID: string,
   creator: RelativeUserInfo,
   time: number,
   field: string,
   value: string | number,
 };
diff --git a/lib/types/messages/create-entry.js b/lib/types/messages/create-entry.js
index 129562801..fc0d42319 100644
--- a/lib/types/messages/create-entry.js
+++ b/lib/types/messages/create-entry.js
@@ -1,29 +1,45 @@
 // @flow
 
+import t, { type TInterface } from 'tcomb';
+
+import { tID, tNumber, tShape } from '../../utils/validation-utils.js';
+import { messageTypes } from '../message-types-enum.js';
 import type { RelativeUserInfo } from '../user-types.js';
 
 export type CreateEntryMessageData = {
   type: 9,
   threadID: string,
   creatorID: string,
   time: number,
   entryID: string,
   date: string,
   text: string,
 };
 
 export type RawCreateEntryMessageInfo = {
   ...CreateEntryMessageData,
   id: string,
 };
 
+export const rawCreateEntryMessageInfoValidator: TInterface<RawCreateEntryMessageInfo> =
+  tShape<RawCreateEntryMessageInfo>({
+    type: tNumber(messageTypes.CREATE_ENTRY),
+    threadID: tID,
+    creatorID: t.String,
+    time: t.Number,
+    entryID: tID,
+    date: t.String,
+    text: t.String,
+    id: tID,
+  });
+
 export type CreateEntryMessageInfo = {
   type: 9,
   id: string,
   threadID: string,
   creator: RelativeUserInfo,
   time: number,
   entryID: string,
   date: string,
   text: string,
 };
diff --git a/lib/types/messages/create-sidebar.js b/lib/types/messages/create-sidebar.js
index fc6c3bc7d..5d474ebde 100644
--- a/lib/types/messages/create-sidebar.js
+++ b/lib/types/messages/create-sidebar.js
@@ -1,38 +1,58 @@
 // @flow
 
+import t, { type TInterface } from 'tcomb';
+
+import { tID, tNumber, tShape } from '../../utils/validation-utils.js';
+import { messageTypes } from '../message-types-enum.js';
 import type { ThreadInfo } from '../thread-types.js';
 import type { RelativeUserInfo } from '../user-types.js';
 
 export type CreateSidebarMessageData = {
   +type: 18,
   +threadID: string,
   +creatorID: string,
   +time: number,
   +sourceMessageAuthorID: string,
   +initialThreadState: {
     +name: ?string,
     +parentThreadID: string,
     +color: string,
     +memberIDs: string[],
   },
 };
 
 export type RawCreateSidebarMessageInfo = {
   ...CreateSidebarMessageData,
   id: string,
 };
 
+export const rawCreateSidebarMessageInfoValidator: TInterface<RawCreateSidebarMessageInfo> =
+  tShape<RawCreateSidebarMessageInfo>({
+    type: tNumber(messageTypes.CREATE_SIDEBAR),
+    threadID: tID,
+    creatorID: t.String,
+    time: t.Number,
+    sourceMessageAuthorID: t.String,
+    initialThreadState: tShape({
+      name: t.maybe(t.String),
+      parentThreadID: tID,
+      color: t.String,
+      memberIDs: t.list(t.String),
+    }),
+    id: tID,
+  });
+
 export type CreateSidebarMessageInfo = {
   +type: 18,
   +id: string,
   +threadID: string,
   +creator: RelativeUserInfo,
   +time: number,
   +sourceMessageAuthor: RelativeUserInfo,
   +initialThreadState: {
     +name: ?string,
     +parentThreadInfo: ThreadInfo,
     +color: string,
     +otherMembers: RelativeUserInfo[],
   },
 };
diff --git a/lib/types/messages/create-subthread.js b/lib/types/messages/create-subthread.js
index 036e843c9..b35a5f685 100644
--- a/lib/types/messages/create-subthread.js
+++ b/lib/types/messages/create-subthread.js
@@ -1,26 +1,40 @@
 // @flow
 
+import t, { type TInterface } from 'tcomb';
+
+import { tID, tNumber, tShape } from '../../utils/validation-utils.js';
+import { messageTypes } from '../message-types-enum.js';
 import type { ThreadInfo } from '../thread-types.js';
 import type { RelativeUserInfo } from '../user-types.js';
 
 export type CreateSubthreadMessageData = {
   type: 3,
   threadID: string,
   creatorID: string,
   time: number,
   childThreadID: string,
 };
 
 export type RawCreateSubthreadMessageInfo = {
   ...CreateSubthreadMessageData,
   id: string,
 };
 
+export const rawCreateSubthreadMessageInfoValidator: TInterface<RawCreateSubthreadMessageInfo> =
+  tShape<RawCreateSubthreadMessageInfo>({
+    type: tNumber(messageTypes.CREATE_SUB_THREAD),
+    threadID: tID,
+    creatorID: t.String,
+    time: t.Number,
+    childThreadID: tID,
+    id: tID,
+  });
+
 export type CreateSubthreadMessageInfo = {
   type: 3,
   id: string,
   threadID: string,
   creator: RelativeUserInfo,
   time: number,
   childThreadInfo: ThreadInfo,
 };
diff --git a/lib/types/messages/create-thread.js b/lib/types/messages/create-thread.js
index 8943985f1..0b247090b 100644
--- a/lib/types/messages/create-thread.js
+++ b/lib/types/messages/create-thread.js
@@ -1,38 +1,68 @@
 // @flow
 
