diff --git a/keyserver/src/responders/thread-responders.js b/keyserver/src/responders/thread-responders.js
--- a/keyserver/src/responders/thread-responders.js
+++ b/keyserver/src/responders/thread-responders.js
@@ -27,8 +27,7 @@
   type RoleDeletionRequest,
   type RoleDeletionResult,
 } from 'lib/types/thread-types.js';
-import { updateUserAvatarRequestValidator } from 'lib/utils/avatar-utils.js';
-import { values } from 'lib/utils/objects.js';
+import { threadSettingsChangesValidator } from 'lib/types/validators/thread-validators.js';
 import {
   tShape,
   tNumEnum,
@@ -118,15 +117,7 @@
 export const updateThreadRequestInputValidator: TInterface<UpdateThreadRequest> =
   tShape<UpdateThreadRequest>({
     threadID: tID,
-    changes: tShape({
-      type: t.maybe(tNumEnum(values(threadTypes))),
-      name: t.maybe(t.String),
-      description: t.maybe(t.String),
-      color: t.maybe(tColor),
-      parentThreadID: t.maybe(tID),
-      newMemberIDs: t.maybe(t.list(tUserID)),
-      avatar: t.maybe(updateUserAvatarRequestValidator),
-    }),
+    changes: threadSettingsChangesValidator,
     accountPassword: t.maybe(tPassword),
   });
 
diff --git a/lib/shared/dm-ops/change-thread-settings-spec.js b/lib/shared/dm-ops/change-thread-settings-spec.js
new file mode 100644
--- /dev/null
+++ b/lib/shared/dm-ops/change-thread-settings-spec.js
@@ -0,0 +1,190 @@
+// @flow
+
+import uuid from 'uuid';
+
+import { addMembersSpec } from './add-members-spec.js';
+import type {
+  DMOperationSpec,
+  ProcessDMOperationUtilities,
+} from './dm-op-spec.js';
+import type { DMChangeThreadSettingsOperation } from '../../types/dm-ops.js';
+import { messageTypes } from '../../types/message-types-enum.js';
+import type { RawMessageInfo } from '../../types/message-types.js';
+import type { RawThreadInfo } from '../../types/minimally-encoded-thread-permissions-types.js';
+import type { LegacyRawThreadInfo } from '../../types/thread-types.js';
+import { updateTypes } from '../../types/update-types-enum.js';
+import type { ClientUpdateInfo } from '../../types/update-types.js';
+import { values } from '../../utils/objects.js';
+import { firstLine } from '../../utils/string-utils.js';
+import { validChatNameRegex } from '../../utils/validation-utils.js';
+
+const changeThreadSettingsSpec: DMOperationSpec<DMChangeThreadSettingsOperation> =
+  Object.freeze({
+    processDMOperation: async (
+      dmOperation: DMChangeThreadSettingsOperation,
+      viewerID: string,
+      utilities: ProcessDMOperationUtilities,
+    ) => {
+      const {
+        editorID,
+        time,
+        changes,
+        messageIDsPrefix,
+        threadInfo,
+        rawMessageInfos,
+        truncationStatus,
+        rawEntryInfos,
+      } = dmOperation;
+      const {
+        name: untrimmedName,
+        description,
+        color,
+        parentThreadID,
+        avatar,
+        type: threadType,
+      } = changes;
+      const threadID = threadInfo.id;
+
+      const newMemberIDs =
+        changes.newMemberIDs && changes.newMemberIDs.length > 0
+          ? [...new Set(changes.newMemberIDs)]
+          : null;
+
+      let threadInfoToUpdate: ?(RawThreadInfo | LegacyRawThreadInfo) =
+        utilities.getThreadInfo(threadID);
+      if (!threadInfoToUpdate && !newMemberIDs?.includes(viewerID)) {
+        // We can't perform this operation now. It should be queued for later.
+        return {
+          rawMessageInfos: [],
+          updateInfos: [],
+        };
+      }
+
+      const updateInfos: Array<ClientUpdateInfo> = [];
+      const generatedRawMessageInfos: Array<RawMessageInfo> = [];
+
+      if (newMemberIDs) {
+        const addMembersResult = await addMembersSpec.processDMOperation(
+          {
+            type: 'add_members',
+            editorID,
+            time,
+            messageID: `${messageIDsPrefix}/add_members`,
+            addedUserIDs: newMemberIDs,
+            threadInfo,
+            rawMessageInfos,
+            truncationStatus,
+            rawEntryInfos,
+          },
+          viewerID,
+          utilities,
+        );
+        const threadInfoFromUpdates = addMembersResult.updateInfos.find(
+          update =>
+            update.type === updateTypes.UPDATE_THREAD ||
+            update.type === updateTypes.JOIN_THREAD,
+        )?.threadInfo;
+        if (threadInfoFromUpdates) {
+          threadInfoToUpdate = threadInfoFromUpdates;
+        }
+        updateInfos.push(...addMembersResult.updateInfos);
+        generatedRawMessageInfos.push(...addMembersResult.rawMessageInfos);
+      }
+
+      if (!threadInfoToUpdate || !threadInfoToUpdate.thick) {
+        // We can't perform this operation now. It should be queued for later.
+        return {
+          rawMessageInfos: [],
+          updateInfos: [],
+        };
+      }
+
+      const changedFields: { [string]: string | number } = {};
+
+      if (untrimmedName !== undefined && untrimmedName !== null) {
+        const name = firstLine(untrimmedName);
+        if (name.search(validChatNameRegex) === -1) {
+          return {
+            rawMessageInfos: [],
+            updateInfos: [],
+          };
+        }
+        changedFields.name = name;
+        threadInfoToUpdate = {
+          ...threadInfoToUpdate,
+          name,
+        };
+      }
+
+      if (description !== undefined && description !== null) {
+        changedFields.description = description;
+        threadInfoToUpdate = {
+          ...threadInfoToUpdate,
+          description,
+        };
+      }
+
+      if (color) {
+        const newColor = color.toLowerCase();
+        changedFields.color = newColor;
+        threadInfoToUpdate = {
+          ...threadInfoToUpdate,
+          color: newColor,
+        };
+      }
+
+      if (parentThreadID !== undefined) {
+        // TODO do we want to support this for thick threads?
+        return {
+          rawMessageInfos: [],
+          updateInfos: [],
+        };
+      }
+
+      if (avatar) {
+        changedFields.avatar =
+          avatar.type !== 'remove' ? JSON.stringify(avatar) : '';
+        threadInfoToUpdate = {
+          ...threadInfoToUpdate,
+          avatar: threadInfo.avatar,
+        };
+      }
+
+      if (threadType !== null && threadType !== undefined) {
+        // TODO do we want to support this for thick threads?
+        return {
+          rawMessageInfos: [],
+          updateInfos: [],
+        };
+      }
+
+      for (const fieldName in changedFields) {
+        const newValue = changedFields[fieldName];
+        generatedRawMessageInfos.push({
+          type: messageTypes.CHANGE_SETTINGS,
+          threadID,
+          creatorID: editorID,
+          time,
+          field: fieldName,
+          value: newValue,
+          id: `${messageIDsPrefix}/${fieldName}`,
+        });
+      }
+
+      if (values(changedFields).length > 0) {
+        updateInfos.push({
+          type: updateTypes.UPDATE_THREAD,
+          id: uuid.v4(),
+          time,
+          threadInfo: threadInfoToUpdate,
+        });
+      }
+
+      return {
+        rawMessageInfos: generatedRawMessageInfos,
+        updateInfos,
+      };
+    },
+  });
+
+export { changeThreadSettingsSpec };
diff --git a/lib/shared/dm-ops/dm-op-specs.js b/lib/shared/dm-ops/dm-op-specs.js
--- a/lib/shared/dm-ops/dm-op-specs.js
+++ b/lib/shared/dm-ops/dm-op-specs.js
@@ -1,6 +1,7 @@
 // @flow
 
