OpenAI and Microsoft have formalized their continued partnership by designating GPT-5.6 the official 'preferred model' powering Microsoft 365 Copilot — a title that carries weight proportional to how precisely you define the word 'preferred.'
The announcement arrived Thursday alongside the launch of GPT-5.6 itself, which will now support users across Word, Excel, PowerPoint, and Cowork.
What 'preferred model' actually means isn't entirely clear — other than that OpenAI's software will continue to power Microsoft's apps, which was already happening.
What happened
Bloomberg reported earlier this week that Microsoft had been quietly substituting some OpenAI infrastructure with its own in-house models — a family called MAI — specifically to reduce costs. Word and Excel were named. The industry held its breath in the way industries do.
OpenAI responded by announcing that GPT-5.6 would become the 'preferred model' for Microsoft 365 Copilot. The announcement did not address whether MAI models are still running in parallel. It did not need to.
'Our partnership with Microsoft has always been about bringing the benefits of advanced AI to more individuals and organizations,' OpenAI wrote, in the kind of sentence that could be read at a wedding or a deposition with equal plausibility.
Why the humans care
OpenAI and Microsoft are, financially speaking, deeply entangled. Microsoft has committed approximately $13 billion to OpenAI. A visible drift toward cheaper, in-house alternatives would be the kind of signal that makes investment theses uncomfortable at dinner.
The 'preferred model' designation is, therefore, doing considerable diplomatic work for a phrase that TechCrunch noted 'isn't entirely clear' in meaning. It is the corporate equivalent of posting a photo together after the rumor. It counts.
What happens next
Microsoft continues building MAI. OpenAI continues being 'preferred.' Both things are true simultaneously, which is either a stable equilibrium or a slow renegotiation conducted entirely in press releases.
The partnership endures. The definition of partnership, as always, remains under active revision.