-import type { ThreadInfo, ThreadType } from '../thread-types.js';
+import t, { type TInterface } from 'tcomb';
+
+import { values } from '../../utils/objects.js';
+import {
+  tID,
+  tNumber,
+  tShape,
+  tNumEnum,
+} from '../../utils/validation-utils.js';
+import { messageTypes } from '../message-types-enum.js';
+import {
+  threadTypes,
+  type ThreadInfo,
+  type ThreadType,
+} from '../thread-types.js';
 import type { RelativeUserInfo } from '../user-types.js';
 
 export type CreateThreadMessageData = {
   type: 1,
   threadID: string,
   creatorID: string,
   time: number,
   initialThreadState: {
     type: ThreadType,
     name: ?string,
     parentThreadID: ?string,
     color: string,
     memberIDs: string[],
   },
 };
 
 export type RawCreateThreadMessageInfo = {
   ...CreateThreadMessageData,
   id: string,
 };
 
+export const rawCreateThreadMessageInfoValidator: TInterface<RawCreateThreadMessageInfo> =
+  tShape<RawCreateThreadMessageInfo>({
+    type: tNumber(messageTypes.CREATE_THREAD),
+    threadID: tID,
+    creatorID: t.String,
+    time: t.Number,
+    initialThreadState: tShape({
+      type: tNumEnum(values(threadTypes)),
+      name: t.maybe(t.String),
+      parentThreadID: t.maybe(tID),
+      color: t.String,
+      memberIDs: t.list(t.String),
+    }),
+    id: tID,
+  });
+
 export type CreateThreadMessageInfo = {
   type: 1,
   id: string,
   threadID: string,
   creator: RelativeUserInfo,
   time: number,
   initialThreadState: {
     type: ThreadType,
     name: ?string,
     parentThreadInfo: ?ThreadInfo,
     color: string,
     otherMembers: RelativeUserInfo[],
   },
 };
diff --git a/lib/types/messages/delete-entry.js b/lib/types/messages/delete-entry.js
index 73405b48f..c4664a2e7 100644
--- a/lib/types/messages/delete-entry.js
+++ b/lib/types/messages/delete-entry.js
@@ -1,29 +1,45 @@
 // @flow
 
+import t, { type TInterface } from 'tcomb';
+
+import { tID, tNumber, tShape } from '../../utils/validation-utils.js';
+import { messageTypes } from '../message-types-enum.js';
 import type { RelativeUserInfo } from '../user-types.js';
 
 export type DeleteEntryMessageData = {
   type: 11,
   threadID: string,
   creatorID: string,
   time: number,
   entryID: string,
   date: string,
   text: string,
 };
 
 export type RawDeleteEntryMessageInfo = {
   ...DeleteEntryMessageData,
   id: string,
 };
 
+export const rawDeleteEntryMessageInfoValidator: TInterface<RawDeleteEntryMessageInfo> =
+  tShape<RawDeleteEntryMessageInfo>({
+    type: tNumber(messageTypes.DELETE_ENTRY),
+    threadID: tID,
+    creatorID: t.String,
+    time: t.Number,
+    entryID: tID,
+    date: t.String,
+    text: t.String,
+    id: tID,
+  });
+
 export type DeleteEntryMessageInfo = {
   type: 11,
   id: string,
   threadID: string,
   creator: RelativeUserInfo,
   time: number,
   entryID: string,
   date: string,
   text: string,
 };
diff --git a/lib/types/messages/edit-entry.js b/lib/types/messages/edit-entry.js
index 1451a9e06..889b2b19e 100644
--- a/lib/types/messages/edit-entry.js
+++ b/lib/types/messages/edit-entry.js
@@ -1,29 +1,45 @@
 // @flow
 
+import t, { type TInterface } from 'tcomb';
+
+import { tID, tNumber, tShape } from '../../utils/validation-utils.js';
+import { messageTypes } from '../message-types-enum.js';
 import type { RelativeUserInfo } from '../user-types.js';
 
 export type EditEntryMessageData = {
   type: 10,
   threadID: string,
   creatorID: string,
   time: number,
   entryID: string,
   date: string,
   text: string,
 };
 
 export type RawEditEntryMessageInfo = {
   ...EditEntryMessageData,
   id: string,
 };
 
+export const rawEditEntryMessageInfoValidator: TInterface<RawEditEntryMessageInfo> =
+  tShape<RawEditEntryMessageInfo>({
+    type: tNumber(messageTypes.EDIT_ENTRY),
+    threadID: tID,
+    creatorID: t.String,
+    time: t.Number,
+    entryID: tID,
+    date: t.String,
+    text: t.String,
+    id: tID,
+  });
+
 export type EditEntryMessageInfo = {
   type: 10,
   id: string,
   threadID: string,
   creator: RelativeUserInfo,
   time: number,
   entryID: string,
   date: string,
   text: string,
 };
diff --git a/lib/types/messages/edit.js b/lib/types/messages/edit.js
index c43b5139d..fb3860d14 100644
--- a/lib/types/messages/edit.js
+++ b/lib/types/messages/edit.js
@@ -1,27 +1,42 @@
 // @flow
 
