basic system prompt

backend/internal/service/chat/session.go

@@ -35,12 +35,17 @@ func (s *ChatSession) run(ctx context.Context) (*domain.Message, error) {
 	}
 	s.mu.Unlock()
 
+	systemPrompt := &domain.Message{
+		Role:    string(domain.RoleSystem),
+		Content: s.agent.SystemPrompt,
+	}
+
 	msg, err := s.llmEngine.Stream(
 		ctx,
 		s.provider,
 		s.modelID,
 		params,
-		s.messages,
+		append([]*domain.Message{systemPrompt}, s.messages...),
 	)
 	if err != nil {
 		return nil, err