diff --git a/packages/react/src/store/settingsStore.js b/packages/react/src/store/settingsStore.js
index 4f9d78b68..f3e613729 100644
--- a/packages/react/src/store/settingsStore.js
+++ b/packages/react/src/store/settingsStore.js
@@ -1,7 +1,7 @@
 import { create } from 'zustand';
 
 const useSettingsStore = create((set) => ({
-  messageLimit: 5000,
+  messageLimit: null, // Will be fetched from RC server (Message_MaxAllowedSize)
   setMessageLimit: (messageLimit) => set(() => ({ messageLimit })),
 }));
 
diff --git a/packages/react/src/views/AttachmentPreview/AttachmentPreview.js b/packages/react/src/views/AttachmentPreview/AttachmentPreview.js
index 01123dafb..fe9fdc4ba 100644
--- a/packages/react/src/views/AttachmentPreview/AttachmentPreview.js
+++ b/packages/react/src/views/AttachmentPreview/AttachmentPreview.js
@@ -1,10 +1,18 @@
 import React, { useContext, useState, useRef, useEffect } from 'react';
 import { css } from '@emotion/react';
-import { Box, Icon, Button, Input, Modal } from '@embeddedchat/ui-elements';
+import {
+  Box,
+  Icon,
+  Button,
+  Input,
+  Modal,
+  useTheme,
+} from '@embeddedchat/ui-elements';
 import useAttachmentWindowStore from '../../store/attachmentwindow';
 import CheckPreviewType from './CheckPreviewType';
 import RCContext from '../../context/RCInstance';
 import { useMessageStore, useMemberStore } from '../../store';
+import useSettingsStore from '../../store/settingsStore';
 import getAttachmentPreviewStyles from './AttachmentPreview.styles';
 import { parseEmoji } from '../../lib/emoji';
 import MembersList from '../Mentions/MembersList';
@@ -13,29 +21,38 @@ import useSearchMentionUser from '../../hooks/useSearchMentionUser';
 
 const AttachmentPreview = () => {
   const { RCInstance, ECOptions } = useContext(RCContext);
+  const { theme } = useTheme();
   const styles = getAttachmentPreviewStyles();
 
   const toggle = useAttachmentWindowStore((state) => state.toggle);
   const data = useAttachmentWindowStore((state) => state.data);
   const setData = useAttachmentWindowStore((state) => state.setData);
+
   const [isPending, setIsPending] = useState(false);
   const messageRef = useRef(null);
+
+  // Mention UI states
   const [showMembersList, setShowMembersList] = useState(false);
   const [filteredMembers, setFilteredMembers] = useState([]);
   const [mentionIndex, setMentionIndex] = useState(-1);
   const [startReadMentionUser, setStartReadMentionUser] = useState(false);
-  const [keyPressed, setKeyPressed] = useState(null);
 
-  const [fileName, setFileName] = useState(data?.name);
+  // File name
+  const [fileName, setFileName] = useState(data?.name ?? '');
+  useEffect(() => setFileName(data?.name ?? ''), [data?.name]);
 
-  const threadId = useMessageStore((state) => state.threadMainMessage?._id);
-  const handleFileName = (e) => {
-    setFileName(e.target.value);
-  };
+  // Description
+  const [description, setDescription] = useState('');
+  const charCount = description.length;
 
-  const { members } = useMemberStore((state) => ({
-    members: state.members,
-  }));
+  // Character limit is fetched from RC server (Message_MaxAllowedSize)
+  // via ChatHeader and stored in settingsStore.
+  const msgMaxLength = useSettingsStore((s) => s?.messageLimit);
+
+  const isOverLimit = msgMaxLength && charCount > msgMaxLength;
+
+  const threadId = useMessageStore((state) => state.threadMainMessage?._id);
+  const { members } = useMemberStore((state) => ({ members: state.members }));
 
   const searchMentionUser = useSearchMentionUser(
     members,
@@ -46,47 +63,49 @@ const AttachmentPreview = () => {
     setShowMembersList
   );
 
+  const handleFileName = (e) => setFileName(e.target.value);
+
   const handleFileDescription = (e) => {
-    const description = e.target.value;
-    messageRef.current.value = parseEmoji(description);
-    searchMentionUser(description);
+    const raw = e.target.value || '';
+    setDescription(raw);
+
+    // If Input forwards ref to native input, keep it in sync (safe-guard)
+    if (messageRef.current && typeof messageRef.current.value !== 'undefined') {
+      try {
+        messageRef.current.value = raw;
+      } catch (err) {
+        // ignore if ref doesn't allow direct value set
+      }
+    }
+
+    searchMentionUser(raw);
   };
 
   const submit = async () => {
+    if (isPending) return;
+    if (msgMaxLength && description.length > msgMaxLength) return;
+
     setIsPending(true);
-    await RCInstance.sendAttachment(
-      data,
-      fileName,
-      messageRef.current.value,
-      ECOptions?.enableThreads ? threadId : undefined
-    );
-    toggle();
-    setData(null);
-    if (isPending) {
+    try {
+      await RCInstance.sendAttachment(
+        data,
+        fileName,
+        parseEmoji(description),
+        ECOptions?.enableThreads ? threadId : undefined
+      );
+      toggle();
+      setData(null);
+    } finally {
       setIsPending(false);
     }
   };
 
