diff --git a/backend/internal/api/conversation.go b/backend/internal/api/conversation.go
index c3eed70..e21471a 100644
--- a/backend/internal/api/conversation.go
+++ b/backend/internal/api/conversation.go
@@ -273,6 +273,9 @@ func (h *ConversationHandler) GetMessages(c *gin.Context) {
 			return
 		}
 		count, _ := h.msgRepo.GetMessageCount(c.Request.Context(), sessionID)
+		if messages == nil {
+			messages = []store.StoredMessage{}
+		}
 		c.JSON(http.StatusOK, gin.H{
 			"messages": messages,
 			"total":    count,
@@ -314,6 +317,9 @@ func (h *ConversationHandler) GetMessages(c *gin.Context) {
 	}
 	messages := allMessages[start:]
 
+	if messages == nil {
+		messages = []models.Message{}
+	}
 	c.JSON(http.StatusOK, gin.H{
 		"messages": messages,
 		"total":    total,
diff --git a/backend/internal/store/message_pg.go b/backend/internal/store/message_pg.go
index 014194b..b393c9c 100644
--- a/backend/internal/store/message_pg.go
+++ b/backend/internal/store/message_pg.go
@@ -90,7 +90,7 @@ func (r *PgMessageRepository) queryMessages(ctx context.Context, query string, a
 	}
 	defer pgxRows.Close()
 
-	var messages []StoredMessage
+	messages := make([]StoredMessage, 0)
 	for pgxRows.Next() {
 		var m StoredMessage
 		if err := pgxRows.Scan(&m.ID, &m.SessionID, &m.Role, &m.Content, &m.TokensUsed, &m.CreatedAt); err != nil {
diff --git a/frontend/src/App.css b/frontend/src/App.css
index 9afbf9a..268cc55 100644
--- a/frontend/src/App.css
+++ b/frontend/src/App.css
@@ -217,7 +217,15 @@ body {
   background: rgba(10, 10, 15, 0.45);
   backdrop-filter: blur(3px);
   -webkit-backdrop-filter: blur(3px);
-  animation: fadeIn 0.2s ease;
+  cursor: pointer;
+  opacity: 0;
+  pointer-events: none;
+  transition: opacity 0.3s var(--transition-smooth);
+}
+
+.sidebar-backdrop--visible {
+  opacity: 1;
+  pointer-events: auto;
 }
 
 .sidebar {
@@ -232,13 +240,18 @@ body {
   background: var(--color-surface);
   border-right: 1px solid var(--color-border);
   overflow: hidden;
-  animation: slideInLeft 0.3s var(--transition-smooth);
   box-shadow: 8px 0 40px rgba(10, 10, 15, 0.4);
+  transition: transform 0.3s var(--transition-smooth);
 }
 
-@keyframes slideInLeft {
-  from { transform: translateX(-100%); }
-  to { transform: translateX(0); }
+.sidebar--collapsed {
+  transform: translateX(-100%);
+  pointer-events: none;
+}
+
+.sidebar--open {
+  transform: translateX(0);
+  pointer-events: auto;
 }
 
 .sidebar--collapsed {
diff --git a/frontend/src/components/SessionSidebar/index.tsx b/frontend/src/components/SessionSidebar/index.tsx
index 7d444d7..043e380 100644
--- a/frontend/src/components/SessionSidebar/index.tsx
+++ b/frontend/src/components/SessionSidebar/index.tsx
@@ -118,8 +118,6 @@ export function SessionSidebar({
     return groups;
   }, [sessions, searchQuery]);
 
-  if (!open) return null;
-
   const groupLabels: Record<TimeGroup, string> = {
     today: t("sidebar.today"),
     yesterday: t("sidebar.yesterday"),
@@ -128,8 +126,11 @@ export function SessionSidebar({
 
   return (
     <>
-      <div className="sidebar-backdrop" onClick={onClose} />
-      <div className="sidebar">
+      <div
+        className={`sidebar-backdrop ${open ? 'sidebar-backdrop--visible' : ''}`}
+        onClick={onClose}
+      />
+      <div className={`sidebar ${open ? 'sidebar--open' : 'sidebar--collapsed'}`}>
         {/* 头部：新建 + 收起 */}
         <div className="sidebar__header">
           <button className="sidebar__new-btn" onClick={onNewSession}>
diff --git a/frontend/src/hooks/useSessionList.ts b/frontend/src/hooks/useSessionList.ts
index 841a3e4..c33e212 100644
--- a/frontend/src/hooks/useSessionList.ts
+++ b/frontend/src/hooks/useSessionList.ts
@@ -80,7 +80,7 @@ export function useSessionList(accessToken?: string | null) {
     try {
       const res = await listConversations(accessToken);
       if (res.data) {
-        const list = res.data.conversations.map(toSessionSummary);
+        const list = (res.data.conversations || []).map(toSessionSummary);
         setSessions(list);
         // 恢复上次选中的会话（如果仍然存在）
         const lastId = localStorage.getItem(LAST_ACTIVE_KEY);
@@ -193,7 +193,7 @@ export function useSessionList(accessToken?: string | null) {
       try {
         const res = await getConversationMessages(accessToken, sessionId);
         if (res.data) {
-          return res.data.messages.map(toChatMessage);
+          return (res.data.messages || []).map(toChatMessage);
         }
       } catch (err) {
         console.error("[SessionList] 加载消息失败:", err);