Microsoft quietly began replacing OpenAI’s models with its own in-house MAI software across Word and Excel, and nobody from OpenAI said a word — until now.
The partnership that looked like it was fraying just got a public patch
Enterprise teams running Microsoft 365 Copilot had no clear answer for which AI model was actually powering their productivity suite, or whether that answer was about to change under them. That uncertainty makes budget justification and vendor planning nearly impossible for IT leads and procurement officers.
OpenAI just put its name back on the door
OpenAI says GPT 5.6 is the ‘preferred model’ for Microsoft Copilot 365 amid breakup chatter was announced Thursday as the designated model powering Microsoft 365 Copilot across Word, Excel, PowerPoint, and Cowork. You do not install anything separately — if your organization runs Microsoft 365 Copilot, GPT-5.6 is now the named engine behind it. The input is your document, prompt, or meeting transcript; the output is whatever Copilot was already generating, now attributed to a specific model.
The people most exposed to this decision work in three places
- IT procurement managers who need a named vendor model on record before renewing a Microsoft 365 enterprise license
- AI strategy leads at mid-market companies who were actively evaluating whether to build internal workflows on Copilot or a competing platform
- Compliance officers at regulated firms who must document which AI model processed employee data inside productivity software
The word “preferred” is doing significant work in OpenAI’s announcement — it does not preclude Microsoft from continuing to expand its MAI models elsewhere in the product suite.
Microsoft’s in-house AI push just got a very public counter-move
Bloomberg reported this week that Microsoft was already routing Word and Excel tasks to its own MAI models to cut costs, a signal that the OpenAI dependency was eroding faster than either company acknowledged publicly. If MAI continues expanding quietly while GPT-5.6 holds the headline slot, enterprise buyers will need to ask Microsoft directly which model is running any given task.
What enterprise teams can actually do with this information now
- Confirm with Microsoft account reps which tasks route to GPT-5.6 versus MAI
- Document the named model in AI usage policies before your next compliance audit
- Test GPT-5.6 output quality in Excel and Word against your current Copilot baseline
- Revisit vendor lock-in risk assessments given the dual-model reality inside one product
Pricing for Microsoft 365 Copilot remains tied to existing Microsoft enterprise licensing — check our directory for current plan details.
The “preferred model” designation tells you OpenAI is still in the building, but it does not tell you how much of the building Microsoft now owns.
Alternatives worth watching
Google Workspace with Gemini offers a single-vendor AI stack where the model identity is not in question. For teams willing to leave Microsoft entirely, Notion AI gives document-layer AI without the dual-model ambiguity.
The Microsoft-OpenAI model split is accelerating faster than enterprises realize
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