diff --git a/backend/src/modules/chat/application/chat.service.spec.ts b/backend/src/modules/chat/application/chat.service.spec.ts
index c393379..1a71ac2 100644
--- a/backend/src/modules/chat/application/chat.service.spec.ts
+++ b/backend/src/modules/chat/application/chat.service.spec.ts
@@ -168,6 +168,16 @@ describe('ChatService', () => {
       expect(mockMessageRepository.create).toHaveBeenCalledTimes(1);
     });
 
+    it('should throw ForbiddenException when SUPPORT tries to send message and is not a participant', async () => {
+      mockChatRepository.findById.mockResolvedValue(mockChat);
+
+      await expect(
+        service.sendMessage(CHAT_ID, OUTSIDER_ID, UserRole.SUPPORT, 'Intruso suporte!'),
+      ).rejects.toThrow(ForbiddenException);
+
+      expect(mockMessageRepository.create).not.toHaveBeenCalled();
+    });
+
     it('should throw ForbiddenException when sender is not a participant', async () => {
       mockChatRepository.findById.mockResolvedValue(mockChat);
 
@@ -211,6 +221,29 @@ describe('ChatService', () => {
       expect(mockMessageRepository.findByChatId).toHaveBeenCalledWith(CHAT_ID);
     });
 
+    it('should allow ADMIN to view history even if not a participant', async () => {
+      mockChatRepository.findById.mockResolvedValue(mockChat);
+      mockMessageRepository.findByChatId.mockResolvedValue(mockMessages as any);
+
+      const result = await service.getChatHistory(
+        CHAT_ID,
+        OUTSIDER_ID,
+        UserRole.ADMIN,
+      );
+
+      expect(result).toEqual(mockMessages);
+    });
+
+    it('should throw ForbiddenException when SUPPORT tries to view history and is not a participant', async () => {
+      mockChatRepository.findById.mockResolvedValue(mockChat);
+
+      await expect(
+        service.getChatHistory(CHAT_ID, OUTSIDER_ID, UserRole.SUPPORT),
+      ).rejects.toThrow(ForbiddenException);
+
+      expect(mockMessageRepository.findByChatId).not.toHaveBeenCalled();
+    });
+
     it('should throw ForbiddenException when user is not a participant', async () => {
       mockChatRepository.findById.mockResolvedValue(mockChat);
 
diff --git a/backend/src/modules/chat/application/chat.service.ts b/backend/src/modules/chat/application/chat.service.ts
index 62a7190..9d2c591 100644
--- a/backend/src/modules/chat/application/chat.service.ts
+++ b/backend/src/modules/chat/application/chat.service.ts
@@ -55,7 +55,8 @@ export class ChatService {
       throw new NotFoundException('Chat not found');
     }
 
-    if (senderRole !== UserRole.ADMIN && senderRole !== UserRole.SUPPORT) {
+    // ADMINs podem enviar mensagem em qualquer chat
+    if (senderRole !== UserRole.ADMIN) {
       if (chat.clientId !== senderId && chat.agentId !== senderId) {
         throw new ForbiddenException('You are not a participant of this chat');
       }
@@ -83,7 +84,8 @@ export class ChatService {
       throw new NotFoundException('Chat not found');
     }
 
-    if (userRole !== UserRole.ADMIN && userRole !== UserRole.SUPPORT) {
+    // ADMINs podem ver histórico de qualquer chat
+    if (userRole !== UserRole.ADMIN) {
       if (chat.clientId !== userId && chat.agentId !== userId) {
         throw new ForbiddenException('You are not a participant of this chat');
       }
diff --git a/backend/src/modules/chat/presentation/chat.gateway.spec.ts b/backend/src/modules/chat/presentation/chat.gateway.spec.ts
index 34daa79..26305e5 100644
--- a/backend/src/modules/chat/presentation/chat.gateway.spec.ts
+++ b/backend/src/modules/chat/presentation/chat.gateway.spec.ts
@@ -121,6 +121,31 @@ describe('ChatGateway', () => {
         mensagem: 'Você não é participante deste chat',
       });
     });
+
+    it('should emit error when non-participant support tries to join', async () => {
+      const client = createMockSocket();
+      client.data.user = { id: OUTSIDER_ID, email: 'suporte@e.com', role: 'support' };
+      mockChatService.isParticipant.mockResolvedValue(false);
+
+      await gateway.handleEntrarChat({ chatId: CHAT_ID }, client);
+
+      expect(client.join).not.toHaveBeenCalled();
+      expect(client.emit).toHaveBeenCalledWith('erro', {
+        mensagem: 'Você não é participante deste chat',
+      });
+    });
+
+    it('should emit error when user is not authenticated', async () => {
+      const client = createMockSocket();
+      // client.data.user is undefined
+
+      await gateway.handleEntrarChat({ chatId: CHAT_ID }, client);
+
+      expect(client.join).not.toHaveBeenCalled();
+      expect(client.emit).toHaveBeenCalledWith('erro', {
+        mensagem: 'Usuário não autenticado',
+      });
+    });
   });
 
   describe('enviarMensagem', () => {
diff --git a/backend/src/modules/chat/presentation/chat.gateway.ts b/backend/src/modules/chat/presentation/chat.gateway.ts
index 2ac4606..e782664 100644
--- a/backend/src/modules/chat/presentation/chat.gateway.ts
+++ b/backend/src/modules/chat/presentation/chat.gateway.ts
@@ -74,8 +74,10 @@ export class ChatGateway implements OnGatewayConnection, OnGatewayDisconnect {
 
     const isParticipant = await this.chatService.isParticipant(data.chatId, user.id);
 
-    if (!isParticipant && user.role !== 'admin' && user.role !== 'support') {
-      client.emit('erro', { mensagem: 'Você não é participante deste chat' });
+    if (!isParticipant && user.role !== 'admin') {
+      client.emit('erro', {
+        mensagem: 'Você não é participante deste chat',
+      });
       return;
     }
 
diff --git a/package-lock.json b/package-lock.json
new file mode 100644
index 0000000..6872ff4
--- /dev/null
+++ b/package-lock.json
@@ -0,0 +1,6 @@
+{
+  "name": "ProDesk-backend",
+  "lockfileVersion": 3,
+  "requires": true,
+  "packages": {}
+}