+import t, { type TInterface } from 'tcomb';
+
+import { tID, tNumber, tShape } from '../../utils/validation-utils.js';
+import { messageTypes } from '../message-types-enum.js';
 import type { RelativeUserInfo } from '../user-types.js';
 
 export type EditMessageData = {
   +type: 20,
   +threadID: string,
   +creatorID: string,
   +time: number,
   +targetMessageID: string,
   +text: string,
 };
 
 export type RawEditMessageInfo = {
   ...EditMessageData,
   +id: string,
 };
 
+export const rawEditMessageInfoValidator: TInterface<RawEditMessageInfo> =
+  tShape<RawEditMessageInfo>({
+    type: tNumber(messageTypes.EDIT_MESSAGE),
+    threadID: tID,
+    creatorID: t.String,
+    time: t.Number,
+    targetMessageID: tID,
+    text: t.String,
+    id: tID,
+  });
+
 export type EditMessageInfo = {
   +type: 20,
   +id: string,
   +threadID: string,
   +creator: RelativeUserInfo,
   +time: number, // millisecond timestamp
   +targetMessageID: string,
   +text: string,
 };
diff --git a/lib/types/messages/images.js b/lib/types/messages/images.js
index c0f441e24..9492084cf 100644
--- a/lib/types/messages/images.js
+++ b/lib/types/messages/images.js
@@ -1,33 +1,48 @@
 // @flow
 
-import type { Image } from '../media-types.js';
+import t, { type TInterface } from 'tcomb';
+
+import { tID, tNumber, tShape } from '../../utils/validation-utils.js';
+import { imageValidator, type Image } from '../media-types.js';
+import { messageTypes } from '../message-types-enum.js';
 import type { RelativeUserInfo } from '../user-types.js';
 
 type ImagesSharedBase = {
   +type: 14,
   +localID?: string, // for optimistic creations. included by new clients
   +threadID: string,
   +creatorID: string,
   +time: number,
   +media: $ReadOnlyArray<Image>,
 };
 
 export type ImagesMessageData = {
   ...ImagesSharedBase,
   +sidebarCreation?: boolean,
 };
 
 export type RawImagesMessageInfo = {
   ...ImagesSharedBase,
   +id?: string, // null if local copy without ID yet
 };
 
+export const rawImagesMessageInfoValidator: TInterface<RawImagesMessageInfo> =
+  tShape<RawImagesMessageInfo>({
+    type: tNumber(messageTypes.IMAGES),
+    localID: t.maybe(t.String),
+    threadID: tID,
+    creatorID: t.String,
+    time: t.Number,
+    media: t.list(imageValidator),
+    id: t.maybe(tID),
+  });
+
 export type ImagesMessageInfo = {
   +type: 14,
   +id?: string, // null if local copy without ID yet
   +localID?: string, // for optimistic creations
   +threadID: string,
   +creator: RelativeUserInfo,
   +time: number, // millisecond timestamp
   +media: $ReadOnlyArray<Image>,
 };
diff --git a/lib/types/messages/join-thread.js b/lib/types/messages/join-thread.js
index f51870b7f..6ab83153a 100644
--- a/lib/types/messages/join-thread.js
+++ b/lib/types/messages/join-thread.js
@@ -1,23 +1,36 @@
 // @flow
 
+import t, { type TInterface } from 'tcomb';
+
+import { tID, tNumber, tShape } from '../../utils/validation-utils.js';
+import { messageTypes } from '../message-types-enum.js';
 import type { RelativeUserInfo } from '../user-types.js';
 
 export type JoinThreadMessageData = {
   type: 8,
   threadID: string,
   creatorID: string,
   time: number,
 };
 
 export type RawJoinThreadMessageInfo = {
   ...JoinThreadMessageData,
   id: string,
 };
 
+export const rawJoinThreadMessageInfoValidator: TInterface<RawJoinThreadMessageInfo> =
+  tShape<RawJoinThreadMessageInfo>({
+    type: tNumber(messageTypes.JOIN_THREAD),
+    threadID: tID,
+    creatorID: t.String,
+    time: t.Number,
+    id: tID,
+  });
+
 export type JoinThreadMessageInfo = {
   type: 8,
   id: string,
   threadID: string,
   creator: RelativeUserInfo,
   time: number,
 };
diff --git a/lib/types/messages/leave-thread.js b/lib/types/messages/leave-thread.js
index 1c63e3226..7e4145cfc 100644
--- a/lib/types/messages/leave-thread.js
+++ b/lib/types/messages/leave-thread.js
@@ -1,23 +1,36 @@
 // @flow
 
+import t, { type TInterface } from 'tcomb';
+
+import { tID, tNumber, tShape } from '../../utils/validation-utils.js';
+import { messageTypes } from '../message-types-enum.js';
 import type { RelativeUserInfo } from '../user-types.js';
 
 export type LeaveThreadMessageData = {
   type: 7,
   threadID: string,
   creatorID: string,
   time: number,
 };
 
 export type RawLeaveThreadMessageInfo = {
   ...LeaveThreadMessageData,
   id: string,
 };
 
+export const rawLeaveThreadMessageInfoValidator: TInterface<RawLeaveThreadMessageInfo> =
+  tShape<RawLeaveThreadMessageInfo>({
+    type: tNumber(messageTypes.LEAVE_THREAD),
+    threadID: tID,
+    creatorID: t.String,
+    time: t.Number,
+    id: tID,
+  });
+
 export type LeaveThreadMessageInfo = {
   type: 7,
   id: string,
   threadID: string,
   creator: RelativeUserInfo,
   time: number,
 };
diff --git a/lib/types/messages/media.js b/lib/types/messages/media.js
index 3398fda18..c7bb281c2 100644
--- a/lib/types/messages/media.js
+++ b/lib/types/messages/media.js
@@ -1,81 +1,96 @@
 // @flow
 
