GPT-5.6 is now the preferred model in Microsoft 365 Copilot

In early July 2026, Bloomberg reported that Microsoft was replacing some OpenAI software with its own MAI models to reduce operating costs. These self-developed models have been used in apps like Word and Excel. This news sparked speculation about a cooling relationship between the two companies—after all, Microsoft was once OpenAI's largest investor and partner, and their collaboration was once seen as the 'gold standard' in AI.

However, on July 9, when OpenAI released GPT-5.6, it specifically announced that the model would become the 'preferred model' for Microsoft 365 Copilot. OpenAI wrote in its official blog: 'Our partnership with Microsoft has always been about bringing advanced AI to more individuals and organizations, and we are excited to continue building on this shared commitment.' This statement was widely interpreted as a response to the 'breakup' rumors.

In OpenAI's statement, the term 'preferred model' raised many questions. TechCrunch noted that the specific meaning of the term is unclear, and aside from indicating that OpenAI's software will continue to power Microsoft applications, it provides no further details. Notably, the earlier Bloomberg report never claimed that OpenAI's software would completely exit the Microsoft ecosystem; rather, it emphasized that Microsoft is increasing its use of self-developed models to cut costs. Therefore, the announcement of 'preferred model' does not negate Microsoft's use of its own models.

From a technical perspective, 'preferred' may mean that GPT-5.6 is the default option, but users or the system could still switch to other models in specific scenarios. This arrangement preserves OpenAI's involvement while leaving room for Microsoft's own models. In fact, Microsoft has previously stated that its AI strategy is diversified, including self-developed models, OpenAI models, and other third-party models.

The relationship between OpenAI and Microsoft has always been a delicate balance of cooperation and competition. On one hand, Microsoft is a major investor in OpenAI and has deeply integrated OpenAI's models into its products; on the other hand, Microsoft is also heavily investing in its own AI capabilities to reduce reliance on external suppliers. This 'co-opetition' is not uncommon in the tech industry, but OpenAI's statement seems to try to maintain a cooperative-first image in the public eye.

However, the Bloomberg report revealed Microsoft's concrete actions to cut costs. Using self-developed models can significantly reduce inference costs, which is crucial for Microsoft's profit margins. Although OpenAI's statement emphasized GPT-5.6's 'preferred' status, it did not provide any financial or technical details to prove the actual depth of the partnership. Therefore, some analysts believe this is more of a PR move aimed at calming investor and customer concerns about the uncertainty of the partnership.

Overall, the news that GPT-5.6 has become the preferred model for Microsoft 365 Copilot neither proves that the partnership is 'rock-solid' nor that a 'breakup is imminent.' It is more like a carefully crafted signal: OpenAI wants to show that it remains central to Microsoft's AI strategy, while Microsoft retains flexibility by keeping its own model options. For users, there will be no noticeable change in the short term, but in the long run, the rise of Microsoft's self-developed models may gradually reshape the landscape.

This event also reminds us that in today's rapidly evolving AI industry, corporate partnerships are often more complex than they appear on the surface. Public statements need to be interpreted in conjunction with concrete actions and financial motives, and terms like 'preferred' may simply be a simplified label for a complex reality.