diff --git a/web/app/components/base/user-avatar-list/index.tsx b/web/app/components/base/user-avatar-list/index.tsx
index d31a82912d..03d71c3c4d 100644
--- a/web/app/components/base/user-avatar-list/index.tsx
+++ b/web/app/components/base/user-avatar-list/index.tsx
@@ -1,9 +1,10 @@
 import type { FC } from 'react'
 import type { AvatarSize } from '@/app/components/base/avatar'
 import { memo } from 'react'
-import { Avatar } from '@/app/components/base/avatar'
+import { AvatarFallback, AvatarImage, avatarPartClassNames, AvatarRoot, getAvatarSizeClassNames } from '@/app/components/base/avatar'
 import { getUserColor } from '@/app/components/workflow/collaboration/utils/user-color'
 import { useAppContext } from '@/context/app-context'
+import { cn } from '@/utils/classnames'
 
 type User = {
   id: string
@@ -60,6 +61,8 @@ export const UserAvatarList: FC<UserAvatarListProps> = memo(({
   const remainingCount = users.length - actualMaxVisible
 
   const currentUserId = userProfile?.id
+  const avatarSize = numericPxToAvatarSize(size)
+  const avatarSizeClassNames = getAvatarSizeClassNames(avatarSize)
 
   return (
     <div className={`flex items-center -space-x-1 ${className}`}>
@@ -72,13 +75,21 @@ export const UserAvatarList: FC<UserAvatarListProps> = memo(({
             className="relative"
             style={{ zIndex: visibleUsers.length - index }}
           >
-            <Avatar
-              name={user.name}
-              avatar={user.avatar_url || null}
-              size={numericPxToAvatarSize(size)}
-              className="ring-2 ring-components-panel-bg"
-              backgroundColor={userColor}
-            />
+            <AvatarRoot className={cn(avatarPartClassNames.root, avatarSizeClassNames.root, 'ring-2 ring-components-panel-bg')}>
+              {user.avatar_url && (
+                <AvatarImage
+                  src={user.avatar_url}
+                  alt={user.name}
+                  className={avatarPartClassNames.image}
+                />
+              )}
+              <AvatarFallback
+                className={cn(avatarPartClassNames.fallback, avatarSizeClassNames.text)}
+                style={userColor ? { backgroundColor: userColor } : undefined}
+              >
+                {user.name?.[0]?.toLocaleUpperCase()}
+              </AvatarFallback>
+            </AvatarRoot>
           </div>
         )
       },
diff --git a/web/app/components/workflow/comment/thread.tsx b/web/app/components/workflow/comment/thread.tsx
index 63189f16b4..2b415dda19 100644
--- a/web/app/components/workflow/comment/thread.tsx
+++ b/web/app/components/workflow/comment/thread.tsx
@@ -6,7 +6,7 @@ import { RiArrowDownSLine, RiArrowUpSLine, RiCheckboxCircleFill, RiCheckboxCircl
 import { memo, useCallback, useEffect, useMemo, useRef, useState } from 'react'
 import { useTranslation } from 'react-i18next'
 import { useReactFlow, useViewport } from 'reactflow'
-import { Avatar } from '@/app/components/base/avatar'
+import { Avatar, AvatarFallback, AvatarImage, avatarPartClassNames, AvatarRoot, getAvatarSizeClassNames } from '@/app/components/base/avatar'
 import Divider from '@/app/components/base/divider'
 import InlineDeleteConfirm from '@/app/components/base/inline-delete-confirm'
 import { PortalToFollowElem, PortalToFollowElemContent, PortalToFollowElemTrigger } from '@/app/components/base/portal-to-follow-elem'
@@ -19,6 +19,8 @@ import { cn } from '@/utils/classnames'
 import { useStore } from '../store'
 import { MentionInput } from './mention-input'
 
