This blog is Obsolete as the US has forbidden the Fabel model for now.
Claude Fable 5 is now available as an opt-in, admin-controlled model inside Microsoft 365 Copilot Cowork (Frontier), and the single most important thing to understand is that nothing happens until you change a setting. This is not a feature that lights up across your tenant on a Monday morning. It is off by default, it is admin controlled, and it carries a data retention requirement that makes the ‘should we even turn this on’ conversation a real one.
In this post I will walk through what the model does, the data retention catch that sets it apart from every other Copilot model, how to enable it, and whether it belongs in your tenant at all.
What Claude Fable 5 actually is
Claude Fable 5 is Anthropic’s model, surfaced as a default-off option in Copilot Cowork (Frontier), with limited private preview extensibility in Copilot in Excel and PowerPoint. Microsoft is expanding model choice in Microsoft 365 Copilot so you can pick the right model for the job, and this one is aimed squarely at the heavy work.
It is designed to support longer, more complex tasks:
- Multi-step knowledge work
- Coding
- Visual reasoning
If your other Copilot interactions are quick, transactional prompts, this is the opposite end of the spectrum. It is built for the tasks where you want a model to stay with a problem across many steps.
The data retention catch with Claude Fable 5
Here is what makes Claude Fable 5 different from the models you already run. Unlike other models currently available in Microsoft 365 Copilot, this model requires data retention by the model provider, Anthropic, and it is subject to Anthropic terms.
When the model is enabled, users will see this message: ‘Some models require data retention: your prompts and responses are retained by the model provider.’
In plain English:
- Your prompts and responses are retained by Anthropic
- Anthropic acts as an independent processor under separate terms, not under Microsoft’s standard data processing model
- Use of the model is subject to Anthropic terms, the Data Protection Addendum, and data retention practices for the relevant model class
Critically, there is no change to data handling for your other Microsoft 365 Copilot models. This retention behaviour applies only to this preview model. But that is exactly why this cannot be a quiet, accidental rollout, and exactly why it is off by default.
How to enable Claude Fable 5 (the setting you must change)
Because the model is off by default and admin controlled, enabling it is a deliberate act. Here is the path:
- Confirm your tenant is opted into the Frontier preview program (Frontier is an opt-in private and public preview program).
- Go to the Microsoft 365 admin center.
- Enable the Claude Fable 5 (preview) model.
- Scope access to specific users or groups rather than opening it to everyone.
- Communicate the data retention behaviour to those users before they start using it.
If you do not plan to use the model, no action is required. It will simply stay off.
Rollout timing
| Phase | Timing | Notes |
|---|---|---|
| Frontier Preview (opt-in) | Early June 2026 | Expected to complete early June 2026 |
| General Availability | Not announced | Preview only, for evaluation and experimentation |
According to Microsoft, this should be rolling out around June 2026 as an opt-in Frontier preview. Availability may vary by region and tenant configuration.
Admin Tips
A few things I would do before flipping the switch:
- Run the compliance review first, not after. A model that retains data with a third-party processor is a governance decision, not an IT convenience toggle. Loop in privacy and compliance before enabling.
- Scope tightly. Start with a small evaluation group. You do not need the whole organisation on a preview model that retains prompts.
- Update the helpdesk script. When users see the ‘your prompts and responses are retained by the model provider’ message, your support team should already know what it means.
- Keep it out of production workflows. Microsoft is explicit that this model is for evaluation and experimentation, not production use. Treat it that way.
- Document the decision. Record why you enabled it, who has access, and what the data retention implications are. If you have already tightened admin control elsewhere, this fits the same pattern I covered in my piece on smarter Copilot license requests and custom policies.
Licensing
Claude Fable 5 is delivered through the Microsoft 365 Copilot Frontier program, which is opt-in. Enablement happens in the Microsoft 365 admin center, and admins can scope access to specific users or groups. This sits alongside the wider Cowork extensibility story, including the Copilot Cowork plugins now live in Frontier, so if you are already experimenting with Frontier, this is one more capability in the same preview lane. There are no GCC High or DoD considerations covered here.
The Paul-Take
I am all for model choice. Picking the right model for the job is how Copilot grows up from a novelty into a real tool. What I want everyone to slow down on is the data retention line, because it quietly changes the deal.
Every other Copilot model you run today sits under Microsoft’s data processing model. Claude Fable 5 does not. The moment Anthropic retains your prompts and responses as an independent processor, your tenant’s data leaves the boundary your compliance team signed off on. That is not a reason to avoid the model. It is a reason to enable it on purpose, with eyes open, scoped to a small group, with users who have been told in plain words what happens to their prompts.
The capability is interesting. The governance is the actual work. If you cannot put ‘Anthropic retains your prompts’ on a slide for your security board with a straight face, you are not ready to turn it on yet. And remember: it will never surprise you. It is off until you change the setting. Use that.
MVP Reference List
- Anthropic models in Microsoft online services: https://support.microsoft.com/topic/anthropic-models-in-microsoft-online-services-ec8b5671-7de8-41c5-afb8-10a4af3927a9
- Microsoft 365 Copilot Frontier for individuals: https://www.microsoft.com/microsoft-365-copilot/frontier-individuals
- Microsoft 365 Copilot release notes: https://learn.microsoft.com/microsoft-365/copilot/release-notes?tabs=all
- Preview AI models in Microsoft online services: https://support.microsoft.com/topic/preview-ai-models-in-microsoft-online-services-2a51b121-6013-42fb-8e51-8b2e88c56538