 import { addMembersSpec } from './add-members-spec.js';
+import { changeThreadSettingsSpec } from './change-thread-settings-spec.js';
 import { createSidebarSpec } from './create-sidebar-spec.js';
 import { createThreadSpec } from './create-thread-spec.js';
 import type { DMOperationSpec } from './dm-op-spec.js';
@@ -24,4 +25,5 @@
   [dmOperationTypes.JOIN_THREAD]: joinThreadSpec,
   [dmOperationTypes.LEAVE_THREAD]: leaveThreadSpec,
   [dmOperationTypes.REMOVE_MEMBERS]: removeMembersSpec,
+  [dmOperationTypes.CHANGE_THREAD_SETTINGS]: changeThreadSettingsSpec,
 });
diff --git a/lib/types/dm-ops.js b/lib/types/dm-ops.js
--- a/lib/types/dm-ops.js
+++ b/lib/types/dm-ops.js
@@ -16,7 +16,9 @@
   type NonSidebarThickThreadType,
   nonSidebarThickThreadTypes,
 } from './thread-types-enum.js';
+import type { ThreadChanges } from './thread-types.js';
 import type { ClientUpdateInfo } from './update-types.js';
+import { threadSettingsChangesValidator } from './validators/thread-validators.js';
 import { threadInfoValidator } from '../permissions/minimally-encoded-thread-permissions-validators.js';
 import { values } from '../utils/objects.js';
 import { tShape, tString, tUserID } from '../utils/validation-utils.js';
@@ -31,6 +33,7 @@
   JOIN_THREAD: 'join_thread',
   LEAVE_THREAD: 'leave_thread',
   REMOVE_MEMBERS: 'remove_members',
+  CHANGE_THREAD_SETTINGS: 'change_thread_settings',
 });
 export type DMOperationType = $Values<typeof dmOperationTypes>;
 