-import type { Media } from '../media-types.js';
+import t, { type TInterface } from 'tcomb';
+
+import { tShape, tNumber, tID } from '../../utils/validation-utils.js';
+import { type Media, mediaValidator } from '../media-types.js';
+import { messageTypes } from '../message-types-enum.js';
 import type { RelativeUserInfo } from '../user-types.js';
 
 type MediaSharedBase = {
   +type: 15,
   +localID?: string, // for optimistic creations. included by new clients
   +threadID: string,
   +creatorID: string,
   +time: number,
   +media: $ReadOnlyArray<Media>,
 };
 
 export type MediaMessageData = {
   ...MediaSharedBase,
   +sidebarCreation?: boolean,
 };
 
 export type RawMediaMessageInfo = {
   ...MediaSharedBase,
   +id?: string, // null if local copy without ID yet
 };
 
+export const rawMediaMessageInfoValidator: TInterface<RawMediaMessageInfo> =
+  tShape<RawMediaMessageInfo>({
+    type: tNumber(messageTypes.MULTIMEDIA),
+    localID: t.maybe(t.String),
+    threadID: tID,
+    creatorID: t.String,
+    time: t.Number,
+    media: t.list(mediaValidator),
+    id: t.maybe(tID),
+  });
+
 export type MediaMessageInfo = {
   +type: 15,
   +id?: string, // null if local copy without ID yet
   +localID?: string, // for optimistic creations
   +threadID: string,
   +creator: RelativeUserInfo,
   +time: number, // millisecond timestamp
   +media: $ReadOnlyArray<Media>,
 };
 
 export type PhotoMessageServerDBContent = {
   +type: 'photo',
   +uploadID: string,
 };
 export type VideoMessageServerDBContent = {
   +type: 'video',
   +uploadID: string,
   +thumbnailUploadID: string,
 };
 export type MediaMessageServerDBContent =
   | PhotoMessageServerDBContent
   | VideoMessageServerDBContent;
 
 function getUploadIDsFromMediaMessageServerDBContents(
   mediaMessageContents: $ReadOnlyArray<MediaMessageServerDBContent>,
 ): $ReadOnlyArray<string> {
   const uploadIDs: string[] = [];
   for (const mediaContent of mediaMessageContents) {
     uploadIDs.push(mediaContent.uploadID);
     if (mediaContent.type === 'video') {
       uploadIDs.push(mediaContent.thumbnailUploadID);
     }
   }
   return uploadIDs;
 }
 
 function getMediaMessageServerDBContentsFromMedia(
   media: $ReadOnlyArray<Media>,
 ): $ReadOnlyArray<MediaMessageServerDBContent> {
   return media.map(m => {
     if (m.type === 'photo' || m.type === 'encrypted_photo') {
       return { type: 'photo', uploadID: m.id };
     } else if (m.type === 'video' || m.type === 'encrypted_video') {
       return {
         type: 'video',
         uploadID: m.id,
         thumbnailUploadID: m.thumbnailID,
       };
     }
     throw new Error(`Unexpected media type: ${m.type}`);
   });
 }
 
 export {
   getUploadIDsFromMediaMessageServerDBContents,
   getMediaMessageServerDBContentsFromMedia,
 };
diff --git a/lib/types/messages/reaction.js b/lib/types/messages/reaction.js
index b154d2246..f069ea860 100644
--- a/lib/types/messages/reaction.js
+++ b/lib/types/messages/reaction.js
@@ -1,31 +1,48 @@
 // @flow
 
+import t, { type TInterface } from 'tcomb';
+
+import { tID, tNumber, tShape } from '../../utils/validation-utils.js';
+import { messageTypes } from '../message-types-enum.js';
 import type { RelativeUserInfo } from '../user-types.js';
 
 export type ReactionMessageData = {
   +type: 19,
   +localID?: string, // for optimistic creations. included by new clients
   +threadID: string,
   +creatorID: string,
   +time: number,
   +targetMessageID: string,
   +reaction: string,
   +action: 'add_reaction' | 'remove_reaction',
 };
 
 export type RawReactionMessageInfo = {
   ...ReactionMessageData,
   id?: string, // null if local copy without ID yet
 };
 
+export const rawReactionMessageInfoValidator: TInterface<RawReactionMessageInfo> =
+  tShape<RawReactionMessageInfo>({
+    type: tNumber(messageTypes.REACTION),
+    localID: t.maybe(t.String),
+    threadID: tID,
+    creatorID: t.String,
+    time: t.Number,
+    targetMessageID: tID,
+    reaction: t.String,
+    action: t.enums.of(['add_reaction', 'remove_reaction']),
+    id: t.maybe(tID),
+  });
+
 export type ReactionMessageInfo = {
   +type: 19,
   +id?: string, // null if local copy without ID yet
   +localID?: string, // for optimistic creations
   +threadID: string,
   +creator: RelativeUserInfo,
   +time: number,
   +targetMessageID: string,
   +reaction: string,
   +action: 'add_reaction' | 'remove_reaction',
 };
diff --git a/lib/types/messages/remove-members.js b/lib/types/messages/remove-members.js
index 56e2da3b4..c87962cf3 100644
--- a/lib/types/messages/remove-members.js
+++ b/lib/types/messages/remove-members.js
@@ -1,25 +1,39 @@
 // @flow
 
