From a84032f40a6ab1dadc344914a1ab92a2fb934577 Mon Sep 17 00:00:00 2001
From: Harrison Healey <harrisonmhealey@gmail.com>
Date: Tue, 2 Jun 2026 01:43:55 -0400
Subject: [PATCH] MM-69053 Log server message when a user has concurrent React
 enabled (#36837)

* MM-69053 Log server message when a user has concurrent React enabled

* Add session_id and user_id to server-logged messages sent by the client

* Fix linting

* Fix test
---
 server/channels/api4/system.go                |  2 ++
 .../src/components/root/actions/index.ts      | 19 ++++++++++++++++++-
 webapp/channels/src/components/root/index.ts  |  2 ++
 .../src/components/root/root.test.tsx         |  1 +
 webapp/channels/src/components/root/root.tsx  |  2 ++
 5 files changed, 25 insertions(+), 1 deletion(-)

diff --git a/server/channels/api4/system.go b/server/channels/api4/system.go
index 7de04c0676d..4b96ba5f45c 100644
--- a/server/channels/api4/system.go
+++ b/server/channels/api4/system.go
@@ -478,6 +478,8 @@ func postLog(c *Context, w http.ResponseWriter, r *http.Request) {
 	fields := []mlog.Field{
 		mlog.String("type", "client_message"),
 		mlog.String("user_agent", c.AppContext.UserAgent()),
+		mlog.String("session_id", c.AppContext.Session().Id),
+		mlog.String("user_id", c.AppContext.Session().UserId),
 	}
 
 	if !forceToDebug && lvl == "ERROR" {
diff --git a/webapp/channels/src/components/root/actions/index.ts b/webapp/channels/src/components/root/actions/index.ts
index a21c8f074bd..cb6766cfa46 100644
--- a/webapp/channels/src/components/root/actions/index.ts
+++ b/webapp/channels/src/components/root/actions/index.ts
@@ -3,6 +3,7 @@
 
 import type {History} from 'history';
 
+import {LogLevel} from '@mattermost/types/client4';
 import type {ServerError} from '@mattermost/types/errors';
 import type {UserProfile} from '@mattermost/types/users';
 
@@ -25,7 +26,7 @@ import {reloadPage} from 'utils/browser_utils';
 import {StoragePrefixes} from 'utils/constants';
 import {doesCookieContainsMMUserId} from 'utils/utils';
 
-import type {ThunkActionFunc} from 'types/store';
+import type {ActionFuncAsync, ThunkActionFunc} from 'types/store';
 import type {Translations} from 'types/store/i18n';
 
 export type TranslationPluginFunction = (locale: string) => Translations
@@ -156,3 +157,19 @@ export function handleLoginLogoutSignal(e: StorageEvent): ThunkActionFunc<void>
         }
     };
 }
+
+export function logIfConcurrentReactEnabled(): ActionFuncAsync<boolean> {
+    return async () => {
+        const concurrentReactEnabled = localStorage.getItem('enable_concurrent_react_experimental') === 'true';
+
+        if (concurrentReactEnabled) {
+            Client4.logClientError(
+                "This user's session is using experimental concurrent React which may cause visual bugs. It can be " +
+                    'disabled from Settings > Advanced or by clearing their browser storage.',
+                LogLevel.Debug,
+            );
+        }
+
+        return {data: concurrentReactEnabled};
+    };
+}
diff --git a/webapp/channels/src/components/root/index.ts b/webapp/channels/src/components/root/index.ts
index 6f505e91d3b..1710a8ffefc 100644
--- a/webapp/channels/src/components/root/index.ts
+++ b/webapp/channels/src/components/root/index.ts
@@ -32,6 +32,7 @@ import {
     loadConfigAndMe,
     handleLoginLogoutSignal,
     redirectToOnboardingOrDefaultTeam,
+    logIfConcurrentReactEnabled,
 } from './actions';
 import Root from './root';
 
@@ -77,6 +78,7 @@ function mapDispatchToProps(dispatch: Dispatch) {
         actions: bindActionCreators({
             loadConfigAndMe,
             loadRecentlyUsedCustomEmojis,
+            logIfConcurrentReactEnabled,
             migrateRecentEmojis,
             initializeProducts,
             handleLoginLogoutSignal,
diff --git a/webapp/channels/src/components/root/root.test.tsx b/webapp/channels/src/components/root/root.test.tsx
index 3d0d8103796..c9c26b7fd45 100644
--- a/webapp/channels/src/components/root/root.test.tsx
+++ b/webapp/channels/src/components/root/root.test.tsx
@@ -71,6 +71,7 @@ describe('components/Root', () => {
                 });
             }),
             loadRecentlyUsedCustomEmojis: jest.fn(),
+            logIfConcurrentReactEnabled: jest.fn(),
             migrateRecentEmojis: jest.fn(),
             initializeProducts: jest.fn(),
             ...bindActionCreators({
diff --git a/webapp/channels/src/components/root/root.tsx b/webapp/channels/src/components/root/root.tsx
index f019498d917..6a3142afb47 100644
--- a/webapp/channels/src/components/root/root.tsx
+++ b/webapp/channels/src/components/root/root.tsx
@@ -231,6 +231,8 @@ export default class Root extends React.PureComponent<Props, State> {
     initiateMeRequests = async () => {
         const {isLoaded, isMeRequested} = await this.props.actions.loadConfigAndMe();
 
+        this.props.actions.logIfConcurrentReactEnabled();
+
         if (isLoaded) {
             const isUserAtRootRoute = this.props.location.pathname === '/';