diff --git a/plugins/chat/assets/javascripts/discourse/components/chat-channel.gjs b/plugins/chat/assets/javascripts/discourse/components/chat-channel.gjs
index 11abaee3c04..0b2f14ba3a3 100644
--- a/plugins/chat/assets/javascripts/discourse/components/chat-channel.gjs
+++ b/plugins/chat/assets/javascripts/discourse/components/chat-channel.gjs
@@ -18,6 +18,7 @@ import {
 import i18n from "discourse-common/helpers/i18n";
 import discourseDebounce from "discourse-common/lib/debounce";
 import { bind } from "discourse-common/utils/decorators";
+import I18n from "I18n";
 import ChatChannelStatus from "discourse/plugins/chat/discourse/components/chat-channel-status";
 import firstVisibleMessageId from "discourse/plugins/chat/discourse/helpers/first-visible-message-id";
 import ChatChannelSubscriptionManager from "discourse/plugins/chat/discourse/lib/chat-channel-subscription-manager";
@@ -62,9 +63,11 @@ export default class ChatChannel extends Component {
   @service("chat-channel-composer") composer;
   @service("chat-channel-pane") pane;
   @service currentUser;
+  @service dialog;
   @service messageBus;
   @service router;
   @service site;
+  @service siteSettings;
 
   @tracked sending = false;
   @tracked showChatQuoteSuccess = false;
@@ -496,6 +499,17 @@ export default class ChatChannel extends Component {
 
   @action
   async onSendMessage(message) {
+    if (
+      message.message.length > this.siteSettings.chat_maximum_message_length
+    ) {
+      this.dialog.alert(
+        I18n.t("chat.message_too_long", {
+          count: this.siteSettings.chat_maximum_message_length,
+        })
+      );
+      return;
+    }
+
     await message.cook();
     if (message.editing) {
       await this.#sendEditMessage(message);
diff --git a/plugins/chat/assets/javascripts/discourse/components/chat-thread.gjs b/plugins/chat/assets/javascripts/discourse/components/chat-thread.gjs
index 1bbd1d063e7..ebfd382dee7 100644
--- a/plugins/chat/assets/javascripts/discourse/components/chat-thread.gjs
+++ b/plugins/chat/assets/javascripts/discourse/components/chat-thread.gjs
@@ -11,6 +11,7 @@ import { popupAjaxError } from "discourse/lib/ajax-error";
 import { NotificationLevels } from "discourse/lib/notification-levels";
 import discourseDebounce from "discourse-common/lib/debounce";
 import { bind } from "discourse-common/utils/decorators";
+import I18n from "I18n";
 import ChatThreadTitlePrompt from "discourse/plugins/chat/discourse/components/chat-thread-title-prompt";
 import firstVisibleMessageId from "discourse/plugins/chat/discourse/helpers/first-visible-message-id";
 import ChatChannelThreadSubscriptionManager from "discourse/plugins/chat/discourse/lib/chat-channel-thread-subscription-manager";
@@ -49,6 +50,7 @@ export default class ChatThread extends Component {
   @service chatDraftsManager;
   @service chatThreadComposer;
   @service chatThreadPane;
+  @service dialog;
   @service currentUser;
   @service router;
   @service siteSettings;
@@ -359,6 +361,17 @@ export default class ChatThread extends Component {
 
   @action
   async onSendMessage(message) {
+    if (
+      message.message.length > this.siteSettings.chat_maximum_message_length
+    ) {
+      this.dialog.alert(
+        I18n.t("chat.message_too_long", {
+          count: this.siteSettings.chat_maximum_message_length,
+        })
+      );
+      return;
+    }
+
     await message.cook();
     if (message.editing) {
       await this.#sendEditMessage(message);
diff --git a/plugins/chat/config/locales/client.en.yml b/plugins/chat/config/locales/client.en.yml
index 2550f725af7..7d1f101e653 100644
--- a/plugins/chat/config/locales/client.en.yml
+++ b/plugins/chat/config/locales/client.en.yml
@@ -259,6 +259,7 @@ en:
       copy_link: "Copy link"
       copy_text: "Copy text"
       rebake_message: "Rebuild HTML"
+      message_too_long: "Message is too long, messages must be a maximum of %{count} characters."
       retry_staged_message:
         title: "Network error"
         action: "Send again?"
diff --git a/plugins/chat/spec/system/message_errors_spec.rb b/plugins/chat/spec/system/message_errors_spec.rb
index 8b2336aa45a..5d751cbc52e 100644
--- a/plugins/chat/spec/system/message_errors_spec.rb
+++ b/plugins/chat/spec/system/message_errors_spec.rb
@@ -1,26 +1,55 @@
 # frozen_string_literal: true
 