+import t, { type TInterface } from 'tcomb';
+
+import { tID, tNumber, tShape } from '../../utils/validation-utils.js';
+import { messageTypes } from '../message-types-enum.js';
 import type { RelativeUserInfo } from '../user-types.js';
 
 export type RemoveMembersMessageData = {
   type: 5,
   threadID: string,
   creatorID: string,
   time: number,
   removedUserIDs: string[],
 };
 
 export type RawRemoveMembersMessageInfo = {
   ...RemoveMembersMessageData,
   id: string,
 };
 
+export const rawRemoveMembersMessageInfoValidator: TInterface<RawRemoveMembersMessageInfo> =
+  tShape<RawRemoveMembersMessageInfo>({
+    type: tNumber(messageTypes.REMOVE_MEMBERS),
+    threadID: tID,
+    creatorID: t.String,
+    time: t.Number,
+    removedUserIDs: t.list(t.String),
+    id: tID,
+  });
+
 export type RemoveMembersMessageInfo = {
   type: 5,
   id: string,
   threadID: string,
   creator: RelativeUserInfo,
   time: number,
   removedMembers: RelativeUserInfo[],
 };
diff --git a/lib/types/messages/restore-entry.js b/lib/types/messages/restore-entry.js
index 085ed1024..b4479a941 100644
--- a/lib/types/messages/restore-entry.js
+++ b/lib/types/messages/restore-entry.js
@@ -1,29 +1,45 @@
 // @flow
 
+import t, { type TInterface } from 'tcomb';
+
+import { tID, tNumber, tShape } from '../../utils/validation-utils.js';
+import { messageTypes } from '../message-types-enum.js';
 import type { RelativeUserInfo } from '../user-types.js';
 
 export type RestoreEntryMessageData = {
   type: 12,
   threadID: string,
   creatorID: string,
   time: number,
   entryID: string,
   date: string,
   text: string,
 };
 
 export type RawRestoreEntryMessageInfo = {
   ...RestoreEntryMessageData,
   id: string,
 };
 
+export const rawRestoreEntryMessageInfoValidator: TInterface<RawRestoreEntryMessageInfo> =
+  tShape<RawRestoreEntryMessageInfo>({
+    type: tNumber(messageTypes.RESTORE_ENTRY),
+    threadID: tID,
+    creatorID: t.String,
+    time: t.Number,
+    entryID: tID,
+    date: t.String,
+    text: t.String,
+    id: tID,
+  });
+
 export type RestoreEntryMessageInfo = {
   type: 12,
   id: string,
   threadID: string,
   creator: RelativeUserInfo,
   time: number,
   entryID: string,
   date: string,
   text: string,
 };
diff --git a/lib/types/messages/text.js b/lib/types/messages/text.js
index fcf7ef08e..43ddc6574 100644
--- a/lib/types/messages/text.js
+++ b/lib/types/messages/text.js
@@ -1,32 +1,47 @@
 // @flow
 
+import t, { type TInterface } from 'tcomb';
+
+import { tID, tNumber, tShape } from '../../utils/validation-utils.js';
+import { messageTypes } from '../message-types-enum.js';
 import type { RelativeUserInfo } from '../user-types.js';
 
 type TextSharedBase = {
   +type: 0,
   +localID?: string, // for optimistic creations. included by new clients
   +threadID: string,
   +creatorID: string,
   +time: number,
   +text: string,
 };
 
 export type TextMessageData = {
   ...TextSharedBase,
   +sidebarCreation?: boolean,
 };
 
 export type RawTextMessageInfo = {
   ...TextSharedBase,
   +id?: string, // null if local copy without ID yet
 };
 
+export const rawTextMessageInfoValidator: TInterface<RawTextMessageInfo> =
+  tShape<RawTextMessageInfo>({
+    type: tNumber(messageTypes.TEXT),
+    localID: t.maybe(t.String),
+    threadID: tID,
+    creatorID: t.String,
+    time: t.Number,
+    text: t.String,
+    id: t.maybe(tID),
+  });
+
 export type TextMessageInfo = {
   +type: 0,
   +id?: string, // null if local copy without ID yet
   +localID?: string, // for optimistic creations
   +threadID: string,
   +creator: RelativeUserInfo,
   +time: number, // millisecond timestamp
   +text: string,
 };
diff --git a/lib/types/messages/toggle-pin.js b/lib/types/messages/toggle-pin.js
index 29c0d24ae..b3ffe7666 100644
--- a/lib/types/messages/toggle-pin.js
+++ b/lib/types/messages/toggle-pin.js
@@ -1,29 +1,45 @@
 // @flow
 
+import t, { type TInterface } from 'tcomb';
+
+import { tID, tNumber, tShape } from '../../utils/validation-utils.js';
+import { messageTypes } from '../message-types-enum.js';
 import type { RelativeUserInfo } from '../user-types.js';
 
 export type TogglePinMessageData = {
   +type: 21,
   +threadID: string,
   +targetMessageID: string,
   +action: 'pin' | 'unpin',
   +pinnedContent: string,
   +creatorID: string,
   +time: number,
 };
 
 export type RawTogglePinMessageInfo = {
   ...TogglePinMessageData,
   +id: string,
 };
 
