diff --git a/packages/backend/server/src/plugins/copilot/resolver.ts b/packages/backend/server/src/plugins/copilot/resolver.ts
index b7ddba8501..067105df72 100644
--- a/packages/backend/server/src/plugins/copilot/resolver.ts
+++ b/packages/backend/server/src/plugins/copilot/resolver.ts
@@ -273,12 +273,7 @@ export class CopilotResolver {
     @Parent() copilot: CopilotType,
     @CurrentUser() user: CurrentUser,
     @Args('docId', { nullable: true }) docId?: string,
-    @Args({
-      name: 'options',
-      type: () => QueryChatHistoriesInput,
-      nullable: true,
-    })
-    options?: QueryChatHistoriesInput
+    @Args('options', { nullable: true }) options?: QueryChatHistoriesInput
   ) {
     const workspaceId = copilot.workspaceId;
     if (!workspaceId) {
diff --git a/packages/backend/server/src/plugins/copilot/session.ts b/packages/backend/server/src/plugins/copilot/session.ts
index cb121f5b81..f4f0496ac9 100644
--- a/packages/backend/server/src/plugins/copilot/session.ts
+++ b/packages/backend/server/src/plugins/copilot/session.ts
@@ -254,6 +254,7 @@ export class ChatSessionService {
             // connect
             userId: state.userId,
             promptName: state.prompt.name,
+            parentSessionId: state.parentSessionId,
           },
         });
       }
@@ -384,17 +385,36 @@ export class ChatSessionService {
     return await this.db.aiSession
       .findMany({
         where: {
-          userId,
-          workspaceId: workspaceId,
-          docId: workspaceId === docId ? undefined : docId,
-          prompt: {
-            action: options?.action ? { not: null } : null,
-          },
-          id: options?.sessionId ? { equals: options.sessionId } : undefined,
-          deletedAt: null,
+          OR: [
+            {
+              userId,
+              workspaceId: workspaceId,
+              docId: workspaceId === docId ? undefined : docId,
+              id: options?.sessionId
+                ? { equals: options.sessionId }
+                : undefined,
+              deletedAt: null,
+            },
+            ...(options?.action
+              ? []
+              : [
+                  {
+                    userId: { not: userId },
+                    workspaceId: workspaceId,
+                    docId: workspaceId === docId ? undefined : docId,
+                    id: options?.sessionId
+                      ? { equals: options.sessionId }
+                      : undefined,
+                    // should only find forked session
+                    parentSessionId: { not: null },
+                    deletedAt: null,
+                  },
+                ]),
+          ],
         },
         select: {
           id: true,
+          userId: true,
           promptName: true,
           tokenCost: true,
           createdAt: true,
@@ -419,15 +439,30 @@ export class ChatSessionService {
       .then(sessions =>
         Promise.all(
           sessions.map(
-            async ({ id, promptName, tokenCost, messages, createdAt }) => {
+            async ({
+              id,
+              userId: uid,
+              promptName,
+              tokenCost,
+              messages,
+              createdAt,
+            }) => {
               try {
+                const prompt = await this.prompt.get(promptName);
+                if (!prompt) {
+                  throw new CopilotPromptNotFound({ name: promptName });
+                }
+                if (
+                  // filter out the user's session that not match the action option
+                  (uid === userId && !!options?.action !== !!prompt.action) ||
+                  // filter out the non chat session from other user
+                  (uid !== userId && !!prompt.action)
+                ) {
+                  return undefined;
+                }
+
                 const ret = ChatMessageSchema.array().safeParse(messages);
                 if (ret.success) {
-                  const prompt = await this.prompt.get(promptName);
-                  if (!prompt) {
-                    throw new CopilotPromptNotFound({ name: promptName });
-                  }
-
                   // render system prompt
                   const preload = withPrompt
                     ? prompt
diff --git a/packages/backend/server/tests/copilot.e2e.ts b/packages/backend/server/tests/copilot.e2e.ts
index b2dd5ab222..cff25dff76 100644
--- a/packages/backend/server/tests/copilot.e2e.ts
+++ b/packages/backend/server/tests/copilot.e2e.ts
@@ -36,6 +36,7 @@ import {
   chatWithWorkflow,
   createCopilotMessage,
   createCopilotSession,
+  forkCopilotSession,
   getHistories,
   MockCopilotTestProvider,
   sse2array,
@@ -164,6 +165,123 @@ test('should create session correctly', async t => {
   }
 });
 