 RSpec.describe "Message errors", type: :system do
-  fab!(:current_user) { Fabricate(:admin) }
-  let(:chat_page) { PageObjects::Pages::Chat.new }
-  let(:channel_page) { PageObjects::Pages::ChatChannel.new }
-  let(:max_length) { SiteSetting.chat_maximum_message_length }
-
-  before { chat_system_bootstrap }
-
   context "when message is too long" do
-    fab!(:channel) { Fabricate(:chat_channel) }
+    let(:chat_page) { PageObjects::Pages::Chat.new }
+    let(:dialog_page) { PageObjects::Components::Dialog.new }
+    let(:max_length) { SiteSetting.chat_maximum_message_length }
+    let(:message) { "atoolongmessage" + "a" * max_length }
 
-    before { channel.add(current_user) }
+    fab!(:current_user) { Fabricate(:admin) }
 
-    it "only shows the error, not the message" do
+    before do
+      chat_system_bootstrap
       sign_in(current_user)
-      chat_page.visit_channel(channel)
+    end
 
-      channel_page.send_message("atoolongmessage" + "a" * max_length)
+    context "when in channel" do
+      fab!(:channel) { Fabricate(:chat_channel) }
 
-      expect(page).to have_content(I18n.t("chat.errors.message_too_long", count: max_length))
-      expect(page).to have_no_content("atoolongmessage")
+      let(:channel_page) { PageObjects::Pages::ChatChannel.new }
+
+      before { channel.add(current_user) }
+
+      it "shows a dialog with the error and keeps the message in the input" do
+        chat_page.visit_channel(channel)
+
+        channel_page.send_message(message)
+
+        expect(dialog_page).to have_content(
+          I18n.t("chat.errors.message_too_long", count: max_length),
+        )
+        expect(channel_page.composer).to have_value(message)
+      end
+    end
+
+    context "when in thread" do
+      fab!(:thread) { Fabricate(:chat_thread) }
+
+      let(:thread_page) { PageObjects::Pages::ChatThread.new }
+
+      before { thread.add(current_user) }
+
+      it "shows a dialog with the error and keeps the message in the input" do
+        chat_page.visit_thread(thread)
+
+        thread_page.send_message(message)
+
+        expect(dialog_page).to have_content(
+          I18n.t("chat.errors.message_too_long", count: max_length),
+        )
+        expect(thread_page.composer).to have_value(message)
+      end
     end
   end
 end
diff --git a/plugins/chat/spec/system/page_objects/chat/chat_channel.rb b/plugins/chat/spec/system/page_objects/chat/chat_channel.rb
index 92c514ea6eb..15b31e7a473 100644
--- a/plugins/chat/spec/system/page_objects/chat/chat_channel.rb
+++ b/plugins/chat/spec/system/page_objects/chat/chat_channel.rb
@@ -35,7 +35,9 @@ module PageObjects
       end
 
       def click_composer
-        find(".chat-channel .chat-composer__input").click # ensures autocomplete is closed and not masking anything
+        if has_no_css?(".dialog-overlay", wait: 0) # we can't click composer if a dialog is open, in case of error for exampel
+          find(".chat-channel .chat-composer__input").click # ensures autocomplete is closed and not masking anything
+        end
       end
 
       def click_send_message
diff --git a/plugins/chat/spec/system/page_objects/chat/chat_thread.rb b/plugins/chat/spec/system/page_objects/chat/chat_thread.rb
index 5ec9364c9be..600426b0d22 100644
--- a/plugins/chat/spec/system/page_objects/chat/chat_thread.rb
+++ b/plugins/chat/spec/system/page_objects/chat/chat_thread.rb
@@ -94,7 +94,9 @@ module PageObjects
       end
 
       def click_composer
-        find(".chat-thread .chat-composer__input").click # ensures autocomplete is closed and not masking anything
+        if has_no_css?(".dialog-overlay", wait: 0) # we can't click composer if a dialog is open, in case of error for exampel
+          find(".chat-thread .chat-composer__input").click # ensures autocomplete is closed and not masking anything
+        end
       end
 
       def send_message(text = nil)
diff --git a/plugins/chat/spec/system/page_objects/chat/components/composer.rb b/plugins/chat/spec/system/page_objects/chat/components/composer.rb
index 07695148542..255fd8f11fd 100644
--- a/plugins/chat/spec/system/page_objects/chat/components/composer.rb
+++ b/plugins/chat/spec/system/page_objects/chat/components/composer.rb
@@ -48,6 +48,10 @@ module PageObjects
           input.value
         end
 
+        def has_value?(expected)
+          value == expected
+        end
+
         def reply_to_last_message_shortcut
           input.click
           input.send_keys(%i[shift arrow_up])