diff --git a/src/features/Common/AIChatModal.tsx b/src/features/Common/AIChatModal.tsx
index ef4c5b9..457e7e8 100644
--- a/src/features/Common/AIChatModal.tsx
+++ b/src/features/Common/AIChatModal.tsx
@@ -1,4 +1,4 @@
-import { useQueryClient } from '@tanstack/react-query' // 1. useQueryClient 임포트
+import { useQuery, useQueryClient } from '@tanstack/react-query'
 import React, { useEffect, useRef, useState } from 'react'
 
 import ChatIcon from '@/assets/icons/common/chat.svg'
@@ -20,11 +20,31 @@ function AIChatModal({ isHome = true }: AIChatModalProps) {
   const [isLoading, setIsLoading] = useState(false)
   const chatBoxRef = useRef<HTMLDivElement>(null)
 
+  const { data: historyData, isLoading: isHistoryLoading } = useQuery({
+    queryKey: ['chatHistory'],
+    queryFn: nlpApi.getHistory,
+  })
+
+  useEffect(() => {
+    if (historyData?.isSuccess && historyData.result) {
+      const rawMessages = historyData.result.messages
+      const mappedMessages: ChatMessage[] = Array.isArray(rawMessages)
+        ? rawMessages.map((msg) => ({
+            id: crypto.randomUUID(),
+            sender: msg.role === 'user' ? 'user' : 'bot',
+            text: msg.content ?? '',
+          }))
+        : []
+
+      setMessages(mappedMessages)
+    }
+  }, [historyData])
+
   useEffect(() => {
     if (chatBoxRef.current) {
       chatBoxRef.current.scrollTop = chatBoxRef.current.scrollHeight
     }
-  }, [messages, isLoading])
+  }, [messages, isLoading, isHistoryLoading])
 
   const handleSendMessage = async () => {
     if (!inputValue.trim() || isLoading) return
@@ -52,6 +72,8 @@ function AIChatModal({ isHome = true }: AIChatModalProps) {
         }
         setMessages((prev) => [...prev, botMessage])
 
+        queryClient.invalidateQueries({ queryKey: ['chatHistory'] })
+
         if (response.result.action === 'UPDATED') {
           queryClient.invalidateQueries({ queryKey: ['calendar'] })
           queryClient.invalidateQueries({ queryKey: ['events'] })
@@ -67,14 +89,18 @@ function AIChatModal({ isHome = true }: AIChatModalProps) {
           },
         ])
       }
-      // eslint-disable-next-line @typescript-eslint/no-unused-vars
     } catch (error) {
+      const errorMessage =
+        error instanceof Error
+          ? error.message
+          : 'AI 비서 서버와 연결에 실패했습니다. 잠시 후 다시 시도해주세요.'
+
       setMessages((prev) => [
         ...prev,
         {
           id: crypto.randomUUID(),
           sender: 'bot',
-          text: 'AI 비서 서버와 연결에 실패했습니다. 잠시 후 다시 시도해주세요.',
+          text: `연결에 실패했습니다. (원인: ${errorMessage})`,
         },
       ])
     } finally {
@@ -88,7 +114,7 @@ function AIChatModal({ isHome = true }: AIChatModalProps) {
     }
   }
 
-  const isChatEmpty = messages.length === 0 && !isLoading
+  const isChatEmpty = messages.length === 0 && !isLoading && !isHistoryLoading
   const hideEmptyChatBox = !isHome && isChatEmpty
 
   return (
@@ -101,7 +127,14 @@ function AIChatModal({ isHome = true }: AIChatModalProps) {
       </S.Title>
 
       <S.ChatBox ref={chatBoxRef} isEmpty={isChatEmpty} isHidden={hideEmptyChatBox}>
-        {isChatEmpty ? (
+        {isHistoryLoading ? (
+          <S.BotMessageWrapper>
+            <img src={RobotIcon} width={32} height={32} style={{ flexShrink: 0 }} alt="robot" />
+            <S.BotContentArea>
+              <S.BotFallbackBubble>잠시만 기다려주세요...</S.BotFallbackBubble>
+            </S.BotContentArea>
+          </S.BotMessageWrapper>
+        ) : isChatEmpty ? (
           <S.EmptyState>
             <img src={ChatIcon} alt="채팅 시작" width="150" height="150" />
           </S.EmptyState>
@@ -150,11 +183,11 @@ function AIChatModal({ isHome = true }: AIChatModalProps) {
           onChange={(e) => setInputValue(e.target.value)}
           onKeyDown={handleKeyDown}
           placeholder="예시) 내일 오후 3시 치과 진료 받으러 감"
-          disabled={isLoading}
+          disabled={isLoading || isHistoryLoading}
         />
         <S.SendButton
           onClick={handleSendMessage}
-          disabled={isLoading || !inputValue.trim()}
+          disabled={isLoading || isHistoryLoading || !inputValue.trim()}
           aria-label="전송"
         >
           ↑
diff --git a/src/features/Friends/SharedScheduleItem.tsx b/src/features/Friends/SharedScheduleItem.tsx
index 1d19a6c..53cad40 100644
--- a/src/features/Friends/SharedScheduleItem.tsx
+++ b/src/features/Friends/SharedScheduleItem.tsx
@@ -1,3 +1,9 @@
+import { useMutation, useQueryClient } from '@tanstack/react-query'
+
+import { eventShareApi } from '@/shared/api/friends/eventShare'
+import { getErrorMessage } from '@/shared/utils'
+import { useToastStore } from '@/store/useToastStore'
+
 import * as S from './SharedScheduleItem.style'
 
 interface SharedScheduleItemProps {
@@ -19,6 +25,9 @@ export default function SharedScheduleItem({
   accentColor = '#5c6ac4',
   onCancelSuccess,
 }: SharedScheduleItemProps) {
+  const queryClient = useQueryClient()
+  const { showToast } = useToastStore()
+
   const formatDate = (dateStr: string) => {
     if (!dateStr) return ''
     const date = new Date(dateStr)
@@ -35,9 +44,45 @@ export default function SharedScheduleItem({
       ? formatDate(startDate)
       : `${formatDate(startDate)} - ${formatDate(endDate)}`
 
