diff --git a/packages/backend/server/src/plugins/copilot/resolver.ts b/packages/backend/server/src/plugins/copilot/resolver.ts
index ae0a544485..7d767a2591 100644
--- a/packages/backend/server/src/plugins/copilot/resolver.ts
+++ b/packages/backend/server/src/plugins/copilot/resolver.ts
@@ -111,8 +111,9 @@ class CopilotHistoriesType implements Partial<ChatHistory> {
 
   @Field(() => String, {
     description: 'An mark identifying which view to use to display the session',
+    nullable: true,
   })
-  action!: string;
+  action!: string | undefined;
 
   @Field(() => Number, {
     description: 'The number of tokens used in the session',
diff --git a/packages/backend/server/src/plugins/copilot/session.ts b/packages/backend/server/src/plugins/copilot/session.ts
index 6fca6d688e..9de9b83980 100644
--- a/packages/backend/server/src/plugins/copilot/session.ts
+++ b/packages/backend/server/src/plugins/copilot/session.ts
@@ -138,6 +138,11 @@ export class ChatSessionService {
         if (id) sessionId = id;
       }
 
+      const messages = state.messages.map(m => ({
+        ...m,
+        params: m.params || undefined,
+      }));
+
       await tx.aiSession.upsert({
         where: {
           id: sessionId,
@@ -145,12 +150,9 @@ export class ChatSessionService {
         },
         update: {
           messages: {
-            // delete old messages
-            deleteMany: {},
-            create: state.messages.map(m => ({
-              ...m,
-              params: m.params || undefined,
-            })),
+            // skip delete old messages if no new messages
+            deleteMany: messages.length ? {} : undefined,
+            create: messages,
           },
         },
         create: {
@@ -158,10 +160,7 @@ export class ChatSessionService {
           workspaceId: state.workspaceId,
           docId: state.docId,
           messages: {
-            create: state.messages.map(m => ({
-              ...m,
-              params: m.params || undefined,
-            })),
+            create: messages,
           },
           // connect
           user: { connect: { id: state.userId } },
diff --git a/packages/backend/server/src/schema.gql b/packages/backend/server/src/schema.gql
index ba1e50db18..bea9322f39 100644
--- a/packages/backend/server/src/schema.gql
+++ b/packages/backend/server/src/schema.gql
@@ -24,7 +24,7 @@ type Copilot {
 
 type CopilotHistories {
   """An mark identifying which view to use to display the session"""
-  action: String!
+  action: String
   messages: [ChatMessage!]!
   sessionId: String!