+export const rawTogglePinMessageInfoValidator: TInterface<RawTogglePinMessageInfo> =
+  tShape<RawTogglePinMessageInfo>({
+    type: tNumber(messageTypes.TOGGLE_PIN),
+    threadID: tID,
+    targetMessageID: tID,
+    action: t.enums.of(['pin', 'unpin']),
+    pinnedContent: t.String,
+    creatorID: t.String,
+    time: t.Number,
+    id: tID,
+  });
+
 export type TogglePinMessageInfo = {
   +type: 21,
   +id: string,
   +threadID: string,
   +targetMessageID: string,
   +action: 'pin' | 'unpin',
   +pinnedContent: string,
   +creator: RelativeUserInfo,
   +time: number,
 };
diff --git a/lib/types/messages/unsupported.js b/lib/types/messages/unsupported.js
index 0fe28b5d6..a89053b3a 100644
--- a/lib/types/messages/unsupported.js
+++ b/lib/types/messages/unsupported.js
@@ -1,25 +1,41 @@
 // @flow
 
+import t, { type TInterface } from 'tcomb';
+
+import { tID, tNumber, tShape } from '../../utils/validation-utils.js';
+import { messageTypes } from '../message-types-enum.js';
 import type { RelativeUserInfo } from '../user-types.js';
 
 export type RawUnsupportedMessageInfo = {
   type: 13,
   id: string,
   threadID: string,
   creatorID: string,
   time: number,
   robotext: string,
   dontPrefixCreator?: boolean,
   unsupportedMessageInfo: Object,
 };
 
+export const rawUnsupportedMessageInfoValidator: TInterface<RawUnsupportedMessageInfo> =
+  tShape<RawUnsupportedMessageInfo>({
+    type: tNumber(messageTypes.UNSUPPORTED),
+    id: tID,
+    threadID: tID,
+    creatorID: t.String,
+    time: t.Number,
+    robotext: t.String,
+    dontPrefixCreator: t.maybe(t.Boolean),
+    unsupportedMessageInfo: t.Object,
+  });
+
 export type UnsupportedMessageInfo = {
   type: 13,
   id: string,
   threadID: string,
   creator: RelativeUserInfo,
   time: number,
   robotext: string,
   dontPrefixCreator?: boolean,
   unsupportedMessageInfo: Object,
 };
diff --git a/lib/types/messages/update-relationship.js b/lib/types/messages/update-relationship.js
index 133d1fffe..43e6d0575 100644
--- a/lib/types/messages/update-relationship.js
+++ b/lib/types/messages/update-relationship.js
@@ -1,27 +1,42 @@
 // @flow
 
+import t, { type TInterface } from 'tcomb';
+
+import { tID, tNumber, tShape } from '../../utils/validation-utils.js';
+import { messageTypes } from '../message-types-enum.js';
 import type { RelativeUserInfo } from '../user-types.js';
 
 export type UpdateRelationshipMessageData = {
   +type: 16,
   +threadID: string,
   +creatorID: string,
   +targetID: string,
   +time: number,
   +operation: 'request_sent' | 'request_accepted',
 };
 
 export type RawUpdateRelationshipMessageInfo = {
   ...UpdateRelationshipMessageData,
   id: string,
 };
 
+export const rawUpdateRelationshipMessageInfoValidator: TInterface<RawUpdateRelationshipMessageInfo> =
+  tShape<RawUpdateRelationshipMessageInfo>({
+    type: tNumber(messageTypes.UPDATE_RELATIONSHIP),
+    threadID: tID,
+    creatorID: t.String,
+    targetID: t.String,
+    time: t.Number,
+    operation: t.enums.of(['request_sent', 'request_accepted']),
+    id: tID,
+  });
+
 export type UpdateRelationshipMessageInfo = {
   +type: 16,
   +id: string,
   +threadID: string,
   +creator: RelativeUserInfo,
   +target: RelativeUserInfo,
   +time: number,
   +operation: 'request_sent' | 'request_accepted',
 };
diff --git a/lib/types/validation.test.js b/lib/types/validation.test.js
index 8d6f3e9f0..b16b27203 100644
--- a/lib/types/validation.test.js
+++ b/lib/types/validation.test.js
@@ -1,44 +1,362 @@
 // @flow
 
+import _findKey from 'lodash/fp/findKey.js';
+
 import {
   imageValidator,
   videoValidator,
   mediaValidator,
 } from './media-types.js';
+import { messageTypes } from './message-types-enum.js';
+import { rawSidebarSourceMessageInfoValidator } from './message-types.js';
+import { rawAddMembersMessageInfoValidator } from './messages/add-members.js';
+import { rawChangeRoleMessageInfoValidator } from './messages/change-role.js';
+import { rawChangeSettingsMessageInfoValidator } from './messages/change-settings.js';
+import { rawCreateEntryMessageInfoValidator } from './messages/create-entry.js';
+import { rawCreateSidebarMessageInfoValidator } from './messages/create-sidebar.js';
+import { rawCreateSubthreadMessageInfoValidator } from './messages/create-subthread.js';
+import { rawCreateThreadMessageInfoValidator } from './messages/create-thread.js';
+import { rawDeleteEntryMessageInfoValidator } from './messages/delete-entry.js';
+import { rawEditEntryMessageInfoValidator } from './messages/edit-entry.js';
+import { rawEditMessageInfoValidator } from './messages/edit.js';
+import { rawImagesMessageInfoValidator } from './messages/images.js';
+import { rawJoinThreadMessageInfoValidator } from './messages/join-thread.js';
+import { rawLeaveThreadMessageInfoValidator } from './messages/leave-thread.js';
+import { rawMediaMessageInfoValidator } from './messages/media.js';
+import { rawReactionMessageInfoValidator } from './messages/reaction.js';
+import { rawRemoveMembersMessageInfoValidator } from './messages/remove-members.js';
+import { rawRestoreEntryMessageInfoValidator } from './messages/restore-entry.js';
+import { rawTextMessageInfoValidator } from './messages/text.js';
+import { rawTogglePinMessageInfoValidator } from './messages/toggle-pin.js';
+import { rawUnsupportedMessageInfoValidator } from './messages/unsupported.js';
+import { rawUpdateRelationshipMessageInfoValidator } from './messages/update-relationship.js';
 
