Grok 4.1 Fast is a fast‑reasoning, text‑generation model (generation of images and other media types are not supported) that is designed for large context, deep tool use, and can be used to handle complex workflows. This addition reflects our ongoing commitment to give you more flexibility when designing and optimizing agents—so you can choose the right model for every business scenario.

Expanding our model line-up

Copilot Studio aims to give makers the ability to evaluate and use the model best suited to transform their business. With the addition of xAI Grok 4.1 Fast, we’re building on that commitment.

Alongside OpenAI and Anthropic models, xAI adds even more depth to your multi‑model lineup—while still keeping responsible AI principles at the center. Before rollout, every model in your Copilot Studio lineup goes through security, safety, and quality evaluations.

When using Grok 4.1 Fast in Copilot Studio, customer data is not retained or used to train xAI’s models. xAI’s models are hosted outside Microsoft-managed environments, and when you use Grok 4.1 Fast in Copilot Studio, your relationship with xAI will be independent of Microsoft and governed by xAI’s Enterprise Terms of Service and Data Protection Addendum.

Unlocking the power of model choice

Starting today, Grok 4.1 Fast is available in preview in early access environments, and is off by default. Your organization’s admin must explicitly opt in to use the model before US-based makers can build with it.

If an admin doesn’t opt in, nothing changes and makers keep their current model options. Existing agents continue running exactly as they do today.

Learn more about admin opt-in controls:

• Allowing external language models for generative responses
• How to connect to xAI’s models

The post More choice, more flexibility: xAI Grok 4.1 Fast now available in Microsoft Copilot Studio appeared first on Microsoft Copilot Blog.

For anyone building agents in Copilot Studio, we know that model choice enables you to solve your unique business problems and realize continuous improvement in agent performance. That’s why in the past 60 days, we’ve enabled major models like GPT-5, GPT-5.1, Claude Sonnet 4.5 and Claude Opus 4.5 in Copilot Studio on the same day as their public release. And with new Copilot Studio platform capabilities like agent evaluations, we’re making it even easier to test your agent with multiple models to find the right fit.

Hear directly from the team on how we are enabling model choice across Copilot Studio and Microsoft 365 Copilot:

Claude Opus 4.5 will replace Claude Opus 4.1 in Copilot Studio as an experimental model. As with any experimental model, we encourage testing it in non-production scenarios. To use Anthropic models in Copilot Studio, admins must opt in via the Microsoft 365 Admin Center. You can learn more about doing so here. If you have already opted into using Anthropic models in your tenant, there’s no action required.

You can learn more about Claude Opus 4.5 from Anthropic’s launch announcement.

The post Announcing Claude Opus 4.5 in Microsoft Copilot Studio appeared first on Microsoft Copilot Blog.

Experimental models give you the opportunity to test cutting-edge capabilities before they reach general availability. You can evaluate performance against your use cases and existing models to prepare for deployment. As experimental models, we recommend using them in non-production scenarios while we complete our evaluation gates. This approach allows you to stay ahead of the curve, experimenting with the latest AI models while we ensure they meet quality standards.

You can learn more about using the latest models in Copilot Studio here.

The post Available now: GPT-5.1 in Microsoft Copilot Studio appeared first on Microsoft Copilot Blog.

Claude Sonnet 4.5 will replace Claude Sonnet 4 in Copilot Studio and can be chosen for orchestration. Availability from prompt builder will arrive later in October. If you have already opted into using Anthropic models in your tenant, there’s no action required. Otherwise, you can get started by enabling access in the Microsoft Admin Center (MAC). 

You can learn more about Claude Sonnet 4.5 from Anthropic’s launch announcement: Introducing Claude Sonnet 4.5 \ Anthropic. Read more about model choice in Copilot Studio here.

The post Available today: Claude Sonnet 4.5 in Microsoft Copilot Studio appeared first on Microsoft Copilot Blog.