+test('should fork session correctly', async t => {
+  const { app } = t.context;
+
+  const assertForkSession = async (
+    token: string,
+    workspaceId: string,
+    sessionId: string,
+    lastMessageId: string,
+    error: string,
+    asserter = async (x: any) => {
+      const forkedSessionId = await x;
+      t.truthy(forkedSessionId, error);
+      return forkedSessionId;
+    }
+  ) =>
+    await asserter(
+      forkCopilotSession(
+        app,
+        token,
+        workspaceId,
+        randomUUID(),
+        sessionId,
+        lastMessageId
+      )
+    );
+
+  // prepare session
+  const { id } = await createWorkspace(app, token);
+  const sessionId = await createCopilotSession(
+    app,
+    token,
+    id,
+    randomUUID(),
+    promptName
+  );
+
+  let forkedSessionId: string;
+  // should be able to fork session
+  {
+    for (let i = 0; i < 3; i++) {
+      const messageId = await createCopilotMessage(app, token, sessionId);
+      await chatWithText(app, token, sessionId, messageId);
+    }
+    const histories = await getHistories(app, token, { workspaceId: id });
+    const latestMessageId = histories[0].messages.findLast(
+      m => m.role === 'assistant'
+    )?.id;
+    t.truthy(latestMessageId, 'should find last message id');
+
+    // should be able to fork session
+    forkedSessionId = await assertForkSession(
+      token,
+      id,
+      sessionId,
+      latestMessageId!,
+      'should be able to fork session with cloud workspace that user can access'
+    );
+  }
+
+  {
+    const {
+      token: { token: newToken },
+    } = await signUp(app, 'test', 'test@affine.pro', '123456');
+    await assertForkSession(
+      newToken,
+      id,
+      sessionId,
+      randomUUID(),
+      '',
+      async x => {
+        await t.throwsAsync(
+          x,
+          { instanceOf: Error },
+          'should not able to fork session with cloud workspace that user cannot access'
+        );
+      }
+    );
+
+    const inviteId = await inviteUser(
+      app,
+      token,
+      id,
+      'test@affine.pro',
+      'Admin'
+    );
+    await acceptInviteById(app, id, inviteId, false);
+    await assertForkSession(
+      newToken,
+      id,
+      sessionId,
+      randomUUID(),
+      '',
+      async x => {
+        await t.throwsAsync(
+          x,
+          { instanceOf: Error },
+          'should not able to fork a root session from other user'
+        );
+      }
+    );
+
+    const histories = await getHistories(app, token, { workspaceId: id });
+    const latestMessageId = histories
+      .find(h => h.sessionId === forkedSessionId)
+      ?.messages.findLast(m => m.role === 'assistant')?.id;
+    t.truthy(latestMessageId, 'should find latest message id');
+
+    await assertForkSession(
+      newToken,
+      id,
+      forkedSessionId,
+      latestMessageId!,
+      'should able to fork a forked session created by other user'
+    );
+  }
+});
+
 test('should be able to use test provider', async t => {
   const { app } = t.context;
 
diff --git a/packages/backend/server/tests/utils/copilot.ts b/packages/backend/server/tests/utils/copilot.ts
index c3aed677fb..d6e32a2472 100644
--- a/packages/backend/server/tests/utils/copilot.ts
+++ b/packages/backend/server/tests/utils/copilot.ts
@@ -174,6 +174,35 @@ export async function createCopilotSession(
   return res.body.data.createCopilotSession;
 }
 
+export async function forkCopilotSession(
+  app: INestApplication,
+  userToken: string,
+  workspaceId: string,
+  docId: string,
+  sessionId: string,
+  latestMessageId: string
+): Promise<string> {
+  const res = await request(app.getHttpServer())
+    .post(gql)
+    .auth(userToken, { type: 'bearer' })
+    .set({ 'x-request-id': 'test', 'x-operation-name': 'test' })
+    .send({
+      query: `
+        mutation forkCopilotSession($options: ForkChatSessionInput!) {
+          forkCopilotSession(options: $options)
+        }
+      `,
+      variables: {
+        options: { workspaceId, docId, sessionId, latestMessageId },
+      },
+    })
+    .expect(200);
+
+  handleGraphQLError(res);
+
+  return res.body.data.forkCopilotSession;
+}
+
 export async function createCopilotMessage(
   app: INestApplication,
   userToken: string,
@@ -286,6 +315,7 @@ export function textToEventStream(
 }
 
 type ChatMessage = {
+  id?: string;
   role: string;
   content: string;
   attachments: string[] | null;
@@ -333,6 +363,7 @@ export async function getHistories(
               action
               createdAt
               messages {
+                id
                 role
                 content
                 attachments
diff --git a/packages/backend/server/tests/utils/utils.ts b/packages/backend/server/tests/utils/utils.ts
index b8bd9910bf..1db32b7984 100644
--- a/packages/backend/server/tests/utils/utils.ts
+++ b/packages/backend/server/tests/utils/utils.ts
@@ -145,7 +145,14 @@ export function handleGraphQLError(resp: Response) {
   if (errors) {
     const cause = errors[0];
     const stacktrace = cause.extensions?.stacktrace;
-    throw new Error(stacktrace ? stacktrace.join('\n') : cause.message, cause);
+    throw new Error(
+      stacktrace
+        ? Array.isArray(stacktrace)
+          ? stacktrace.join('\n')
+          : String(stacktrace)
+        : cause.message,
+      cause
+    );
   }
 }
 
diff --git a/packages/frontend/graphql/src/graphql/get-copilot-histories.gql b/packages/frontend/graphql/src/graphql/get-copilot-histories.gql
index 3779afd3d9..2b3af6c1da 100644
--- a/packages/frontend/graphql/src/graphql/get-copilot-histories.gql
+++ b/packages/frontend/graphql/src/graphql/get-copilot-histories.gql
@@ -11,6 +11,7 @@ query getCopilotHistories(
         action
         createdAt
         messages {
+          id
           role
           content
           attachments
diff --git a/packages/frontend/graphql/src/graphql/index.ts b/packages/frontend/graphql/src/graphql/index.ts
index b17ca4ee0f..a52dde498d 100644
--- a/packages/frontend/graphql/src/graphql/index.ts
+++ b/packages/frontend/graphql/src/graphql/index.ts
@@ -267,6 +267,7 @@ query getCopilotHistories($workspaceId: String!, $docId: String, $options: Query
         action
         createdAt
         messages {
+          id
           role
           content
           attachments
diff --git a/packages/frontend/graphql/src/schema.ts b/packages/frontend/graphql/src/schema.ts
index c72980b334..2b1ed8dee9 100644
--- a/packages/frontend/graphql/src/schema.ts
+++ b/packages/frontend/graphql/src/schema.ts
@@ -1405,6 +1405,7 @@ export type GetCopilotHistoriesQuery = {
         createdAt: string;
         messages: Array<{
           __typename?: 'ChatMessage';
+          id: string | null;
           role: string;
           content: string;
           attachments: Array<string> | null;