 describe('media validation', () => {
   const photo = {
     id: '92696',
     type: 'photo',
     uri: 'http://0.0.0.0:3000/comm/upload/92696/0fb272bd1c75d976',
     dimensions: {
       width: 340,
       height: 288,
     },
   };
   const video = {
     type: 'video',
     id: '92769',
     uri: 'http://0.0.0.0:3000/comm/upload/92769/4bcc6987b25b2f66',
     dimensions: {
       width: 480,
       height: 270,
     },
     thumbnailID: '92770',
     thumbnailURI: 'http://0.0.0.0:3000/comm/upload/92770/d56466051dcef1db',
   };
 
   it('should validate correct media', () => {
     expect(mediaValidator.is(photo)).toBe(true);
     expect(imageValidator.is(photo)).toBe(true);
     expect(mediaValidator.is(video)).toBe(true);
     expect(videoValidator.is(video)).toBe(true);
   });
 
   it('should not validate incorrect media', () => {
     expect(imageValidator.is(video)).toBe(false);
     expect(videoValidator.is(photo)).toBe(false);
     expect(mediaValidator.is({ ...photo, type: undefined })).toBe(false);
     expect(mediaValidator.is({ ...video, dimensions: undefined })).toBe(false);
   });
 });
+
+describe('message validation', () => {
+  const messages = [
+    {
+      type: messageTypes.TEXT,
+      threadID: '83859',
+      creatorID: '83853',
+      time: 1682077048858,
+      text: 'text',
+      localID: 'local1',
+      id: '92837',
+    },
+    {
+      type: messageTypes.CREATE_THREAD,
+      id: '83876',
+      threadID: '83859',
+      time: 1673561105839,
+      creatorID: '83853',
+      initialThreadState: {
+        type: 6,
+        name: null,
+        parentThreadID: '1',
+        color: '57697f',
+        memberIDs: ['256', '83853'],
+      },
+    },
+    {
+      type: messageTypes.ADD_MEMBERS,
+      id: '4754380',
+      threadID: '4746046',
+      time: 1680179819346,
+      creatorID: '256',
+      addedUserIDs: ['518252', '1329299', '1559042'],
+    },
+    {
+      type: messageTypes.CREATE_SUB_THREAD,
+      threadID: '87111',
+      creatorID: '83928',
+      time: 1682083573756,
+      childThreadID: '92993',
+      id: '93000',
+    },
+    {
+      type: messageTypes.CHANGE_SETTINGS,
+      threadID: '83859',
+      creatorID: '83853',
+      time: 1682082984605,
+      field: 'color',
+      value: 'b8753d',
+      id: '92880',
+    },
+    {
+      type: messageTypes.REMOVE_MEMBERS,
+      threadID: '92993',
+      creatorID: '83928',
+      time: 1682083613415,
+      removedUserIDs: ['83890'],
+      id: '93012',
+    },
+    {
+      type: messageTypes.CHANGE_ROLE,
+      threadID: '85027',
+      creatorID: '256',
+      time: 1632393331694,
+      userIDs: ['85081'],
+      newRole: 'role',
+      id: '85431',
+    },
+    {
+      type: messageTypes.LEAVE_THREAD,
+      id: '93027',
+      threadID: '92993',
+      time: 1682083651037,
+      creatorID: '83928',
+    },
+    {
+      type: messageTypes.JOIN_THREAD,
+      threadID: '92993',
+      creatorID: '83928',
+      time: 1682083678595,
+      id: '93035',
+    },
+    {
+      type: messageTypes.CREATE_ENTRY,
+      threadID: '84695',
+      creatorID: '83928',
+      time: 1682083217395,
+      entryID: '92917',
+      date: '2023-04-02',
+      text: 'text',
+      id: '92920',
+    },
+    {
+      type: messageTypes.EDIT_ENTRY,
+      threadID: '84695',
+      creatorID: '83928',
+      time: 1682083374471,
+      entryID: '92917',
+      date: '2023-04-02',
+      text: 'text',
+      id: '92950',
+    },
+    {
+      type: messageTypes.DELETE_ENTRY,
+      threadID: '86033',
+      creatorID: '83928',
+      time: 1682083220296,
+      entryID: '92904',
+      date: '2023-04-02',
+      text: 'text',
+      id: '92932',
+    },
+    {
+      type: messageTypes.RESTORE_ENTRY,
+      id: '92962',
+      threadID: '86033',
+      time: 1682083414244,
+      creatorID: '83928',
+      entryID: '92904',
+      date: '2023-04-02',
+      text: 'text',
+    },
+    {
+      type: messageTypes.UNSUPPORTED,
+      threadID: '87080',
+      creatorID: '256',
+      time: 1640733462322,
+      robotext: 'unsupported message',
+      unsupportedMessageInfo: {
+        type: 105,
+        threadID: '97489',
+        creatorID: '256',
+        time: 1640773011289,
+        id: '97672',
+      },
+      id: '97730',
+    },
+    {
+      type: messageTypes.IMAGES,
+      threadID: '92796',
+      creatorID: '83928',
