What happened
Bloomberg reported that Microsoft has started routing a meaningful and growing number of Copilot tasks inside Excel and Outlook to its own MAI models rather than the OpenAI and Anthropic models those apps previously relied on more heavily. According to a person familiar with the work, tens of thousands of AI prompts a week in the two applications are now completed by Microsoft's internal models. Microsoft itself did not confirm the details, and a spokesperson declined to comment on the report. The reason behind the shift is not disputed. Mustafa Suleyman, Microsoft's AI chief, said in remarks confirmed by Bloomberg and separately by SiliconANGLE: 'We pay a lot of money to Anthropic, so our goal is to reduce and ultimately eliminate that cost,' adding in a separate interview that 'Anthropic is extremely expensive and I think many people are urgently looking for alternatives.' This follows Microsoft's June Build developer conference, where it introduced seven new MAI models, including a reasoning model called MAI-Thinking-1 and a coding model Microsoft said could match the coding performance of Anthropic's Opus 4.6 at a lower cost. MAI models are also already available inside GitHub Copilot, and Microsoft has said a company-built transcription model is coming to Microsoft Teams.
Why it matters for business owners
Most businesses running Microsoft 365 Copilot did not choose OpenAI or Anthropic specifically. They bought Copilot, and Copilot happened to run on those models behind the scenes. That same arrangement now means Microsoft can substitute its own models for the same feature, at the same price to the customer, for reasons that have nothing to do with whether the new model is better suited to a given task. The Decoder's reporting adds an important detail: independent benchmarks published around Microsoft's June announcement showed MAI-Thinking-1 trailing OpenAI's and Anthropic's newest models, performing roughly on par with DeepSeek's V3.2, a more modest result than Microsoft's own comparison against an older Anthropic model. Whether or not that gap closes over time, the immediate point for an owner is this: a bundled AI feature is not a fixed product. The vendor can and will change what powers it, on its own schedule, driven by its own cost pressure, and a business paying the same subscription fee has no built-in way to know when that happened.
What owners should not misunderstand
This is not a story about Microsoft doing something improper. Multi-model platforms are common across the industry, and choosing the most cost-effective model for a given request, a practice generally called model routing, is a legitimate and increasingly standard way vendors manage compute cost at scale. Microsoft has not confirmed exactly which features moved, how its 'Auto' or default mode is weighted, or what share of total Copilot traffic MAI models now handle. Reporting is explicit that this remains a small fraction of Microsoft's overall AI usage today, and Microsoft continues to license OpenAI and Anthropic models broadly, including a discounted OpenAI arrangement that reportedly runs through 2032. Do not read this as Microsoft abandoning its frontier-lab partners, and do not assume every Copilot response you get today is coming from a weaker model. The accurate read is narrower and, for planning purposes, more useful: the model behind a bundled AI feature can change without a corresponding change in your bill, your contract, or the interface you see.
The operational lesson
When an AI feature is bundled into software you already pay for, 'AI included' is not one fixed product. It is a moving target the vendor controls, and the vendor's incentive to route your requests to the cheapest available model is not the same as your incentive to get the best available answer for a specific task. This matters most where the specific model behind a result actually affects the outcome: technical or coding work where capability gaps show up in edge cases, any output tied to a compliance or data-handling claim about a specific model, or a workflow your team has already tuned prompts around a particular model's behavior. It matters less for routine, low-stakes drafting where any competent model produces an acceptable result. The mistake is assuming a bundled AI feature is a stable, single-vendor product just because the interface never changes. It is closer to a utility with a variable, vendor-controlled supply behind the meter.
What a serious business should do next
Ask your primary AI-bundled software vendors, not just Microsoft, whether their platform uses multi-model routing on the tier you are paying for, and whether you can see or control which model answered a given request. For any workflow where the specific model genuinely matters, check whether your subscription tier lets you pin a named model instead of relying on 'Auto' or default settings, and use that option where the stakes justify it. Periodically retest a small, consistent set of real tasks through your bundled AI features and compare the output quality over time, the same way you would monitor any vendor's service level rather than assuming a flat subscription means a flat product. Do not treat this as a reason to disable or distrust Copilot broadly. Reporting is clear that this change today affects a small share of total usage, and MAI models still need to prove themselves against the field over time. Treat it instead as a prompt to add one recurring question to your AI vendor reviews: not just what does this cost, but what is actually answering, and has that changed since I last checked.
The Atlacis view
Atlacis does not take a position on whether Microsoft's own models are as good as OpenAI's or Anthropic's, and that comparison will keep shifting regardless. What matters to a business owner is a pattern Atlacis sees repeatedly: AI capability arrives bundled inside software a business already trusts, and the specific model doing the work is treated as an implementation detail rather than a decision the owner ever consciously made. That was tolerable while the bundled feature was a novelty. It stops being tolerable once a workflow depends on consistent output, or once a claim about data handling or model behavior is tied to a specific model that quietly stopped being the one running the task. Atlacis helps owners map which models actually sit behind the AI tools they already use, decide where that choice needs to be pinned down rather than left to the vendor's default, and build that question into how they evaluate any AI-bundled software going forward.
The short version
- Bloomberg reported on July 7, 2026 that Microsoft has started routing some Excel and Outlook Copilot tasks to its own MAI models instead of OpenAI or Anthropic, still a small share of total usage but a stated cost-reduction strategy.
- Microsoft AI chief Mustafa Suleyman confirmed the motive directly: reducing and ultimately eliminating what Microsoft pays Anthropic, which he separately called 'extremely expensive.'
- Independent benchmark reporting around Microsoft's June Build conference showed its new MAI-Thinking-1 model trailing OpenAI's and Anthropic's latest models, roughly on par with DeepSeek V3.2, a more modest result than Microsoft's own comparison against an older Anthropic model.
- A bundled AI feature inside software you already pay for is not a fixed product. The vendor can change the model behind it, for its own cost reasons, without changing your price, your contract, or the interface you see.
- For workflows where the specific model matters, check whether your subscription tier lets you pin a named model instead of a default or Auto setting, and periodically retest output quality rather than assuming a flat subscription means a flat product.
Where ATLACIS can help
Sources
- Bloomberg via Yahoo Finance (Brody Ford): Microsoft Replaces OpenAI, Anthropic With Own AI in Some Apps (July 7, 2026)
- SiliconANGLE: Microsoft is reportedly ditching OpenAI's and Anthropic's AI models in favor of its own to cut costs (July 7, 2026)
- The Decoder: Copilot goes cheap as Microsoft phases out OpenAI and Anthropic models to cut costs (July 7, 2026)
- Office-Watch: Microsoft quietly swaps the AI inside Excel and Outlook (July 8, 2026)