OpenAI's GPT-5 Integrates "Router" System for Dynamic Model Selection in ChatGPT

OpenAI has officially launched GPT-5, its latest flagship large language model, which introduces a sophisticated "router" system within ChatGPT. This system dynamically selects the most appropriate underlying model for a user's query, optimizing for factors such as cost and the presumed ability required to answer a question. This approach means that when users interact with "GPT-5" in ChatGPT, they may be engaging with various models, not just a single, monolithic AI.

The dual nature of "GPT-5" as both a model name and an internal routing mechanism was highlighted by Ethan Mollick, a prominent Wharton professor and AI researcher, in a recent social media post. Mollick, known for his expertise in AI's impact on work and education, stated, > "The odd bit is that GPT-5 is two things, a router and a model name. So when you use 'GPT-5' in ChatGPT you might get any of these models (maybe not the very lowest, but we don’t know for sure), as OpenAI optimizes cost versus presumed model ability to answer a question."

OpenAI confirmed this operational strategy, explaining that GPT-5 in ChatGPT is powered by a "unified system" that includes a smart, efficient model for most questions, a deeper reasoning model (GPT-5 Thinking) for more complex problems, and a real-time router to decide which to use. This system aims to deliver optimal performance by intelligently allocating computational resources. The company has also released GPT-5 in three sizes for developers via its API—gpt-5, gpt-5-mini, and gpt-5-nano—allowing for flexibility in performance, cost, and latency.

The launch of GPT-5, while praised for advancements in coding, writing, and reasoning, initially faced some user backlash regarding its perceived "personality" and the removal of access to older models like GPT-4o. OpenAI responded by reintroducing legacy models and adjusting GPT-5's personality to be "warmer and friendlier." This iterative adjustment underscores the company's efforts to balance cutting-edge AI capabilities with user experience.

The integration of a routing system is seen by some experts as a pragmatic step in the evolution of large language models, allowing for more efficient resource utilization and tailored responses. While the GPT-5 release did not represent as dramatic a leap as some previous generations, its underlying architecture signals a move towards more adaptive and economically viable AI deployment strategies, particularly within high-usage applications like ChatGPT.