Understanding the Models Behind Microsoft 365 Copilot: GPT-5, GPT-5.2, Response Modes and Claude Explained

There's More Than One Model Behind Copilot Now

If you've opened Microsoft 365 Copilot recently and noticed a dropdown in the top-right corner of Copilot Chat, you're not imagining things. Microsoft has been quietly rolling out model choice, and most users now have access to more than one AI model and multiple response modes.

The problem is that none of this is explained particularly well inside the product. So if you've been wondering what the difference is between the default experience and GPT-5.2, what Auto, Quick Response and Think Deeper actually do, or why there's now a Claude option appearing, this post breaks it all down in plain English.

GPT-5: The Default Model Powering Copilot

As of late 2025, GPT-5 is the standard model that powers Microsoft 365 Copilot for all licensed users. It became the default in a phased rollout between October and November 2025, and by now it's mandatory across web, desktop and mobile. You can't opt out of it, and you don't need to do anything to enable it.

GPT-5 introduced something Microsoft calls dynamic model routing. Behind the scenes, Copilot looks at your prompt and automatically decides which variant of the model to use. Simple questions get routed to a fast, high-throughput model that responds quickly. More complex prompts get sent to a deeper reasoning model that takes more time but produces more thoughtful, structured answers.

For most everyday use, GPT-5 with its automatic routing does a solid job. If you're summarising emails, drafting messages, asking quick questions or getting meeting recaps, the default experience handles it well without you needing to think about models at all.

The Response Modes: Auto, Quick Response and Think Deeper

Alongside the model selector, Microsoft has introduced a response mode selector that gives you direct control over how much reasoning Copilot applies before answering. You'll find this near the prompt area in Copilot Chat, and there are three options.

Auto

This is the default mode. Copilot assesses your prompt and decides for itself whether to give you a fast answer or take more time to reason through it. For most users, this is the sensible choice to leave selected. It balances speed and quality without you having to think about it.

Quick Response

This tells Copilot to prioritise speed. It answers right away without extended reasoning. Use it when you're doing things like drafting emails, polishing text, translating content, getting quick definitions or iterating fast on short-form work. You don't need Copilot to think hard about these tasks. You just want it to get on with it.

Think Deeper

This is the opposite. Copilot takes additional time, often around 10 seconds, to plan its response, reason through the problem, and check its own work before answering. Use it when you're analysing complex documents, building business cases, working through multi-step problems, comparing options, or generating detailed reports where accuracy matters.

Your mode selection persists across chats, so once you've set it, it stays until you change it.

GPT-5.2: The Optional Upgrade in the Model Selector

This is where it gets interesting. In addition to the default GPT-5 experience, Microsoft has made GPT-5.2 available as an optional model you can select from the model dropdown in the top-right corner of Copilot Chat. It started rolling out to licensed users in December 2025 and should now be available across most tenants.

GPT-5.2 is OpenAI's latest and most capable model. Compared to GPT-5, it delivers better instruction following, improved maths and coding performance, stronger multi-step reasoning, and clearer explanations. It also handles significantly longer context, meaning it's better at maintaining coherence across long chat threads or when working with large documents.

When you select GPT-5.2, you still have access to the same response modes. GPT-5.2 Quick Response uses the Instant variant for fast, everyday tasks. GPT-5.2 Think Deeper uses the Thinking variant for complex reasoning. The combination of GPT-5.2 with Think Deeper is currently the most powerful option available in Microsoft 365 Copilot.

The quality difference is significant. On OpenAI's GDPval benchmark, which measures AI performance across 44 real-world professional tasks, GPT-5.2 Thinking achieved a 70.9% win or draw rate against human experts. For context, GPT-5 Thinking scored 38.8% on the same benchmark. If you're asking Copilot to do something that requires genuine reasoning rather than pattern matching, selecting GPT-5.2 with Think Deeper is worth the extra wait.

Why Not Just Use GPT-5.2 All the Time?

This is the question everyone asks, and it's a fair one. If GPT-5.2 is better, why wouldn't you just leave it selected permanently?

