Revamping the 13-year-old Siri service is part of Apple’s efforts to become a force in artificial intelligence. The company debuted its much-ballyhooed Apple Intelligence platform last month, but it still lacks many of the features offered by other tech giants. The new Siri, details of which haven’t been reported, uses more advanced large language models, or LLMs, to allow for back-and-forth conversations, said the people, who asked not to be identified because the effort hasn’t been announced.