-  useEffect(() => {
-    const keyHandler = (e) => {
-      if (e.key === 'Enter') {
-        e.preventDefault();
-        setKeyPressed('Enter');
-      }
-    };
-
-    document.addEventListener('keydown', keyHandler);
-    return () => {
-      document.removeEventListener('keydown', keyHandler);
-    };
-  }, []);
-
-  useEffect(() => {
-    if (keyPressed === 'Enter') {
+  const onDescKeyDown = (e) => {
+    if (e.key === 'Enter' && !e.shiftKey) {
+      e.preventDefault();
       submit();
-      setKeyPressed(null);
     }
-  }, [keyPressed, submit]);
+  };
 
   return (
     <Modal onClose={toggle}>
@@ -98,11 +117,12 @@ const AttachmentPreview = () => {
             css={css`
               margin-right: 0.5rem;
             `}
-          />{' '}
+          />
           File Upload
         </Modal.Title>
         <Modal.Close onClick={toggle} />
       </Modal.Header>
+
       <Modal.Content>
         <Box css={styles.modalContent}>
           <Box
@@ -113,11 +133,13 @@ const AttachmentPreview = () => {
           >
             <CheckPreviewType data={data} />
           </Box>
+
           <Box
             css={css`
               margin: 30px;
             `}
           >
+            {/* FILE NAME */}
             <Box css={styles.inputContainer}>
               <Box
                 is="span"
@@ -129,9 +151,7 @@ const AttachmentPreview = () => {
                 File name
               </Box>
               <Input
-                onChange={(e) => {
-                  handleFileName(e);
-                }}
+                onChange={handleFileName}
                 value={fileName}
                 type="text"
                 css={styles.input}
@@ -140,6 +160,7 @@ const AttachmentPreview = () => {
               <TypingUsers />
             </Box>
 
+            {/* FILE DESCRIPTION */}
             <Box css={styles.inputContainer}>
               <Box
                 is="span"
@@ -150,6 +171,7 @@ const AttachmentPreview = () => {
               >
                 File description
               </Box>
+
               <Box css={styles.fileDescription}>
                 <Box css={styles.mentionListContainer}>
                   {showMembersList && (
@@ -161,21 +183,77 @@ const AttachmentPreview = () => {
                       setFilteredMembers={setFilteredMembers}
                       setStartReadMentionUser={setStartReadMentionUser}
                       setShowMembersList={setShowMembersList}
-                      css={css`
-                        width: auto;
-                      `}
                     />
                   )}
                 </Box>
+
+                {/* DESCRIPTION INPUT */}
                 <Input
-                  onChange={(e) => {
-                    handleFileDescription(e);
-                  }}
+                  onChange={handleFileDescription}
+                  onKeyDown={onDescKeyDown}
                   type="text"
-                  css={styles.input}
                   placeholder="Description"
                   ref={messageRef}
+                  value={description}
+                  css={css`
+                    ${styles.input};
+                    border-color: ${isOverLimit
+                      ? theme.colors.destructive
+                      : null};
+                    color: ${isOverLimit ? theme.colors.destructive : null};
+                  `}
                 />
+
+                {/* ALERT (left) and COUNTER (right) on the same row below the input */}
+                {msgMaxLength && (
+                  <Box
+                    css={css`
+                      width: 100%;
+                      display: flex;
+                      justify-content: space-between;
+                      align-items: center;
+                      margin-top: 6px;
+                      gap: 12px;
+                      font-size: 0.875rem;
+                    `}
+                  >
+                    {/* ALERT: left aligned (starts at left of the box). Only visible when over limit. */}
+                    <Box
+                      css={css`
+                        color: ${isOverLimit
+                          ? theme.colors.destructive
+                          : 'transparent'};
+                        font-weight: 500;
+                        text-align: left;
+                        flex: 1 1 auto;
+                        white-space: nowrap;
+                        overflow: hidden;
+                        text-overflow: ellipsis;
+                      `}
+                      aria-hidden={!isOverLimit}
+                      role={isOverLimit ? 'alert' : undefined}
+                    >
+                      {isOverLimit
+                        ? `Cannot upload file, description is over the ${msgMaxLength} character limit`
+                        : ''}
+                    </Box>
+
+                    {/* COUNTER: right aligned */}
+                    <Box
+                      css={css`
+                        color: ${isOverLimit
+                          ? theme.colors.destructive
+                          : '#6b7280'};
+                        min-width: 68px;
+                        text-align: right;
+                        flex: 0 0 auto;
+                      `}
+                      aria-hidden="true"
+                    >
+                      ({charCount}/{msgMaxLength})
+                    </Box>
+                  </Box>
+                )}
               </Box>
             </Box>
           </Box>
@@ -190,12 +268,8 @@ const AttachmentPreview = () => {
         <Button type="secondary" onClick={toggle}>
           Cancel
         </Button>
-        <Button
-          disabled={isPending}
-          onClick={() => {
-            submit();
-          }}
-        >
+
+        <Button disabled={isPending || isOverLimit} onClick={submit}>
           {isPending ? 'Sending...' : 'Send'}
         </Button>
       </Modal.Footer>