There are a couple of practical reasons. First, GPT-5.2 consumes more compute resources than the default GPT-5 routing. The Thinking variant in particular processes significantly more tokens internally as it reasons, plans and self-checks. Microsoft 365 Copilot operates on a fair use basis for licensed users. There's no publicly disclosed hard token limit, but Microsoft applies rate limiting behind the scenes to ensure fair resource allocation across tenants. If you're running GPT-5.2 Think Deeper constantly across a large team, you're more likely to hit those fair use thresholds than if everyone is on the default Auto mode.

Second, not every task needs it. If you're asking Copilot to summarise an email or draft a quick reply, GPT-5.2 Think Deeper is overkill. The default GPT-5 with Auto routing will give you a perfectly good answer in a fraction of the time. Save GPT-5.2 Think Deeper for the work that genuinely benefits from deeper reasoning: strategy documents, complex analysis, detailed reports, and multi-step problem solving.

For consumer plans (Microsoft 365 Personal and Family), the limits are more explicit at 60 AI credits per month. The newer Microsoft 365 Premium plan lifts this to what Microsoft calls "Extensive Use," which is essentially fair use without a disclosed cap. For enterprise Copilot licence holders, usage is effectively unlimited under normal conditions, but Microsoft reserves the right to throttle if it's genuinely excessive.

Claude Is Now Available Too, But There's a Catch for UK Organisations

Microsoft has also started offering Anthropic's Claude models within Microsoft 365 Copilot. Claude Sonnet 4.5 and Claude Opus 4.5 are available in Copilot Studio for building agents, and Claude can also power the Researcher agent for deep reasoning tasks.

As of January 2026, Anthropic has been onboarded as a Microsoft subprocessor, meaning Claude usage in Copilot is covered under Microsoft's Product Terms and Data Protection Addendum. That's a significant improvement from the initial September 2025 launch, where organisations had to accept Anthropic's own separate commercial terms.

Admins can manage this from the Microsoft 365 admin centre under Copilot > Settings > Data access > AI providers operating as Microsoft subprocessors.

The UK and EU Problem

Here's the important detail for UK organisations: Anthropic's models are currently excluded from the EU Data Boundary and in-country processing commitments. All Claude processing happens on Anthropic's infrastructure in the United States. Your data leaves Microsoft's managed environment, gets processed on Anthropic's US-based servers, and then the response is returned.

For most commercial tenants globally, Microsoft has enabled Anthropic by default. But for organisations in the EU, EFTA, and the United Kingdom, the toggle is set to Off by default. This is a deliberate decision because the data processing arrangement doesn't currently meet EU Data Boundary or UK data residency expectations.

If your organisation has strict GDPR or data residency requirements (and most UK enterprises should), you'll want to think carefully before enabling Claude. The data protection is covered by Microsoft's DPA, but the physical processing location is the US. That introduces considerations around international data transfers that your compliance team needs to assess.

UK and EU admins can opt in, but it requires an active decision. It won't be switched on for you.

A Quick Summary

Here's the simple version of how it all fits together:

• GPT-5 is the default model. It powers Copilot automatically and routes your prompts to the right variant behind the scenes. Good for everyday use.
• Auto lets Copilot decide how much reasoning to apply. Leave it here unless you have a reason to change.
• Quick Response prioritises speed. Use it for fast drafting, translations and simple questions.
• Think Deeper prioritises quality. Use it for analysis, strategy and complex reasoning tasks.
• GPT-5.2 is the optional upgrade. More capable than GPT-5 but uses more compute. Best reserved for work that genuinely needs it.
• Claude is available via the admin centre but is Off by default for UK and EU tenants due to US-based data processing.

The key takeaway is that you now have real choices about how Copilot works for you. The default experience is solid, but knowing when to reach for Think Deeper or GPT-5.2 can make a meaningful difference to the quality of output you get.

If you'd like help getting your team trained on these new features, or need guidance on the admin settings and compliance implications, book a consultation with us.