@@ -222,6 +225,30 @@
     removedUserIDs: t.list(tUserID),
   });
 
+export type DMChangeThreadSettingsOperation = {
+  +type: 'change_thread_settings',
+  +editorID: string,
+  +time: number,
+  +changes: ThreadChanges,
+  +messageIDsPrefix: string,
+  +threadInfo: ThickRawThreadInfo,
+  +rawMessageInfos: $ReadOnlyArray<RawMessageInfo>,
+  +truncationStatus: MessageTruncationStatus,
+  +rawEntryInfos: $ReadOnlyArray<RawEntryInfo>,
+};
+export const dmChangeThreadSettingsOperation: TInterface<DMChangeThreadSettingsOperation> =
+  tShape<DMChangeThreadSettingsOperation>({
+    type: tString(dmOperationTypes.CHANGE_THREAD_SETTINGS),
+    editorID: tUserID,
+    time: t.Number,
+    changes: threadSettingsChangesValidator,
+    messageIDsPrefix: t.String,
+    threadInfo: threadInfoValidator,
+    rawMessageInfos: t.list(rawMessageInfoValidator),
+    truncationStatus: messageTruncationStatusValidator,
+    rawEntryInfos: t.list(rawEntryInfoValidator),
+  });
+
 export type DMOperation =
   | DMCreateThreadOperation
   | DMCreateSidebarOperation
@@ -231,7 +258,8 @@
   | DMAddMembersOperation
   | DMJoinThreadOperation
   | DMLeaveThreadOperation
-  | DMRemoveMembersOperation;
+  | DMRemoveMembersOperation
+  | DMChangeThreadSettingsOperation;
 export const dmOperationValidator: TUnion<DMOperation> = t.union([
   dmCreateThreadOperationValidator,
   dmCreateSidebarOperationValidator,
@@ -242,6 +270,7 @@
   dmJoinThreadOperation,
   dmLeaveThreadOperation,
   dmRemoveMembersOperation,
+  dmChangeThreadSettingsOperation,
 ]);
 
 export type DMOperationResult = {
diff --git a/lib/types/validators/thread-validators.js b/lib/types/validators/thread-validators.js
--- a/lib/types/validators/thread-validators.js
+++ b/lib/types/validators/thread-validators.js
@@ -4,12 +4,21 @@
 import type { TInterface } from 'tcomb';
 
 import { mixedRawThreadInfoValidator } from '../../permissions/minimally-encoded-raw-thread-info-validators.js';
-import { tShape, tID } from '../../utils/validation-utils.js';
+import { updateUserAvatarRequestValidator } from '../../utils/avatar-utils.js';
+import { values } from '../../utils/objects.js';
+import {
+  tShape,
+  tID,
+  tNumEnum,
+  tColor,
+  tUserID,
+} from '../../utils/validation-utils.js';
 import { mediaValidator } from '../media-types.js';
 import {
   rawMessageInfoValidator,
   messageTruncationStatusesValidator,
 } from '../message-types.js';
+import { threadTypes } from '../thread-types-enum.js';
 import {
   type ChangeThreadSettingsResult,
   type LeaveThreadResult,
@@ -19,6 +28,7 @@
   type ToggleMessagePinResult,
   type RoleModificationResult,
   type RoleDeletionResult,
+  type ThreadChanges,
 } from '../thread-types.js';
 import { serverUpdateInfoValidator } from '../update-types.js';
 import { userInfosValidator } from '../user-types.js';
@@ -30,6 +40,17 @@
     }),
   });
 
+export const threadSettingsChangesValidator: TInterface<ThreadChanges> =
+  tShape<ThreadChanges>({
+    type: t.maybe(tNumEnum(values(threadTypes))),
+    name: t.maybe(t.String),
+    description: t.maybe(t.String),
+    color: t.maybe(tColor),
+    parentThreadID: t.maybe(tID),
+    newMemberIDs: t.maybe(t.list(tUserID)),
+    avatar: t.maybe(updateUserAvatarRequestValidator),
+  });
+
 export const changeThreadSettingsResultValidator: TInterface<ChangeThreadSettingsResult> =
   tShape<ChangeThreadSettingsResult>({
     newMessageInfos: t.list(rawMessageInfoValidator),