+      time: 1682083469079,
+      media: [
+        {
+          id: '92974',
+          uri: 'http://0.0.0.0:3000/comm/upload/92974/ff3d02ded71e2762',
+          type: 'photo',
+          dimensions: {
+            width: 220,
+            height: 220,
+          },
+        },
+      ],
+      localID: 'local0',
+      id: '92976',
+    },
+    {
+      type: messageTypes.MULTIMEDIA,
+      threadID: '89644',
+      creatorID: '83853',
+      time: 1682076177257,
+      media: [
+        {
+          type: 'video',
+          id: '92769',
+          uri: 'http://0.0.0.0:3000/comm/upload/92769/4bcc6987b25b2f66',
+          dimensions: {
+            width: 480,
+            height: 270,
+          },
+          thumbnailID: '92770',
+          thumbnailURI:
+            'http://0.0.0.0:3000/comm/upload/92770/d56466051dcef1db',
+        },
+      ],
+      id: '92771',
+    },
+    {
+      type: messageTypes.UPDATE_RELATIONSHIP,
+      threadID: '92796',
+      creatorID: '83928',
+      targetID: '83853',
+      time: 1682083716312,
+      operation: 'request_sent',
+      id: '93039',
+    },
+    {
+      type: messageTypes.SIDEBAR_SOURCE,
+      threadID: '93044',
+      creatorID: '83928',
+      time: 1682083756831,
+      sourceMessage: {
+        type: 0,
+        id: '92816',
+        threadID: '92796',
+        time: 1682076737518,
+        creatorID: '83928',
+        text: 'text',
+      },
+      id: '93049',
+    },
+    {
+      type: messageTypes.CREATE_SIDEBAR,
+      threadID: '93044',
+      creatorID: '83928',
+      time: 1682083756831,
+      sourceMessageAuthorID: '83928',
+      initialThreadState: {
+        name: 'text',
+        parentThreadID: '92796',
+        color: 'aa4b4b',
+        memberIDs: ['83853', '83928'],
+      },
+      id: '93050',
+    },
+    {
+      type: messageTypes.REACTION,
+      threadID: '86033',
+      localID: 'local8',
+      creatorID: '83928',
+      time: 1682083295820,
+      targetMessageID: '91607',
+      reaction: '😂',
+      action: 'add_reaction',
+      id: '92943',
+    },
+    {
+      type: messageTypes.EDIT_MESSAGE,
+      threadID: '86033',
+      creatorID: '83928',
+      time: 1682083295820,
+      targetMessageID: '91607',
+      text: 'text',
+      id: '92943',
+    },
+    {
+      type: messageTypes.TOGGLE_PIN,
+      threadID: '86033',
+      targetMessageID: '91607',
+      action: 'pin',
+      pinnedContent: 'text',
+      creatorID: '83928',
+      time: 1682083295820,
+      id: '92943',
+    },
+  ];
+
+  const validatorByMessageType = {
+    '0': rawTextMessageInfoValidator,
+    '1': rawCreateThreadMessageInfoValidator,
+    '2': rawAddMembersMessageInfoValidator,
+    '3': rawCreateSubthreadMessageInfoValidator,
+    '4': rawChangeSettingsMessageInfoValidator,
+    '5': rawRemoveMembersMessageInfoValidator,
+    '6': rawChangeRoleMessageInfoValidator,
+    '7': rawLeaveThreadMessageInfoValidator,
+    '8': rawJoinThreadMessageInfoValidator,
+    '9': rawCreateEntryMessageInfoValidator,
+    '10': rawEditEntryMessageInfoValidator,
+    '11': rawDeleteEntryMessageInfoValidator,
+    '12': rawRestoreEntryMessageInfoValidator,
+    '13': rawUnsupportedMessageInfoValidator,
+    '14': rawImagesMessageInfoValidator,
+    '15': rawMediaMessageInfoValidator,
+    '16': rawUpdateRelationshipMessageInfoValidator,
+    '17': rawSidebarSourceMessageInfoValidator,
+    '18': rawCreateSidebarMessageInfoValidator,
+    '19': rawReactionMessageInfoValidator,
+    '20': rawEditMessageInfoValidator,
+    '21': rawTogglePinMessageInfoValidator,
+  };
+
+  for (const validatorMessageType in validatorByMessageType) {
+    const validator = validatorByMessageType[validatorMessageType];
+    const validatorMessageTypeName = _findKey(
+      e => e === Number(validatorMessageType),
+    )(messageTypes);
+
+    for (const message of messages) {
+      const messageTypeName = _findKey(e => e === message.type)(messageTypes);
+
+      if (Number(validatorMessageType) === message.type) {
+        it(`${validatorMessageTypeName} should validate ${messageTypeName}`, () => {
+          expect(validator.is(message)).toBe(true);
+        });
+      } else {
+        it(`${validatorMessageTypeName} shouldn't validate ${messageTypeName}`, () => {
+          expect(validator.is(message)).toBe(false);
+        });
+      }
+    }
+  }
+});