+const threadAvatarSizeClassNames = getAvatarSizeClassNames('sm')
+
 type CommentThreadProps = {
   comment: WorkflowCommentDetail
   loading?: boolean
@@ -120,13 +122,21 @@ const ThreadMessage: FC<{
   return (
     <div className={cn('flex gap-3 pt-1', className)}>
       <div className="shrink-0">
-        <Avatar
-          name={authorName}
-          avatar={avatarUrl || null}
-          size="sm"
-          className={cn('h-8 w-8 rounded-full')}
-          backgroundColor={userColor}
-        />
+        <AvatarRoot className={cn(avatarPartClassNames.root, threadAvatarSizeClassNames.root, 'h-8 w-8 rounded-full')}>
+          {avatarUrl && (
+            <AvatarImage
+              src={avatarUrl}
+              alt={authorName}
+              className={avatarPartClassNames.image}
+            />
+          )}
+          <AvatarFallback
+            className={cn(avatarPartClassNames.fallback, threadAvatarSizeClassNames.text)}
+            style={userColor ? { backgroundColor: userColor } : undefined}
+          >
+            {authorName?.[0]?.toLocaleUpperCase()}
+          </AvatarFallback>
+        </AvatarRoot>
       </div>
       <div className="min-w-0 flex-1 pb-4 text-text-primary last:pb-0">
         <div className="flex flex-wrap items-center gap-x-2 gap-y-1">
diff --git a/web/app/components/workflow/header/online-users.tsx b/web/app/components/workflow/header/online-users.tsx
index 016d7bbf70..d2dcccb990 100644
--- a/web/app/components/workflow/header/online-users.tsx
+++ b/web/app/components/workflow/header/online-users.tsx
@@ -4,7 +4,7 @@ import { ChevronDownIcon } from '@heroicons/react/20/solid'
 import { useEffect, useState } from 'react'
 import { useTranslation } from 'react-i18next'
 import { useReactFlow } from 'reactflow'
-import { Avatar } from '@/app/components/base/avatar'
+import { AvatarFallback, AvatarImage, avatarPartClassNames, AvatarRoot, getAvatarSizeClassNames } from '@/app/components/base/avatar'
 import Divider from '@/app/components/base/divider'
 import {
   PortalToFollowElem,
@@ -51,6 +51,38 @@ const useAvatarUrls = (users: OnlineUser[]) => {
   return avatarUrls
 }
 
+const onlineUserAvatarSizeClassNames = getAvatarSizeClassNames('sm')
+
+type OnlineUserAvatarProps = {
+  name: string
+  avatar: string | null
+  className?: string
+  fallbackColor?: string
+}
+
+const OnlineUserAvatar = ({
+  name,
+  avatar,
+  className,
+  fallbackColor,
+}: OnlineUserAvatarProps) => (
+  <AvatarRoot className={cn(avatarPartClassNames.root, onlineUserAvatarSizeClassNames.root, className)}>
+    {avatar && (
+      <AvatarImage
+        src={avatar}
+        alt={name}
+        className={avatarPartClassNames.image}
+      />
+    )}
+    <AvatarFallback
+      className={cn(avatarPartClassNames.fallback, onlineUserAvatarSizeClassNames.text)}
+      style={fallbackColor ? { backgroundColor: fallbackColor } : undefined}
+    >
+      {name?.[0]?.toLocaleUpperCase()}
+    </AvatarFallback>
+  </AvatarRoot>
+)
+
 const OnlineUsers = () => {
   const { t } = useTranslation()
   const appId = useStore(s => s.appId)
@@ -135,12 +167,11 @@ const OnlineUsers = () => {
                     style={{ zIndex: visibleUsers.length - index }}
                     onClick={() => !isCurrentUser && jumpToUserCursor(user.user_id)}
                   >
-                    <Avatar
+                    <OnlineUserAvatar
                       name={user.username || t('comments.fallback.user', { ns: 'workflow' })}
                       avatar={getAvatarUrl(user) ?? null}
-                      size="sm"
                       className="ring-1 ring-components-panel-bg"
-                      backgroundColor={userColor}
+                      fallbackColor={userColor}
                     />
                   </TooltipTrigger>
                   <TooltipContent
@@ -216,11 +247,10 @@ const OnlineUsers = () => {
                           }}
                         >
                           <div className="relative">
-                            <Avatar
+                            <OnlineUserAvatar
                               name={user.username || t('comments.fallback.user', { ns: 'workflow' })}
                               avatar={getAvatarUrl(user) ?? null}
-                              size="sm"
-                              backgroundColor={userColor}
+                              fallbackColor={userColor}
                             />
                           </div>
                           {renderDisplayName(