Something significant is happening inside Microsoft 365, and it's not getting nearly enough attention.
Anthropic, the company behind Claude, now has official add-ins for both Excel and PowerPoint. Claude in Excel first launched as a beta research preview back in October 2025, initially for Max, Team, and Enterprise plans, before expanding to Pro subscribers in late January. I've been using it regularly. It's genuinely impressive. Claude in PowerPoint just launched alongside Anthropic's new Opus 4.6 model, and it's currently in research preview.
But that's only half the story.
Agent Mode now lets you choose your AI model
Microsoft's Agent Mode in Excel - the feature that lets Copilot build, edit, and analyse workbooks for you - now includes a model switcher. You can toggle between OpenAI's GPT-5.2 (the default) and Anthropic's Claude Opus 4.5 from within the same interface.
Read that again. Microsoft is letting you use a competitor's AI model inside their own product.
There's also an Auto mode where Copilot picks the best model for the task. Different models have different strengths - some are better at structured, step-by-step work; others handle open-ended reasoning and explanation more naturally. Microsoft and GitHub have both acknowledged this publicly. It's not about one model being "better" - it's about the right tool for the job.
This is a meaningful shift. Microsoft has spent billions on its relationship with OpenAI, and yet here they are, building a model switcher into one of their flagship products. That tells you something about where enterprise AI is heading: towards choice, not lock-in.
The UK and EU catch
Here's the part that'll frustrate a few of you.
Agent Mode with Claude isn't currently available by default in the UK or EU. Anthropic's models are excluded from Microsoft's EU Data Boundary, which means data processed by Claude goes through Anthropic's servers outside of Microsoft's environment. For organisations bound by GDPR and data residency requirements, that's a problem.
UK and EU tenants have the Anthropic toggle set to Off by default in the Microsoft 365 Admin Centre. Admins can choose to opt in, and if you're part of the Frontier preview programme you can enable it, but it's not a simple "turn it on and forget about it" situation. There are data processing implications that IT teams and compliance leads need to consider first.
Microsoft says EU and UK availability is "coming soon," which is the kind of timeline that could mean anything. But the intent is clearly there.
What about Opus 4.6?
As of today, Agent Mode in Excel supports Claude Opus 4.5. Anthropic has just released Opus 4.6 - their most capable model to date, with a 1 million token context window and stronger performance across coding, financial modelling, and long-form reasoning tasks.
I'd expect Microsoft to upgrade the model available in Agent Mode before too long. When they do, the gap between what Copilot can do natively and what Claude can do inside the same apps will be worth paying close attention to.
This isn't a Copilot critique
I want to be clear about something. I'm a Copilot trainer and consultant - it's what I do every day. I work with organisations across the UK helping them get real value from Microsoft 365 and Copilot. This isn't about picking sides.
What it is about is recognising that AI inside the tools businesses already use is evolving fast. The fact that Microsoft is building multi-model support into Excel and PowerPoint - actively inviting competitors into their ecosystem - benefits everyone. It pushes all of these companies to build better products. It gives organisations more flexibility. And it means the tools your team uses every day are going to keep getting more capable.
The competition between Anthropic, OpenAI, Google, and Microsoft isn't something to be anxious about. It's the thing that's going to make all of these tools actually useful for the people doing the work.
What should you do about it?
If you're a Microsoft 365 admin in the UK, it's worth understanding the Anthropic subprocessor toggle in your Admin Centre - even if you're not ready to enable it yet. Know what's coming.
If you're already using Copilot, start paying attention to Agent Mode. It's moving from preview to general availability on desktop, and the model switching capability makes it a genuinely different proposition from standard Copilot features.
And if you're still figuring out where AI fits in your organisation - whether that's Copilot, Claude, or something else entirely - the pace of change right now is exactly why having a plan matters more than having a preference.
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