+  const leaveEventMutation = useMutation({
+    mutationFn: () => eventShareApi.leaveEvent(eventId),
+    onSuccess: (response) => {
+      if (response.isSuccess) {
+        queryClient.invalidateQueries({ queryKey: ['calendar'] })
+        queryClient.invalidateQueries({ queryKey: ['events'] })
+        queryClient.invalidateQueries({ queryKey: ['todos'] })
+
+        showToast({
+          title: '그룹 탈퇴 완료',
+          message: '성공적으로 탈퇴되었습니다.',
+          toastType: 'success',
+        })
+
+        onCancelSuccess?.()
+      } else {
+        showToast({
+          title: '탈퇴 처리 실패',
+          message: response.message || '탈퇴 처리에 실패했습니다.',
+          toastType: 'error',
+        })
+      }
+    },
+    onError: (error) => {
+      console.error(error)
+      const errorMessage = getErrorMessage(error)
+
+      showToast({
+        title: '오류 발생',
+        message: errorMessage || '서버 연결에 실패했습니다. 잠시 후 다시 시도해주세요.',
+        toastType: 'error',
+      })
+    },
+  })
+
   const handleCancelShare = () => {
-    console.log(`eventId ${eventId} 공유 취소 클릭`)
-    onCancelSuccess?.()
+    if (window.confirm('정말 이 공유 이벤트에서 탈퇴하시겠습니까?')) {
+      leaveEventMutation.mutate()
+    }
   }
 
   return (
@@ -50,8 +95,13 @@ export default function SharedScheduleItem({
 
       <S.MetaArea>
         <S.SharerBadge>공유자: {sharerName}</S.SharerBadge>
-        <S.CancelButton bgColor="#fff1f0" textColor="#ff4d4f" onClick={handleCancelShare}>
-          공유 취소
+        <S.CancelButton
+          bgColor="#fff1f0"
+          textColor="#ff4d4f"
+          onClick={handleCancelShare}
+          disabled={leaveEventMutation.isPending}
+        >
+          {leaveEventMutation.isPending ? '취소 중...' : '공유 취소'}
         </S.CancelButton>
       </S.MetaArea>
     </S.Container>
diff --git a/src/shared/api/friends/eventShare.ts b/src/shared/api/friends/eventShare.ts
index ceb5742..d234902 100644
--- a/src/shared/api/friends/eventShare.ts
+++ b/src/shared/api/friends/eventShare.ts
@@ -1,6 +1,7 @@
 import type {
   ActionApiResponse,
   InvitationsApiResponse,
+  LeaveEventResponse,
   SharedEventsApiResponse,
 } from '@/shared/types/eventShare/eventShare'
 
@@ -32,4 +33,10 @@ export const eventShareApi = {
     const { data } = await axiosInstance.get<InvitationsApiResponse>(`${BASE_URL}/invitations`)
     return data
   },
+  leaveEvent: async (eventId: number): Promise<LeaveEventResponse> => {
+    const { data } = await axiosInstance.delete<LeaveEventResponse>(
+      `/events/${eventId}/participants/leave`,
+    )
+    return data
+  },
 }
diff --git a/src/shared/api/home/home.ts b/src/shared/api/home/home.ts
index 7bb53ca..7458adc 100644
--- a/src/shared/api/home/home.ts
+++ b/src/shared/api/home/home.ts
@@ -1,5 +1,6 @@
 import type {
   BriefingResponse,
+  ChatHistoryResponse,
   ChatResponse,
   ReminderResponse,
   SuggestionListResponse,
@@ -47,4 +48,8 @@ export const nlpApi = {
     const res = await axiosInstance.post<ChatResponse>('/chat', { message })
     return res.data
   },
+  getHistory: async (): Promise<ChatHistoryResponse> => {
+    const res = await axiosInstance.get<ChatHistoryResponse>('/chat/history')
+    return res.data
+  },
 }
diff --git a/src/shared/types/eventShare/eventShare.ts b/src/shared/types/eventShare/eventShare.ts
index 3999690..43ffe2e 100644
--- a/src/shared/types/eventShare/eventShare.ts
+++ b/src/shared/types/eventShare/eventShare.ts
@@ -32,3 +32,5 @@ export interface InvitationsResult {
 export type InvitationsApiResponse = TCommonResponse<InvitationsResult>
 
 export type ActionApiResponse = TCommonResponse<null>
+
+export type LeaveEventResponse = TCommonResponse<null>
diff --git a/src/shared/types/home/home.ts b/src/shared/types/home/home.ts
index 732e8dc..326252d 100644
--- a/src/shared/types/home/home.ts
+++ b/src/shared/types/home/home.ts
@@ -75,3 +75,16 @@ export interface ChatMessage {
   text: string
   action?: ChatActionType
 }
+
+export type ChatHistoryResponse = TCommonResponse<ChatHistory>
+
+export interface ChatHistory {
+  messages: boolean | undefined
+  result: {
+    messages: {
+      role: 'user' | 'assistant'
+      content: string
+    }[]
+    summary: string | null
+  }
+}